Sustainable Land Management through Soil Organic Carbon Management and Sequestration

Download Sustainable Land Management through Soil Organic Carbon Management and Sequestration

Post on 02-Jan-2016

22 views

Category:

Documents

1 download

DESCRIPTION

Sustainable Land Management through Soil Organic Carbon Management and Sequestration. The GEFSOC Modelling System Mohamed Sessay Eleanor Milne. Overview of Presentation. Background Why assess SOC stocks and change Regional Approaches GEFSOC Project: Aims and Objectives - PowerPoint PPT Presentation

TRANSCRIPT

  • Sustainable Land Management through Soil Organic Carbon Management and SequestrationThe GEFSOC Modelling System

    Mohamed SessayEleanor Milne

  • Overview of PresentationBackground

    Why assess SOC stocks and change

    Regional Approaches

    GEFSOC Project: Aims and Objectives

    Methodology: GEFSOC Project Approach

    Final Output

  • BackgroundImportance of Soil Organic Carbon

    Soils represent largest terrestrial stock of C, holding between 1400 x1015 g (Post et al 1982) and 1500 x 1015 g C (Batjes, 1996)

    Approximately 2x the amount in atmosphere and 3x amount in terrestrial vegetation

    Majority of C is held in form of soil organic carbon (SOC) (Batjes & Sombreck, 1997)

  • Changes in terrestrial SOC stocks (both increase and decrease) can be of global significance and may either mitigate or worsen climate change

    SOC is vital for ecosystem functions with major influence on:- Soil structure, Water holding capacity- CEC - Ability to form complexes with metal ion - Fertility (to store nutrients) - Above and below ground biodiversity

  • Why Assess SOC Stocks and Changes?Knowledge of SOC stocks and changes would help us device plans for:

    Appropriate management of soils to increase SOC levels to increase productivity and sustainability of agricultural systems

    The sustainable management of ecosystems

    The mitigation of GHG emissions

    The likely impact of climate change on soils/ecosystems in the future (Jones et al 2004)

  • The Kyoto ProtocolThe Kyoto Protocol - CO2 emissions can be offset against removal of C from the atmosphere

    1st commitment period 2008 2012

    Article 3.3, forestry activities Article 3.4, management of agricultural soils

    Changes before 2008?

    UNFCCC -Inventories of CO2 emissions from LUC

  • Why assess SOC Stocks and Changes?

    Rothamsted long term experimentsVersailles long term experimentsSOC is sensitive to changes in land use

  • Why assess SOC Stocks and Changes?Knowledge of SOC stocks and changes would help us device plans for:

    Appropriate management of soils to increase SOC levels to increase productivity and sustainability of agricultural systems

    The sustainable management of ecosystems

    The mitigation of GHG emissions

    The likely impact of climate change on soils/ecosystems in the future (Jones et al 2004)

  • Important Areas GloballyRates of land use change greatest in the tropicsFeed 70% of the population (Lal and Sanchez 1992)Increasing demand for land will be met by converting forest and pasture C release~ 26% of global SOC stocks are in the tropics (Batjes 1996)Relatively little information on soils and how they react to land use changeThe Tropics

  • Important Areas GloballyLow SOC stocks per unit areaOccupy ~47% of land surface (Lal 2003)Many areas are degraded with the potential for rehabilitationDrylands

  • Problem of ScalePlot ScaleMany studies, site specific, limited value Global ScaleRegional and National ScaleAllows consideration of varying land use policy, relevant to resource managementInformative, limited affect on policy at ground level

  • A generically applicable systems for estimating SOC stocks at national or regional scale is necessary to:

    Increase the accuracy of global estimates of SOC stocks and changes

    Understand the consequences of land use change for the global C cycle

    Understand the GHG mitigation potential of changes in land use/land management

    Identify geographic areas with potential for C release or sequestration

    Allow countries in tropical and arid areas to take advantage of opportunities presented through global carbon trading, (CDMs)

  • Regional ApproachesApproaches used estimate changes in SOM/SOC include IPCC inventory method:-Series of factors (climate, soil type, history, tillage & productivity)20 year periodIdentifies changes between first and last year of the 20 year periodSimple accounting methodSoil C stock is a function of soil C under native vegetation and changes in land use or land management

  • Regional ApproachesStatistical approaches:

    Regression based approaches (Gupta and Rao 1994, Smith et al 2000, 2001)

    Regression approaches based on spatial soil databases (Kern and Johnson 1993, Kotto-Same et al 1997)

