Department for Environment, Food and Rural Affairs

Research project final report

Project title Assessment of the response of organo-mineral soils to change in management practices

Sub-Project ii of Defra Project SP1106: Soil carbon: studies to explore greenhouse gas emissions and mitigation

Defra project code SP1106

Contractor SKM Enviros organisations Rothamsted Research / North Wyke

CEH

Cranfield University

ADAS

Report authors Roland Bol ([email protected]), Martin Blackwell, Bridget Emmett, Brian Reynolds, Jane Hall Anne Bhogal, Karl Ritz.

Project start date October 2010

Sub-project end May 2011 date

Contents

Title page 1 Executive summary 7 Background to the project 10 Objectives 12

Section 1. Definition of organo-mineral soils in England and Wales 1.1. Rationale 13 1.2 Comparison with other definitions of organo-mineral soils 17 1.3 Organo-mineral soils in an European context 19

Section 2. Distribution of organo-mineral soils in England and Wales 2.1 Methods 22 2.2 Distribution organo-mineral soils in relation to national boundaries 26 2.3 Distribution of organo-mineral soils in relation to Environmental Zone 30 2.4 Distribution of organo-mineral soils in relation to land cover type 31 2.5 Distribution of organo-mineral soils in relation to designated areas 32 2.6 Estimates of C storage in organo-mineral soil (0-15 cm) using CS2007 data 39

Section 3. Ecosystem services provided by organo-mineral soils 3.1 Introduction 42 3.2 Approach 42 3.3 Initial assessment of ecosystem services by land cover on organo-mineral soils 47 3.4 Assessment of ecosystem services of organo-mineral soils by environmental zone 52 3.5 Assessment of ecosystem services of organo-mineral soils by soil type 53 3.6 Impacts of climate change on ecosystem services from organo-mineral soils 55 3.7 Comparison of ecosystem services delivered by organo-mineral soils with organic soils and mineral soils 56 3.8 Concluding remarks and comments 59

Section 4. Best practices for managing carbon in organo-mineral soils 4.1 Introduction 61 4.2 Carbon turnover and storage in soils 61 4.3 Approaches 62 4.4 Best Practices for retaining carbon in organo-mineral soils 64 4.5 Designated areas 76 4.6 Conclusions 76

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Section 5. Impact of changing land use and management on ecosystem services provided by organo-mineral soils 5.1 Approach 77 5.2 Results 78 5.3 Summary 83

Final conclusion 84

Acknowledgements 84

References 84

Annex 1 92

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List of Tables

Table 1 Definitions of organo-mineral Soils – based on the National Soil Map of England and Wales Table 2 WRB Soil Reference Groups representing organo-mineral soils Table 3 LCM2000 land cover types used in the analysis of organo-mineral soils Table 4 The Environmental Zones used in Countryside Survey Table 5 Areal extent (ha) of organic-soils in England and Wales derived from NSRI data Table 6 Areas of organo-mineral soils in Wales estimated by SP0116 and the ECOSSE project (SEERAD, 2007) Table 7 Area (ha) of each soil category within each Environmental Zone Table 8 Organo-mineral soil-land cover type combinations showing areas (ha), percentage of total area of each soil category in England and percentage of total area of each LCM2000 land cover type in England for those combinations accounting for 10% or more of the total area (shaded grey) Table 9 Organo-mineral soil-land cover type combinations showing: areas (ha); percentage of total area of each soil category in Wales and percentage of total area of each LCM2000 land cover type in Wales for those combinations accounting for 10% or more of the total area (shaded grey) Table 10 Areas of organo-mineral soils in England and Wales included within designated areas Table 11 Estimated soil (0-15 cm) C stocks held in each organo-mineral soil category across England and Wales (E&W) in 2007 and comparison with soil (0-15 cm) stocks for E&W and Great Britain (GB) from Emmett et al . (2010) Table 12 Estimated soil (0-15 cm) C stocks held in organo-mineral soils in England and in Wales in 2007 and comparison with country level and GB soil (0-15 cm) C stocks from Emmett et al . (2010) Table 13 Assessment of ecosystem services delivered by the dominant land cover types occurring on organo-mineral soils in England and Wales Table 14 Dominant (>5% total spatial extent of soil type within each environmental zone) land cover types for three organo-mineral soil types Table 15 Dominant (>5% total spatial extent of environmental zone) land cover types for organo-mineral soils occurring within five environmental zones Table 16 Assessment of ecosystem services of organo-mineral soils in England and Wales by environmental zone Table 17 Assessment of ecosystem services of organo-mineral soils in England and Wales by soil type Table 18 Qualitative comparison of ecosystem services delivered by organic, organo-mineral and mineral soils in England and Wales Table 19 Potential best practices for retaining carbon in organo-mineral soils

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Table 20 Summary matrix of the relative benefits/disbenefits of best practices for semi-natural grassland Table 21 Summary matrix of the relative benefits/disbenefits of best practices for improved grassland Table 22 Summary matrix of the relative benefits/disbenefits of best practices for cropland Table 23 Summary matrix of the relative benefits/disbenefits of best practices for forestry Table 24 Summary matrix of the relative benefits/disbenefits of best practices for heathland Table 25 Potential impact of changing to ‘best practice for retaining carbon in organo-mineral soils’ on overall ecosystem services for semi-natural grasslands Table 26 Potential impact of changing to ‘best practice for retaining carbon in organo-mineral soils’ on overall ecosystem services for improved grassland Table 27 Potential impact of changing to ‘best practice for retaining carbon in organo-mineral soils’ on overall ecosystem services for cropland Table 28 Potential impact of changing to ‘best practice for retaining carbon in organo-mineral soils’ on overall ecosystem services for forest Table 29 Potential impact of changing to ‘best practice for retaining carbon in organo-mineral soils’ on overall ecosystem services for heathland

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List of Figures

Figure 1 Reference Section for Peat soils Figure 2 Limiting percentages of organic carbon/organic matter and clay for organic and organo-mineral soils. Figure 3 Distribution of Leptosols in Europe Figure 4 Distribution of Umbrisols in Europe Figure 5 Distribution of Podzols in Europe Figure 6 Distribution of Gleysols in Europe Figure 7 Land Cover Map 2000 for England and Wales showing broad groupings of land cover types. Figure 8 Map of the Environmental Zones for England and Wales used in the analysis of organo-mineral soils by land cover type Figure 9 Distribution of organo-mineral soils in England and Wales. Figure 10 Percentage of the total areas of England, Wales and England and Wales covered by organo-mineral soils. Figure 11 Percentage cover of each soil category by Environmental Zone in England and Wales Figure 12 Percentage of the total area of each organo-mineral soil category in England falling within a designated area. Figure 13 Percentage of the total area of each designation in England underlain by organo- mineral soils. Figure 14 Percentage of the total area of each organo-mineral soil category falling within designated areas in Wales. Figure 15 Percentage of the total area of each designation in Wales underlain by organo-mineral soils. Figure 16 Land use capability map of England and Wales with respect to suitability for grazing winter cereals Figure 17 Key elements of the soil carbon budget Figure 18 Distribution of broad land-cover classes associated with organo-mineral soils in England and Wales

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Assessment of the response of organo-mineral soils to change in management practices

Executive summary

A generic definition of organo-mineral soils is those soils that have a surface horizon (otherwise referred to as topsoil) relatively rich in organic matter but with less than 40 cm of peaty surface layer, and include rankers, rendzinas, podzolic and gleyed soils. These are further defined to three types of organo-mineral soils: (1) Humose topsoil greater than 15 cm thick; (2) Peaty loam or peaty sand topsoil greater than 15 cm thick; or (3) Peat less than 40cm thick starting at or near the surface, or less than 30 cm thick where the peat lies directly on bedrock. Using our definition of organo-mineral soils, it was estimated that they occupy 30.5 % of Europe’s land surface.

The main occurrence of organo-mineral soils in England is in the north and west, especially the Pennines and the Lake District. Organo-mineral soils are found throughout much of Wales, and are typically associated with the upland areas of the Cambrian Mountains, the Brecon Beacons and Snowdonia. More isolated, discrete areas of organo-mineral soils are associated with the moors of south-west and north-east England, along with areas of heathland in the South and low lying areas in East Anglia.

Organo-mineral soils occupy approximately 1.6 million hectares of England and Wales or 10.5 % of the land area; when considering Wales alone, this figure increases to 20.5 %. Grassland is the most common land use for organo-mineral soils in England and Wales, but they also occur under cropland, forest and heathland, with more than 40% of heathlands established on organo- mineral soils.

In Wales, and to a lesser extent England, organo-mineral soils contribute significantly to the shallow store of soil carbon (C) held by these countries. In England and Wales 14.7% of the total topsoil (0-15 cm) C stock occurs in organo-mineral soils. In England, organo-mineral soils contain 12.5% of the 795 Tg of C present in topsoil, whilst in Wales they contain 25.5% of the 159 Tg of the topsoil C.

Importantly, organo-mineral soils occupy landscape positions that make them highly vulnerable, attracting a variety of agricultural and forestry activities which may often involve cultivation by ploughing, addition of fertiliser and lime as well as drainage. Additionally, they are commonly subjected to major changes in land management such as afforestation of grasslands. These activities can lead to significant changes in soil C cycling and storage, which will be further influenced by responses to climate change. Furthermore, despite uncertainties in the precise quantities, it is evident that a substantial proportion of the C present in organo-mineral soils occurs in the upper part of the profile, which is most vulnerable to the effects of environmental change.

