II

Thesis for the degree of Licentiate of Philosophy

Forest biomass production potential and its implications for

carbon balance

Bishnu Chandra Poudel

Ecotechnology and Environmental Science

Department of Engineering and Sustainable Development

Mid Sweden University

Östersund, Sweden

2012

Mid Sweden University Licentiate Thesis 87

Forest biomass production potential and its implications for carbon

balance

Bishnu Chandra Poudel

© 2012 Bishnu Chandra Poudel

Ecotechnology and Environmental Science

Department of Engineering and Sustainable Development

Mid Sweden University

SE-83125 Östersund

Sweden

Mid Sweden University Licentiate Thesis 87

ISBN 978-91-87103-27-8

ISSN 1652-8948

Cover photo: Managed spruce forest, Sweden, ©Bishnu Chandra Poudel

Printed by: Kopieringen Mid Sweden University, Sundsvall, Sweden, 2012

I

Abstract

An integrated methodological approach is used to analyse the forest

biomass production potential in the Middle Norrland region of Sweden, and its

use to reduce carbon emissions. Forest biomass production, forest management,

biomass harvest, and forest product use are analyzed in a system perspective

considering the entire resource flow chains. The system-wide carbon flows as well

as avoided carbon emissions are quantified for the activities of forest biomass

production, harvest, use and substitution of non-biomass materials and fossil fuels.

Five different forest management scenarios and two biomass use alternatives are

developed and used in the analysis. The analysis is divided into four main parts. In

the first part, plant biomass production is estimated using principles of plant-

physiological processes and soil-water dynamics. Biomass production is compared

under different forest management scenarios, some of which include the expected

effects of climate change based on IPCC B2 scenario. In the second part, forest

harvest potentials are estimated based on plant biomass production data and

Swedish national forest inventory data for different forest management

alternatives. In the third part, soil carbon stock changes are estimated for different

litter input levels from standing biomass and forest residues left in the forest

during the harvest operations. The fourth and final part is the estimation of carbon

emissions reduction due to the substitution of fossil fuels and carbon-intensive

materials by the use of forest biomass. Forest operational activities such as

regeneration, pre-commercial thinning, commercial thinning, fertilisation, and

harvesting are included in the analysis. The total carbon balance is calculated by

summing up the carbon stock changes in the standing biomass, carbon stock

changes in the forest soil, forest product carbon stock changes, and the substitution

effects. Fossil carbon emissions from forest operational activities are calculated and

deducted to calculate the net total carbon balance.

The results show that the climate change effect most likely will increase

forest biomass production over the next 100 years compared to a situation with

unchanged climate. As an effect of increased biomass production, there is a

possibility to increase the harvest of usable biomass. The annual forest biomass

production and harvest can be further increased by the application of more

intensive forestry practices compared to practices currently in use. Deciduous trees

are likely to increase their biomass production because of climate change effects

whereas spruce biomass is likely to increase because of implementation of

intensive forestry practices.

II

Intensive forestry practices such as application of pre-commercial

thinning, balanced fertilisation, and introduction of fast growing species to replace

slow growing pine stands can increase the standing biomass carbon stock. Soil

carbon stock increase is higher when only stem-wood biomass is used, compared

to whole-tree biomass use. The increase of carbon stocks in wood products

depends largely on the magnitude of harvest and the use of the harvested biomass.

The biomass substitution benefits are the largest contributor to the total carbon

balance, particularly for the intensive forest management scenario when whole-

tree biomass is used and substitutes coal fuel and non-wood construction

materials. The results show that the climate change effect could provide up to 104

Tg carbon emissions reduction, and intensive forestry practices may further

provide up to 132 Tg carbon emissions reduction during the next 100 years in the

area studied.

This study shows that production forestry can be managed to balance

biomass growth and harvest in the long run, so that the forest will maintain its

capacity to increase standing biomass carbon and provide continuous harvests.

Increasing standing biomass in Swedish managed forest may not be the most

effective strategy to mitigate climate change. Storing wood products in building

materials delays the carbon emissions into the atmosphere, and the wood material

in the buildings can be used as biofuel at the end of a building life-cycle to

substitute fossil fuels.

These findings show that the forest biomass production potential in the

studied area increases with climate change and with the application of intensive

forestry practices. Intensive forestry practice has the potential for continuous

increased biomass production which, if used to substitute fossil fuels and

materials, could contribute significantly to net carbon emissions reductions and

help mitigate climate change.

III

Sammanfattning

Ett integrerat tillvägagångssätt används för att analysera skogens potential

för produktion av biomassa i mellersta Norrland i Sverige och dess användning för

att minska koldioxidutsläppen. Produktion av skogsbiomassa, skogsskötsel, skörd

av biomassa och användning av skogsprodukter analyseras i ett systemperspektiv

med beaktande av hela resursflödeskedjan. Kolflöden i hela systemet och de

koldioxidutsläpp som undviks kvantifieras för följande aktiviteter i

resursflödeskedjan: Produktion av biomassa, skörd, användning samt substitution

av icke biomassebaserade material och fossila bränslen. Fem olika

skogsskötselscenarier och två alternativ för användning av biomassa tas fram och

analyseras. Analysen är uppdelad i fyra huvuddelar. I den första delen uppskattas

produktionen av trädbiomassa baserat på principer för växtfysiologiska processer

och markvattendynamik. Produktion av biomassa jämförs för de olika

skogsskötselscenarierna av vilka några innefattar de förväntade effekterna av

klimatförändringar som bygger på IPCC B2-scenariot. I den andra delen

uppskattas skogens produktion av biomassa och skördepotentialer utifrån

produktionsdata för trädbiomassa från den svenska riksskogstaxeringen för olika

skogsskötselalternativ. I den tredje delen beräknas förändringar i markens

kolförråd för olika tillförselnivåer till förnan från trädbiomassa och skogsavfall

som lämnas kvar efter skörd. I den fjärde och sista delen uppskattas minskningar

av koldioxidutsläpp till följd av substitution av fossila bränslen och kolintensiva

material mot skogsbiomassa. Skogsbruksaktiviteter såsom föryngring, röjning,

gallring, gödsling och skörd ingår i analysen. Den totala kolbalansen beräknas

genom summering av kolförrådets förändring i trädbiomassan, skogsmarken och

träprodukter samt summering av substitutionseffekter. Fossila koldioxidutsläpp

från skogsbruket beräknas och dras av från den totala kolbalansen för att beräkna

nettokolbalansen.

Resultaten visar att effekter av klimatförändring sannolikt kommer att öka

produktionen av skogsbiomassa under de närmaste 100 åren jämfört med en

situation med oförändrat klimat. Som en effekt av ökad produktion av biomassa är

det möjligt att även öka skörden av användbar biomassa. Årlig produktion och

skörd av skogsbiomassa kan ökas ytterligare genom användning av intensivare

skogsbruksmetoder än nuvarande. Lövträd kommer sannolikt att öka sin

produktion av biomassa till följd av klimatförändringens effekter, medan

granbiomassan sannolikt kommer att öka till följd av intensivare

skogsbruksmetoder.

IV

Intensivare skogsskötselmetoder såsom röjning, balanserad gödsling och

introduktion av snabbväxande arter för att ersätta långsamt växande tallbestånd

bidrar till att öka kolförrådet i trädbiomassan. Ökningen av kolförrådet i marken är

högre när endast stambiomassa skördas jämfört med när hela trädet tas ut.

Ökningen av kolförrådet i träprodukter beror till stor del på avverkningsnivåerna

och vad den skördade biomassan används till. Substitution av fossila bränslen och

råvaror mot biomassan ger det största bidraget till den totala kolbalansen, särskilt

när hela trädbiomassan används och när den ersätter fossilt kol som bränsle och

icke träbaserade byggnadsmaterial. Resultaten visar att effekten av

klimatförändringar kan ge upp till 104 Tg minskade koldioxidutsläpp, och att

intensivare skogsbruk därtill kan ge upp till 132 Tg minskning under de närmaste

hundra åren i det studerade området.

Denna studie visar att ett produktionsskogsbruk kan skötas så att tillväxt

och skörd av biomassa balanseras långsiktigt, så att skogen kommer att bibehålla

sin förmåga att öka kolförrådet i trädbiomassan och ge kontinuerliga skördar.

Ökad trädbiomassa i Sveriges skogar är kanske inte den mest effektiva strategin

för att motverka klimatförändringarna. Lagring av trä i byggmaterial fördröjer

koldioxidutsläppen till atmosfären, och vid slutet av byggnaders livscykel kan

träprodukterna användas som biobränsle och då ersätta fossila bränslen.

Resultaten visar att potentialen för skogens produktion av biomassa i det

studerade området ökar med klimatförändringarna och med ett intensivare

skogsbruk. Intensivare skogsbruk har potential att kontinuerligt öka produktionen

av biomassa som, om den används till att ersätta fossila bränslen och material, kan

bidra till betydande nettoutsläppsminskningar och till att minska

klimatförändringarna.

V

Preface

This work was performed as a doctoral research project in the Ecotechnology

Research Group at Mid Sweden University in Östersund, Sweden. It is a part of an

interdisciplinary programme to study “Forest as a resource in sustainable societal

development”. The financial support of the European Union, Jämtland County

Council, Sveaskog AB, and Swedish Energy Agency is gratefully acknowledged.

I would like to thank my supervisor Professor Inga Carlman for her both

professional and personal support that motivated me to continue this work.

I would like to thank Professor Leif Gustavsson who supervised my work from

March 2009 to 2011 December. His professional support helped to improve my

knowledge on this work.

I would like to thank my co-supervisors Prof. Johan Bergh, and Dr. Roger

Sathre, for their invaluable guidance in research, without which this work could

not have been completed.

I acknowledge the fellow Ph.D. students and staffs for their cooperation

and support. Particularly, I would like express my thanks to Nils Nilsson and Ulf

Persson who has made my days in Östersund much easier by many reasons. Many

discussions, including sharing ideas, with you all helped me to understand

research life both professionally and personally.

My parents have dreamed about my higher education and this work is a

part of their invaluable support for long time. Finally, I thank my wife, Sabita, for

her every support, without which this journey could not have been possible. My

thanks to our sons, Shashwat and Saatvik, who has made our every day special in

Östersund.

Bishnu Chandra Poudel

Östersund, 2012

VI

List of Papers

This licentiate thesis is based on the following papers:

1. Poudel, B.C., Sathre, R., Gustavsson, L., Bergh, J., Lundström, A.,

Hyvönen, R., 2011. Effects of climate change on biomass production and

substitution in north-central Sweden. Biomass and Bioenergy 35(10), 4340-

4355.

2. Poudel, B.C., Sathre, R., Bergh, J., Gustavsson, L., Lundström, A.,

Hyvönen, R., 2012. Potential effects of intensive forestry on biomass

production and total carbon balance in north-central Sweden.

Environmental Science and Policy 15(1), 106-124.

3. Poudel, B.C., Sathre, R., Gustavsson, L., Bergh, J., 2011. Climate change

mitigation through increased biomass production and substitution: A case

study in north-central Sweden. Peer reviewed conference paper In: World

Renewable Energy Congress 2011, 8-11 May 2011, Linköping, Sweden.

VII

Contents

ABSTRACT ......................................................................................................................... I

SAMMANFATTNING................................................................................................... III

PREFACE ........................................................................................................................... V

LIST OF PAPERS ............................................................................................................ VI

FIGURES ........................................................................................................................... IX

TABLES ............................................................................................................................... X

1 INTRODUCTION .......................................................................................................... 1

1.1 CLIMATE CHANGE AND FORESTS ............................................................................... 1

1.2 FOREST MANAGEMENT AND CARBON BALANCE ....................................................... 2

1.3 REVIEW OF PREVIOUS STUDIES ................................................................................... 6

1.3.1 Forest biomass production and harvest ............................................................... 6

1.3.2 Soil carbon stock .................................................................................................. 7

1.3.3 Substitution of fossil fuels and carbon-intensive products .................................. 8

1.4 KNOWLEDGE GAPS ..................................................................................................... 9

1.5 STUDY OBJECTIVES .................................................................................................... 10

1.6 THESIS ORGANISATION ............................................................................................. 10

2 METHODS .................................................................................................................... 11

2.1 INTEGRATED APPROACH .......................................................................................... 11

2.2 FUNCTIONAL UNIT ................................................................................................... 12

2.3 REFERENCE SYSTEM .................................................................................................. 12

2.4 ACTIVITIES INCLUDED IN SYSTEM ANALYSIS ........................................................... 13

2.5 STUDY AREA ............................................................................................................. 13

2.6 SCENARIOS ................................................................................................................ 14

2.7 CLIMATE CHANGE .................................................................................................... 15

2.8 FOREST BIOMASS PRODUCTION MODELLING WITH BIOMASS ............................... 15

2.9 FOREST BIOMASS HARVEST MODELLING WITH HUGIN .......................................... 16

2.10 THE USE OF FOREST BIOMASS AS BIOENERGY AND CONSTRUCTION MATERIALS ... 17

2.11 CARBON BALANCE ................................................................................................. 17

2.11.1 Total carbon balance ........................................................................................ 17

2.11.2 Standing biomass carbon stock ........................................................................ 18

2.11.3 Soil carbon stock .............................................................................................. 19

2.11.4 Wood product carbon stock ............................................................................. 19

2.11.5 Substitution of fossil fuels and carbon-intensive products .............................. 20

2.11.6 Forestry operations and carbon emission ........................................................ 20

2.12 DATA QUALITY ....................................................................................................... 20

3 RESULTS ....................................................................................................................... 22

VIII

3.1 FOREST BIOMASS PRODUCTION AND HARVEST ........................................................ 22

3.2 STANDING BIOMASS CARBON STOCK ....................................................................... 24

3.3 SOIL CARBON STOCK................................................................................................. 25

3.4 SUBSTITUTION OF FOSSIL FUELS AND CARBON-INTENSIVE PRODUCTS .................... 26

3.5 WOOD PRODUCT CARBON STOCK ............................................................................ 28

3.6 CARBON EMISSIONS FROM FOREST OPERATIONS ..................................................... 28

3.7 TOTAL CARBON BALANCE ........................................................................................ 29

4 DISCUSSIONS ............................................................................................................. 33

4.1 FOREST PRODUCTION AND HARVEST ....................................................................... 33

4.2 CARBON-INTENSIVE PRODUCTS SUBSTITUTION ....................................................... 34

4.3 CARBON BALANCE ................................................................................................... 34

4.4 UNCERTAINTIES AND LIMITATIONS ......................................................................... 36

5 CONCLUSIONS ........................................................................................................... 38

6 FUTURE RESEARCH .................................................................................................. 39

7 REFERENCES ............................................................................................................... 40

IX

Figures

Figure 1 Schematic diagram of carbon balances during forest production and

biomass utilization ........................................................................................................... 12

Figure 2 Annual biomass productions and harvests at the beginning and end of the

study period for all scenarios. ........................................................................................ 22

Figure 3 Standing forest biomass carbon stock at the beginning (2010) and end

(2109) of the study period in the different scenarios (Paper II, Figure 6). ................ 25

Figure 4 Annual carbon stocks in forest soil in the different scenarios during 100-

years with whole-tree biomass use. ............................................................................... 26

Figure 5 Average annual carbon emission reduction (Tg carbon year-1) for whole

study area as a result of whole-tree (WT) and stem-wood (SW) biomass use to

replace fossil fuels and non-wood construction materials. ........................................ 27

Figure 6 Wood product carbon stock (Tg carbon) due to non-wood material

substitution (Paper III)..................................................................................................... 28

Figure 7 Carbon emissions due to forest operations and fertilisation for all

scenarios for whole-tree biomass (Mg carbon year-1). ................................................ 29

Figure 8 The average annual carbon emissions reduction (Tg carbon year-1) for

different scenarios when whole-tree biomass was used to replace coal and fossil

gas. ...................................................................................................................................... 30

Figure 9 The average annual carbon emissions reductions per hectare of forest land

(Mg carbon ha-1 year-1) due to the benefits associated with the use of whole-tree

