Biomass & soil quality Patricia Bruneau (SNH) with contribution from Willie Towers (MLURI) Soils in Scotland / Soil quality Biomass 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%)

Soil carbon Scotland’s soil > 50% of C in UK soils SOM : key properties for soil function

Properties that differentiate soils PHYSICAL PROPERTIES Depth of horizons Soil texture Moisture content Soil structure Porosity CHEMICAL PROPERTIES Nutrient status Soil reaction (alkaline, neutral, acidic) Organic matter content BIOLOGICAL PROPERTIES Soil 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 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 beet For 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

Chaney and Swift (1984)

Land use change in vegetation and management alter soil biodiversity Stockdale et al 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

Soil as a medium for plant growth Upland ecosystems Decreasing nutrient inputs Annual to perennial

Soil biodiversity