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A total of 10 land cover types were found to have significant occurrence (5 % or more of the total area of each soil type in each environmental zone), namely: arable and horticultural cropland; improved, rough, acid and bracken grassland; deciduous and coniferous forest; dense dwarf shrub and open dwarf shrub heathland. Each of the land cover types was assessed with regard to the ecosystem services they delivered in a semi-quantitative way. This was not so much a review, but an assessment based on expert opinion of the authors and by consultation with other experts. This approach was necessary because generally there is very little information available in the scientific literature on the specific ecosystem services that organo-mineral soils deliver. The assessment found that: (1) Organo-mineral soils generally deliver a wide range of ecosystem services, (2) Intensive agricultural systems (e.g. arable, horticultural or improved grassland systems) on organo-mineral soils generally deliver different combinations of ecosystem services to those delivered by less intensive or semi-natural systems, (3) Intensive agricultural systems on organo-mineral soils are important for the delivery of provisioning services, but have a (more) detrimental effect on the environment, (4) Woodland (especially deciduous) delivers the highest number of ecosystem services of all the significant land cover types occurring on organo-mineral soils, and generally to a higher degree than other land cover types, (5) Nearly all provisioning and cultural services delivered by all three organo-mineral soil types are positive, while regulating and supporting services are delivered both positively and negatively, and (6) With respect to predicted future climate change: a) intensive agricultural land is likely to be impacted more than less intensive land, b) most of the climate change impacts are likely to be detrimental or negative, however c) there is still great uncertainty over these impacts because of the lack of information on how soil biota and plants will respond and interact under climate change.

A range of methods for maintaining or increasing soil C storage were identified in this study for both mineral and peat soils, with good agreement on best practices. There has been a paucity of studies specific to organo-mineral soils and the effects of changes in land-use or management practices on the C content of these soils has had to be inferred from studies on mineral (or peat) soils, or derived from first principles on the behaviour of C in soils. The study identified a total of 15 ‘best practices’ which were compared in terms of their potential benefit to soil C, likely uptake and potential environmental impact (e.g. impact on diffuse water pollution, biodiversity, erosion, greenhouse gas emissions). The greatest benefit (to soil C) was considered to arise from land use change options, such as establishing grassland or woodland on cropland and increasing the height of the water table in grasslands. However, these are extreme changes in land-use that are unlikely to be adopted without the provision of substantial financial incentives. Many of the practices were compatible with the way agricultural land management is currently regulated (via Cross Compliance) and incentivised (via agri-environment schemes). Practices that would most likely be delivered via Cross Compliance measures and incorporated into the requirement to maintain soils in Good Agricultural and Environmental Condition include:

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- Reducing stocking levels on grassland - Encouraging the use of organic material additions - Introducing rotational grass - Using reduced or zero tillage to establish crops

Practices that would most likely be delivered via agri-environment schemes include:

- Establishing woodland/forestry on grassland/cropland - Increasing the height of the water table in grasslands - Establishing grassland on cropland.

The potential impact of changing to ‘best practice for retaining C in organo-mineral soils’ on various ecosystem services varies considerably between land use types. A complex picture of responses was suggested, but is currently only based on expert advice and opinion, with very little underpinning field based experimental information. The delivery of food and fibre production by intensive agriculture is often to the detriment of many other ecosystem services, in line with Pilgrim et al . (2010). Woodland (especially deciduous) provides the greatest range and degree of services of all evaluated land cover types, but to the detriment of food production.

Increasing the quantity of C in organo-mineral soils can result in some unintended and both desirable and undesirable consequences, in part due to the fact that the soil C and N cycles are intimately linked. Increased soil C may affect the release of other greenhouse gases (GHG) (e.g. nitrous oxide (N2O) and methane (CH 4)) or diffuse water pollution (nitrate (NO 3) and phosphorus (P)) i.e. there is a risk of ‘pollution swapping’ where the reduction of one form of pollution increases another, although in some cases (e.g. reducing stocking density), emission of gaseous and water-borne pollutants may be reduced.

We conclude that several knowledge gaps or uncertainties still exist: (1) A lack of field measurements (for UK conditions) of the potential C storage/saving benefits of implementation of many of the proposed methods and (2) Variable impact responses of ecosystem services for the different land use cover types for implementing ‘best practice for retaining C in organo- mineral soils’ and (3) Uncertainty of how the timescale over which they are considered may influence which of ‘best’ management options’ should be selected for implementation. Therefore, the overall evidence base to support any policy implementation remains weak.

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SP1106: SOIL CARBON: STUDIES TO EXPLORE GREENHOUSE GAS EMISSIONS AND MITIGATION

SUBPROJECT ii: Assessment of the response of organo-mineral soils to change in management practices

This subproject was undertaken by Dr. Roland Bol and Dr. Martin Blackwell (Rothamsted Research, North Wyke), Prof. Bridget Emmett, Prof. Brian Reynolds and Dr. Jane Hall of CEH Bangor, and Dr. Anne Bhogal of ADAS) and Prof. Karl Ritz, Dr. Bob Jones and Dr. Ian Truckell (Cranfield University). Where required we drew on the wider expertise within the SP1106 team, of which Dr. Phil Wallace (PW) of SKM Enviros (Enviros) was the overall project manager.

Background to the project Defra’s SP0567 (Assembling UK-wide data on soil carbon (and greenhouse gas fluxes) in the context of land management) project highlighted organo-mineral soils as a potential source of uncertainty with regard to the behaviour and fate of soil organic C, and consequently the total soil C stocks and fluxes in the UK. However, research on these soils tends to be hidden under more generic topics. For example, many case studies on the environmental effects of plantation forestry on organo-mineral soils in the uplands are undertaken, but often organo-mineral soils are not explicit in the title or abstract of the report or paper. A recent study commissioned by the Scottish Executive and Welsh Assembly Government (ECOSSE Estimating Carbon in Organic Soils – Sequestration and Emissions) addressed aspects of the knowledge gap about the distribution, C content, management and likely response to climate change of organo-mineral soils in Scotland and Wales (SEERAD, 2007). A follow-up study to ECOSSE in Wales looked at case study applications of the ECOSSE C model to selected field research sites (WAG, 2009) in order to weigh up the implications for soil C of land use versus climate change. The outcomes from this project will be critically reviewed to identify key messages for land management on organo-mineral soils in England and Wales under a changing climate.

Previous studies have suggested that in the UK organo-mineral soils are extensive comprising ca. 40% of land cover. Furthermore these soils hold around 22% of the soil organic C stock, which is distributed as ca. 10% in England, ca 18% in Wales, ca 29% in Scotland and ca 13% Northern Ireland. The 2007 SEERAD study estimated that organo-mineral soils cover 17% of the land area (3592 km 2) of Wales compared to just 3% for peats in that country (SEERAD, 2007). Furthermore, the study highlighted that for Wales, organo-mineral soils when compared with peat soils accounted for 74.5 MtC compared to 121 MtC for C storage and 40% of the total soil C held in organic soils. In comparison, for Scotland, organo-mineral soils accounted for 35% of the total soil C held in organic soils (SEERAD, 2007). Thus organo-mineral soils are not only spatially extensive but also hold significant quantities of soil C. More importantly they occupy a landscape position that makes them highly vulnerable to being managed for a variety of

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agricultural and forestry activities which may often involve cultivation by ploughing, addition of fertiliser and lime as well as drainage. Additionally they are commonly subject to major changes in land management such as afforestation (Reynolds, 2007). These activities can lead to significant changes in soil C cycling and storage which will be further influenced by responses to climate change (Jones and Emmett, 2009).

Consideration must be given to what Janzen (2006) described as the soil C dilemma; ‘Shall we hoard it or use it?’ Sequestering C in soils is often seen as a 'win-win' proposition; it not only removes excess CO 2 from the air, but also improves soils by augmenting organic matter which is an important energy and nutrient source for biota. Organic matter is useful biologically, when it decays and is being used by micro-organisms to drive the soil system. It is a function of input and outputs of the system (FAO, 2010), albeit not necessarily solely dependent upon the size, activity and composition of the microbial biomass present (Kemmitt et al ., 2008). Hence it is important when thinking about soil C dynamics to tune them for the services expected of our ecosystems. This demands the assessment of the role of biology along with other disciplines (soil chemistry and physics), particularly when we contemplate the stresses soon to be imposed by upcoming climate and land use changes. Clearly, organo-mineral interactions and associated stabilisation mechanisms are fundamental to the retention of C and organic matter in soils (see review Kögel-Knabner et al ., 2008; Bol et al ., 2009) and hence to the maintenance of soil functioning and ecosystem service provision.

Protecting and enhancing soil organic C quantities is a key component of the Defra Soils Evidence Plan 2011/12 (Defra, 2011), and will have beneficial effects for overall soil quality/fertility, C storage and erosion control. This cannot be achieved if incomplete knowledge exists on specific soil types, such as organo-mineral soils, especially when they cover significant areas of the UK and/or contain a significant amount of C. Such lack of information will also hinder attempts to develop specific recommendations for ‘best farming practices’ on these soils with respect to soil C, in order to build on suggestions provided in Defra’s SP08016 ‘Best Practice for Managing Soil Organic Matter in Agriculture’.

With the increasing global demand for a steady supply of nutritious food, there is increasing recognition that we must manage our land for multiple purposes or ecosystem services (Pilgrim et al ., 2004, 2010; Porter et al ., 2009). These pressures almost certainly have to involve bringing new areas of land into production and increasing outputs per unit area on existing managed land. Historically, both strategies have reduced the provision of other ecosystem goods and services that are also important to human well-being (Millennium Ecosystem Assessment, 2005b, Millennium Ecosystem Assessment 2005a, McIntyre et al ., 2009) with the priority given to meeting contemporary human needs at the expense of future requirements. This is something that we can no longer afford to do. Soil is a natural resource that, if well managed, is essential for supporting future demands for ecosystem services (Posthumus et al ., 2010 and Defra sub project

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SP1106, this report). The ecosystem services associated with healthy soil function include food production, water quality, water regulation (hazard control), air quality regulation, climate regulation, nutrient cycling, biodiversity conservation and landscape quality. With the publication of Defra’s Soils Evidence Plan (Defra, 2011), steps have been taken towards a greater understanding of the delivery and trade-offs associated with the provisioning of these ecosystem services from soils, e.g. Defra subproject SP1106 through a literature review to assess the current knowledge on the threats to healthy soils due to external pressures, namely erosion, compaction and loss of organic matter (Defra, 2011). However as yet there has been no specific analysis of these for organo-mineral soils and their vulnerability.