(WT) and stem-wood (SW) biomass to replace fossil gas and coal. .......................... 31

Figure 10 Differences in cumulative carbon emission reduction (Tg carbon)

between the Climate, Environment, Production and Maximum scenarios and the

Reference scenario for each 10-year period. ................................................................... 32

X

Tables

Table 1 Activities and processes included in the life cycle carbon balance .............. 13

Table 2 Overview of scenarios ........................................................................................ 14

Table 3 Differences in forest biomass production and harvest between the Reference

scenario and other scenarios (Tg dry biomass) ............................................................ 23

Table 4 Average annual tree biomass carbon stock changes during each 10-year

period (Tg carbon year-1) for Jämtland and Västernorrland ...................................... 24

Table 5 Average annual carbon emissions reductions (Tg carbon year-1) due to

fossil fuel and carbon-intensive material substitution by the use of stem-wood and

whole-tree biomass during each 10-year period .......................................................... 27

Table 6 The total carbon balance including forest production, forest biomass

harvest, soil carbon stock change, and stem-wood and whole-tree biomass use to

replace of fossil fuels and carbon-intensive materials (Tg C year-1) during each 10-

year period in Jämtland and Västernorrland. .............................................................. 30

XI

Abbreviations

C Carbon

CO2 Carbon dioxide

CORRIM Consortium for Research on Renewable Industrial Materials

CPF Collaborative Partnership in Forests

EU European Union

GHG Greenhouse Gas

GJ Gigajoule (109 joules)

GJe Gigajoule of electricity

GPP Gross Primary Production

Gt Gigatonne (109 tonne)

IEA International Energy Agency

IPCC Intergovernmental Panel on Climate Change

ISO International Organization for Standardization

Mg Megagram (106 grams, or 1 tonne)

N Nitrogen

NEP Net Ecosystem Productivity

NFI Swedish National Forest Inventory

NPK Nitrogen Phosphorus and Potassium

NPP Net Primary Production

OECD Organization for Co-operation and Development

ppm Parts per million

SMHI Swedish Meteorological and Hydrological Institute

SOM Soil Organic Matter

SOU Swedish Government’s Official Reports

Tg Teragram (1012 grams, or 106 tonne)

UNFCCC United Nations Framework Convention on Climate Change

US United States

1

1 Introduction

1.1 Climate change and forests

Climate change is one of the most widely recognised environmental issues

today. A consensus in the climate science research community has emerged that

emissions of anthropogenic greenhouse gases (GHGs) into the atmosphere are

altering the global climate system (2007c). Emissions of GHGs into the atmosphere

are likely to increase the earth’s mean surface temperature, thereby affecting

physical and biological systems (Rosenzweig et al., 2008; Trenberth et al., 2009;

UNFCCC, 2011). Many effects of temperature increase have been observed,

including threats to natural phenomena, societal disturbances, and threats to

economic growth (IPCC, 2007a; UNFCCC, 2011).

The atmospheric concentration of the most significant GHG, carbon

dioxide (CO2), has increased substantially during the last 20 decades, primarily as

a result of fossil fuel combustion (IPCC, 2007c). Currently, fossil fuels provide over

80% of the world’s primary energy and are responsible for over 50% of all

anthropogenic GHG emissions (OECD/IEA, 2010). The global energy supply is

largely dependent on fossil fuels of which 27% of the total primary energy is

dependent on coal (OECD/IEA, 2010). The International Energy Agency (IEA) has

examined the global energy scenarios for future energy supply and has indicated

that coal fuel use is likely to increase until the year 2035 if the current energy

policies are not changed (OECD/IEA, 2010). These findings may explain the

severity of fossil fuel use in the future which may result in increasing total

anthropogenic GHG emissions in the future (OECD/IEA, 2010).

The likely increase of global mean surface temperature (Nakicenovic and

Swart, 2000) is expected to be greater at higher latitudes (IPCC, 2001), which may

result in a temperature increase of up to 1-2 °C in summer and 2-3 °C in winter in

northern Europe in the next 50 years (Carter et al., 2005). The European Union (EU)

suggests that limiting temperature increase to 2 °C, relative to pre-industrial levels,

may avoid the risks of climate change (European-Commission, 2007). The

projection of CO2 emissions reduction that is required to avoid climate change is

difficult to predict because of the complexity of the global system. However,

stabilising atmospheric GHG concentration levels below 450 ppm CO2-eq is likely to

avoid a 50% chance of increasing temperature above 2 °C (EU, 2008). This

stabilisation target is unlikely to be met unless strong and timely actions are taken

2

to reduce CO2 emissions, considering the current atmospheric CO2 concentration

level of 394 ppm CO2-eq (NOAA/ESRL, 2012).

The Intergovernmental Panel on Climate Change (IPCC) has presented

several strategies that may help mitigate climate change (IPCC, 2007b). Various

initiatives have been taken to reduce the atmospheric CO2 concentration such as

the Kyoto protocol requiring industrial countries to reduce GHG emissions below

1990 levels by the year 2012. The EU has set an ambitious target of reaching a 20%

share of energy from renewable sources by 2020 (European-Commission, 2009) in

the pursuit of reducing CO2 emissions. Sweden, an EU member state, already

obtains more than 20% of its energy from renewable sources (Swedish Forest

Agency, 2011) and has a target of extending this share to 49% by the year 2020

(Swedish Energy Agency, 2008).

The global society’s attempt to mitigate climate change may include

reducing carbon emissions and increasing carbon sinks. Strategies to reduce CO2

emissions by reducing fossil fuel use and by increasing carbon sinks through a

sustainable production forestry may be one of the practical solutions. A

Sustainable production forestry in this context may be considered as a practice that

maintains indefinitely the natural productive capacity of forest ecosystems, while

providing an opportunity for harvesting and using at least a certain amount of

forest product at regular intervals. Thus, such practice will ensure the continued

existence of forest ecosystems and the availability of forest biomass for use in

future. By doing so, forest biomass use for bioenergy may play a vital role in

replacing fossil fuels and reaching the aim of increasing renewable energy use.

Forest biomass can also replace carbon-intensive construction materials. Hence, the

greater the forest biomass production, the greater the amount of harvest that is

possible, and the earlier the biomass is harvested, the earlier the fossil fuels and

carbon-intensive materials can be replaced (Malmsheimer et al., 2008). A strategy

aimed to increase forest biomass production and use could thus be effective in

mitigating climate change (Easterling et al., 2007).

1.2 Forest management and carbon balance

The role of a sustainable forest management in reducing atmospheric

carbon emissions is very important. The IPCC suggests that the conservation of

biological carbon in the forest ecosystem, the storage of carbon in wood products,

and the use of forest biomass to replace fossil fuels and carbon-intensive materials

would help to mitigate climate change (IPCC, 1996). The strategies of a forest

3

management for increasing carbon benefit needs to increase the carbon sink into

the forest biomass by increasing biomass production, increase soil carbon stock,

and increase the potential biomass harvest to contribute in obtaining higher carbon

benefits.

Forests constitute approximately 30% of the world’s land surface and

contribute to the global net removal of three gigatonnes (Gt) of anthropogenic

carbon per year (Canadell and Raupach, 2008). Forest ecosystems, including forest

soil, store approximately 1200 Gt of carbon, which is considerably more than the

762 Gt of carbon present in the atmosphere (Freer-Smith et al., 2009). Annually,

global forests turn over approximately one twelfth of the atmospheric stock of CO2

through gross primary production (GPP1), accounting for 50% of all terrestrial GPP

(Malhi et al., 2002). It is estimated that, in 2005, forests contained 572 Gt of standing

biomass (equivalent to 280 Gt of carbon) (IPCC, 2007b; CPF, 2008).

The carbon stock increase in a forest ecosystem is limited. Phenomena such as

plant respiration, soil decomposition processes, plant mortality, fire, and soil

disturbance release carbon into the atmosphere. It is estimated that less than 1% of

the carbon that is taken up by terrestrial ecosystems remains as a long-term

terrestrial carbon sink (IPCC, 2000). Several studies suggested that increasing

atmospheric CO2 and nitrogen (N) deposition rates are likely to increase the forest

biomass in the future (Norby et al., 1999; Norby et al., 2005; Canadell et al., 2007a;

IPCC, 2007c; Galloway et al., 2008; Malmsheimer et al., 2008; Dupre et al., 2010). Luo

(2007) observed that elevated atmospheric CO2 concentrations result in enhanced

biomass production and subsequently increased carbon pools in living biomass,

litter, and soil. Although uncertain, climate change projections predict temperature

increases and longer growing seasons at higher latitudes, implying that more

sunlight will be utilised for photosynthesis, thereby stimulating the biomass

production of boreal forests (Bergh et al., 2003; Rosenzweig et al., 2008; Raupach

and Canadell, 2010). In addition, biomass production can be further increased by

various forest management practices (Bergh et al., 2005; Houghton, 2007;

Skogsstyrelsen, 2008).

Forest management involves the integration of silvicultural practices and

economic alternatives (Bettinger et al., 2009) to achieve production and ecological

objectives through a series of silvicultural operations, such as regeneration,

fertilisation, tending operations (commercial and pre-commercial thinning),

1 Gross primary production is the sum of the photosynthesis by all leaves measured at the

ecosystem scale, represented as biomass (Chapin et al. 2002).

4

harvesting, and reforestation (Buongiorno and Gilless, 2003; Bettinger et al., 2009).

The scope of this thesis limits the definition of silvicultural activities to those that

are relevant to forest production and management for CO2 emission reduction.

Forest management strategies are associated with forest production and harvest

goals, with defined goals for carbon sequestration and accumulation as above-and

below-ground biomass, litter that falls to the ground, dead wood, soil organic

matter, and harvested products and their utilisation. A harvest goal that has higher

frequency and intensity of thinning and shorter rotation length may influence the

biomass stock in the following generation (Liski et al., 2001; Kaipainen et al., 2004).

The influence can be related to the types of forest products harvested. For instance,

the removal of stem-wood-only biomass adds all litters to the soil, while whole-

tree removal adds a part of litter to the soil.

A forest sequesters carbon by removing carbon from the atmosphere

through the photosynthesis process and storing the carbon in living biomass. A

forest’s capacity for sequestrating carbon is a function of the productivity of the

site and the potential sizes of the various carbon pools, including soil, litter,

subterraneous woody materials, standing and fallen dead wood, live stems,

branches, and foliage (Chapin et al., 2002; Malmsheimer et al., 2008). The carbon

accumulation in biomass is typically higher when the tree is in its fast growing

stage, and as the tree reaches maturity (older than 80 years in boreal forests) it

becomes almost carbon neutral and may eventually become a carbon source if dies

and decays (Gower et al., 1996; Gower et al., 2001; Nabuurs et al., 2003). Shortening

rotation periods would encourage the growth of young stand forests in the long

run and thus may result in the sequestering of carbon at higher rates.

Soil type, texture, structure, and air and water availability inside the soil

pores govern the soil carbon development process. The rates of accumulation and

magnitudes of soil carbon stocks depend on the litter input into the soil and in part

on nutrient management (Lal, 2004). Fertilisation may help to increase nutrient

level in the soil thus may help to build up carbon stocks (Johnson, 1992). Changes

in tree phenology, species composition, soil temperature, and water balance can

change soil respiration and decomposition rates (Davidson et al., 2000; Luo, 2007).

When the litter is fresh, nutrient cycling and oxidation stimulate its decomposition;

however, later, as litter quality decreases, higher temperatures might increase

decomposition and carbon cycling rates (Kirschbaum, 2004). Hyvönen et al. (2008)

explained that elevated CO2 would encourage carbon sequestration by activating

the carbon cycling process by adding litter to the soil, which can later assimilate

with soil organic material (SOM), thereby increasing soil carbon stock. Ågren et al.

5

(2007) suggested that the soil carbon stocks in Swedish forests will increase but

that the rate of increase will quickly slow down when the input is stopped. Ågren

et al. (2007) warned that reducing litter input by harvesting more forest biomass

would lead to a decline in soil carbon stocks. Nevertheless, increasing forest

biomass production to allow more litterfall and input may reverse the positive

feedback.

Nitrogen is one of the limiting factors in boreal forest production (Pastor

and Post, 1988; Tamm, 1991). If nutrients are a limiting factor, balanced

fertilisation, which includes three major nutrients Nitrogen, Phosphorus and

Potassium (NPK), may allow for increased productivity especially at nutrient-poor

sites (Oren et al., 2001; Malmsheimer et al., 2008). Bergh et al. (2005) suggested that

the forest production in northern Sweden could be increased by 300% if an

additional nitrogen fertiliser is applied to address the nutrient deficiency.

Providing a balanced nutrient supply to reduce the nitrogen deficiency,

particularly in the young stands, could increase the production. Forest biomass

production can be increased by improving site conditions for plantations and by

selecting improved genetic plant materials and productive tree species suitable to

local site conditions and microclimates. Density regulation through pre-

commercial thinning reduces the competition between trees and shortens rotation

periods, and shortened periods between two rotations will allow more time for

biomass production.

Forest biomass can be used to substitute fossil fuels to reduce

GHG emissions (Zebre, 1983; Gustavsson et al., 1995; Bergman and Zebre, 2004).

The IPCC (2007b) suggests that material substitution is an important part of

climate change mitigation strategy through the production of forest biomass.

Eriksson et al. (2007) claimed that there could be significant reductions in CO2

emissions if forest biomass from sustainably managed forests replaced fossil fuels.

The burning of biomass grown in sustainably managed forests is part of a cyclical

flow, as carbon emitted during combustion will be absorbed by re-growth of the

harvested forest stand. Using wood products from sustainably managed forests

can reduce net CO2 emissions, as less energy is used to manufacture such materials

compared to carbon-intensive materials. Substitution of carbon-intensive materials

also avoids non-energy process emissions during the manufacture of non-wood-

based products, such as cement and steel. The use of wood products may also

delay the emission of biogenic carbon into the atmosphere by allowing the wood to

be used for a longer period of time. Furthermore, biomass by-products of wood

production chains and wood from construction work at the end of its useful life

6

can be used (Sirkin and Houten, 1994; Gustavsson et al., 2006b; Gustavsson and

Sathre, 2006; Sathre et al., 2010). The wood product life cycle optimised for

mitigating climate change would entail the use and possible reuse of wood

products (Sathre, 2007). Nevertheless, the net carbon benefits depend on

substitution efficiency, i.e., on how and where the wood products are used and on

which products are substituted (Schlamadinger and Marland, 1996; Schlamadinger

et al., 1996; Gustavsson et al., 2006a; Sathre and O'Connor, 2010).

1.3 Review of previous studies

Several studies have discussed potential forest biomass production and

harvest over the past decades. Carbon balance studies in the past were largely

focused on ecosystem production (Houghton, 2005, 2007) but recent studies have

included the forest biomass use as material and bioenergy and their implications

for carbon emissions reduction.

1.3.1 Forest biomass production and harvest

Studies to assess the effects of increased temperatures and CO2

concentrations on plant photosynthesis and biomass production began early in the

1980s. Solomon (1986) and Pastor and Post (1988) performed studies on the effect

of increased atmospheric CO2 concentrations on forest growth and composition in

North America. They found that the forest biomass carbon in the boreal forests

would be increasing because of increased CO2 concentrations. Kauppi et al. (1992)

explored the increasing forest biomass and carbon budget for most of western

Europe. Prentice et al. (1993) developed a model to describe the transient effects of

climate change-induced temperature and precipitation change on the dynamics of

forest landscapes, growth processes, and species compositions. Swedish forest

production in response to climate change was explored in several studies (Bergh et

al., 1998; Bergh and Linder, 1999; Bergh et al., 1999). Furthermore, several studies

explored forest productivities in boreal forests (Pussinen et al., 2002; Bergh et al.,

2005; Briceño-Elizondo et al., 2006; Kirilenko and Sedjo, 2007; Eggers et al., 2008).