    Local variability in soil conditions

  • Process Based Modelling ApproachDynamic SOM models linked to spatial data bases

  • Aims of GEFSOC Project

    To improve national assessment methodologies relating to land use options and UNFCC requirements and to support core activities of the GEF IEM OP and IPCC by developing and demonstrating a generic tool that quantifies impact of land use/management and climate change scenarios on carbon sequestration in soils at the national and regional scale

  • Specific Research ObjectivesIdentify and use long term experimental data sets to systematically evaluate and refine modelling techniques to quantify carbon sequestration potential in tropical soils

    Define, collate and format national-scale soils, climate and land use data sets to use them in development of a coupled modelling-GIS tool to estimate soil carbon stocks

    Demonstrate this tool by estimating current soil organic carbon stocks at the national and regional scale (using The Brazil Amazon, The Indo-Gangetic Plains, India, Jordan and Kenya as case studies) and to compare these estimates with the existing techniques of combining soil mapping units and interpolating point data

    Quantify the impact of defined changes in land use on carbon sequestration in soils with a view to assisting in the formulation of improved policies to optimise resource use in the four case study countries Brazil, India, Jordan and Kenya

  • Case Studies

  • Methodology

  • GEFSOC Project ApproachTwo soil organic carbon models were chosen

    Roth-C (developed in the UK) is a SOM model that accounts for the effects of soil type, climate, moisture content and plant cover on turnover of organic C in soils. Uses monthly time-step to calculate total SOC and microbial biomass content

    Century (developed in the United States) is a general ecosystem model which stimulates the dynamic of C, N, P and S in different plant/soil systems. Has plant productivity, water movement and nitrogen leaching sub models

  • Evaluated under many conditions (including forestry, grasslands and arable in the tropics)

    Two of the most widely used SOM models

    Good performance in comparison of 9 models (Powlson et al 1996, Smith et al 1997)

    Used in regional applications

    Model GIS linkageRoth CCentury

  • Rothamsted Carbon Model (Roth C)Colman and Jenkinson (1996)

  • Century Ecosystem Model (Century)Parton et al (1987)

  • Stage 1. Model Evaluation

  • Stage 2. National Data

  • Stage 3: Model/GIS coupling

  • Stage 4: Current StocksCurrent land useGlobal level information +Landscape level

  • Stage 5. Future Stocks

  • Regional carbon stocks: current and futureSOC stocks in the 0-20cm soil layer for the year 1990SOC stocks (t C ha-1)

  • Regional carbon stocks: current and futureSOC stocks (t C ha-1)SOC stocks in the 0-20cm soil layer for the year 2030

  • The Final Output A transferable system for estimating SOC stocks and changes in a range of soils and climatic conditions (The GEFSOC Modeling System), designed to help in formulating national and sub-national land management and carbon sequestration policy by:

    Quantifying current soil organic carbon stocks at national and sub-national level and

    (ii) Analyzing the impacts of land management options on carbon storage , GHG emissions and sequestration possibilities

  • Website ReferenceThe GEFSOC Modelling System can be downloaded free of charge via the project website http://www.nrel.colostate.edu/projects/gefsoc-uk

    And the UNEP website www.unep.org

    And is accompanied by a use manual

  • THANK YOU FOR

    YOUR ATTENTION

    So why do is it important for us to assess soil organic C stocks and changes?Soils represent a significant stock of C making up 2/3 of C held in the biosphereWith approximately 1500 Pg stored in the top 100cmThis is twice the amount held in the atmosphere and 3 times the amount held in terrestrial vegetation

    CLICKExcluding calcareous soils, most of this C is held in the form of Soil Organic Carbon, which is vital to the functioning of ecosystems and agricultural systems, being a major determinant of soil structure, water holding capacity, the soils ability to form complexes with metal ions, soil fertility and above and below ground biodiversity.

    In addition to these benefits there is also the potential that soils have for sequestering or storing C, therefore playing a role in mitigating the effects of rising atmospheric CO2 levels.

    This is recognised by the Kyoto Protocol which will allow CO2 emissions to be offset against C credits (or removal of C from the atmosphere) during the first commitment period (2008 2012)

    Specifically article 3.3 refers to sequestering C through forestry activities, and this includes sequestration of C in forest soils as well as biomass and article 3.4 talks about the sequestration of C through the improved management of agricultural soils.

    Many countries will implement changes before 2008 and hence need to be able to assess their options and make appropriate plans now.