Overall objectives 1. Assessment of the response of organo-mineral soils to change in management practices through review, using best-available evidence or expert judgement where sufficient knowledge is not available. 2. Identify and explore the ecosystems services provided by organo-mineral soils. 3. Assess and prioritise best practice options and likelihood of their acceptance and uptake by farmers and land managers. This will be achieved by compiling best-available evidence and on-the-ground expertise from scientific experts, land manager, farmers and members of stakeholder groups

Specific Objectives 1a. Assess the definitions of organo-mineral soils in the UK and compare to other countries. 1b. Review and identify the locations and types of these soils in England and Wales, their formation processes, cycling of C and the management practices that exist on them. 1c. Review the existing evidence base on the current status of response of organo-mineral soils to change in management practices in England and Wales underpinned by the review under 1b. 2a. Review the ecosystems services that organo-mineral soils deliver under varying land use, environmental zone and soil type and how these services are affected by both changes in management and climate change issues. 2b. Compare the provision of ecosystem services by organo-mineral soils with mineral and organic soils. 3a. Review the potential best practice(s) currently in use or proposed for retaining soil C in organo-mineral soils. 3b. Evaluation of current status of farming practices with respect to ‘best’ practice for retaining soils C in organo-mineral soils. Compare with outcomes from 3a.

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Section 1: Review of organo-mineral soils

1. Definition of organo-mineral soils in England and Wales (RJA Jones, IG Truckell and K Ritz; NSRI, Cranfield University)

1.1 Rationale In the soil classification of England and Wales, organic matter content is used to differentiate soils at Soil Major Group, Soil Group and Soil Subgroup levels (Avery 1980). A distinction is made between soil materials and soil classes. Hence peat as a soil material is defined as having more than 20% organic carbon (C)), which is equivalent to ~>30% organic matter. To classify soils, a Reference Section of 80cm depth is adopted (see Figure 1).

Figure 1 Reference Section for Peat soils (after Clayden and Hollis, 1984, p.13).

However, Peat soils, as a Major Group in the classification, are defined as having a layer of peat material at least 40cm thick within the Reference Section, usually starting at the surface (Figure 1). Other soils are then classified as humose-mineral or non-humose mineral soils (see Figure 2). An overtly simple definition of organo-mineral soils is not straightforward, but a pragmatic

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generic definition is to describe them as soils that have a surface horizon relatively rich in organic matter: beyond this, rather more detail is necessarily required.

For the purposes of this project, we then define organo-mineral soils as those rich enough in organic matter to have: (1) Humose topsoil > 15cm thick; (2) Peaty loam or peaty sand topsoil (<20% organic carbon) >15cm thick; or (3) Peat (loamy, sandy, fibrous, semi-fibrous or amorphous) <40cm thick starting at or near the surface, or <30cm thick where the peat lies directly on bedrock. There are thus three groups of soil that comprise ‘organo-mineral soils’. They are precisely defined in Figure 2 and Table 1, and, where used hereafter in this report, the term includes these three groups of soil. This definition has been chosen since it reconciles the various complexities involved with the prescription, and accommodates the Soil Survey of England and Wales (Hodgson, 1997) and Agricultural Development and Advisory Service (ADAS, 1984) perspectives. It also allows mutually exclusive differentiation on the basis of the National Soil Map Units in LandIS.

Figure 2 Limiting percentages of organic C/organic matter and clay for organic and organo- mineral soils. (After Hodgson, 1997, p.23)

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Humose and peaty topsoils are diagnostic horizons that are defined below in terms of horizon nomenclature and depth or thickness.

Peaty topsoil This is a peaty (O) horizon 7.5-40 cm thick, overlying mineral soil or rock. It normally occurs at the surface or beneath a thin layer of more or less decomposed litter (L, F) not qualifying as O, and may be divisible into distinct sub-horizons, including Oh or Op. It may also be buried beneath a non-organic surface layer up to 30 cm thick.

In an uncultivated soil, the peaty horizon should be thick enough and contain enough organic matter to give an Op horizon if the soil is mixed to a depth of 15 cm. In uncultivated soils O horizons can be difficult to distinguish from relatively well aerated F or H horizons, particularly where the superficial organic horizons are relatively thin. A peaty topsoil under grassy or heath vegetation normally includes an Oh horizon that is denser and more plastic than H horizons of similar composition and breaks into firm angular blocks when dried. This diagnostic horizon is conceptually equivalent to the histic epipedon 1 (Soil Survey Staff 1999, p22-3) or histic horizon in the World Reference Base (WRB; IUSS Working Group WRB 2006, p.23) but is permitted to be thinner.

Humose topsoil This is an A horizon or a sequence of H or Oh and Ah horizons that meets the following requirements over a thickness of more than 15 cm or 10-15 cm if directly over bedrock (R or Cr): 1. Moist rubbed colour with value and chroma 2 of 3 or less 2. Humose or partly humose and partly organic (< 7.5 cm thick).

The requirements apply to the soil as it exists in the field not after mixing to a depth of 15 cm. When a peaty topsoil is cultivated, it is commonly transformed into a humose topsoil as a result of admixture with underlying mineral material, increased mineralization of organic matter, or both. Similarly, reduction of organic-matter content under continuous cultivation also causes humose topsoils to be transformed into distinct topsoils (see below).

A humose topsoil usually qualifies as a mollic 3 or umbric 4 epipedon (Soil Survey Staff, 1999, p23-5, p26-8) or a mollic horizon if high in base saturation (FAO, 2006, p.25) or umbric horizon

1 epipedon – Combinations of specific soil characteristics that are indicative of certain classes of soils at the surface horizons; hence histic epipedon - a thin organic soil horizon that is saturated with water at some period of the year unless artificially drained and that is at or near the surface of a mineral soil.

2 Standard colour definitions for soils – see Soil Survey Staff (1993).

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in the WRB if base-depleted (IUSS Working Group WRB 2006, p.38). Soils with humose A, H, and Oh horizons 5 are classified in Humic subgroups. 6

Formation Organo-mineral soils are formed via the accumulation of organic matter in the surface horizons which occur via a wide range of complex mechanisms (Jones et al ., 2004). Organic material in soil is essentially derived from residual plant and animal material, synthesised by microbes and decomposed under the influence of temperature, moisture and ambient soil conditions. Such material tends to predominantly deposited in the surface zones of soils, hence an accumulation in this zone is in general more prevalent. The pervasiveness and nature of such material then relates to the interaction between natural factors such as climate, parent material, land cover, vegetation type, topography; and anthropogenic-factors such as land-use, land management and degradation pressures (van Bremen & Buurman 2002).

Organo-mineral soils are typically formed in environments where high rainfall and/or low summer temperatures inhibit decomposition allowing organic matter to accumulate at the surface of the mineral soil. Intense leaching and translocation of material in these soils can lead to podzolisation. In this process, the surface layer of organic matter releases organic acids which form complexes with iron and aluminium and that migrate readily down the soil profile with percolating water. As a result, the soil layer or horizon directly below the peaty surface may become bleached and depleted of iron and aluminium, whilst subsurface horizons become correspondingly enriched by precipitation of humus-iron and aluminium compounds. This results in the formation the characteristic ochre-coloured podzolic B horizon.

On shallow slopes, water-logging leads to the reduction, mobilisation and/or redistribution of iron compounds producing distinctive horizons. The reduction of ferric iron to grey or colourless

3 mollic - soil that is dark colored and relatively thick, contains at least 5.8 g kg -1organic carbon, is not massive and hard or very hard when dry, has a base saturation of >50% when measured at pH 7, and is dominantly saturated with divalent cations.

4 umbric - soil that has the same requirements as the mollic epipedon with respect to color, thickness, organic carbon content, consistence, structure, and phosphorus content, but that has a base saturation <;50% when measured at pH 7.

5 Horizon nomenclature: A – topmost; H – organic horizon characterized by accumulation of decomposed organic matter in which the organic structures are indiscernible.; Oh – the most decomposed organic layer, containing only small amounts of raw fibre and called the humic layer.

6 These are precise and specialised terms adopted in pedology. For further explanations see for example Soil Science Glossary Terms Committee (2008). Glossary of Soil Science Terms. Soil Science Society of America, Madison, WI

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ferrous iron by soil microbes and the products of organic matter decomposition is known as gleying. Gley soils typically form where slowly permeable subsoil impedes drainage creating stagnogley soils. Where organic matter is accumulating at the surface, the soils are called stagnohumic gleys. Where more permeable sub-soils allow upward ingress of groundwater, ground-water gley soils are formed. In all these soil types, seasonal or periodic water-logging can allow local aeration to occur. Ferrous iron is re-oxidised under these more aerobic conditions and the subsoils become mottled grey, yellow or ochre coloured. Where subsoil water-logging is persistent the soils will be blue or blue-grey in colour. In upland areas with high rainfall, intense leaching and podzolisation can lead to the formation of a thin hard and often continuous iron pan. An iron pan usually forms where percolating water meets iron-rich relatively un-weathered subsoil or parent material below seasonally waterlogged surface horizons. These soils will show features of both gleys and podzols due to the impeded drainage of the upper layers and are known as stagnopodzols.

The nature of the soil found in any one place in the landscape is defined by the interaction of five main factors: i) the physical and chemical constitution of the parent material; ii) past and present climate including any effects of glaciation; iii) relief and hydrology; iv) how long soil forming processes have been active (typically in GB this is following the last glacial retreat and of the order of 10-12,000 years) and v) ecology and land management. The interaction of these factors will result in the mosaic of soils seen in the landscape. Thus for example, at high altitudes on hard resistant bedrock, rankers will form where thin accumulations of organic matter lie directly over relatively unweathered parent material interspersed with rock outcrops. On sloping land at middle elevations in the uplands, podzols will form where lateral drainage largely prevents water-logging and gleying. On foot-slopes and in basins gley soils will form in fine textured glacial till. The further influence of land management on these edaphic factors can be seen where, for example in Wales the clearance of woodland in Neolithic times changed the micro- climate and nutrient cycling which favoured the formation of brown earth soils to one which in which heather invaded causing acidification and podzolisation (Rudeforth et al ., 1984). In more recent times, intensive agricultural management may result in the reduction or loss of the surface organic layer following ploughing, drainage and application of lime.