Several studies suggested that forest biomass production might increase in

northern Europe with increased atmospheric temperatures and CO2

concentrations. Swedish Forest Agency (2008) predicted a 25% increase in annual

stem-wood production in Swedish forests due to the direct effects of climate

change over the next 100 years. A larger amount of biomass production may

7

correspond to a larger biomass removal. Currently in Sweden, residues and

stumps harvesting is in practice. In the year 2010, Sweden gave permission to

harvest forest residues from 155 thousand hectares and stumps from 7.5 thousand

hectares of forest (Swedish Forest Agency, 2011).

1.3.2 Soil carbon stock

The influence of increased harvest level on soil carbon stock and nutrients

have been discussed in the recent literature (Liski et al., 2001; Egnell and Valinger,

2003; Kaipainen et al., 2004; Egnell, 2011). The studies found that the effect of

increased harvest level in soil carbon and nutrients are only temporary. Various

studies have analysed the effects on forest soil carbon stock due to land use

changes, forest management, climate change and other disturbances. Liski et al.

(2002) found that the soil carbon stock in western Europe is increasing because of

increased litter fall from living trees. Early studies reported that increased

temperatures do not necessarily increase the nutrient cycling and oxidation of

SOM and therefore decomposition (Lloyd and Taylor, 1994). However, later

studies suggested that a warmer climate may govern a major role in the

decomposition of SOM leading to an increase in CO2 release to the atmosphere and

a decrease in soil carbon content (Davidson et al., 2000; Jones et al., 2005; Davidson

and Janssens, 2006; Friedlingstein et al., 2006). Because of the release of soil carbon,

positive feedback leading to additional climate warming of 0.1-1.5 °C may take

place (Kirschbaum, 2000, 2004; Knorr et al., 2005; Friedlingstein et al., 2006; Luo,

2007; Piao et al., 2008). A significant loss of terrestrial carbon stock in the higher

latitude is also possible because of the temperature-dependent net primary

production system in the boreal forests compared to other parts of the world

(Canadell et al., 2007b; Canadell and Raupach, 2008). However, Hyvönen et al.

(2007) suggested that, as long as forest input is increasing, soil carbon loss will not

be significant. Therefore, increasing the productivity of forests is a key factor.

Moreover, reducing disturbances in forests may help retain soil carbon for a longer

period of time (Karhu et al., 2010; O'Donnell et al., 2010). Davidson and Janssens

(2006) suggested that a significant fraction of relatively unstable SOM is clearly

subject to temperature-sensitive decomposition. Karhu et al. (2010) studied the

temperature sensitivity of soil carbon and found that 30-45% more soil carbon will

be lost in a warmer climate over the next few decades assuming that there will be

no change in carbon input. To compensate for this loss, forest biomass productivity

would need to increase by 100-120% (Karhu et al., 2010). O'Donnell et al. (2010)

8

performed an analysis on the sensitivity of soil to climate change and found severe

losses of organic carbon from soil. Climate changes, particularly temperature

increases, have effects on terrestrial ecosystems and have the potential to act as

positive feedback in the climate change system (Friedlingstein et al., 2006;

O'Donnell et al., 2010).

1.3.3 Substitution of fossil fuels and carbon-intensive products

In the past, forest production has been used mostly for wood products and

pulp and paper. Recently, the concept of whole-tree utilisation has emerged, which

focuses on the carbon benefits of forest management and product use. Recovered

forest residues, tree stumps, wood chips, sawdust, and bark are important sources

for bioenergy. In addition, wood material is widely used for building construction,

and its use will be growing in the future (Ministry of Industry, 2004).

Schulz (1993) speculated that dependency on wood would increase with

increased interest in renewable resources to replace conventional materials and

energy for environmental reasons. The use of forest biomass as a source of energy

was considered during the global energy crisis in the 1970s. It was also in the 1970s

when wood products were thought of as a sustainable source of materials for

construction in place of energy-intensive products such as cement and steel (Boyd

et al., 1976). A methodology for conducting energy analysis was developed in 1974

to provide consistency and comparability among studies (IFIAS, 1974). The

Consortium for Research on Renewable Industrial Materials (CORRIM) was

established by the National Academy of Sciences of United States (US) to study the

effects of producing and using renewable materials (Lippke et al., 2004). CORRIM

developed a comprehensive life cycle inventory of environmental inputs and

outputs from forest regeneration through product manufacturing, building

construction, use of wood in buildings and their maintenance, and disposal

(Malmsheimer et al., 2008). The analysis focused on the energy impacts associated

with various wood-based building materials and showed that wood-based

materials are less carbon-intensive than other structural materials that perform the

same function (Lippke et al., 2004). Methodologies for the analysis of forest

biomass as an input in the energy system and for comparisons with carbon-

intensive materials for carbon balance were developed in the US, New Zealand,

Australia and in Europe. Some noted developments have been highlighted in

several reports (Boustead and Hancock, 1979; Buchanan and Honey, 1994; Fossdal,

1995; Gustavsson et al., 1995; Schlamadinger and Marland, 1996; Börjesson et al.,

9

1997; Schlamadinger et al., 1997; Gustavsson and Karlsson, 2006; Eriksson et al.,

2007). Schlamadinger et al. (1997) and Marland and Schlamadinger (1997)

developed methodologies to assess forest biomass use for fossil fuel substitution.

Börjesson and Gustavsson (2000) calculated GHG emissions from the life cycles of

multi-story building construction. Pingoud and Lehtilä (2002) studied the energy

efficiencies of different types of wood products. Lippke et al. (2004) compared

energy consumption of energy-intensive materials to CORRIM’s life cycle

assessment of wood-based building construction. Werner et al. (2005) explored

GHG emission reduction as a result of the use of wood materials in construction

and interior finishing. Gustavsson et al. (2006a) explored the possibility of wood

recovery in different stages of the wood chain and its role in GHG emission

mitigation. Eriksson et al. (2007) considered different scenarios for forest

production and biomass use and found that forest stand fertilisation, residue and

stump harvesting, and the use of wood as a construction material provided high

reductions in CO2 emissions. Further studies have shown that the use of wood

products and biomass residues significantly reduces net CO2 emissions, provided

that the wood material used comes from sustainably managed forests and that

biomass residues are used responsibly (Salazar and Meil, 2009; Gustavsson et al.,

2010; Sathre and O'Connor, 2010).

1.4 Knowledge gaps

Previous studies have made significant contributions to assessing forest biomass

production, soil carbon stock change, and substitution benefits for carbon

emissions reductions. Nonetheless, biomass production projections in north-

central Sweden due to the regional climate change effect have not been carried out

before. Biomass growth projections in most cases include only the forest growth

data (from inventory) instead of physiological processes of plant biomass

production with the interaction to the environment. Studies of soil carbon stock

changes may require a comprehensive approach such as input of organic materials,

decomposition processes, and the climate change temperature increase effect to

explain. Forest biomass production and product use were considered most often at

the stand level. When this study began, there were no comprehensive studies that

quantified the full chain of forest biomass production, harvest, effects in soil

carbon stocks, and biomass use implications for carbon balances on a landscape

level including climate change effects. In general, little work has been done using

10

an integrated methodological approach with a system perspective to draw a

complete picture of carbon balance from forest biomass production and utilization.

1.5 Study objectives

This study explores carbon balances using an integrated analytical framework

for the entire forest product chain, including forest management on a landscape

level. The aims of the study are as follows:

To quantify the potential biomass production due to climate change in the

Middle Norrland region of Sweden and the total carbon balance effects of

biomass production and substitution of carbon-intensive materials.

To quantify the potential biomass production due to intensive forestry

practices and the total carbon balance effects of biomass production and

substitution of carbon intensive materials.

1.6 Thesis organisation

This thesis is based on three original papers and is divided into two parts.

The first part includes an introduction, a discussion of methodology, a synthesis of

the results presented in the papers, and a discussion and conclusion. The second

part contains the three original papers. Paper I analyses the effects of climate

change on forest biomass production and subsequent effects on carbon stock

changes in standing biomass, soil carbon, and carbon emission reduction as a

result of fossil fuel and building material substitution. Paper II analyses the effects

of intensive forestry on biomass production, the carbon stock changes in forest

biomass and forest soil, and carbon emission reduction as a result of fossil fuel and

building material substitution. Paper III provides integrated results of total carbon

balances in standing biomass, forest soil, and wood products as well as

substitution effects. The major portions of the results and discussion sections are

based on Paper I and II.

11

2 Methods

2.1 Integrated approach

An integrated carbon analysis includes modelling of forest generation,

growth and harvest, the use of products, and the end-of-life management of

products. The integrated approach used in this thesis consists of four different sub-

models (BIOMASS, HUGIN, Q model, and SUBSTITUTION). A process-based

model for forest biomass growth (see Paper I, II and III) provides biomass

production values. These values serve as input for the empirical model HUGIN to

estimate the harvest levels in the forests. The use of forest products as bioenergy

and wood and its potential carbon reduction are calculated in a system analysis-

based model (SUBSTITUTION). Soil carbon developments under different types of

forest management practices are modelled using the Q model. The analysis is

made for a 100-year period, starting from the year 2010 and ending at the year

2109.

The flow chart used in this study is presented in Figure 1. The balance

between net primary production (NPP2) and biomass loss during ecological

processes determines the annual change in plant biomass (Chapin et al., 2002). At

the same time, the changes in plant biomass have influence on changes in below-

ground nutrient content. The analysis begins with a calculation of NPP in the

BIOMASS model to provide NPP data, which is fed into the HUGIN system. The

annual change in tree biomass based on all silvicultural activities, from

regeneration to the final felling, is incorporated into HUGIN to calculate the

amount of harvestable biomass. There are several possibilities for the utilisation of

tree biomass after harvesting. For example, stem-wood may be utilised as

construction materials, and tree residues may be utilised for bioenergy. The model

outputs, in the form of different assortments of forest products from a landscape,

are used in the SUBSTITUTION model to conduct a system analysis of forest

biomass utilisation based on a life cycle perspective. Fossil carbon emissions from

forest operations (CO2 emissions during regeneration, pre-commercial thinning,

commercial thinning, fertilisation, and final felling) are included. Finally, carbon

balances in standing biomass, harvested wood products, and forest soil are

2 NPP is the balance of carbon gained by GPP and the carbon lost by respiration of all plant

parts (Chapin et al. 2002).

12

estimated. The carbon reduction associated with the use of harvested biomass to

replace fossil fuel and carbon-intensive construction materials is also calculated.

Figure 1 Schematic diagram of carbon balances during forest production and

biomass utilization

2.2 Functional unit

In this study, the carbon balance associated with forest production and the

utilisation of wood and non-wood products is analysed. A “functional unit” is a

key element for defining the function(s) to enable the objective comparison of

different systems. This analysis focuses on the potential climate change mitigation

effects of forest management and use. Hence, the overall net carbon emissions

reduction in grams of carbon per unit of forest land is considered as a functional

unit in this study.

2.3 Reference system

Forest management in this study is based on clear-cut forestry with one

pre-commercial thinning and two to three commercial thinnings before the final

harvest. The harvested biomass is assumed to be used as “‘stem-wood” and

Carbon balance

Biofuel

Processing residuesConstruction and

Demolition residues

Soil carbon

Biomass utilisation

Plant physiological

processes

Tree mortalityRetained residues

Materials

Nutrient cyclingLitter and branch fall

Below-ground biomass

Forest growth and harvest

PhotosynthesisGPPNPP

Biomass increment

Annual increment,Silvicultural

activities

Standing biomass

Residues

Building

13

“whole-tree”. It is assumed that stem-wood is used as construction material to

replace carbon-intensive materials, while the remaining processing residues, small-

diameter pine and spruce stem-wood, and all deciduous stem-wood are used as

biofuels. The Wälludden building constructed in Växjö, Sweden, which is

functionally equivalent to a concrete frame building, is used as a reference

building for wood use. The Wälludden building is described in detail by Dodoo

(2011), Sathre and Gustavsson (2007), Sathre (2007), Gustavsson et al. (2006b), and

Gustavsson and Sathre (2006). Coal and fossil gas are considered as substituted

reference fossil fuels, which currently covers 80% of the world’s primary energy

(OECD/IEA, 2010).

2.4 Activities included in system analysis

Various activities and processes included in the study show the life cycle

carbon balance (Table 1). The activities are defined to include the life cycle of forest

biomass and in case of non-wood building materials, the analysis includes carbon

emissions during the material production and its processes to be substituted by

forest biomass. All energy inputs are accounted in the analysis.

Table 1 Activities and processes included in the life cycle carbon balance

Description Activities and processes

included

Carbon implications

Production of

materials

(forest

biomass and

non-wood)

Forest operation activities

(regeneration, pre-commercial

thinning, thinning, harvesting,

fertilisation);

Wood processing, extraction of

process residues and

transportation;

Non-wood material extraction,

processing, and transportation.

Carbon stock change in forest and

building materials;

Carbon stock changes in forest soil;

Fossil fuel use for forest operation,

non-wood material production;

Cement process.

Use of

materials

Forest biofuel and Wood

processing residues use in

power plant;

Wood materials use in

buildings.

Forest residues and wood-process

residues replaces fossil fuel;

Wood materials replace non-wood

materials.

End use of

materials

Building demolition,

Recovery of wood materials.

Wood use as biofuel replaces fossil

fuel.

2.5 Study area

14

The study area (Paper I, Figure 1) encompasses the counties of Jämtland

and Västernorrland in north-central Sweden, from 61° 33’ to 65° 07’ N latitude and

from 12° 09’ to 19° 18’ E longitude. The elevation ranges from sea level to 1500 m in

altitude. The annual precipitation ranges from 600-700 mm in the eastern part to

1500 mm in the western part (SMHI, 2009), and the duration of the growing season

(mean temperature above +5 °C) is approximately 120-160 days per year (Sveriges-

Nationalatlas, 1995). The average monthly temperatures during 1961-1990 varied

in January between +1 °C to -12 °C and in July between 10 °C to 14 °C. The forest

land areas of the counties of Jämtland and Västernorrland are 3.5 and 1.9 million

hectare, respectively. The dominant tree species are Norway spruce (Picea abies (L.)

Karst.), Scots pine (Pinus sylvestris L.) and birch (Betula spp.) (Swedish Forest

Agency, 2010). The study area accounts for approximately 10% of the total forest

land of Sweden. Detailed descriptions of the study area are given in Papers I and

II.

2.6 Scenarios

Five different forest management scenarios are formulated (Table 2) to

describe the potential variability of climate and forest management practices

through 2109.

Table 2 Overview of scenarios

Scenario Climate Forest management goals Biomass use

Reference No change Reference (current management) Stem wood or whole tree

Climate Change Current management Stem wood or whole tree

Environment Change Fulfil environmental goals Stem wood or whole tree

Production Change Increase biomass production Stem wood or whole tree

Maximum Change Maximize biomass production Stem wood or whole tree

The Reference scenario in Paper I assumes an unchanged climate, and the

Climate scenario assumes climate change as described in Section 2.7 below. These

two scenarios assume current forest management practices. Paper II includes four

scenarios, with the Climate scenario in Paper I serving as a Reference scenario in

Paper II. The remaining scenarios assume different forest management practices to

meet different objectives. The Environment scenario satisfies Swedish

environmental goals by increasing the forest area allocated to natural set aside

area. The Production and Maximum scenarios aim to meet higher production goals,

with intensive forestry practices adopted to increase forest production. The

Production scenario assumes to include improved genetic material in seedling

plantations, soil scarification, selection of tree species suitable for particular site

15

conditions, and shorter time between clear-cut and re-planting. In addition, pre-

commercial thinning and traditional fertilization area is increased. Balanced

nutrient supply in young stands of Norway spruce and in former agricultural land

forest are also included. The Maximum scenario includes all those activities, and

also assumes to replace Scots pine with Lodgepole pine, and balanced nutrient

supply in young stands of Lodgepole pine and Norway spruce forest land.

Harvested biomass is used as “stem-wood” and “whole-tree”. Stem-wood harvest

assumes the extraction of 95% of tree stems of >20 cm diameter with the rest of the

biomass left on the forest floor. Whole-tree harvest assumes a harvest of 95% of the

felled stem-wood, 75% of needles, branches and tops (referred to as “residue”),

and 50% of stumps and coarse roots.