    There are also requirements for UNFCCC signatory countries to provide inventories of CO2 emissions from Land Use Change, a large part of which are emissions from soils.

    Understanding the part that soils play as sources or sinks of greenhouse gases is, therefore crucial.

    Past long-term experimental studies have shown that soil organic C is highly sensitive to changes in land use, with changes from native ecosystems such as forest to agricultural systems, almost always resulting in a loss of SOC

    Conversely land use change from agricultural systems back to native ecosystems such as forest tend to lead to an increase in SOC. As shown by the Broadbalk Wilderness long term experiment, carried out at Rothamsted Research in the UK.

    The subsequent management of agricultural land following land use change also effects SOC levels and depends on the level of tillage and the use of residues manures and cover crops. Cole et al estimate historical losses of C from soils due to cultivation to be ~ 55 Pg.

    Soils therefore have a large potential for C release or C sequestration.CLICKAnd make a significant contribution to the estimated 1.6 Gt of C released to the atmosphere each year as a result of land use change.

    So in answer to our question why do we need to assess soil organic C stocks and changes we can say that doing so would

    Help us devise plans for the sustainable use of soils and ecosystems

    Help us devise plans for the mitigation of GHG emissions

    And would help us plan for the likely impacts of climate change on soils and ecosystems in the future

    Rates of land use change are greatest in the tropics, where the demand for agricultural land is increasing as population levels rise.This makes the tropics an important area in terms of SOC stocks, along with the fact that tropical agricultural currently feeds 70% of the worlds population a figure which is likely to increase in the future Much of this demand will be met by converting native forest to cultivated or pasture land, releasing C from soils to the atmosphere (Batjes 1997). Subsequent poor management of newly converted land can then lead to further losses of SOC and eventual land degradation. The importance of land use change in this area becomes apparent when we consider that the tropics hold 26% of global SOC stocks (when considering the first 1m of soil).

    Despite the importance of tropical areas in terms of the percentage of global SOC stocks they account for and the vulnerability of these stocks, we still have relatively little information about soils and how they react to land use/land management practices in these areas.

    The same can be said of dry lands or arid regions that have relatively low SOC stocks per unit area, but are never the less important globally because they occupy such large areas of the land (47 % according to Lal 2003).

    Also many pastures and crop lands in dry land areas are degraded, with potential for rehabilitation and therefore C sequestration

    A few studies of SOC stocks have been carried out in tropical and arid areas, however most studies of soil C stocks and fluxes have been carried out in Europe and North America, with tropical and arid areas being underrepresented. This is apparent if you look at the participants in the GCTE Soil Organic Matter Network a network of scientists who have carried out long-term experiments which have measured soil organic matter and developed soil organic matter models.The result of this is that most SOC models have been developed using temperate data sets and and there are problems applying them to tropical and arid conditions, where rates of mineralisation and production are different.There is, therefore, a need to develop a generic system which is applicable to a much wider range of climates and soil types.In addition to this there is a problem of scale. Many studies of soil C stocks and changes have been carried out at the plot scale, however these are by their nature site specific, making them of limited value.

    Global scale predictions have also been made and are informative but have limited affect on policy at the ground level

    whereas regional and national scale predictions allow the benefits of varying land use policies to be considered, potentially leading to appropriate resource management in the future. Although examples of national and regional scale estimates do exist they are mainly confined to temperate areas and, there is a crucial need for estimates to be made at this scale for different soil types and climates. National and regional scale estimates of SOC stocks and changes made using a consistent method could then be amalgamated to give global predictions with increased accuracy.ReadReadSeveral different approaches have been used to estimate changes in SOC stocks at the regional scale.

    The IPCC method for determining inventories of green house gas emissions, can be used to account for terrestrial changes in soil C storage in both plant biomass and soils.A series of factors (climate, soil type, land use history, etc.) are used to estimate changes in soil C stocks over a 20 year periodThe method identifies changes between the first and last year of the 20 year period and is a simple accounting method.The soil C stock derived is a function of soil C under native vegetation and changes in land use or land management.Other studies have used regression approaches, where long term experimental data sets are simply extrapolated into the future, assuming a linear change over timeor regression approaches based on spatially explicit soil data bases. This approach has the advantage of being able to take into account local variability in soil conditions. Both these approaches assume a constant rate of change in SOC, which is unrealistic, given the fact that many studies have shown rapid initial changes in SOC immediately following land use change, followed by a slower rate of change.