1.2 Comparison with other definitions of organo-mineral soils The definition of organo-mineral soils used within this project is broader than that used by the ECOSSE project (SEERAD, 2007) which excluded the following soil sub-groups: Humic Rendzinas, Humic Brown Podzolic soils, Typical-gley podzols, stagnogley podzols, Pelo-alluvial gley soils, Typical humic-alluvial gley soils, Typical humic sandy gley soils. The effect of the difference in definitions on the areas mapped as organo-mineral soils in England and Wales is discussed in Section 2.

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Table 1 Definitions of organo-mineral soils – based on the National Soil Map of England and Wales

Category Description Wetness class(1) Soil Subgroup (SSG) name (2) SSG_code Soil Association Humic Rankers 311 All Humic Rendzinas 341 All 1 Freely and moderately well drained with humose or thin (<40cm thick) peaty surface horizon (topsoil) I, II Humic Brown Podzolic soils 612 All Humo-ferric Podzols 631 All

Ferric Podzols 633 All Typical-gley Podzols 641 All Stagnogley Podzols 643 All 2 Poorly drained Podzols with humose or thin (<40cmthick) peaty surface horizon IV, V, VI Ironpan Stagnopodzols 651 All Humus-ironpan Stagnopodzols 652 All Ferric Stagnopodzols 654 All

Stagnohumic Gley soils 721 All Pelo-alluvial Gley soils 813 813a, 813f only Poorly drained Stagnohumic Gleys, Pelo-alluvial Gleys and Humic Gley soils with humose or thin (<40cm Typical Humic-alluvial Gley soils 851 All 3 V, VI thick) peaty surface horizon Typical Humic-sandy Gley soils 861 All Typical Humic Gley soils 871 All Argillic Humic Gley soils 873 All

4 Peat Soils V, VI Peat soils 10nn All

(1) Hodgson, J.M. (Ed.), (1997). Soil Survey Field Handbook. Soil Survey Technical Monograph No. 5, Harpenden, UK, p.107 (2) Mackney, D., Hodgson, J.M., Hollis, J.M., Staines, S.J. from contributions by the field staff. (1983). Legend for the 1:250,000 Soil Map of England and Wales (Abrief explanation of the constituent soil associations). Lawes Agricultural Trust, Soil Survey

Subsequently, in tables and figures, the categories are referred to using the following descriptive terms: category 1 – well drained soils; category 2 - podzols; category 3 – gley soils; category 4 – peat soils.

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1.3 Organo-mineral soils in an European context At the European scale, the organo-mineral soils defined in project SP1106 can be placed within the following main Soil Reference Groups of the World Reference Base (WRB) classification (Table 2):

Table 2 WRB Soil Reference Groups representing organo-mineral soils

O-M Soil Category Soil subgroup WRB Soil Reference %age cover in (from Table 1) Group Europe 1 (well drained soils) Rankers and Leptosols 9 Rendzinas 1 (well drained soils) Humic Brown Umbrisols 2.5 Podzolic soils 1 and 2 (well drained Humo-ferric podzols Podzols 14 soils and podzols) & Podzols 3 (gley soils) Gley soils Gleysols 5

Taken together these Soil Reference Groups cover 30.5% of Europe (EC, 2005) although their distribution is quite variable. Leptosols which are thin soils formed directly over hard rock occur mainly in the west of Scandinavia and across the more mountainous areas of central and south central Europe (Figure 3).

Figure 3 Distribution of Leptosols in Europe (EC, 2005)

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Figure 4 Distribution of Umbrisols in Europe (EC, 2005)

In contrast, Umbrisols are more restricted in distribution, typically occurring in north west Spain and the western parts of the UK, with small areas scattered throughout the rest of Europe (Figure 4). They require acidic parent materials and typically form in cool humid climates where annual precipitation exceeds evapotranspiration.

Podzols are a common soil, widely distributed throughout northern Europe and Scandinavia; accounting for 14% of the surface area (Figure 5; EC, 2005). They typically form on acidic parent materials in humid, well drained areas.

Gleysols occur mainly in lowland areas where groundwater is found close to the surface so that the soils remain saturated for extended periods of time. They are common in England (see Section 2) and in eastern central Europe (Figure 6).

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Figure 5 Distribution of Podzols in Europe (EC, 2005)

Figure 6 Distribution of Gleysols in Europe (EC, 2005)

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Section 2. Distribution of organo-mineral soils in England and Wales (B Reynolds, J Hall, A. Keith, J. Hall and B. Emmett; CEH Bangor)

2.1 Methods The coverage of the individual soil associations representing organo-mineral soils as defined in Section 1, were provided by the National Soil Resources Institute (NSRI) to the Centre for Ecology and Hydrology (CEH) Bangor as an Arc-GIS shape file. These data were used to derive all statistics for the areas covered by organo-mineral soils in respect of national borders, land cover, designated sites and the boundaries of agri-environment schemes. To make the task more tractable, analysis and interpretation of cover statistics are presented for the three broad categories of organo-mineral soils defined in Table 1 rather than for the 45 individual sub-groups. Analysis of organo-mineral soil coverage with respect to national boundaries used country boundary data held within the Geographic Information System (GIS) at CEH Bangor. These data are used on behalf of Defra for the national assessment of critical loads of acidity and nitrogen.

Land Cover Map 2000 (LCM2000, Fuller et al ., 2002 a,b) was used to analyse organo- mineral soils by land cover type. Twenty two land cover classes, collated into six broad groups, were used in the analysis (Table 3 and Figure 7). In order to capture the main contrast in management for organo-mineral soils between uplands and lowlands, the land cover analysis was performed with respect to Environmental Zone (EZ). Total areas of land cover classes by country were based on the overlay of LCM2000 and country-borders, and this may exclude some coastal areas.

Table 3 LCM2000 land cover types used in the analysis of organo-mineral soils. Broad groupings are shown in italics.

Land cover type LCM Brief description code Cropland Arable cereal 4.1 Barley, maize, oats & wheat Horticulture 4.2 Bare ground, root crops, beans, peas, linseed Non-annual 4.3 Orchard, leys & setaside (rotation). Grassland Improved grass 5.1 Intensive grazing, hay/silage cut & grazing marsh Setaside 5.2 Grass setaside Rough grass 6.1 Unmanaged rough grass Calcareous grass 7.1 Managed & rough calcareous grass Acid grass 8.1 Unmanaged Bracken 9.1 Dominated at height of growing season by bracken Heath/Montane Dense dwarf shrub heath 10.1 Ericaceous & gorse species comprise >25% of plant cover (dense canopy)

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Open dwarf shrub heath 10.2 Ericaceous & gorse species comprise >25% of plant cover (open canopy) Montane 15.1 Montane vegetation: prostrate dwarf shrub heath, sedge, rush, moss heath Forest Broadleaved & mixed 1.1 Scrub, open birch & deciduous, mixed woodland broadleaved evergreen and yew Coniferous woodland 2.1 Conifers, new plantations and felled Wetland Fen, marsh & swamp 11.1 Vegetation that is permanently, seasonally or periodically waterlogged. Swamp, fen/marsh, fen willow Bog 12.1 Ericaceous, herbaceous and mossy vegetation Standing/inland water 13.1 Water bodies >= 0.5 ha; rivers & canals > 50 m wide Coastal Saltmarsh 21.2 Grazed and ungrazed saltmarsh Supra-littoral rock 18.1 Rock Supra-littoral sediment 19.1 Shingle, vegetated shingle, dune, dune shrubs Littoral rock 20.1 Rock & rock with algae Littoral sediment 21.1 Mud, sand & sand with algae

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Figure 7 Land Cover Map 2000 for England and Wales showing broad groupings of land cover types.

Environmental Zones are derived from amalgamations of the ITE Land Classes that form the basis of the sampling strategy for Countryside Survey. The ITE Land Classes are a product of a multivariate classification of data relating to climate, geology and topography within each 1-km square in Great Britain (Bunce et al ., 1996). The Environmental Zones formed from

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these classes therefore reflect an array of characteristics and provide a useful means of representing the geographically distinct regions of Britain. Five EZs are used in Countryside Survey to cover the range of environmental conditions found in England and Wales from the lowlands of the south and east through to the uplands of the north and west (Table 4 and Figure 8).

Table 4 The Environmental Zones used in Countryside Survey

Environmental Zone EZ code Easterly Lowlands of England EZ1 Westerly Lowlands of England EZ2 Uplands of England EZ3 Lowlands of Wales EZ8 Uplands of Wales EZ9

The coverage of organo-mineral soils was also analysed in relation to the areas of England and Wales designated for conservation purposes or lying within agri-environment schemes. The scope of this analysis included the following conservation designations in England and Wales: Special Areas of Conservation (SACs), Special Protection Areas (SPAs), National Nature Reserves (NNRs) and Sites of Special Scientific Interest (SSSIs). In England and Wales the following designation boundaries were also included: Environmentally Sensitive Areas (ESAs), Less Favoured Areas (LFAs). Analysis of the management applied to each parcel of land within a designated site or agri-environment scheme is a massive undertaking and beyond the scope of this project. The purpose of this analysis was to identify the areal extent of organo-mineral soils which may be influenced, either directly or indirectly by prescriptive land use management. Areas within each organo-mineral soil category were derived by intersecting designated area data with the organo-mineral soil shape file for the country (England or Wales).

All data were clipped to country and coastline using the GIS country maps to remove data resulting from overlapping country boundaries etc, and to ensure consistency of all data analyses. As a result, there are some small differences in the areas of organo-mineral soils calculated directly from the NSRI soil cover data and the overlays of land cover type etc. This arises because the overlay data have been “clipped” to the mainland coastline of England and Wales, excluding offshore islands which are included in the NSRI soil coverage data.

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Figure 8 Map of the Environmental Zones for England and Wales used in the analysis of organo-mineral soils by land cover type

2.2 Distribution organo-mineral soils in relation to national boundaries The mapped distribution of the three categories of organo-mineral soils in England and Wales are shown in Figure 9. In England the main focus of the soils is to the north and west in the Pennines and the Lake District. Organo-mineral soils occur throughout much of Wales, following the outlines of the upland areas of the Cambrian mountains, the Brecon Beacons and Snowdonia. More isolated, discrete areas of organo-mineral soils are associated with

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moors of southwest England and north east England, along with areas of heathland in the south. East Anglia contains a substantial area of Category 3 gleyed soils.