2.7 Climate change

This study considers climate change based on the IPCC SRES B2 climate

change scenario (Nakicenovic and Swart, 2000). This scenario corresponds to

moderate emissions of greenhouse gases leading to an atmospheric CO2

concentration of 621 ppm by the year 2100 (Levy et al., 2004). The simulations of

temperature change were conducted using the Rossby Centre’s regional

atmospheric model based on IPCC global scenarios with the downscaled climate

model RCA3 with a grid of approximately 50 km x 50 km (SMHI, 2009). In the

calculations, RCA3 uses global driving variables from the general circulation

model ECHAM4/OPYC3 (Kjellström et al., 2006). Climate projections for north-

central Sweden are for an increase in average regional annual temperatures of

more than 4 °C by 2100 for SRES B2 (see Figure 3 in Paper I). Soil carbon modelling

was performed with the assumption of a shift in latitude to 58-59 °N instead of the

actual latitude of 62-63 °N because the temperature change due to climate change

is expected to make the climatic conditions at 62-63 °N similar to those at 58-59 °N.

2.8 Forest biomass production modelling with BIOMASS

The process-based growth model BIOMASS was used to estimate NPP.

BIOMASS uses canopy characteristics, foliage photosynthetic characteristics, and

daily meteorological conditions as inputs and calculates daily evapotranspiration

from the stand. Later, foliage, stem and branch respiration values are subtracted

from the total CO2 uptake by the canopy to obtain daily NPP values. Both litterfall

and stand water balances are incorporated into the model. BIOMASS consists of a

16

series of equations based on established theories of physiological plant processes

and soil-water dynamics. This is summarized by the simple equation

plantNPP GPP R

where GPP is the gross primary production, and Rplant is respiration by tree

components.

All sub-models for the calculation of carbon accumulation in foliage,

branches, stems, bark, and roots, including below-ground components, were

formulated, and respiration in each component was subtracted from the total

accumulation to obtain NPP. A detailed description of the BIOMASS model for

canopy photosynthesis and water balance was given by McMurtrie et al. (1990)

and McMurtrie and Landsberg (1992). BIOMASS uses climatic data from the SRES

B2 scenario. These climatic data were taken from transient simulations of 1961-

2100 with reference to 1961-1990 climatic data. The simulations were performed for

a 30-year cycle to determine the effects of temperature change on NPP increment

which was found to be 21.6%, 11.0%, and 13.0% greater for Norway spruce, Scots

pine, and Silver birch, respectively compared to unchanged climate. The NPP

output data were first estimated and then assimilated with the HUGIN model to

determine the forest growth function at a county level.

2.9 Forest biomass harvest modelling with HUGIN

HUGIN is a model system for long-term forecasts of timber yields and

potential harvest levels that is used for planning at a regional level and for

strategic planning for large forestry companies. The model uses data from sample

plots from the Swedish National Forest Inventory (NFI) to define initial forest

conditions. HUGIN describes all stages in plant development from stand

establishment through treatments, thinning, and final fellings. The growth

simulators in HUGIN are valid for all forest land in Sweden, for all types of stands,

and within a wide range of management practices. The details on stand

establishment, treatments, thinnings, and final fellings are given in Paper I (Section

2.4.2), and further details are provided by Lundström and Söderberg (1996).

17

2.10 The use of forest biomass as bioenergy and construction materials

Forest biomass harvested in the whole-tree scenario is classified as large

diameter stem-wood and residues. Large-diameter stem-wood is defined as stems

with a minimum diameter of 20 cm and is assumed to be used to produce wood

construction materials to substitute conventional reinforced concrete. The material

substitution effects are based on a multi-story apartment building. The details of

wood use for material substitution in building construction are given by

Gustavsson et al. (2006b).

Large-diameter pine and spruce stem-wood is used for the production of

wood construction materials, while the processing residues (bark, sawdust, chips)

are used for bioenergy. In the whole-tree scenario, tops, branches, needles, and

stumps including coarse roots are also used for bioenergy. Small-diameter pine

and spruce stem-wood, and all deciduous stem-wood are used for bioenergy. In

this study, small-diameter stem-wood is not used for pulp and paper production

because we have not analysed whether the demand for additional pulpwood in the

pulp industry in Sweden would increase. The wood materials in the buildings are

assumed to be recovered and used for energy purposes as biofuels at the end of the

building service life. All biofuels are assumed to substitute either coal or fossil gas

in stationary plants with conversion efficiencies of 100% and 96% relative to the

conversion efficiencies of the respective fossil fuel-fired plants (Gustavsson et al.,

2006b). Fossil energy inputs for the recovery and transport of biofuels and forest

management practices are analysed according to Eriksson et al. (2007) and Berg

and Lindholm (2005).

2.11 Carbon balance

2.11.1 Total carbon balance

In this study, total carbon balance is defined as the reduced net carbon

emission into the atmosphere due to forest biomass production and their uses.

Hence, a positive carbon balance refers to a net carbon benefit, and a negative

carbon balance refers to net carbon emission. The activities included in the system

analysis (Section 2.5) are categorised so as to represent either carbon emissions

reductions or carbon emissions. The carbon emissions reductions are expressed as

a positive change as a result of increased standing biomass carbon stock, changes

in forest soil carbon stock, changes in wood product carbon stocks in the buildings,

substitution carbon benefits achieved due to the replacement of fossil fuels by

18

recovered forest biofuels and wood processing residues, and substitution carbon

benefits due to the avoidance of non-wood material production and process

emissions. The carbon emissions are expressed as the fossil fuel emissions during

forest operation activities including fertilisation. Avoided emissions from

production of non-wood materials are included in the calculation of substitution

carbon benefits. The parameters included for material production and process

emissions include fossil-fuel-cycle carbon emission, end-use fossil fuel carbon

emission, emissions due to end-use electricity to extract, process, and transport the

materials, and emissions from industrial process reactions such as the calcination

reaction during manufacture of the cement.

The total carbon balance for the Jämtland and Västernorrland forest

landscape is calculated as:

[ ( )]sb fs wp scb fo fCB C C C C C C

where

CB is the total carbon balance (gram C);

ΔCsb is the change in standing forest biomass carbon stock (gram C);

ΔCfs is the change in forest soil carbon stock (gram C);

ΔCwp is the change in carbon stock in wood products (gram C);

Cscb is the substitution carbon benefits due to the replacing of fossil fuel with

recovered biofuel (gram C) and avoidance of material production and process

emissions (gram C) due to use of wood materials;

Cfo is the carbon emissions due to forestry operation activities (gram C);

Cf is the equivalent carbon emissions due to fertilization in the forest (gram C);

Emissions of nitrous oxide and methane also occur during fertilization.

Global Warming Potentials of nitrous oxide (298) and methane (25) are used to

convert them into equivalent CO2 emissions based on their relative radiative

efficiencies and atmospheric residence times compared to CO2 (IPCC, 2007c).

A positive carbon balance signifies reduction in carbon emission to the

atmosphere, while a negative carbon balance signifies increase in carbon emission

to the atmosphere.

2.11.2 Standing biomass carbon stock

In this study, the annual increase in standing biomass carbon stock is

estimated after the deduction of harvest, mortality, and disturbances from the total

19

annual biomass production of the forest. On average, approximately 95% of the

annual production of forest biomass is felled. HUGIN calculates the standing

biomass carbon stock based on an evaluation of forest production, disturbances,

harvests, and retained standing biomass in the forest. HUGIN uses spruce stumps

as a proxy for the calculation of deciduous and pine tree stumps.

2.11.3 Soil carbon stock

In this study, soil carbon stock changes due to different forest management

practices and removal strategies are estimated. The estimates are based on the

amount of organic carbon available in the SOM, soil carbon development due to

litterfall from the canopy of the standing biomass and below ground carbon stock

development, and carbon development due to biomass residues left in the forest

after harvest and thinning. A fraction of leaves/needles, branches, and fine roots

die and fall in a standing stand, and a fraction of stems and parts of stumps and

coarse roots are left at the site during harvest and thinning, contributing to soil

carbon stock development. The decomposition of the different litter fractions is

calculated using the Q model, which incorporates the invasion rates of different

litter types (Ågren, 1983; Ågren and Bosatta, 1998; Hyvönen and Ågren, 2001). This

study excluded the soil carbon stock available in mineral soil because the land use

history of the landscape was unknown. The details of soil carbon modelling are

given in Paper I (Section 2.5).

2.11.4 Wood product carbon stock

Wood products stored in the buildings are considered for wood product

carbon stock estimation. Increasing the total amount of wood product stock allows

for the storage of more carbon in the products. The carbon content in wood was

assumed to be 49% of the dry weight of the wood (Swedish Forest Agency, 2010).

Wooden buildings store carbon for the lifetime of the buildings but not beyond

that time. Therefore, it was assumed that when the building is demolished, 100%

of the used wood is recovered and used as biofuel to replace fossil fuels. The

carbon in the wood products returns to the atmosphere as CO2 when the wood is

used as biofuel.

20

2.11.5 Substitution of fossil fuels and carbon-intensive products

Carbon emissions reduction due to substitution of fossil fuels and carbon-

intensive products by the use of forest biomass is estimated. This substitution is

calculated by estimating fossil fuel emissions during material production and

during process reactions (e.g., cement calcination) of material production. These

emissions are compared with emissions from wood construction material

production and processes. Fossil fuel substitution by the use of biomass residues as

bioenergy is estimated separately. A full fuel-cycle emission is considered to

estimate carbon emissions reduction. This study assumes that the biomass

considered in this study is harvested from sustainably managed forests thus the

combustion of biofuel is assumed to contribute a net emission of zero. However,

emissions from fossil fuels used to produce, transport, and process the biofuels

contribute net emissions. Detailed methods and processes for bioenergy use,

conversion, and co-generation opportunities are discussed elsewhere

(Schlamadinger and Marland, 1996; Schlamadinger et al., 1997). This study

assumes that construction of the reference building is substituted by a wood-

framed building that is replaced with another wood-framed building using similar

wood products indefinitely.

2.11.6 Forestry operations and carbon emission

Emissions from fossil fuels used for forest operations (stand establishment,

thinnings, final harvest of roundwood, and forwarding and transport of

roundwood to mills and fertilisation) are calculated based on Berg and Lindholm

(2005). Energy use data for forestry operations for northern Sweden are used to

calculate carbon emissions. The details of management activities and fertilisation

and carbon emissions are described in Paper II (Section 3.6).

2.12 Data quality

Many factors can affect the data used in carbon balance calculations. Different

values of solar radiation, water amount in the soil, plant numbers and their

competition in the forest stand, the photosynthesis capability of a single plant, and

growing capacity in terms of carbon content storage capacity may result in

different values in biomass production, thereby affecting the final result. Forest

21

inventory data collected by the Swedish Forest Agency has been used to model

forest growth and harvest by HUGIN. Any error in the data bank may also affect

the final results of this study. This study assumes the existence of only three tree

species; therefore, the existence of any other species in the forest stand would

change the values and results. Forest product removals may not match current

practices, and there will be different results based on different systems of harvest,

removal, and use. Furthermore, the differences in physical properties of raw

materials, processes of material production, types of fossil fuel use, and the

amount of wood to be utilised in the buildings may lead to different results.

22

3 Results

3.1 Forest biomass production and harvest

Figure 2 shows the annual forest biomass production and harvest at the

year 2010 and year 2109 for the five scenarios for both whole-tree and stem-wood

use. The annual biomass in the Reference scenario increased by ~17% in the year

2109 for whole-tree biomass and by ~8% for stem-wood biomass compared to the

base year 2010 (Paper I). More biomass was produced in the other scenarios

compared to the Reference scenario, with values increasing up to ~75% for whole-

tree biomass and ~65% for stem-wood biomass in the Maximum scenario during

the study period from 2010 to 2109 (Paper III).

Figure 2 Annual biomass productions and harvests at the beginning and end of the

study period for all scenarios.

The potential amount of biomass harvested during the study period

increased significantly when taking into account the effect of climate change and

intensive forestry practices. However, the harvest was only slightly larger in the

Environment scenario compared to the Reference scenario. The Climate,

Production and Maximum scenarios all resulted in larger biomass harvests than

the Reference scenario (Figure 2). Harvests were greater in the Climate,

Environment, Production, and Maximum scenarios than in the Reference scenario

(Table 1 in Paper I and Table 3 in Paper II).

The differences in forest production and harvest between the different

scenarios and the Reference scenario for both whole-tree biomass and stem-wood

biomass represent a net increase during the study period (Table 3). The differences

0

5

10

15

20

25

2010 2109 2010 2109 2010 2109 2010 2109 2010 2109

Reference Climate Environment Production Maximum

Dry

bio

mass

Tg

Yea

r-1

Scenario and year

Whole-tree production Whole-tree harvest

Stem-wood production Stem-wood harvest

23

gradually increased throughout the entire study period (Paper I, Table 1 and Paper

II, Table 3).

Table 3 Differences in forest biomass production and harvest between the Reference

scenario and other scenarios (Tg dry biomass)

2010-

2019

2020-

2029

2030-

2039

2040-

2049

2050-

2059

2060-

2069

2070-

2079

2080-

2089

2090-

2099

2100-

2109

Cumu

lative

(Tg)

Differences between the Climate and Reference scenarios

Biomass production

Stem-wood 0.18 0.27 0.50 0.70 0.84 1.10 1.3 1.46 1.85 2.23 104

Whole-tree 0.35 0.51 0.94 1.35 1.57 2.01 2.4 2.72 3.43 4.11 193

Biomass harvest

Stem-wood 0.06 0.18 0.34 0.42 0.52 0.66 1.14 1.21 1.56 1.8 79

Whole-tree 0.10 0.26 0.55 0.68 0.79 1.07 1.77 1.87 2.33 2.81 123

Differences between the Environment and Reference scenarios

Biomass production

Stem-wood 0.18 0.35 0.53 0.72 0.70 0.92 1.12 1.3 1.44 1.76 89

Whole-tree 0.31 0.66 1.04 1.32 1.29 1.54 1.93 2.25 2.53 2.97 157

Biomass harvest

Stem-wood 0.30 0.11 0.04 0.10 0.15 0.25 0.47 0.57 1.27 1.03 33

Whole-tree 0.47 0.27 0.00 0.15 0.10 0.25 0.64 0.86 1.91 1.50 47

Differences between the Production and Reference scenarios

Biomass production

Stem-wood 0.28 0.55 1.13 1.42 1.70 1.82 1.92 2.10 2.24 2.66 158

Whole-tree 0.51 1.16 2.24 2.92 3.29 3.44 3.63 3.95 4.13 4.77 298

Biomass harvest

Stem-wood 0.00 0.19 0.54 0.70 0.85 1.35 1.77 1.87 2.17 2.33 118

Whole-tree 0.03 0.33 0.80 1.25 1.40 2.15 2.74 2.86 3.41 3.70 187

Differences between the Maximum and Reference scenarios

Biomass production

Stem-wood 0.28 0.55 1.13 1.82 2.10 2.42 2.82 3.20 3.54 3.96 218

Whole-tree 0.51 1.16 2.44 3.72 4.09 4.54 5.33 6.05 6.63 7.37 418

Biomass harvest

Stem-wood 0.10 0.29 0.64 0.9 0.95 1.35 1.97 2.17 2.47 2.83 136

Whole-tree 0.13 0.53 1.10 1.45 1.40 2.25 3.04 3.36 3.81 4.50 217

Paper I and II discuss differences in biomass production and harvest in

different tree species (Norway spruce, Scots pine and birch) due to climate change

and intensive forestry practices. The production and harvest of biomass are

classified into different types of forest products. Stem-wood and stump biomass

yield a greater amount of biomass than other biomass components. However, the

stump biomass may be overestimated because the HUGIN model uses spruce

stumps as a proxy for the calculation of deciduous and pine tree stumps.

