Biomass & soil quality Biomass & soil quality Patricia Bruneau (SNH)Patricia Bruneau (SNH)

with contribution from Willie Towers (MLURI)with contribution from Willie Towers (MLURI)

Soils in Scotland / Soil qualityBiomass production impacts on soil

– Direct and indirect impacts– Soil carbon – GHG – Climate change

Soil Classification for Scotland

Podzol (24%)

Gley soil (21%)

Mountain soil

Brown Earth (12%)

Total C-stores in UK soils. Total soil C (x 1012 g) Depth (cm) England and Wales N. Ireland Scotland 0-30 1209

172 1161

30-100 870 124 1025 >100 - - 3248 Total 2079-2890 296 5434-6948

Soil carbonScotland’s soil > 50% of C in UK soilsSOM : key properties for soil function

Properties that differentiate soils

PHYSICAL PROPERTIESDepth of horizons

Soil textureMoisture content

Soil structurePorosity

CHEMICAL PROPERTIESNutrient status

Soil reaction (alkaline, neutral, acidic)Organic matter content

BIOLOGICAL PROPERTIESSoil biodiversity

Above ground biodiversity

Inherent properties of soil soil texture organic matter content the soil reaction - whether the soil is alkaline, neutral or acidic Mineralogy

Transient properties of soil

the nutrient status - how much nitrogen, phosphorus and other nutrients are present in the soil and how available they are to plants

Depth of horizon - whether it is to a hard or contrasting layer or a feature that presents a physical barrier

moisture content - how wet the soils are, how free-draining or impeded, how susceptible to flood or drought

porosity / hydrology– how easy it is for water to move through the soil.

soil fauna – biodiversity

Soil structure

Soil quality or ‘soil health’ “the capacity of a soil to function within the ecosystem boundaries and interact positively with the environment external to this system”

The concept of soil quality was developed to define the capacity within natural or managed ecosystem boundaries of any given soil to deliver one or more of the six function of soil define below:

Food and fibre production Environmental interactions (soil/air/ water)

Ecological habitats, biodiversity

archaeology /cultural heritage (landscape)

Providing platform for construction

Providing raw material

Resilience / resistance of soil function

Scottish soil are generally in good conditions – threats and pressures

Distribution of the modelled inherent erosion susceptibility to overland flowMLURI

Threats to soil associated with biomass productionThreats to soil associated with biomass production..

Energy crops short rotation coppice (SRC) trees Forest residues And others

“Impacts of energy crops can be beneficial, neutral or negative, according to the crops grown and the land-use they replace (in the case of energy crops), and may also depend on the intensity of extraction, in the case of agricultural residues.”

• Energy grass / annual harvest• Liquid biofuel

For Bioethanol from starch/sugar crops eg cereals, potatoes, sugar beetFor Biodiesel from oil crops eg oilseed rape

Energy crops

Change to soil quality• Physical damage to soil – compaction, erosion, drainage• Contamination – sludge/ waste / fertilisation• Loss of biodiversity• Loss of carbon – increase GHG

Organic matter in arable and pasture soils

0 1 2 3 4 5 6 7 8 9 10

Humbie

Kilmarnock

Biel

Stirling

Pow

Ragdale

Forfar

Organic matter %

Pasture

Arable

Chaney and Swift (1984)

Land use change in vegetation and management alter soil biodiversity

0

10

20

30

40

50

60

ferti

liser

ferti

liser

ferti

liser

ferti

liser

ferti

liser

ferti

liser

beetles collembola earthworms enchytraeids nematodes protozoa

farming practice

expe

rimen

tal r

esult

s (n)

higher diversity

no difference

lower diversity

0

2

4

6

8

10

12

14

16

18

20

orga

nic

inpu

t

orga

nic

inpu

t

orga

nic

inpu

t

orga

nic

inpu

t

orga

nic

inpu

t

orga

nic

inpu

t

sewa

geslu

dge

sewa

geslu

dge

sewa

geslu

dge

acari beetles collembola earthwormsenchytraeids protozoa collembola earthworms protozoa

farming practice

expe

rimen

tal r

esul

ts (n

)

higher diversity

no difference

lower diversity

Stockdale et al. 2006 JNCC report 364

• Woody products less than 7cm diameter and are co-products from thinning and clearfell forestry operations.

Forest residues

Change to soil quality• Physical damage to soil – compaction, erosion• Impoverished soil fertility• Acidification• Eutrophication of water course• Degradation of landscape / habitats

• Trees planted primarily as fuel for renewable energy production

• 2-4 yrs rotations.

Short rotation coppice

Table 2: Effects of land-use conversions on losses/gains of carbon in soil

Soil losses or gains (tonnes C per ha per year)

Certainty of Data1

Reference

Losses Gains Arable to Grassland 0.3 - 1.9 * Soussana et al., 2004 Arable to Forestry 0.3 - 1.4 *** Freibauer et al., 2004 Arable to Permanent Pasture 0.27 * Post and Kwon, 2000 Grassland to Arable 0.95 - 1.7 * Soussana et al., 2004; Freibauer

et al., 2004 Grassland to Forestry 0.1 ± 0.02 * Soussana et al., 2004 Forestry to Arable 0.6 ** Freibauer et al., 2004 Forestry to Grassland 0.1 ± 0.1 * Soussana et al., 2004 Agroforestry 0.52 - 0.74 * Sharrow and Ismail, 2004 Peatland Cultivation 2.2 - 5.4 * Freibauer et al., 2004 Wetland to Arable 1.0 - 1.9 * Freibauer et al., 2004 Revegetation on: Abandoned Arable 0.3 - 0.6 ** Wetlands from Arable 2.2 - 4.6 ** Freibauer et al., 2004; Soussana Wetlands from Grasslands 0.8 - 3.9 ** et al., 2004

1* = low certainty / agreement among experts, ** = medium certainty / agreement among experts, *** = high certainty / agreement among experts

Soil as a medium for plant growth

A rab le c rop s Im p roved g rass

F ood p rod u c tion

B ioen erg y F ores try

F ib re p rod u c tion

G raz in g A m en ity

S em i-n a tu ra lveg eta tion

P lan t g row th

Upland ecosystemsDecreasing nutrient inputs

Annual to perennial

Soil biodiversity

Soil In verteb rate D iversity (Sh an n on -W ein er In d ex H ') Mean Mean±SE Mean±1.96*SE

crops/weeds

tall grass/herbs

fertile grass

infertile grass

lowland w

ood

upland wood

moorland/grass

heath/bog

Vegetation Aggregate C lass (C VS)

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

H'