Organo-mineral soils cover about 1.6 million hectares of England and Wales (Table 5) or about 10.5% of the land area (Figure 10). Although the largest absolute area occurs in England (1,165,665 ha), the largest proportional cover is found in Wales where organo- mineral soils account for just over fifth (20.5%) of the land area (Figure 10). In Wales the area covered by podzolic (Category 2) and gleyed (Category 3) soils is approximately equal and amounts in total to just over 350,000 ha (17% of land area) whereas (Category 3) soils are the dominant organo-mineral soils in England covering approximately 670,000 ha or just over 5% of the land area.

Table 5 Areal extent (ha) of organic-soils in England and Wales derived from NSRI data.

Soil Category England Wales England +Wales %age of England & Wales cover 1 (well drained) 230763 72648 303411 19.1 2 (podzols) 265192 186296 451487 28.4 3 (gley soils) 669710 167267 836978 52.6 All 1165665 426211 1591876 100.0

The major fraction (73%) of the total coverage of organo-mineral soils resides in England, which also contains more than three quarters of the total coverage of Category 1 and Category 3 soils. The total “stock” of Podzolic (Category 2) soil is more evenly distributed between countries with ~40% of the total England + Wales coverage occurring in Wales. Category 3 soils (poorly drained gley soils) account for more than 50% of the total organo- mineral soil cover in England and Wales (Table 4) with Category 2 and Category 1 soils accounting for 28% and 19% of total cover respectively.

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Figure 9 Distribution of organo-mineral soils in England and Wales.

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20.53

10.52 8.93 8.97 8.06 Cover(%) 5.53 5.13 3.50 1.77 2.03 2.01 2.98

England Wales England & Wales Category 1 Category 2 Category 3 All categories (well drained soils) (podzols) (gley soils)

Figure 10 Percentage of the total areas of England, Wales and England & Wales covered by organo-mineral soils.

The ECOSSE project (SEERAD, 2007) provides the only other estimate of the area of organo-mineral soils calculated for countries in Great Britain, but unfortunately only data for Wales are relevant to project SP1103. ECOSSE also used a different definition of organo- mineral soils from SP0116 (see Section 1) and produced a smaller area estimate (359200 ha; Table 6). The difference in areas (67011 ha; Table 6) cannot be accounted for simply by the variation in definitions used by the two projects. Using the SP0116 data, the area of soil subgroups excluded by the ECOSSE project definition (30387 ha) accounts for only 45% of the difference. One explanation might be that the two projects used different GIS masks for the country border and coastline resulting in different estimates for the total area of Wales. Strangely however, the proportion of the total area of Wales covered by organo-mineral soils estimated independently by the ECOSSE project (17.3%) is exactly the same as that estimated using the area of organo-mineral soils published in the ECOSSE report and the area of Wales used in SP0116, suggesting that the GIS masks used by the two projects were similar. An alternative explanation is that some areas of organo-mineral soils were omitted accidentally from the calculations performed by the ECOSSE project. Relative to the total area of Wales, the differences are small and less than 5%.

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Table 6 Areas of organo-mineral soils in Wales estimated by SP0116 and the ECOSSE project (SEERAD, 2007).

Area (ha) Proportion by area of Wales 1 (%) Area of O-M soils estimated by ECOSSE 359200 17.3 Area of O-M soils estimated by SP0116 426211 20.5 Area of Subgroups excluded by ECOSSE 2 30387 1.5 Difference in areas between SP0116 and 67011 3.2 ECOSSE projects 1 Based on area of Wales calculated by CTE1011 project (2076139 ha) 2Based on areas calculated by CTE1011 project

2.3 Distribution of organo-mineral soils in relation to Environmental Zone The largest area of organo-mineral soils in England and Wales (~ 0.56 million ha) is found in EZ3 (Upland England) which accounts for 35% of the total areal extent of these soils (Table 7 and Figure 11). The majority of gleyed soils (Category 3; 38%) and moderate to freely drained soils (Category 1; 36%) also occur in EZ3, with a further 28% and 27% respectively in EZ1 (Eastern Lowland England). Forty percent of poorly drained podzolic soils (Category 2; ~182,000 ha) occur in EZ9 (Upland Wales) with most of the remainder (30%) in EZ3. The coverage of organo-mineral soils in Lowland Wales (EZ8) is relatively small (63,000 ha), accounting for a little under 4% of the total (Figure 11).

Table 7 Area (ha) of each soil category within each Environmental Zone.

Environmental Zone Soil Category Soil Category Soil Category All Categories 1 (well 2 (podzols) 3 (gley soils) drained) Lowland Eastern England EZ1 80862 47926 237844 366632 Lowland Western England EZ2 40050 80769 106725 227544 Upland England EZ3 108696 135417 319397 563510 Lowland Wales EZ8 16647 4532 41721 62900 Upland Wales EZ9 55998 181664 125456 363118

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38.8 41.4 36.8 36.2 30.9

28.6 25.6 22.7 23.1 15.0 17.1 14.2 18.7 Percentage cover 13.4 12.9 9.5

5.5 4.7 3.8 1.0

Low. E. Eng. Low. W. Eng. Up. Eng. Low Wales Up. Wales Environmental Zone Category 1 Category 2 Category 3 All categories (well drained soils) (podzols) (gley soils) Figure 11 Percentage cover of each soil category by Environmental Zone in England and Wales

2.4 Distribution of organo-mineral soils in relation to land cover type The data describing the area of organo-mineral soils in relation to land cover type are presented in full in Annex 1 and have been summarised for England in Table 8 and for Wales in Table 9. The data presented in these Tables have been summarised by including only those organo-mineral / land cover type combinations which equal or exceed 10% of the total area of each soil or LCM class for each country. In this way the most important soil/land cover type combinations can be identified as those which might be targeted for management. It should be noted that no organo-mineral soils were associated with montane land cover so the heath/montane group comprises entirely of dwarf shrub heath.

In England, the largest area of organo-mineral soils (342,000 ha) occurs under grassland in EZ3 (Upland England), accounting for ~30% of the total area of organo-mineral soils (Table 8). However, the area of grassland supported by organo-mineral soils in EZ3 is a relatively small proportion (~7%) of the total grassland cover for England. More detailed examination reveals that ~22% of rough grass in England (110,612 ha) occurs on Category 3 soils in EZ3 while the more freely drained Category 1 soils in this zone support just over one fifth (14,562 ha) of the total cover of bracken. Overall organo-mineral soils in the uplands of England (EZ3) support 29% (145,801 ha) of the total area in England of rough grassland, 35% of bracken (25,174 ha) and about one third of the acid grassland (92,609 ha). Organo-mineral soils also support ~106,000 ha of grassland in each of EZ1 (Eastern Lowland England) and

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EZ2 (Western Lowland England). This is equivalent to 18% of the total area of organo- mineral soils in England, but less than 5% of the total area of grassland in England. In EZ1, total cropland accounts for 21% (142,352 ha) of the area of Category 3 soils in England. This is primarily made up of cereals and horticultural crops but these areas represent less than 4% of the total area in England of each crop. Overall in EZ1, ~160,000 ha of organo-mineral soils (~14% of the total area in England) support 3.3% of the total area of English cropland. Conversely, 42% of the area of heathland in England (111,005 ha) occurs on organo-mineral soils in the uplands (EZ3) with around 23% of the English total cover of both dense (31,197 ha) and closed (29,678 ha) dwarf shrub heath supported by Category 3 soils in EZ3.

The largest area of organo-mineral soils in Wales (~267,000 ha) occurs under grassland (Table 9). Approximately 17% of the total area in Wales of Category 1 soils (12,460 ha) and a similar proportion of Category 3 soils (29,121 ha) support grassland in Lowland Wales (EZ8) and together these account for about 3% of the total Welsh grassland cover (Table 9). By contrast, in Upland Wales (EZ9) 52% of the total area of organo-mineral soils in Wales (222,120 ha) supports grassland. Nearly 60% of the total area of poorly drained podzol (Category 2) soils in Wales (107,009 ha) is under grassland and 44% (81,842 ha) is under acid grass. Taking both EZs together, organo-mineral soils account for nearly a fifth of the total grassland area in Wales. Much higher proportions of the total Welsh cover of rough grass (42%; 56,410 ha), acid grass (41%; 130,187 ha) and bracken (32%; 9411 ha) occur on organo-mineral soils in EZ9. A substantial proportion (~57%; 64,057 ha) of heathland in Wales occurs on organo-mineral soils in EZ9. This corresponds to 15% of the total area of organo-mineral soils in Wales. The majority (~27%; 30,922 ha) of Welsh heathland occurs on poorly drained podzol (Category 2) soils in EZ9 corresponding to 16,334 ha of dense canopy and 14,579 ha of open canopy dwarf shrub heath. In total, organo-mineral soils in EZ9 support about half of the Welsh area of dense dwarf shrub heath and ~64% of dense dwarf shrub heath (Table 9).

In the Welsh uplands (EZ9), organo-mineral soils support 37% of the total area of conifer forest in Wales (53,223 ha; Table 9). In Lowland Wales (EZ8), 2058 ha of conifers grow on organo-mineral soils (Annex 1; Table A2). Of the total area of podzol soils (Category 2) in Wales, 33,794 ha (18%) support conifers in the uplands (EZ9), corresponding to ~24% of the total cover of conifers in Wales. Large proportions of the total area of bog (54%; 3046 ha) and fen, marsh and swamp (42%; 643 ha) in Wales are associated with organo-mineral soils in the uplands (EZ9). However, taken together, these land cover classes account for a very small proportion (~1%) of the total cover of organo-mineral soils in Wales.

2.5 Distribution of organo-mineral soils in relation to designated areas Analysis of organo-mineral soil coverage in each country by designated area provides an indication of the extent to which these soils may already be under some form of prescriptive land use management. While the data in Table 10 show the areas of organo-mineral soils under each form of designation, it should be remembered that designated sites such as NNRs and SSSIs, for example, can be located within a designated area such as an SAC, which itself can fall within an LFA. This reflects the different objectives of designation (summarised in

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Annex 1, Table A3) and means that it is inappropriate to summate individual designated areas to give a country total.