Furthermore, because of very few deciduous trees in the past, forest management

practices in the past did not consider promoting their production. But today, the

number of deciduous trees in forests has increased more than the model expected,

which may result in an overestimation of deciduous tree biomass production. It

24

may be also because the model considers deciduous trees to live longer than

coniferous trees, so the model could have considered the larger deciduous tree

sizes compared to coniferous trees.

3.2 Standing biomass carbon stock

The average annual carbon stock in the tree biomass for all scenarios

increased continuously during the study period (Table 4). Overall, the Maximum

and Environment scenarios had higher rates of carbon stock increase than the

Reference and Production scenarios.

Table 4 Average annual tree biomass carbon stock changes during each 10-year

period (Tg carbon year-1) for Jämtland and Västernorrland (Paper I and II) 2010-

2019

2020-

2029

2030-

2039

2040-

2049

2050-

2059

2060-

2069

2070-

2079

2080-

2089

2090-

2099

2100-

2109

Reference scenario 0.38 0.76 0.22 0.55 0.34 0.20 0.35 0.40 0.67 0.45

Climate scenario 0.49 0.85 0.35 0.80 0.63 0.53 0.45 0.61 0.96 0.75

Environment scenario 0.81 1.25 0.75 1.08 0.90 0.81 0.93 0.97 0.76 0.98

Production scenario 0.61 1.08 0.79 1.22 1.07 0.59 0.47 0.59 0.65 0.53

Maximum scenario 0.54 1.01 0.73 1.52 1.44 1.08 1.07 1.34 1.58 1.31

The total standing biomass at the beginning and end of the study period for each

scenario was calculated (Figure 3). All scenarios had larger standing biomasses at

the end of the study period than at the beginning. The stock increases for the

Maximum and Environment scenarios were 56% and 44%, respectively, compared to

a 21% increase in the Reference scenario. The production increase in the Reference

scenario is because the large areas with low productive forests are replaced with

new planted forests with improved genetic material. The greater standing biomass

in the Production and Maximum scenario may be explained as increased production

due to climate change and intensive forestry practices, while it may be explained in

the Environment scenario as a result of an increase in the amount of land set aside

and a lower harvest intensity.

25

Figure 3 Standing forest biomass carbon stock at the beginning (2010) and end

(2109) of the study period in the different scenarios (Paper II, Figure 6).

3.3 Soil carbon stock

Soil carbon changes due to different types of forest management and residues

harvest were analysed. The results for soil carbon changes are presented in Table 2

of Paper I and Table 5 of Paper II, and the total soil carbon stock are presented in

Figure 3 of Paper III. Figure 4 shows that the soil carbon changes occurred

throughout the entire study period. The soil carbon stock increased more following

stem-wood biomass harvest than following whole-tree biomass harvest. Total soil

carbon stock was the highest for Maximum scenario and the lowest for Climate

scenario compared to all other scenarios.

0

100

200

300

400

500

600

700

Year

2010

Reference

2109

Climate

2109

Environment

2109

Production

2109

Maximum

2109

Dry

ma

ss T

g

Scenario and year

Stemwood Stump Branch Bark Needle

26

Figure 4 Carbon stocks in forest soil in the different scenarios during 100-years

with whole-tree biomass use.

3.4 Substitution of fossil fuels and carbon-intensive products

The average annual carbon emissions reductions due to the use of forest

biomass in place of fossil fuel and materials during each 10-year period are given

in

Table 5. Carbon emission reduction amounts were smaller when only

biofuel substitution or non-wood construction material substitution was

considered. The carbon emission reductions were smaller when biofuel only

considered for fossil fuel substitution compared to both biofuel and construction

material considered for fossil fuel substitution.

10

12

14

16

18

202

00

0-2

00

9

20

10

-20

19

20

20

-20

29

20

30

-20

39

20

40

-20

49

20

50

-20

59

20

60

-20

69

20

70

-20

79

20

80

-20

89

20

90

-20

99

21

00

-21

09

Ca

rbo

n s

tock

(T

g C

)

Forest soil carbon stockReference

Climate

Environment

Production

Maximum

27

Table 5 Average annual carbon emissions reductions (Tg C year-1) due to fossil fuel

and carbon-intensive material substitution by the use of stem-wood and whole-

tree biomass during each 10-year period (emissions reduction is shown with coal

as a reference fuel, with values in parentheses representing substitutions using

fossil gas as a reference fuel) (Paper I and II) 2010-

2019

2020-

2029

2030-

2039

2040-

2049

2050-

2059

2060-

2069

2070-

2079

2080-

2089

2090-

2099

2100-

2109

Reference scenario

Stem-wood 4.9(3.4) 4.9(3.4) 4.8(3.2) 4.9(3.3) 5.3(3.6) 5.2(3.5) 5.4(3.7) 5.3(3.7) 5.7(4.0) 6.1(4.3)

Whole-tree 3.8(2.9) 3.8(2.8) 3.7(2.6) 3.7(2.7) 4.1(3.0) 4.0(2.9) 4.3(3.1) 4.2(3.1) 4.6(3.4) 5.0(3.6)

Climate scenario

Stem-wood 3.9(2.9) 3.8(2.8) 3.8(2.7) 3.9(2.8) 4.3(3.1) 4.4(3.2) 4.7(3.4) 4.7(3.4) 5.1(3.7) 5.6(4.1)

Whole-tree 5.0(3.5) 4.9(3.4) 5.0(3.4) 5.1(3.5) 5.6(3.8) 5.7(3.9) 6.1(4.2) 6.1(4.2) 6.5(4.5) 7.1(4.9)

Environmental scenario

Stem-wood 3.6(2.7) 3.6(2.7) 3.6(2.6) 3.7(2.7) 4.0(2.9) 4.1(3.0) 4.3(3.2) 4.5(3.3) 4.8(3.5) 5.0(3.7)

Whole-tree 4.6(3.2) 4.6(3.2) 4.7(3.2) 4.9(3.3) 5.2(3.5) 5.3(3.6) 5.5(3.8) 5.7(4.0) 6.1(4.2) 6.4(4.4)

Production scenario

Stem-wood 3.8(2.9) 3.8(2.9) 4.0(2.9) 4.2(3.0) 4.6(3.3) 5.0(3.6) 5.3(3.9) 5.4(4.0) 5.8(4.3) 6.2(4.6)

Whole-tree 4.9(3.5) 5.0(3.5) 5.2(3.5) 5.5(3.7) 6.0(4.1) 6.4(4.4) 6.7(4.7) 6.8(4.8) 7.3(5.1) 7.8(5.5)

Maximum Scenario

Stem-wood 3.9(2.9) 3.9(2.9) 4.1(2.9) 4.3(3.1) 4.7(3.4) 5.0(3.6) 5.5(4.0) 5.7(4.2) 6.0(4.4) 6.6(5.0)

Whole-tree 5.0(2.9) 5.0(2.9) 5.4(2.9) 5.6(3.1) 6.0(3.4) 6.4(3.6) 7.0(4.0) 7.2(4.2) 7.6(4.4) 8.4(5.0)

Production increase associated with climate change (see Paper I) could

increase carbon reduction by 10% using coal as a reference fuel and by 8% using

fossil gas as a reference fuel compared to the Reference scenario. With intensive

forestry practices, the Maximum scenario yielded a larger carbon emission

reduction. The average annual carbon emission reductions as a result of whole-tree

and stem-wood biomass use to replace fossil fuels and non-wood construction

materials are shown in Figure 5. For all scenarios, the substitution of coal fuel with

whole-tree biomass provided the greatest carbon emission reduction.

28

Figure 5 Average annual carbon emission reduction (Tg carbon year-1) for whole

study area as a result of whole-tree (WT) and stem-wood (SW) biomass use to

replace fossil fuels and non-wood construction materials.

Climate change and intensive forestry significantly increased carbon

emission reductions. Carbon emission reductions due to whole-tree use were

compared to reductions due to the use of stem-wood. The greater carbon emission

reduction occurred with whole-tree use. The Production and Maximum scenarios

yielded the largest carbon reductions due to the greater amounts of biomass

production and harvest in these scenarios compared to other scenarios. Overall

carbon emission reductions due to substitution were greater compared to

reductions due to standing biomass increases. Forest operation emissions were

negligible compared to the carbon emission reductions.

3.5 Wood product carbon stock

Harvested wood products used as construction materials in buildings

store carbon until the building is demolished. The carbon stocks calculated to be in

the buildings are shown in Figure 6. The carbon stocks increased in all scenarios

throughout the study period. A larger increase was observed in the Maximum and

Production scenarios than in the other scenarios.

0

1

2

3

4

5

6

7

Reference Climate Environment Production Maximum

Tg

ca

rbo

n y

ea

r-1

Emission reduction by WT

biomass use replacing coal fuel

Emission reduction by SW

biomass use replacing coal fuel

Emission reduction by WT

biomass use replacing fossil gas

Emission reduction by SW

biomass use replacing fossil gas

0

1

2

3

4

5

6

7

8

Reference Climate Environment Production Maximum

Tg

Car

bo

n y

ear-1

Avoided emission by WT

biomass use replacing coal

fuel

Avoided emission by SW

biomass use replacing coal

fuel

Avoided emission by WT

biomass use replacing

fossil gas

Avoided emission by SW

biomass use replacing

fossil gas

0

1

2

3

4

5

6

7

8

Reference Climate Environment Production Maximum

Tg

Car

bo

n y

ear-1

Avoided emission by WT

biomass use replacing coal

fuel

Avoided emission by SW

biomass use replacing coal

fuel

Avoided emission by WT

biomass use replacing

fossil gas

Avoided emission by SW

biomass use replacing

fossil gas

0

1

2

3

4

5

6

7

8

Reference Climate Environment Production Maximum

Tg

Car

bo

n y

ear-1

Avoided emission by WT

biomass use replacing coal

fuel

Avoided emission by SW

biomass use replacing coal

fuel

Avoided emission by WT

biomass use replacing

fossil gas

Avoided emission by SW

biomass use replacing

fossil gas

0

1

2

3

4

5

6

7

8

Reference Climate Environment Production Maximum

Tg

Ca

rbo

n y

ea

r-1

Avoided emission by WT

biomass use replacing coal

fuel

Avoided emission by SW

biomass use replacing coal

fuel

Avoided emission by WT

biomass use replacing

fossil gas

Avoided emission by SW

biomass use replacing

fossil gas

0

5

10

15

20

25

2010 2109 2010 2109 2010 2109 2010 2109 2010 2109

Reference Climate Environment Production Maximum

Dry

bio

mas

s T

g Y

ear-1

Scenario and year

Whole-tree production Whole-tree production

Stem-wood production Stem-wood production

29

Figure 6 Wood product carbon stock (Tg carbon) due to non-wood material

substitution (Paper III).

3.6 Carbon emissions from forest operations

Intensive forestry requires additional operational activities in the forest. In

addition, a larger biomass production requires additional work for e.g., thinning

and harvest of the biomass. This study includes the calculation of carbon emissions

during forest operational activities from forest regeneration to the final harvest.

The Maximum, Production, and Climate scenarios yielded greater carbon emissions

than the Reference scenario. The greater emissions in these scenarios are due in part

to the fertiliser production and application, and greater amounts of biomass to be

harvested and hauled to the road head (Figure 7). The largest percentage of the

emissions comes from round wood harvest during thinning and final felling.

Stump harvest and haulage result in carbon emissions comparable to those

associated with residue collection and haulage.

0

20

40

60

80

100

120

2000

-200

9

2010

-201

9

2020

-202

9

2030

-203

9

2040

-204

9

2050

-205

9

2060

-206

9

2070

-207

9

2080

-208

9

2090

-209

9

2100

-210

9

Ca

rbo

n s

tock

(T

g C

)

Wood product C stockReference

Climate

Production

Maximum

Environment

30

Figure 7 Carbon emissions due to forest operations and fertilisation for all

scenarios for whole-tree biomass (Mg carbon year-1).

3.7 Total carbon balance

Table 6 shows the total carbon balance, which is reduced net carbon

emissions into the atmosphere due to forest biomass production and their uses.

The calculation of carbon emissions reductions takes into account the carbon stock

increases in living biomass, in forest soil, in wood products, and substitution

carbon benefit due to the substitution of non-wood materials and fossil fuels by the

use of forest biomass. Forest operation emissions were deducted from the carbon

emissions reductions due to substitution effects to obtain net substitution values.

Thus, the total carbon balance is the net carbon emission reduction resulting from

forest production and product use. The carbon balance is increasing every year

because of carbon stock increases in trees, soil, and products, as well as increasing

substitution effects.

Table 6 The total carbon balance including forest production, forest biomass

harvest, soil carbon stock change, and stem-wood and whole-tree biomass use to

replace of fossil fuels and carbon-intensive materials (Tg carbon year-1) during each

10-year period in Jämtland and Västernorrland. The total carbon balance is for coal

as a reference fuel, with values in parentheses representing fossil gas as a reference

fuel (Paper I and II) 2010-

2019

2020-

2029

2030-

2039

2040-

2049

2050-

2059

2060-

2069

2070-

2079

2080-

2089

2090-

2099

2100-

2109

Reference scenario

Stem-wood 5.5(4.5) 5.4(4.4) 4.6(3.5) 4.9(3.8) 4.9(3.8) 5.0(3.9) 5.1(4.0) 5.1(4.3) 5.4(4.3) 5.4(5.0)

0.00

0.05

0.10

0.15

0.20

0.25

2010

-201

9

2020

-202

9

2030

-203

9

2040

-204

9

2050

-205

9

2060

-206

9

2070

-207

9

2080

-208

9

2090

-209

9

2100

-210

9

Car

bo

n e

mis

sio

n, (

Mg

, yea

r-1)

Year

Reference Climate Environment

Production Maximum

31

Whole-tree 6.3(4.8) 6.2(4.8) 5.5(4.0) 5.9(4.3) 5.9(4.3) 6.0(4.4) 6.1(4.5) 6.4(4.8) 6.4(4.8) 6.5(4.8)

Climate scenario

Stem-wood 5.5(4.5) 5.5(4.6) 4.9(3.8) 5.4(4.3) 5.7(4.5) 5.8(4.5) 6.1(4.8) 6.3(5.0) 7.1(5.8) 7.5(6.0)

Whole-tree 6.4(4.9) 6.5(5.1) 6.0(4.4) 6.6(4.9) 6.9(5.1) 7.1(5.2) 7.4(5.5) 7.6(5.7) 8.5(6.5) 9.0(6.8)

Environmental scenario

Stem-wood 5.5(4.5) 5.7(4.7) 5.0(4.0) 5.4(4.4) 5.6(4.5) 5.7(4.5) 6.1(5.0) 6.4(5.2) 6.5(5.2) 7.0(5.7)

Whole-tree 6.3(4.9) 6.6(5.2) 6.1(4.6) 6.6(5.0) 6.8(5.2) 6.9(5.2) 7.3(5.6) 7.6(5.8) 7.8(5.9) 8.4(6.4)

Production scenario

Stem-wood 5.6(4.6) 5.8(4.8) 5.5(4.4) 6.2(5.0) 6.6(5.3) 6.5(5.1) 6.8(5.4) 7.1(5.6) 7.6(6.1) 8.1(6.5)

Whole-tree 6.5(5.0) 6.8(5.3) 6.7(5.0) 7.4(5.7) 7.9(6.0) 7.9(5.9) 8.3(6.2) 8.5(6.4) 9.1(6.0) 9.7(7.3)

Maximum Scenario

Stem-wood 5.6(4.6) 5.8(4.8) 5.6(4.4) 6.6(5.4) 7.0(5.7) 7.0(5.6) 7.7(6.2) 8.2(6.7) 8.8(7.3) 9.4(7.7)

Whole-tree 6.5(5.0) 6.8(5.3) 6.8(5.1) 7.9(6.1) 8.4(6.5) 8.5(6.4) 9.2(7.0) 9.7(7.5) 10.4(8.2) 11.2(8.7)

Figure 8 shows the average annual carbon emission reductions (Tg carbon year-1)

over the 100-year period for all scenarios for whole-tree biomass use to replace coal

and fossil gas. The largest carbon emission reduction was achieved in the

Maximum scenario (8.53 Tg carbon year-1) when compared to the Reference scenario

(6.07 Tg carbon year-1) while replacing coal fuel. The average annual carbon

emission reductions were smaller when fossil gas was replaced.