    Neither of these approaches fully account for the fact that change in SOC is a dynamic process or that changes in land use and climate are also likely to occur in a dynamic fashion.

    Processed based models can be used to take a more dynamic approach. Soil organic matter models (designed for site scale application) can be linked to spatial data bases through Geographic Information Systems.This approach allows account to be taken of local variability in soil and climate conditions and has the added advantage of being able to identify specific geographic areas of SOC stock change. And it is third dynamic approach that our project has taken

    ReadThe Brazilian Amazon case study is being carried out by CENA, part of The University of Sao Paulo, Brazil in association with IRD France.The case study encompasses the entire Brazilian Amazon which covers an area of over 5 million km2. Rainfall can reach up to 3000mm yr-1.

    The Jordanian case study is coordinated by The Badia Research and Development Centre. It includes the whole country which has an area of 89,206 km2The climate ranges from sub-humid in the Jordan valley where 90% of Jordans population live to hyper arid80% of the country is classed as desert, having annual rainfall of less than 200mm/yr

    The Indian case study is concentrating on the Indian part of the Indogangetic plains, which cover an area of 467,000 Km 2The case study is being coordinated by The N B S S L U P, part of the I C A R.The indo-gangetic plains are overwhelmingly flat, agricultural lands, with a reasonable amount of precipitation, which increases from West to East. They cover approximately 20% of the land area of India and 40% of the countries population live here.

    Our 4th case study is Kenya. This is being coordinated by Kenya Soil Survey.The case study includes the whole of Kenya which has an area of nearly 583,000 km2There are 4 major relief zones in Kenya READClimate varies from arid to humid and most of the country is arid to semi arid.The specific research objectives of the project have been to:READ

    I. that quantify C sequestration potentialThese objectives have formed the basis of the project methodology .

    Which is shown here broken down into 5 of stages:

    ReadTwo soil organic matter models were chosen for the study, RothC developed in the UK and Century developed in the USA,These two particular models were chosen because: READ

    They are 2 of the most widely used SOM models.

    There are examples of them having been linked to GIS for specific applications in the past.

    RothC is a soil carbon model that accounts for the effects of soil type, temperature, moisture content and plant cover on the turnover of organic C in soils.It uses a monthly time-step to calculate total organic C and microbial biomass.SOC is split into 4 active compartments and a small amount of inert organic matter.-Both DPM and RPM decompose to form CO2, Bio and Humus and the proportion is determined by clay content of the soil.-The rate of decomposition is determined by rate modifiers such as soil moisture, temperature and plant cover.

    - Century is a general ecosystem model which simulates the dynamics of C,N,P and S in different plant/soil systems. Unlike Roth-C it has plant productivity, water movement, and nitrogen leaching sub-models Century includes 3 organic matter pools, active slow and passive, with the passive being equivalent to the IOM in RothC

    Stage 1 of the project involved the evaluation and refinement of the two soil carbon models in order to assess and improve their performance in the conditions found in each case study area. This procedure is necessary as the application of non-evaluated, unmodified temperate models to tropical conditions can lead to over or under estimations of SOC turnover. In order to do this, time series data sets, which had measured change in SOC, were collated in each of the case study regions.

    The second stage was to collate and format national and regional scale soils climate and land use datasets to act as model input data. This data was needed to carry out the national and regional SOC model runs. The data was put into a standardised format to ensure comparable outputs, consistent with the aims of a generically applicable system. Subsequent use of the GEFSOC system in other case study areas should follow the same formatting conventions.

    The third stage involved the linkage of the two SOM models to a GIS system. This work was carried out by The Natural Resource Ecology Laboratory, USA in conjunction with Rothamsted Research, UK. The system includes two primary elements;- a graphical user interface that allows users to interact with the modelling system, and a set of program modules that run the CENTURY and RothC models and the IPCC method for calculating soil C.The IPCC method is included so that output from the Roth-C and Century components can immediately be compared with output from another standardised method. Further details on the development of the modelling system are given this afternoon.

    Stage 4. Was to assess current SOC stocks using the coupled modelling GIS tool (or GEFSOC system).

    Current land use was determined in each case study area for the most recent year possible, depending on data availability. Global level information (population, transportation infrastructure and agro-ecological zone) was amalgamated with landscape level information.

    The final stage was then to assess likely changes in SOC stocks under a range of plausible land use change scenarios for the period between 2000 and 2030.

Recommended

View more >