The results in Table 10 show that the area of organo-mineral soils falling within LFAs in England is large (684,864 ha) and equivalent to 59% of the total area of these soils in England (Figure 12). Correspondingly, 31% of the total LFA area in England is underlain organo-mineral soil (Figure 13) of which 637,921 ha or 93% is classified as Severely Disadvantaged. The majority (~64% or 170,833 ha) of Category 2 soils in England lie within LFAs although this equates to less than 8% of the total LFA area. In contrast just over 1% of the total coverage of organo-mineral soils in England falls within NNRs (Figure 12), although this area (13611 ha) corresponds to ~21% of the total area of English NNRs (Figure 13). Significant proportions of the total areas of SACs (~41%), SPAs (~39%) and SSSIs (~34%) in England are also underlain by organo-mineral soils.

Approximately 23% of the total area of organo-mineral soils in Wales (97,214 ha) occur within SSSIs (Table 10; Figure 14). Indeed, 25,018 ha (~34%) of Category 1 soils and 49,781 ha (27%) of Category 2 soils lie within SSSIs in Wales. As with England, substantial proportions (40-45%) of the total areas SACs, SPAs and SSSIs in Wales, are underlain by organo-mineral soils (Figure 15). In Wales 27% of the total area of Category 1 soils (19,242 ha) fall within SACs, and approximately one third (6804 ha) of the total area of NNRs is underlain by organo-mineral soils. Nearly all the coverage of Category 2 organo-mineral soils and over 97% of total organo-mineral soil coverage in Wales occurs within LFAs (Figure 14) reflecting the widespread distribution of LFAs; 80% of the total land area in Wales is designated as LFA. However, only 25% of the total LFA area in Wales is supported by organo-mineral soils (Figure 15).

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Table 8 Organo-mineral soil-land cover type combinations showing areas (ha), percentage of total area of each soil category in England and percentage of total area of each LCM2000 land cover type in England for those combinations accounting for 10% or more of the total area (shaded grey). Italics denote data for broad groups of land cover types.

Area Area Area Area % of total area of soil category in % of total area of LCM class in (ha) (ha) (ha) (ha) England England Organo-mineral soil category 1 2 3 All 1 2 3 All 1 2 3 All Well- Podzols Gley Well- Podzols Gley Well- Podzols Gley drained soils drained soils drained soils Eastern Lowland England (EZ1) Cropland total 12970 4510 142352 159832 5.6 1.7 21.3 13.7 0.3 0.1 3.0 3.3 4.2 Horticulture 8003 3146 84769 95918 3.5 1.2 12.7 8.2 0.3 0.1 3.1 3.5 Grassland total 33297 9700 61603 104599 14.4 3.7 9.2 9.0 0.7 0.2 1.3 2.2 Forest total 23733 17143 18546 59422 10.3 6.5 2.8 5.1 1.7 1.2 1.3 4.3 11.1 Fen, marsh & swamp 273 249 3168 3691 0.1 0.1 0.5 0.3 1.5 1.4 17.9 20.9 Western lowland England (EZ2) Grassland total 18598 29835 58280 106713 8.1 11.3 8.7 9.2 0.4 0.6 1.2 2.2 Upland England (EZ3) Grassland total 76812 70070 195482 342364 33.3 26.4 29.2 29.4 1.6 1.5 4.1 7.1 6.1 Rough grass 16992 18198 110612 145801 7.4 6.9 16.5 12.5 3.4 3.6 22.2 29.2 8.1 Acid grass 29142 31971 31496 92609 12.6 12.1 4.7 7.9 10.5 11.5 11.3 33.2 9.1 Bracken 14562 4328 6284 25174 6.3 1.6 0.9 2.2 20.6 6.1 8.9 35.5 Heath/Montane total 13821 36309 60875 111005 6.0 13.2 9.1 9.5 5.2 13.7 22.9 41.8 10.1 Dense dwarf shrub heath 5371 20768 31197 57335 2.3 7.8 4.7 4.9 4.0 15.6 23.4 43.1 10.2 Open dwarf shrub heath 8451 15541 29678 53670 3.7 5.9 4.4 4.6 6.4 11.7 22.4 40.5 2.1 Coniferous 3799 9403 32645 45847 1.6 3.5 4.9 3.9 1.3 3.1 10.9 15.3 Wetland total 3318 5983 11553 20854 1.4 2.3 1.7 1.8 1.8 3.3 6.3 11.4 12.1 Bog 3151 5819 11342 20312 1.4 2.2 1.7 1.7 3.0 5.5 10.7 19.2

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Table 9 Organo-mineral soil-land cover type combinations showing: areas (ha); percentage of total area of each soil category in Wales and percentage of total area of each LCM2000 land cover type in Wales for those combinations accounting for 10% or more of the total area (shaded grey). Italics denote data for broad groups of land cover types.

Area Area Area Area % of total area of soil category in % of total area of LCM class in (ha) (ha) (ha) (ha) Wales Wales Organo-mineral soil 1 2 3 All 1 2 3 All 1 2 3 All category Well- Podzols Gley Well- Podzols Gley Well- Podzols Gley drained soils drained soils drained soils Lowland Wales (EZ8) Grassland total 12460 3042 29121 44623 17.2 1.7 17.4 10.5 0.9 0.2 2.1 3.2 5.1 Improved grass 8514 1079 17665 27258 11.7 0.6 10.6 6.4 1.1 0.1 2.3 3.6 Upland Wales (EZ9) Grassland total 31722 107009 83388 222120 43.7 57.4 49.9 52.1 2.3 7.7 6.0 15.9 6.1 Rough grass 3987 14802 37352 56141 5.5 7.9 22.9 13.2 3.0 11.1 28.1 42.2 8.1 Acid grass 20676 81842 27669 130187 28.5 43.9 16.5 30.5 6.5 25.7 8.7 40.8 9.1 Bracken 1031 4186 4194 9411 1.4 2.2 2.5 2.2 3.5 14.4 14.4 32.4 Heath/Montane total 14958 30922 18176 64057 20.6 16.6 10.9 15.0 13.3 27.4 16.1 56.8 10.1 Dense dwarf shrub heath 7399 16344 5394 29137 10.2 8.8 3.2 6.8 12.8 28.2 9.3 50.3 10.2 Open dwarf shrub heath 7560 14579 12782 34921 10.4 7.8 7.6 8.2 13.8 26.6 23.3 63.7 Forest total 5625 34775 17713 58114 7.7 18.7 10.6 13.6 1.9 11.5 5.8 19.2 2.1 Coniferous 4443 33794 14986 53223 6.1 18.1 9.0 12.5 3.1 23.6 10.5 37.2 Wetland total 620 3332 581 4533 0.9 1.8 0.3 1.1 3.8 20.2 3.5 27.5 11.1 Fen, marsh & swamp 109 284 251 643 0.1 0.2 0.1 0.2 7.0 18.3 16.2 41.6 12.1 Bog 126 2690 230 3046 0.2 1.4 0.1 0.7 2.2 47.6 4.1 53.9

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Table 10 Areas of organo-mineral soils in England and Wales included within designated areas.

England Area (ha) of organo-mineral soil category Total Designation Category 1 Category 2 Category 3 All designated Well-drained Podzols Gley soils Categories area (ha)

SAC 56960 68844 96689 222493 546090 SPA 30076 62923 99952 192951 491248 SSI 70985 90165 129776 290927 846245 NNR 3329 4339 5943 13611 65913 ESA 79079 54278 149292 282649 1167668 LFA (total) 131439 170833 382592 684864 2214755 LFA (Disadvantaged) 13448 14676 18819 46943 588305 LFA (Severely 117991 156157 363773 637921 1626450 disadvantaged)

Wales Area (ha) of organo-mineral soil category Total Designation Category 1 Category 2 Category 3 All designated Well-drained Podzols Gley soils Categories area (ha)

SAC 19242 26632 10918 56792 138902 SPA 5504 23907 4266 33677 81319 SSI 25018 49781 22415 97214 217306 NNR 2950 2504 1350 6804 21260 ESA 1795 12337 4127 18259 80302 LFA (total) 68767 186074 160913 415754 1634970 LFA (Disadvantaged) 6733 23 14997 21753 473938 LFA (Severely 62034 186051 145916 394001 1161032 disadvantaged)

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60.9 69.7 59.0 61.7

d (%) 22.1 23.0 25.5 36.7 0.9 1.2 1.5 1.8 26.2 32.9 36.8 20.0 17.4 13.9 25.7 15.4 26.4 28.1 14.9 20.1 Proportionofarea total of soil category in Englan

(well drained soils) (podzols) (gley soils)

Organo-mineral soil category

SACs SPAs SSSIs NNRs ESAs LFAs (total)

Figure 12 Percentage of the total area of each organo-mineral soil category in England falling within a designated area.

10.4 12.6 17.7 40.7 6.1 12.8 20.3 39.3 8.4 10.7 15.3 34.4 5.1 6.6 9.0 20.7 6.8 4.6 12.8 24.2 7.7 30.9 5.9 17.3 Proportionof designated areain England (%) (well drained soils) (podzols) (gley soils) Organo-mineral soil category SACs SPAs SSSIs NNRs ESAs LFAs (total)

Figure 13 Percentage of the total area of each designation in England underlain by organo- mineral soils.

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36.3

27.9 27.5 23.8

14.7 Wales Wales (%) 13.2 14.1 13.9

8.0 8.2 6.9 4.3 2.7 1.4 0.9 1.7 Proportionofarea total of soil category in

(well drained soils) (podzols) (gley soils) Organo-mineral soil category SACs SPAs SSSIs NNRs

Figure 14 Percentage of the total area of each organo-mineral soil category falling within designated areas in Wales.

44.7 40.9 41.4

32.0 29.4

22.9 19.2

13.9 13.9 11.8 11.5 10.3 6.8 7.9 5.2 6.3 Proportionof designated areain Wales (%)

(well drained soils) (podzols) (gley soils) Organo-mineral soil category SACs SPAs SSSIs NNRs

Figure 15 Percentage of the total area of each designation in Wales underlain by organo- mineral soils.