Figure 8 The average annual carbon emissions reduction (Tg carbon year-1) for

different scenarios when whole-tree biomass was used to replace coal and fossil

gas.

The total carbon balance is highly influenced by substitution effect. The

carbon balance increased for both stem-wood and whole-tree biomass during the

study period, with the greatest increase occurring when whole-tree biomass was

used as an alternative to fossil fuel. The use of whole-tree biomass resulted in

lower soil carbon stock increases than the use of stem-wood biomass, though the

increased substitution benefits more than compensated.

Figure 9 shows the average annual carbon emission reductions per hectare

of forest (Mg ha-1 year-1) for all scenarios for whole-tree biomass use during the

study period. The reduction was greatest in the Maximum scenario. When coal was

0

1

2

3

4

5

6

7

8

9

Reference Climate Environment Production Maximum

Tg

car

bo

n y

ear-1

Scenario

Coal whole-tree

Fossil gas whole-tree

Coal stem-wood

Fossil gas stem-wood

32

replaced with biofuel instead of fossil gas, the overall carbon emission reduction

increased by ~30-35% for whole-tree biomass. Forest carbon stock increases were

greater for the Environment and Maximum scenarios than for the other scenarios.

The increase in the amount of set aside areas and lower harvest levels in the

Environment scenario led to an increase in the forest carbon stock. Greater carbon

emissions reductions in the Maximum scenario compared to other scenarios were

due to forest management practices that promoted biomass production.

Figure 9 The average annual carbon emissions reductions per hectare of forest land

(Mg carbon ha-1 year-1) due to the benefits associated with the use of whole-tree

(WT) and stem-wood (SW) biomass to replace fossil gas and coal.

The carbon emissions reductions were greatest in the Maximum scenario.

The cumulative carbon emissions reductions in different scenarios of whole-tree

biomass use with coal as a reference fuel are presented in Paper I and II. The

largest carbon reduction was found in the Maximum scenario, and the lowest

reduction occurred in the Reference scenario. Figure 10a and 10b shows the

differences in cumulative carbon emission reduction between the Reference

scenario and the Climate, Environment, Production, and Maximum scenarios for

whole-tree biomass use (Figure 10a) and for stem-wood biomass use (Figure 10b)

with coal and fossil gas as reference fuels. The difference is largest between the

Maximum and Reference scenarios for both whole-tree and stem-wood biomass use

with coal as a reference fuel. A greater amount of carbon emissions was reduced

when coal was used as a reference fuel than when fossil gas was used as a

reference fuel.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

Reference Climate Environment Production Maximum

Mg

ca

rbo

n h

a-1

yea

r-1

Scenario

Coal whole-tree Coal stem-woodFossil gas whole-tree Fossil gas stem-wood

33

Figure 10 Differences in cumulative carbon emission reduction (Tg carbon)

between the Climate, Environment, Production and Maximum scenarios and the

Reference scenario for each 10-year period.

0

50

100

150

200

250

2000

-200

9

2010

-201

9

2020

-202

9

2030

-203

9

2040

-204

9

2050

-205

9

2060

-206

9

2070

-207

9

2080

-208

9

2090

-209

9

2100

-210

9Red

uce

d c

arb

on

em

issi

on

(Tg

car

bo

n)

Whole tree biomass use Clim minus Ref Coal

Clim minus Ref Fossil gas

Env minus Ref Coal

Env minus Ref Fossil gas

Prod minus Ref Coal

Prod minus Ref Fossil gas

Max minus Ref Coal

Max minus Ref Fossil gas

a.

0

50

100

150

200

250

2000

-200

9

2010

-201

9

2020

-202

9

2030

-203

9

2040

-204

9

2050

-205

9

2060

-206

9

2070

-207

9

2080

-208

9

2090

-209

9

2100

-210

9

Red

uce

d c

arb

on

em

isso

n (T

g c

arb

on

)

Year

Stem wood biomass use Clim minus Ref Coal

Clim minus Ref Fossil gas

Env minus Ref Coal

Env minus Ref Fossil gas

Prod minus Ref Coal

Prod minus Ref Fossil gas

Max minus Ref Coal

Max minus Ref Fossil gas

b.

34

4 Discussions

4.1 Forest production and harvest

The current average annual forest productivity for the Jämtland and

Västernorrland forests is about 2.1 Mg (dry mass) ha-1 year-1 (Swedish Forest

Agency, 2010). In this study, the forest biomass production started at 2.09 Mg (dry

mass) ha-1 year-1 in the year 2010 and reached up to 3.14 Mg (dry mass) ha-1 year-1 in

2109 due to the effects of climate change. Levels of biomass production were larger

when the effects of climate change and intensive forestry were included compared

to results from a Reference scenario that did not include these effects. The largest

biomass productions at the end of the study period were 3.3 and 3.74 Mg (dry

mass) ha-1 year-1 in the Production and Maximum scenarios, respectively, which

included both climate change and intensive forestry effects. Increasing forest

production increases the potential harvest, substitution potential, standing biomass

and soil carbon.

The harvesting of forest residues from forest land during final felling is a

common practice in Sweden, while stump harvesting is not. The Swedish forest

agency recommends that at least 20% of logging residues and 15-20% of stumps

should be left at the site of the final felling (Swedish Forest Agency, 2008, 2009).

The practice of whole-tree harvest is debated because harvesting residues and

stumps may reduce forest productivity in the following generation because of tree

litters removals. This issue has been discussed in earlier studies (Jacobson et al.,

2000; Egnell and Valinger, 2003; Smolander et al., 2010; Egnell, 2011). However,

results from other studies, such as that performed by Egnell (2011), show that these

effects are only temporary and can be compensated for by fertilisation. Nutrient

deficiencies are assumed to be satisfied because this study includes balanced

fertilisation (except for the Reference scenario).

The forest management practices considered in this study assume that the

biomass production and harvest is continuous without losing the forest’s capacity

to produce and deliver at least the same amount of product every growth cycle.

This study also follows criteria for increased environmental ambitions, for example

increased set-aside areas for special environmental care proposed by the Swedish

Environmental Agency. All scenarios follow, at a minimum, the specified

environmental goals set by current Swedish forest and environmental policy.

35

4.2 Carbon-intensive products substitution

Substituting fossil fuels with forest biomass has a significant impact on the

life cycle carbon balance. Biomass residues left in the forest after harvest release

carbon into the atmosphere for some period of time as they decay; however,

recovering residues to replace fossil fuels reduces net carbon emissions due to

avoided fossil emissions and forest regrowth. Carbon emissions resulting from

forest operations are less for stem-wood harvest than for whole-tree harvest

because of the smaller amount of biomass to be harvested compared to whole-tree

biomass. Although carbon emissions resulting from forest operations are greater

for whole-tree harvest, the overall carbon emission reduction is greater with

whole-tree biomass harvest compared to stem-wood biomass harvest, because of

the increased substitution benefits.

Substituting coal provides greater carbon emission reductions than

substituting fossil gas, because coal emits more CO2 per unit of energy than does

fossil gas. The production of non-wood construction materials such as cement and

steel uses a greater amount of fossil energy compared to the amount needed to

produce wood products. Therefore, replacement of carbon-intensive fuels and

materials with wood products will generally reduce carbon emissions. However,

there may be a question as to whether all of the wood material produced can be

used in building construction or to replace fossil fuels. Jonsson (2009) claimed that

about 30% of multi-storey houses constructed in Sweden by 2015 will be wood-

framed buildings. When the total number of wood-framed buildings increases, the

carbon benefit will increase (Gustavsson et al., 2006b). Wood products can also be

exported to substitute for non-wood products in other countries. The use of

bioenergy is also increasing, and international trade in bioenergy is made feasible

by efficient long-distance transport methods (Junginger et al., 2008). Gustavsson et

al. (2011) calculated that woody biofuels can be economically transported

internationally with little loss of net energy. If additional wood biomass is

exported and used in place of non-wood building materials in other countries,

high emission reductions per unit of biomass could be obtained using a large

amount of the forest biomass, thus resulting in a greater overall emission reduction

globally.

4.3 Carbon balance

This study considers carbon reduction benefits in different stages of forest

production and utilisation. The overall carbon balance depends on the intensity of

36

forest management practices, what reference system is selected for biomass

utilisation, which reference fuel is considered to be replaced during substitution,

and which materials are compared. Sweden has adopted advanced forest

management practices for decades. Continuously increasing the carbon stock in

living forest biomass is not a viable long-term option for the mitigation of climate

change because the carbon stock starts to be released into the atmosphere after its

equilibrium level is reached, thereby limiting total carbon sequestration

(Schlamadinger and Marland, 1996). Furthermore, the dead biomass left in the

forest eventually decomposes and most of its stored carbon is released into the

atmosphere.

The calculated carbon emission reductions are large enough to contribute

significantly to the carbon emission reduction target in Sweden. In the year 2008,

the total amount of CO2 emissions in Sweden was 50 million tonnes (Swedish

Energy Agency, 2010). Based on the calculations performed in this study to

determine the additional potential contribution of forest production and product

use to the reduction of carbon emissions, forest management in Jamtland and

Vasternorrland counties based on the Maximum scenario would reduce annual

average CO2 emissions corresponding to 18% and 15% of the total 2008 carbon

emissions of Sweden if the biomass is used to replace coal fuel and fossil gas fuel

respectively. The CO2 emissions reduction due to forest management based on the

Production scenario corresponds to a 13% and 11% reduction in the total 2008

carbon emissions of Sweden if the biomass is used to replace coal and fossil gas

respectively. In this study, it was not possible to calculate the total carbon benefit

for all of Sweden due to the differences in forest growth, soil carbon, and standing

biomass in the different parts of the country. However, extending this study to all

of Sweden may provide a more comprehensive picture of possible carbon emission

reductions.

In Sweden, forest residue is mainly used within the forest industry for

process heat, for district heating, and in the residential sector. District heating

plants used forest biofuels for the production of 20 TWh of energy out of the total

36 TWh of energy supplied by bioenergy in 2006 (Swedish Energy Agency, 2009).

The share of biofuel used in total energy production in Sweden increased from

10% in 1980 to 22% in 2009, and an increase is expected in the future due to higher

demands for biofuels in heating systems (Swedish Energy Agency, 2010). Biofuel

not utilised in Sweden can be transported and used in other countries in Europe.

The increasing use of wood as a construction material is an important option for

reducing net CO2 emissions because of the low energy requirements for

37

processing, the increased wood product stock, and the increased availability of

biofuel as by-products (Gustavsson and Sathre, 2006). The soil carbon stock was

found to increase, but the increase occurred at a slower rate in the later stages of

the study period, assuming whole-tree harvest. The reduction in soil nutrients and

forest soil carbon due to residue harvest may be only temporary if the forest is

enriched by fertilisation (Paper I and II) (Egnell, 2011).

4.4 Uncertainties and limitations

The integrated analysis method used in this study contains inherent

uncertainties because of the large number of factors to be considered and

assumptions to be made. In addition, the carbon balance analysis is carried out

over long time periods, resulting in a greater number of factors to be considered

and inherent uncertainty about future events. One of the basic assumptions of this

study was the temperature change due to climate change effect. As discussed by

the IPCC, climate change and subsequent temperature changes will depend on

changes in global population, energy demand, climate change mitigation activities

that are implemented, and the additional need for resources, leading to changes in

land use patterns and an increase in the number of methods developed to improve

industrial efficiency to reduce CO2 emissions. This thesis uses the SRES B2 scenario

of climate change, which assumes an increase of temperature of 4 °C, but the actual

future increase is uncertain. A number of factors in plant growth and nutrient

cycling could not be taken into account and might result in different NPP results.

The elevated temperature may encourage the earlier onset of bud-burst in the

spring, which may increase the risk of frost injury during the early growth stage of

planted seedlings (Cannell and Smith, 1986; Hänninen, 1991; Kramer, 1994;

Krasowski et al., 1995). Potential injuries and shoot mortality due to frost were not

included in this study.

The increased demand for nutrients and increased biomass production

must be met by increased mineralisation, nutrient availability, and uptake by

roots; otherwise, the growth response will stagnate at a lower level (Bonan and

Cleve, 1991; Houghton et al., 1998; McMurtrie et al., 2001). In the Reference and

Environment scenarios, traditional fertilisation was assumed to supply additional

nutrients in some part of forest land, whereas in the other two scenarios, balanced

fertilisation was provided to assist soil nutrient dynamics in increased forest area.

Changes in the amount of fertilisation and the availability of water resources

during growth periods might result in slightly different values of NPP. In this

38

landscape study, the site fertility was not known in detail, and the decision to

fertilise forest stands may yield different results in a site-specific analysis.

Increased mineralisation and nutrient availability as effects of increased soil

temperatures have been observed in earlier studies (Jarvis and Linder, 2000). In a

soil-warming experiment in northern Sweden, stem-wood production was greater

for heated plots compared to unheated plots (Strömgren and Linder, 2002). In this

study, a residue harvest of 75% and a 50% stump harvest in the whole-tree harvest

scenario did not affect plant growth in the subsequent years. The amount of soil

nitrogen and plant growth might be affected to some degree in these scenarios,

which could affect biomass production.

Any error in BIOMASS would be multiplied in HUGIN and in the other

models as well. BIOMASS, however, is a suitable model for predicting NPP as

forest productivity in boreal and cold-temperate environments because low-

temperature effects have been included, and the response of elevated temperature

is predicted in a realistic way.

HUGIN uses national forest inventory data for harvest projections. Any

error in NFI data would yield different values for the production and harvest of

products. The Q model used for soil carbon estimation uses slightly different forest

growth functions than HUGIN, so the soil carbon numbers might have been

slightly different than they would have been had they been calculated with a

function similar to that used by HUGIN. Substitution modelling is based on a case

study of a single building, and may give slightly different results if the

architectural or engineering designs of the building were different. However,

climate benefits of wood substitution in general are quite robust (Sathre and

O'Connor, 2010).

Climate change may result in wind damages, fire risk, pathogens, and

insect outbreaks, which may affect forest growth and mortality (Battles et al., 2008;

Kurz et al., 2008; Blennow et al., 2010; Lindner et al., 2010). Such risks have not been

considered in this study but could be substantial in Sweden. A Swedish

governmental survey (SOU, 2007) noted these uncertainties and risks as possible

threats to future forestry in Sweden. The carbon balance analysis is based on both

the forest products derived from a sustainably managed forest and the Swedish

forest production and utilisation recommendations and guidelines. The risks and

advantages of intensive fertilisation in the forest and the use of whole-tree biomass

need to be compared.

39

5 Conclusions

Climate change could significantly increase the forest biomass production in

Jämtland and Västernorrland. Forest productivity could further be increased by

applying intensive forestry practices. Intensive forestry practices are possible for

all of the forest types in Jämtland and Västernorrland and in some cases can be

applied on a large scale, such as soil scarification during regeneration, increased

pre-commercial thinning, and fertilisation. Increased forest biomass production

increases the potential harvest of biomass. The harvest of residues and stumps

could increase the carbon benefit through the substitution of carbon-intensive

fossil fuels and materials. The harvesting of residues and stumps does not

significantly reduce soil carbon, but available biomass could be used to achieve a

greater reduction in carbon emissions. Carbon emission reductions as a result of

forest biomass use can be achieved during each rotation period, and the reductions

would be cumulative in the long run. Carbon emission reduction benefits would

be lower if the forest is not managed to increase biomass production and harvest.

The carbon emission reduction benefits may be greater if the biomass harvest is

larger. In such cases, forests can only sequester carbon until the natural

equilibrium of biomass stock is reached and it then either remains near constant or

is reduced due to mortality. Leaving residues and stumps in the forest during

harvest operations would help increase soil carbon by a small amount compared to

the carbon emission reductions achieved by the use of residues and stumps to

substitute fossil fuels. Forest management strategies that promote an increase in

sustainable biomass production and use would provide a reduced net carbon

emission.

40

6 Future research

Previous studies of the climate implications associated with forest

production have generally focused on ecosystem carbon budgets, bioenergy use

and material substitution. It would be useful to design complete carbon balance

analysis models that include parameters such as forest production, utilisation,

carbon emissions, and radiative forcing effects from different types of forest

management practices. The concept of forest conversion into continuous cover

forestry has emerged, and studies on the standing biomass carbon stock and soil

carbon stock in continuous cover forestry would allow for a comparison of the

carbon balance benefits between continuous cover forestry and clear-cut forestry.

Carbon balance differences due to changes in shorter and longer rotations should

be a topic of future research. Generally, carbon balance studies do not include

economic valuations of the forest production and carbon benefits. Adding

economic analyses to carbon balance studies would provide a clearer picture of the

economic costs and benefits.

Sweden has made commitments to reduce carbon emissions by 2020. It

would be interesting to study carbon storage in forest ecosystems and wood

products for this very short time perspective. It is also necessary to examine the

current physical quantities of forest products and their use so that future plans can

be developed for the energy and construction sectors. Studies on wood

consumption in the building sector would provide information about the potential

demand for wood in the building sector in the future. Sweden produces large

amounts of forest biomass (a recent annual harvest is 90 million m3), but it still

imports biofuels from other countries. The tradeoffs between the production,

harvest, export and import of biomass could be useful.

This study provides a brief assessment of forest production and utilisation

at the landscape level in only part of Sweden. Extending this study over all of

Sweden may provide a clearer picture of the potential effects of forest production

and product use for the entire country. In such studies, the specific quantity of

biomass use in the energy sector, the specific quantity of wood use in the building

sector, and the amounts of energy recovery can be analysed to provide more

precise results for the carbon balance for the entire country. This may be of interest

to the Swedish government and to forest owners for planning their forest

management, harvest and product business both in the national and international

contexts. Future studies should also focus on estimating the value of the

substitution effect that is lost if nothing is harvested from the forest. A study on the

41

history of carbon storage and the substitution effect when the forest biomass stock

was smaller than what it is today would provide a reference for forest product use

in the future.

7 References

Ågren, G., Hyvönen, R., Nilsson, T., 2007. Are Swedish forest soils sinks or sources

for CO2—model analyses based on forest inventory data. Biogeochemistry

82, 217-227.

Ågren, G.I., 1983. Nitrogen productivity of some conifers. Canadian Journal of

Forest Research 13, 494-500.

Ågren, G.I., Bosatta, E., 1998. Theoretical ecosystem ecology : understanding

element cycles. Cambridge University Press, Cambridge ; New York, NY.

Battles, J., Robards, T., Das, A., Waring, K., Gilless, J., Biging, G., et al., 2008.

Climate change impacts on forest growth and tree mortality: a data-driven

modeling study in the mixed-conifer forest of the Sierra Nevada,

California. Climatic Change 87, 193-213.

Berg, S., Lindholm, E.-L., 2005. Energy use and environmental impacts of forest

operations in Sweden. Journal of Cleaner Production 13, 33-42.

Bergh, J., Freeman, M., Sigurdsson, B., Kellomäki, S., Laitinen, K., Niinistö, S., et al.,

2003. Modelling the short-term effects of climate change on the

productivity of selected tree species in Nordic countries. Forest Ecology

and Management 183, 327-340.

Bergh, J., Linder, S., 1999. Effects of soil warming during spring on photosynthetic

recovery in boreal Norway spruce stands. Global Change Biology 5, 245-

253.

Bergh, J., Linder, S., Bergström, J., 2005. Potential production of Norway spruce in

Sweden. Forest Ecology and Management 204, 1-10.

Bergh, J., Linder, S., Lundmark, T., Elfving, B., 1999. The effect of water and

nutrient availability on the productivity of Norway spruce in northern and

southern Sweden. Forest Ecology and Management 119, 51-62.

Bergh, J., McMurtrie, R.E., Linder, S., 1998. Climatic factors controlling the

productivity of Norway spruce: A model-based analysis. Forest Ecology

and Management 110, 127-139.

Bergman, R.D., Zebre, J., 2004. Primer on wood biomass for energy. In. USDA

Forest service, State and Private Forestry Technology Marketing Unit,

Madison, WI.

Bettinger, P., Boston, K., Siry, J., Grebner, D.L., 2009. Forest management and

planning. Academic Press, New York.

42

Blennow, K., Andersson, M., Bergh, J., Sallnäs, O., Olofsson, E., 2010. Potential

climate change impacts on the probability of wind damage in a south

Swedish forest. Climatic Change 99, 261-278.

Bonan, B.G., Cleve, K.v., 1991. Soil temperature, nitrogen mineralisation, and

carbon source-sink relationships in boreal forests. Canadian Journal of

Forest Research 22.

Börjesson, P., Gustavsson, L., 2000. Greenhouse gas balances in building

construction: wood versus concrete from life-cycle and forest land-use

perspectives. Energy Policy 28, 575-588.

Börjesson, P., Gustavsson, L., Christersson, L., Linder, S., 1997. Future production

and utilisation of biomass in Sweden: Potentials and CO2 mitigation.

Biomass and Bioenergy 13, 399-412.

Boustead, I., Hancock, G.F., 1979. Handbook of Industrial Energy Analysis, Ellis

Horwood Publishers, Chichester, UK.

Boyd, C., Koch, P., McKean, H., Morschauser, C., Preston, S., Wangaard, F., 1976.

Wood for Structural and Architectural Purposes. Wood and Fiber Science

8, 3-72.

Briceño-Elizondo, E., Garcia-Gonzalo, J., Peltola, H., Kellomäki, S., 2006. Carbon

stocks and timber yield in two boreal forest ecosystems under current and

changing climatic conditions subjected to varying management regimes.

Environmental Science & Policy 9, 237-252.

Buchanan, A.H., Honey, B.G., 1994. Energy and carbon dioxide implications of

building construction. Energy and Buildings 20, 205-217.

Buongiorno, J., Gilless, J.K., 2003. Decision Methods for Forest Resource

Management. Academic Press, New York.

Canadell, J.G., Kirschbaum, M.U.F., Kurz, W.A., Sanz, M.-J., Schlamadinger, B.,

Yamagata, Y., 2007a. Factoring out natural and indirect human effects on

terrestrial carbon sources and sinks. Environmental Science & Policy 10,

370-384.

Canadell, J.G., Le Quéré, C., Raupach, M.R., Field, C.B., Buitenhuis, E.T., Ciais, P.,

et al., 2007b. Contributions to accelerating atmospheric CO2 growth from

economic activity, carbon intensity, and efficiency of natural sinks.

Proceedings of the National Academy of Sciences 104, 18866-18870.

Canadell, J.G., Raupach, M.R., 2008. Managing Forests for Climate Change

Mitigation. Science 320, 1456-1457.

Cannell, M.G.R., Smith, R.I., 1986. Climatic Warming, Spring Budburst and Forest

Damage on Trees. Journal of Applied Ecology 23, 177-191.

Carter, T.R., Jylhä, K., Perrels, A., Fronzek, S., Kankaanpää, S., 2005. FINADAPT

scenarios for the 21st century: alternative futures for considering

adaptation to climate change in Finland. In. Finnish Environment Institute,

Helsinki, p. 42 Mimeographs 332.

43

Chapin, F.S.I., Matson, P.A., Mooney, H.A., 2002. Principles of terrestrial

ecosystem ecology Springer-Verlag, New York, USA.

CPF, 2008. Strategic framework for forests and climate change. A proposal by the

Collaborative Partnership on Forests for a coordinated forest-sector

response to climate chnage. The Collaborative Partnership on Forests

(CPF).

Davidson, E.A., Janssens, I.A., 2006. Temperature sensitivity of soil carbon

decomposition and feedbacks to climate change. Nature 440, 165-173.

Davidson, E.A., Trumbore, S.E., Amundson, R., 2000. Biogeochemistry: Soil

warming and organic carbon content. Nature 408, 789-790.

Dodoo, A., 2011. Life-cycle pimary energy use and carbon emission of residential

buildings. Doctoral Thesis. Department of Engineering and Sustainable

Development. Mid Sweden University, Östersund, p. 71.

Dupre, C., Stevens, C.J., Ranke, T., Bleeker, A., Peppler-Lisbach, C., Gowing, D.J.G.,

et al., 2010. Changes in species richness and composition in European

acidic grasslands over the past 70 years: the contribution of cumulative

atmospheric nitrogen deposition. Global Change Biology 16, 344-357.

Easterling, W.E., Aggarwal, P.K., Batima, P., Brander, K., Erda, L., Howden, M., et

al., 2007. Chapter 5: Food, Fibre, and Forest Products. In: Parry, M.L.,

Canziani, O.F., Palutikof, J.P., Linden, P.J.v.d., Hanson, C.E. (Eds.), Climate

Change 2007: Impacts, Adaptation and Vulnerability. Contribution of

Working Group II to the Fourth Assessment Report of the

Intergovernmental Panel on Climate Change. Cambridge University Press,

Cambridge, UK, 273-313.

Eggers, J., Lindner, M., Zudin, S., Zaehle, S., Liski, J., 2008. Impact of changing

wood demand, climate and land use on European forest resources and

carbon stocks during the 21st century. Global Change Biology 14, 2288-

2303.

Egnell, G., 2011. Is the productivity decline in Norway spruce following whole-tree

harvesting in the final felling in boreal Sweden permanent or temporary?

Forest Ecology and Management 261, 148-153.

Egnell, G., Valinger, E., 2003. Survival, growth, and growth allocation of planted

Scots pine trees after different levels of biomass removal in clear-felling.

Forest Ecology and Management 177, 65-74.

Eriksson, E., Gillespie, A.R., Gustavsson, L., Langvall, O., Olsson, M., Sathre, R., et

al., 2007. Integrated carbon analysis of forest management practices and

wood substitution. Canadian Journal of Forest Research 37, 671-681.

EU, 2008. EU Climate Change Expert Group: Background on Impacts, Emission

Pathways, Mitigation Options and Costs.Task Group 3: Construction and

Demolition Waste. . In, Final report of the construction and emolition

waste working group, Brussels. Aavailable at: www.ec.europa.eu

[Accessed on May 2011].

44

European-Commission, 2007. Limiting Global Climate Change to 2 Degrees

Celcius: The way for 2020 and beyond. In, Communication from the

Commission to the Council, teh European Parliament, the European

Economic and Social Committee and the Committee of the Regions.

Available at: www.eur-lex.europa.eu [Accessed on: May 2011].

European-Commission, 2009. Directive 2009/28/EC of the European Parliament

and of the Council of 23 April 2009 on the promotion of the use of energy

from renewable sources and amending and subsequently repealing

Directives 2001/77/EC and 2003/30/EC (Text with EEA relevance). In:

European Parliament, C.o.t.M.S. (Ed.). European Union.

Fossdal, S., 1995. Energi- og Miljøregnskap for bygg (Energy and environmental

accounts of building construction). In. The Norwegian Institute of Building

Research, Oslo. (In Norwegian).

Freer-Smith, P.H., Broadmeadow, M.S.J., Lynh, J.M., 2009. Forests and Climate

Change: the Knowledge-base for Action. In: Freer-Smith, P.H.,

Broadmeadow, M.S.J., Lynh, J.M. (Eds.), Forestry and Climate Change.

OECD, Forest Research the research agency of the forestry commission,

and CABI Publishing, Cambridge, p. 253.

Friedlingstein, P., Cox, P., Betts, R., Bopp, L., von Bloh, W., Brovkin, V., et al., 2006.

Climate–Carbon Cycle Feedback Analysis: Results from the C4MIP Model

Intercomparison. Journal of Climate 19, 3337-3353.

Galloway, J.N., Townsend, A.R., Erisman, J.W., Bekunda, M., Cai, Z., Freney, J.R.,

et al., 2008. Transformation of the nitrogen cycle: Recent trends, questions,

and potential solutions. Science 320, 889-892.

Gower, S.T., Krankina, O., Olson, R.J., Apps, M., Linder, S., Wang, C., 2001. Net

primary production and carbon allocation patterns of boreal forest

ecosystems. Ecological Applications 11, 1395-1411.

Gower, S.T., McMurtrie, R.E., Murty, D., 1996. Aboveground net primary

production decline with stand age: potential causes. Trends in Ecology

& Evolution 11, 378-382.

Gustavsson, L., Börjesson, P., Johansson, B., Svenningsson, P., 1995. Reducing CO2

emissions by substituting biomass for fossil fuels. Energy 20, 1097-1113.

Gustavsson, L., Eriksson, L., Sathre, R., 2011. Costs and CO2 benefits of recovering,

refining and transporting logging residues for fossil fuel replacement.

Applied Energy 88, 192-197.

Gustavsson, L., Joelsson, A., Sathre, R., 2010. Life cycle primary energy use and

carbon emission of an eight-storey wood-framed apartment building.

Energy and Buildings 42, 230-242.

Gustavsson, L., Karlsson, Å., 2006. CO2 Mitigation: On Methods and Parameters

for Comparison of Fossil-Fuel and Biofuel Systems. Mitigation and

Adaptation Strategies for Global Change 11, 935-959.

45

Gustavsson, L., Madlener, R., Hoen, H.F., Jungmeier, G., Karjalainen, T., Klöhn, S.,

et al., 2006a. The Role of Wood Material for Greenhouse Gas Mitigation.

Mitigation and Adaptation Strategies for Global Change 11, 1097-1127.

Gustavsson, L., Pingoud, K., Sathre, R., 2006b. Carbon Dioxide Balance of Wood

Substitution: Comparing Concrete-and Wood-Framed Buildings.

Mitigation and Adaptation Strategies for Global Change 11, 667-691.

Gustavsson, L., Sathre, R., 2006. Variability in energy and carbon dioxide balances

of wood and concrete building materials. Building and Environment 41,

940-951.

Hänninen, H., 1991. Does climatic warming increase the risk of frost damage in

northern trees? Plant, Cell & Environment 14, 449-454.

Houghton, R.A., 2005. Aboveground Forest Biomass and the Global Carbon

Balance. Global Change Biology 11, 945-958.

Houghton, R.A., 2007. Balancing the Global Carbon Budget. Annual Review of

Earth and Planetary Sciences 35, 313-347.

Houghton, R.A., Davidsson, E.A., Woodwell, G.M., 1998. Missing sinks, feedbacks,

and understanding the role of terrestrial ecosystems in the global carbon

balance. Global Biogeochemical Cycles 12.

Hyvönen, R., Ågren, G.I., 2001. Decomposer invasion rate, decomposer growth

rate, and substrate chemical quality: how they influence soil organic

matter turnover. Canadian Journal of Forest Research 31, 1594-1601.

Hyvönen, R., Ågren, G.I., Linder, S., Persson, T., Cotrufo, M.F., Ekblad, A., et al.,

2007. The likely impact of elevated [CO2], nitrogen deposition, increased

temperature and management on carbon sequestration in temperate and

boreal forest ecosystems: a literature review. New Phytologist 173, 463-480.

Hyvönen, R., Persson, T., Andersson, S., Olsson, B., Ågren, G., Linder, S., 2008.

Impact of long-term nitrogen addition on carbon stocks in trees and soils

in northern Europe. Biogeochemistry 89, 121-137.

IFIAS, 1974. Energy Analysis (International Federation of Institutes for Advanced

Study). In. Energy Analysis Workshop on Methodology and Conventions,

25-30 August, Guldsmedshyttan, Sweden, .

IPCC, 1996. Climate Change 1995 — Impacts, Adaptations and Mitigation of

Climate Change: Scientific-Technical Analyses. Cambridge University

Press, Cambridge, UK.

IPCC, 2000. Land Use, Land Use Change, and Forestry. Cambridge University

Press, Cambridge, UK.

IPCC, 2001. The Scientific Basis: Contribution of Working Group I to the Third

Assessment Report of the Intergovernmental Panel on Climate Change.

Cambridge University Press, New York , USA.