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2.6 Estimates of C storage in organo-mineral soil (0-15 cm) using CS2007 data

The sampling strategy for Countryside Survey (CS) is structured to provide reliable national statistics (Firbank et al ., 2003) for the parameters measured in each survey square. As a result the soil data collected as part of CS in 2007 can be used to estimate the amount of carbon stored in the top 15 cm of organo-mineral soils in England and Wales. The top 15 cm can be considered that part of the soil profile most responsive to change as a consequence of land management or other environmental pressures. It is therefore important to quantify this potentially vulnerable stock of soil carbon. The figures, however, do not equate to total soil carbon stocks which require additional data from below 15 cm depth.

The data used to estimate the quantity of carbon are derived from the samples collected in 2007 from a subset of 256 1km x 1km squares which made up the first survey in 1978. This subset was used because the soils in these squares are the only ones to have been allocated to Soil Subgroups; CS data are more usually reported by country, habitat type and vegetation type. In 2007 soil samples were collected from the five main survey plots within each square using a fixed depth core of 15 cm following removal of vegetation to expose the soil surface. Samples were returned to the laboratory for analysis which included the determination of soil organic carbon by Loss-on-Ignition and bulk density. Details of the field and laboratory methods are provided by Emmett et al . (2010).

The number of samples representing each category of organo-mineral soil imposes limitations on the estimates of soil (0-15cm) carbon storage as there are too few samples, especially for Wales to provide country-level estimates for each soil category. Two approaches have been used. Firstly, mean carbon density values were calculated for each soil category using the CS2007 data for England and Wales combined. These values were multiplied by the areal cover for each category derived from the National Soil Map to produce a carbon stock estimate to 15 cm for each category in England and Wales (Table 11). Secondly separate estimates for England and Wales were calculated using CS2007 data combined for all organo-mineral soil categories to derive country-level mean soil (0-15 cm) carbon density values. These were multiplied by areal cover estimates of organo-mineral soils in each country (Table 12). The percentage contributions from organo-mineral soils to the England, Wales and GB soil (0-15 cm) carbon stock were also calculated using national estimates derived from CS2007 data and reported in Emmett et al . (2010).

The estimates in Table 11 show that organo-mineral soils generally contribute less than 10% of the GB soil (0-15 cm) carbon stock and about 15% of the England and Wales (0-15 cm) stock. Individual organo-mineral soil categories contribute relatively small fractions of the GB and England and Wales soil (0-15 cm) stock. Sample numbers are low (< 50) for categories one and two and this will affect the accuracy of the estimates. Organo-mineral soil samples comprise ~15% of the potential total number of samples collected from the 256 CS squares in 2007.

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Table 11 Estimated soil (0-15 cm) C stocks held in each organo-mineral (O-M) soil category across England and Wales (E&W) in 2007 and comparison with soil (0-15 cm) stocks for E&W and Great Britain (GB) from Emmett et al . (2010).

O-M soil Area Mean O-M soil No. of O-M soil Fraction of Fraction of category (ha) (0-15 cm) C samples (0-15 E&W soil GB soil density (Mg ha - contributing cm) C (0-15 cm) (0-15 cm) 1) to mean stock C stock 1 C stock 1 (Tg) (%) (%) 1-well drained 303411 92 39 28 2.9 1.8 2-podzols 451487 95 45 43 4.5 2.7 3- gley soils 836978 83 103 69 7.3 4.4 All categories 1591876 88 187 140 14.7 8.9 1Soil (0-15 cm) C stock estimates for England and Wales and for GB are from CS2007; Emmett et al . (2010).

Table 12 Estimated soil (0-15 cm) C stocks held in organo-mineral (O-M) soils in England and in Wales in 2007 and comparison with country level and GB soil (0-15 cm) C stocks from Emmett et al . (2010).

Country Area Mean O-M No. of O-M soil Fraction of Fraction of (ha) soil (0-15 cm) samples (0-15 cm) soil (0-15 GB soil (0- C density (Mg contributing C stock cm) C 15 cm) C ha -1) to mean (Tg) stock 1 in stock 1 in O- O-M soils M soils (%) (%) England 1165665 85 139 99 12.5 6.3 Wales 426211 95 48 41 25.5 2.6 E&W 1591876 88 187 140 14.7 8.9 1Soil (0-15 cm) C stock estimates for England and Wales and for GB from CS2007; Emmett et al ., 2010

The national estimates (Table 12) reveal a different picture with organo-mineral soils contributing 12.5% of the 795 Tg of carbon held in the top 15 cm of soil in England (Emmett et al ., 2010). In Wales approximately a quarter of the soil (0-15 cm) carbon stock of 159 Tg (Emmett et al ., 2010) is held in organo-mineral soils, although this comprises less than 3% of the GB stock of soil (0-15 cm) carbon of 1582 Tg estimated by CS2007 (Table 12). Again low sample numbers in Wales will affect the accuracy of this estimate.

The ECOSSE project estimated the total stock of carbon to the bottom of the profile held by organo-mineral soils in Wales as 74.5 Tg (SEERAD, 2007). As noted earlier, there are differences between SP0116 and ECOSSE relating to the definition of organo-mineral soils

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and the area of Wales covered by them. However, the carbon stock estimates from the two projects indicate that slightly more than 50% of the total soil carbon stock held by organo- mineral soils in Wales occurs in the top 15 cm.

Despite the obvious uncertainties in the numbers, the clear inference is that a substantial proportion of the carbon held by organo-mineral soils occurs in the top part of the profile which is most vulnerable to the effects of environmental change. For Wales, and to a lesser extent England, organo-mineral soils contribute significantly to the shallow store of soil carbon held by these countries.

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Section 3. Ecosystem Services Provided by Organo-mineral Soils

(M.SA. Blackwell; Rothamsted Research, K. Ritz; Cranfield University and Roland Bol; Rothamsted Research )

3.1 Introduction

The Millennium Ecosystem Assessment defines an ecosystem service as “the benefits people obtain from ecosystems,” (Millenium Ecosystem Assessment, 2003). Organo-mineral soils, as defined in section 1 of this report, cover 1.6 million hectares of England and Wales, or 10.5% of the land area (section 2, this report). The characteristics of organo-mineral soils and the wide range of land cover types and environmental zones in which they occur means that currently they deliver a broad range of ecosystem services in England and Wales. Given the paucity of literature on the ecosystem services delivered by organo-mineral soils, we have provided an assessment guided primarily by expert opinion rather than a review of these services, although where available and appropriate, references have been used to guide this assessment. We have considered the ecosystem services in a number of ways, primarily based on land cover type, and subsequently on environmental zone and soil type. Finally an indication of how the delivery of these ecosystem services in each environmental zone is likely to be affected by predicted patterns of climate change is made. As reported in Defra project SP1601, looking at soil functions, quality and degradation, “It is ecologically naïve to expect a soil to optimally provide all functions simultaneously, and hence a strategy founded upon optimal use of soils which are most suited to particular purposes is logical and outwardly sensible. This will potentially require offsetting some functions at the expense of others, and a sophisticated spatial management of soil systems at local, regional and preferably also at national scales”. Section 2 of this report provides a first step towards assessing the spatial distribution and management of organo-mineral soils, but does not provide the sophisticated local detail required to make quantitative assessments of ecosystem service delivery, and optimal usage. However, here we provide an essentially qualitative report on the distribution of ecosystem services, with a semi quantitative indication of the degree to which services are delivered in different environmental zones of England and Wales.

3.2 Approach Organo-mineral soils occur on and within a range of soil types, environmental zones, designated areas and land uses. Each combination of these is potentially likely to deliver a different suite of ecosystem services to differing degrees. It is not within the scope of this study to consider all the possible combinations of these parameters, and indeed many will be insignificant with regard to ecosystem service delivery. Therefore we have considered a range of key combinations of factors as identified in the review by Reynolds and Hall (section 1.b, this report). Initially the dominant land cover types on all soils in each environmental zone were identified. These represent specific land cover types accounting for 5% or more of the total area of each soil type in each environmental zone. A total of 10 land cover sub-types classified more generally as either cropland, grassland, forest or heath were identified as dominant. Specifically these 10 land cover types are:

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1. Cropland – arable 2. Cropland – horticultural 3. Grassland – improved 4. Grassland – rough 5. Grassland – acid 6. Grassland – bracken 7. Forest – deciduous 8. Forest – coniferous 9. Heath – dense dwarf shrub 10. Heath – open dwarf shrub

Next, each of the categories listed above was assessed with regard to the ecosystem services they deliver in a semi-quantitative way. This was not so much a review, but an assessment based on expert opinion of the authors and by consultation with other experts on this topic. This approach was necessary because there is very little information available in the scientific literature on the specific ecosystem services that these soils deliver, apart from a few exceptions such as carbon storage (SEERAD, 2007). The range of ecosystem services considered was based on those being used in the UK National Ecosystem Assessment (NEA), (UK National Ecosystem Assessment, 2010).

The UK NEA classifies services into four broad groups: Provisioning services: the products we obtain from ecosystems such as food, fibre and fresh water. Regulating services: the benefits we obtain from the regulation of ecosystem processes such as regulation of pollination, the climate, noise and water. Supporting services: ecosystem functions that are necessary for the production of all other ecosystem services, such as soil formation and the cycling of nutrients and water. Cultural services: the non-material benefits we obtain from ecosystems, for example through spiritual or religious enrichment, cultural heritage, recreation and tourism or aesthetic experience.

A semi-quantitative approach was adopted in order to give an indication of the degree to which each ecosystem service is delivered, because while some land cover-soil combinations may deliver a similar range of ecosystem services, the importance of them may vary, and it is important that this information is conveyed. Additionally, some ecosystem services may be performed but in a negative way (sometimes referred to as dis-benefits), e.g. soil carbon stores may be degraded because of a land use, and therefore although the soil would be performing the ecosystem service of global climate regulation, this would be in a detrimental way. The results of this initial assessment are shown in Table 13. The performance of a particular ecosystem service is indicated by the presence of a circle in the relevant matrix square. The size of the circle reflects the degree to which the ecosystem service is performed, according to the key. Whether the ecosystem service is delivered in what is considered to be a

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positive or negative way is indicated by the colour of the circle; black for positive, red for negative. The logic behind and key points arising from this assessment are described below.