IPCC, 2007a. Climate Change 2007 : Impacts, Adaptation and Vulnerability.

Contribution of Working Group II to the fourth assessment report of the

46

Intergovernmental Panel on Climate Change. Cambridge University Press,

Cambridge, U.K. ; New York .

IPCC, 2007b. Climate Change 2007: Mitigation of Climate Change. Contribution of

Working Group III to the Fourth Assessment Report of the

Intergovernmental Panel on Climate Change. Cambridge University Press,

United Kingdom and New York, USA.

IPCC, 2007c. Climate Change 2007: The Physical Science Basis. Contribution of

Working Group I to the Fourth Assessment Report of the

Intergovernmental Panel on Climate Change. Cambridge University Press,

United Kingdom and New York, USA.

Jacobson, S., Kukkola, M., Mälkönen, E., Tveite, B., 2000. Impact of whole-tree

harvesting and compensatory fertilization on growth of coniferous

thinning stands. Forest Ecology and Management 129, 41-51.

Jarvis, P.G., Linder, S., 2000. Constraints to growth of boreal forests. Nature 405,

904-905.

Johnson, D.W., 1992. Effects of forest management on soil carbon storage. Water,

Air, and Soil Pollution 64, 83-120.

Jones, C., McConnell, C., Coleman, K., Cox, P., Falloon, P., Jenkinson, D., et al.,

2005. Global climate change and soil carbon stocks; predictions from two

contrasting models for the turnover of organic carbon in soil. Global

Change Biology 11, 154-166.

Jonsson, R., 2009. Prospects for timber frame in multi-storey house building in

England, France, Germany, Ireland, the Netherlands and Sweden. Växjö

University, School of Technology and Design, Växjö, Sweden, p. 30.

Junginger, M., Bolkesjø, T., Bradley, D., Dolzan, P., Faaij, A., Heinimö, J., et al.,

2008. Developments in international bioenergy trade. Biomass and

Bioenergy 32, 717-729.

Kaipainen, T., Liski, J., Pussinen, A., Karjalainen, T., 2004. Managing carbon sinks

by changing rotation length in European forests. Environmental Science &

Policy 7, 205-219.

Karhu, K., Fritze, H., Hämäläinen, K., Vanhala, P., Jungner, H., Oinonen, M., et al.,

2010. Temperature sensitivity of soil carbon fractions in boreal forest soil.

Ecology 91, 370-376.

Kauppi, P.E., Mielikdinen, K., Kuusela, K., 1992. Biomass and Carbon Budget of

European Forests,1971 to 1990. Science 256.

Kirilenko, A.P., Sedjo, R.A., 2007. Climate change impacts on forestry. In.

Proceedings of the National Academy of Sciences of the USA, PNAS, pp.

19697-19702.

Kirschbaum, M.U.F., 2000. Will changes in soil organic carbon act as a positive or

negative feedback on global warming? Biogeochemistry 48, 21-51.

47

Kirschbaum, M.U.F., 2004. Soil respiration under prolonged soil warming: are rate

reductions caused by acclimation or substrate loss? Global Change Biology

10, 1870-1877.

Kjellström, E., Bärring, L., Gollvik, S., Hansson, U., Jones, C., Samuelsson, P., et al.,

2006. A 140-year simulation of European climate with the new version of

the Rossby Centre regional atmospheric climate model (RCA3). In, SMHI

Reports in Meteorology and Climatology, No. 108. SMHI, Norrköping,

Sverige., p. 54.

Knorr, W., Prentice, I.C., House, J.I., Holland, E.A., 2005. Long-term sensitivity of

soil carbon turnover to warming. Nature 433, 298-301.

Kramer, K., 1994. A modelling analysis of the effects of climatic warming on the

probability of spring frost damage to tree species in The Netherlands and

Germany. Plant, Cell & Environment 17, 367-377.

Krasowski, M.J., Letchford, T., Caputa, A., Bergerud, W.A., 1995. Desiccation of

white spruce seedlings planted in the southern boreal forest of British

Columbia. Water, Air, & Soil Pollution 82, 133-146.

Kurz, W.A., Dymond, C.C., Stinson, G., Rampley, G.J., Neilson, E.T., Carroll, A.L.,

et al., 2008. Mountain pine beetle and forest carbon feedback to climate

change. Nature 452, 987-990.

Lal, R., 2004. Soil Carbon Sequestration Impacts on Global Climate Change and

Food Security. Science 304, 1623-1627.

Levy, P.E., Cannell, M.G.R., Friend, A.D., 2004. Modelling the impact of future

changes in climate, CO2 concentration and land use on natural ecosystems

and the terrestrial carbon sink. Global Environmental Change 14, 21-30.

Lindner, M., Maroschek, M., Netherer, S., Kremer, A., Barbati, A., Garcia-Gonzalo,

J., et al., 2010. Climate change impacts, adaptive capacity, and

vulnerability of European forest ecosystems. Forest Ecology and

Management 259, 698-709.

Lippke, B., Wilson, J., Perez-Garcia, J., Boyer, J., Meil, J., 2004. CORRIM: life-cycle

environmental performance of renewable building materials. Forest

Products Journal 54, 8–19.

Liski, J., Perruchoud, D., Karjalainen, T., 2002. Increasing carbon stocks in the

forest soils of western Europe. Forest Ecology and Management 169, 159-

175.

Liski, J., Pussinen, A., Pingoud, K., Kip, R.M., Karjalainen, T., 2001. Which rotation

length is favourable to carbon sequestration? Canadian Journal of Forest

Research 31, 2004.

Lloyd, J., Taylor, J.A., 1994. On the temperature dependence of soil respiration.

Functional Ecology 8, 315-323.

Lundström, A., Söderberg, U., 1996. Outline of the Hugin system for longterm

forecasts of timber yields and possible cut. In, Large-Scale Forestry

Scenario Models: experiences and requirements. EFI proceeding, pp. 63-77.

48

Luo, Y.Q., 2007. Terrestrial carbon-cycle feedback to climate warming. Annual

Review of Ecology Evolution and Systematics 38, 683-712.

Malhi, Y., Meir, P., Brown, S., 2002. Forests, carbon and global climate.

Philosophical Transactions of the Royal Society of London. Series A:

Mathematical, Physical and Engineering Sciences 360, 1567-1591.

Malmsheimer, R.W., Heffernan, P., Brink, S., Crandall, D., Deneke, F., Galik, C., et

al., 2008. Forest Management Solutions for Mitigating Climate Change in

the United States. Journal of Forestry 106, 115-118.

Marland, G., Schlamadinger, B., 1997. Forests for carbon sequestration or fossil fuel

substitution? A sensitivity analysis. Biomass and Bioenergy 13, 389-397.

McMurtrie, R.E., Landsberg, J.J., 1992. Using a simulation model to evaluate the

effects of water and nutrients onthe growth and carbon partitioning of

Pinus radiata. Forest Ecology and Management 52, 243-260.

McMurtrie, R.E., Medlyn, B.E., Dewer, R.C., 2001. Increased understanding of

nutrient immobilisation in soil organic matter is critical for predicting the

carbon sink strength of forest ecosystem over the next 100 years. Tree

Physiology 21, 831-839.

McMurtrie, R.E., Rook, D.A., Kelliher, F.M., 1990. Modelling the yield of Pinus

radiata on a site limited by water and nitrogen. Forest Ecology and

Management 30, 381-413.

Ministry of Industry, 2004. Mer trä i byggandet: Underlag för en nationell strategi

att främja användning av trä i byggandet [More wood in construction:

Basis for a national strategy to promote the use of wood in construction].

In. Swedish Government, Stockholm. (In Swedish).

Nabuurs, G.-J., Schelhaas, M.-J., Mohren, G.M.J., Field, C.B., 2003. Temporal

evolution of the European forest sector carbon sink from 1950 to 1999.

Global Change Biology 9, 152-160.

Nakicenovic, N., Swart, R., 2000. Emission Scenarios, A special report of Working

Group III of the Intergovernmental Panel on Climate Change. In.

Cambridge University Press, Cambridge, United Kingdom.

NOAA/ESRL, 2012. Mauna Loa Observatory (NOAA/ESRL), monthly and annual

mean CO2 concentration (ppm) March 1958 to present. Available at:

ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_mm_mlo.txt. [Accessed:

August 2012]

Norby, R.J., DeLucia, E.H., Gielen, B., Calfapietra, C., Giardina, C.P., King, J.S., et

al., 2005. Forest response to elevated CO2 is conserved across a broad range

of productivity. Proceedings of the National Academy of Sciences of the

United States of America 102, 18052-18056.

Norby, R.J., Wullschleger, S.D., Gunderson, C.A., Johnson, D.W., Ceulemans, R.,

1999. Tree responses to rising CO2 in field experiments: implications for

the future forest. Plant, Cell & Environment 22, 683-714.

49

O'Donnell, J.A., Harden, J.W., McGuire, A.D., Romanovsky, V.E., 2010. Exploring

the sensitivity of soil carbon dynamics to climate change, fire disturbance

and permafrost thaw in a black spruce ecosystem. Biogeosciences

Discussions 7, 8853-8893.

OECD/IEA, 2010. World Energy Outlook 2010. OECD Publishing.

Oren, R., Ellsworth, D.S., Johnsen, K.H., Phillips, N., Ewers, B.E., Maier, C., et al.,

2001. Soil fertility limits carbon sequestration by forest ecosystems in a

CO2-enriched atmosphere. Nature 411, 469-472.

Pastor, J., Post, W.M., 1988. Response of northern forests to CO2-induced climate

change. Nature 334, 55-58.

Piao, S., Ciais, P., Friedlingstein, P., Peylin, P., Reichstein, M., Luyssaert, S., et al.,

2008. Net carbon dioxide losses of northern ecosystems in response to

autumn warming. Nature 451, 49-52.

Pingoud, K., Lehtilä, A., 2002. Fossil carbon emissions associated with carbon

flowsof wood products. Mitigation and Adaptation Strategies for Global

Change 7, 63-83.

Prentice, I.C., Sykes, M.T., Cramer, W., 1993. A simulation model for the transient

effects of climate change on forest landscapes. Ecological Modelling 65, 51-

70.

Pussinen, A., Karjalainen, T., Mäkipää, R., Valsta, L., Kellomäki, S., 2002. Forest

carbon sequestration and harvests in Scots pine stand under different

climate and nitrogen deposition scenarios. Forest Ecology and

Management 158, 103-115.

Raupach, M.R., Canadell, J.G., 2010. Carbon and the Anthropocene. Current

Opinion in Environmental Sustainability 2, 210-218.

Rosenzweig, C., Karoly, D., Vicarelli, M., Neofotis, P., Wu, Q., Casassa, G., et al.,

2008. Attributing physical and biological impacts to anthropogenic climate

change. Nature 453, 353-357.

Salazar, J., Meil, J., 2009. Prospects for carbon-neutral housing: the influence of

greater wood use on the carbon footprint of a single-family residence.

Journal of Cleaner Production 17, 1563-1571.

Sathre, R., 2007. Life-Cycle Energy and Carbon Implications of Wood-Based

Products and Construction. In, Department of Engineering, Physics and

Mathematics. Mid Sweden University, Östersund, Sweden, p. 113.

Sathre, R., Gustavsson, L., 2007. Effects of energy and carbon taxes on building

material competitiveness. Energy and Buildings 39, 488-494.

Sathre, R., Gustavsson, L., Bergh, J., 2010. Primary energy and greenhouse gas

implications of increasing biomass production through forest fertilization.

Biomass and Bioenergy 34, 572-581.

Sathre, R., O'Connor, J., 2010. Meta-analysis of greenhouse gas displacement

factors of wood product substitution. Environmental Science & Policy 13,

104-114.

50

Schlamadinger, B., Apps, M., Bohlin, F., Gustavsson, L., Jungmeier, G., Marland,

G., et al., 1997. Towards a standard methodology for greenhouse gas

balances of bioenergy systems in comparison with fossil energy systems.

Biomass and Bioenergy 13, 359-375.

Schlamadinger, B., Marland, G., 1996. The role of forest and bioenergy strategies in

the global carbon cycle. Biomass and Bioenergy 10, 275-300.

Schlamadinger, B., Marland, G., Apps, M.J., Price, D.T., 1996. Carbon implications

of forest management strategies. Springer-Verlag, Berlin, Germany.

Schulz, H., 1993. Entwicklung der Holzverwendung im 19., 20. und 21.

Jahrhundert (The history of wood utilisation in the 19th, 20th and 21st

Century). Holz als Roh- und Werkstoff 51, 75-82 (In German).

Sirkin, T., Houten, M.t., 1994. The cascade chain: A theory and tool for achieving

resource sustainability with applications for product design. Resources,

Conservation and Recycling 10, 213-276.

Skogsstyrelsen, 2008. Skogliga konsekvensanalyser – SKA-VB 08. Swedish Forest

Agency Rapport. Skogsstyrelsen, Sweden.

SMHI, 2009. Climatic data, Swedish Meteorological and Hydrological Institute. In.

http://www.smhi.se/cmp/jsp/polopoly.jsp?d=8785&l=sv Accessed on

2009/08/02.

Smolander, A., Kitunen, V., Tamminen, P., Kukkola, M., 2010. Removal of logging

residue in Norway spruce thinning stands: Long-term changes in organic

layer properties. Soil Biology and Biochemistry 42, 1222-1228.

Solomon, A.M., 1986. Transient response of forests to CO2-induced climate change:

simulation modeling experiments in eastern North America. Oecologia 68,

567-579.

SOU, 2007. Sweden facing climate change - threats and opportunities. Final Report

of the Climate and Vulnerability. In. Statens offentliga utredningar,

Stockholm.

Strömgren, M., Linder, S., 2002. Effects of nutrition and soil warming on stem

wood production in a boreal Norway spruce stand. Global Change Biology

8, 1194-1204.

Sveriges-Nationalatlas, 1995. Sveriges Nationalatlas: Klimat, Sjöar och Vattendrag

[Swedish National Atlas: Climate, Lakes and Rivers]. Bra Böcker, Höganäs,

Sweden.

Swedish Energy Agency, 2008. Energy Indicators 2008 Theme: Renewable energy.

Swedish Energy Agency, Eskilstuna.

Swedish Energy Agency, 2009. Energy Outlook. In, Bioenergy- an important piece

of the climate change puzzle. Energimyndigheten, Eskilstuna, p. 60.

Swedish Energy Agency, 2010. Energy in Sweden 2010. Swedish Energy Agency,

Eskiltuna.

51

Swedish Forest Agency, 2008. Rekommendationer vid uttag av avverkningsrester

och Askåterföring [Recommendations for extraction of logging residue

and ash recycling]. In, Meddelande. Skogsstyrelsen, Jönköping, p. 33.

Swedish Forest Agency, 2009. Stubbskörd - kunskapssammanställning och

Skogsstyrelsens rekommendationer (Stump harvesting - knowledge

compilation and Forestry Board's recommendations). In, Meddelande.

Skogsstyrelsen, Jönköping, p. 40.

Swedish Forest Agency, 2010. Swedish Statistical Yearbook of Forestry. Swedish

Forest Agency, Jonköping.

Swedish Forest Agency, 2011. Swedish Statistical Yearbook of Forestry. Swedish

Forest Agency, Jonköping.

Tamm, C.O., 1991. Nitrogen in terrestrial ecosystems. Ecological Studies 81, 1-115.

Trenberth, K.E., Fasullo, J.T., Kiehl, J., 2009. Earth's Global Energy Budget. Bulletin

of the American Meteorological Society 90, 311-323.

UNFCCC, 2011. Fact sheet: Climate change science - the status of climate change

science today. Available at http://unfccc.int/press/items/2794txt.php.

Werner, F., Taverna, R., Hofer, P., Richter, K., 2005. Carbon pool and substitution

effects of an increased use of wood in buildings in Switzerland: first

estimates. Ann. For. Sci. 62, 889-902.

Zebre, J.I., 1983. Energy properties of wood. In, Fuelwood management and

utilization seminar. Michigan State University, Michigan State University.