Following the initial assessment of ecosystem services by specific land cover types, the delivery of ecosystem services in relation to organo-mineral soil type and EZ was carried out. This was again based on the findings reported by Reynolds and Hall (section 2, this report). For soil type, all the significant (i.e. >5% total area) land cover types were identified for each soil type (Table 14) in each EZ. The initial assessment of land cover type (Figure 11) was consulted for the categories identified as significant for each soil type and for each ecosystem service the most significant (i.e. the highest ranked assessment) was recorded. In some cases ecosystem services in different significant land cover types are both positive and negative, and this is indicated by recording the most significant value of each in the relevant matrix square, hence the occasional appearance of two dots. This approach was adopted because it gives an indication of the types of ecosystem services being delivered across each soil type, and also indicates, in some of the significant land covers, the level at which it is occurring. More detailed, quantitative assessment is beyond the scope of this study.

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Table 13 Assessment of ecosystem services delivered by the dominant land cover types occurring on organo-mineral soils in England and Wales.

High Medium Low None Negative influence Positive influence

● ● ● ● ●

Ecosystem services Cropland Grassland Forest Heath/montane Arable Horticulture Improved Rough Acid Bracken Deciduous Coniferous Dense Open Provisioning services

Food ● ● ● ● ●

Fibre (thatch, wool, sedge) ● ● ● ● ● ● ● ● ● Fuel ● ● ● Genetic resources ● ● ● ● ● ● ●

Refugia ● ● ● ● ● ● ● ● ● ● Biochemicals/pharmaceutical ● Ornamentals ● Water provision ● ● ● ● ●

Regulating services Global climate ● ● ● ● ● ● ● ● ● ●

Regional climate ● ● ● ● ● ● ● ● ●

Local climate ● ● ● ● ● ●

Flood hazard regulation ● ● ● ● ● ● ● ● ● ●

Erosion control ● ● ● ● ● ● ● ● ● ● Disease Pest regulation

Pollination services ● ● ● ● ● ● ● Toxic hazard regulation

Noise regulation ● ● Soil quality ● ● ● ● ● ● ● ● ● ●

Air quality ● ● ● ● ● ● Water quality ● ● ● ● ● ● ● ● ● ●

Supporting services

Primary production ● ● ● ● ● ● ● ● ● ● Nutrient cycling ● ● ● ● ● ● ● ● ● ● Soil formation ● ● ● ● ● ● ● ● ● ● Water cycling ● ● ● ● ● ● ● ● ● ●

Cultural

Recreation ● ● ● ● ● ● ● ●

Tourism ● ● ● ● ● Cultural heritage ● ● ● ● ● ● ● ● ● ●

Education ● ● ● ● ●

Community development ● ● ●

Spiritual ● ●

Religion ●

Aesthetics ● ● ● ● ● ● ● ● ● ●

Inspirational ● ● ● Sense of place ● ● ● ● ●

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Table 14 Dominant (>5% total spatial extent of soil type within each environmental zone) land cover types for three organo-mineral soil types.

Soil Type 1 (well drained) Soil Type 2 (podzols) Soil Type 3 (gley soils) Improved grassland Horticulture Arable cereals Broadleaved woods Improved grassland Horticulture Rough grassland Rough grassland Improved grassland Acid grassland Acid grassland Rough grassland Bracken Dense dwarf shrub heath Acid grassland Dense dwarf shrub heath Open dwarf shrub heath Open dwarf shrub heath Open dwarf shrub heath Coniferous forest Coniferous forest Coniferous forest

A similar approach was adopted for each EZ, although in this case, the total percentage spatial extent across all soil types was considered. Significant land cover types identified for each EZ are given in Table 15.

Table 15 Dominant (>5% total spatial extent of environmental zone) land cover types for organo-mineral soils occurring within five environmental zones.

EZ1 EZ2 EZ3 EZ8 EZ9 (E. Low. Eng.) (W. Low. Eng) (Up. Eng.) (Low. Wales) (Up. Wales) Arable cereals Improved Improved Improved Rough grassland grassland grassland grassland

Horticulture Rough grassland Acid grassland Acid grassland Dense dwarf shrub heath Dense dwarf Open dwarf shrub heath shrub heath Coniferous forest

Although the selection of the categories of land cover considered in this assessment of organo-mineral soils is based upon significant proportional spatial extent (i.e. > 5% of the total area of each soil type in each environmental zone), with regard to delivery of ecosystem services this is not always a satisfactory measure of importance. Sometimes because of their scarcity, some ecosystems can become more valuable, so it would be wrong to discount certain categories on this basis. Also, some ecosystem services are reliant upon factors such as spatial configuration and length of interface between different systems, rather than total spatial extent (e.g. the role of wetlands and buffer zones for water purification; Blackwell et al ., 2011). However, without detailed analysis of the characteristics of the spatial distribution

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of some of the apparently less significant ecosystems occurring on organo-mineral soils, it is not possible to consider them in this current assessment.

3.3 Initial assessment of ecosystem services by land cover types on organo-mineral soils

3.3.1 Provisioning services The provision of food is the primary purpose of land dedicated to arable (e.g. wheat, barley, maize and oats), horticultural or improved grassland (intensive dairy, beef and sheep) production, hence the high degree to which this ecosystem service is delivered by these systems. For grassland categories food production is less significant for rough and acid grassland systems, with negligible such provision from bracken, forest and heath systems. Woodland, particularly deciduous, provides a modest food provision role in relation to edible fungi, which tends to be focused on an epicurean perspective in the UK. Fibre production generally is low from most of the systems considered here, with small quantities of wool and linseed production occurring. However, timber production from forests means that both deciduous and coniferous systems deliver this ecosystem service to a high degree. Similarly, timber is commonly used as a fuel, especially domestically, while agricultural systems are increasingly producing biofuel crops, hence their delivery of the ecosystem service of fuel. In the sense that these systems provide a provisioning role in terms of genetic resources (related to a biodiversity support function, see below), soil microbial genetic diversity at least is generally very high in all systems (compared to aboveground compartments), but tends to be greatest in unmanaged systems, and particularly unmanaged grassland, woodland and heath systems, where biodiversity is usually greater. Specifically, soil microbial diversity is highest in permanent pasture systems receiving low management (e.g. McCaig et al ., 2001; Kennedy et al ., 2006). As potential sources of genetic resources for biotechnological applications, it is arguable that all habitats have equal potential due to the high diversity which prevails in general, but there is virtually no evidence to this effect. Historically, pharmaceuticals have been gathered from wild plants (e.g. aspirin from Salix spp.), but today artificial manufacturing dominates. However, some crops are used to procure pharmaceutical compounds, such as galanthamine (daffodil bulbs) (Moraes-Cerdeira et al ., 1997). Similarly, horticulture produces ornamental products such as dried and fresh flowers. Water provision is importantly delivered by heath and montane systems, because typically these areas receive higher quantities of precipitation than lowland systems. However, forest systems have been shown to disrupt hydrological cycles and water supply due to increased rates of precipitation interception and evapotranspiration (Kirby et al ., 1991), and this is the only negative provisioning service delivered by any of the significant land cover types.

3.3.2 Regulating services The influence of the land cover types on delivery of regulating services can broadly be divided into two categories; those associated with intensive agriculture and those associated with low intensity agriculture and natural systems. The intensive agricultural systems have highly negative effects on global climate due to cultivation and associated land drainage resulting in the loss of soil carbon (Lal, 2004; Freibauer et al ., 2004), while the lower intensity systems and forest and heath/montane systems tend to accumulate organic matter in

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their soils. Additionally, increased emissions of greenhouse gases occur from intensive agriculture, with systems using N fertilisers being sources of nitrous oxide (N 2O), while grazed grassland systems are associated with the emission of high quantities of methane

(CH 4) from livestock, as well as N 2O from intensively grazed systems (Steinfeld et al ., 2006). Similarly, intensive agriculture tends to result in degradation of soil quality and increased leaching of nutrients to surface waters, while the other systems tend to be beneficial as a result of the lower levels of interventions (e.g. drainage of agricultural land has been identified as one of the key factors affecting the delivery of beneficial services from organo- mineral soils (Lal, 2004; Holden et al ., 2007). Soil quality deteriorates due to loss of soil organic matter and compaction associated with intensive agriculture, while relatively undisturbed soil systems such as rough grassland and forests are associated with greater soil structural integrity. Regional and local climate are also likely to be influenced by land cover because it affects evapotranspiration and air temperature, but to some extent this depends on the spatial pattern and distribution of the land cover types. Generally the more natural systems will have more beneficial properties than the more managed systems. Flood hazard regulation is a complex subject, depending on many factors such as antecedent soil moisture conditions and potential for storage of water. However, generally water storage capacity is decreased by soil degradation associated with intensive agriculture, and associated factors such as soil compaction generally mean that intensive agricultural soils do not provide the benefits of flood hazard regulation, while more natural systems do. Erosion control is provided primarily by permanent, dense vegetation cover, and therefore again the divide between intensive agricultural systems which experience regular periods of bare soil, and less intensive/natural systems is profound. Even intensive grassland systems, although generally having uniform grass cover, are subject to erosion due to the stimulation of surface runoff resulting from compaction by animals and poaching of land by livestock also makes it susceptible to erosion (Bhogal et al ., 2009). Forests generally have low erosion, but coniferous forests typically have some areas subject to felling and re-establishmentat any one time, and these areas can be particularly vulnerable to erosion, hence a low negative benefit has been attributed to coniferous forests (Reynolds, 2007). None of the land cover types considered here provide the services of disease regulation, pest regulation or toxic hazard regulation. Pollination services are provided by the less intensively/natural systems as they provide habitat for pollinating species. Noise regulation is provided to a small extent by forests, and sometimes they are planted to provide shelter belts from roads and industrial practices, but generally this role is small. Air quality is negatively impacted by intensive agriculture, principally through the emission of sprayed herbicides and pesticides, but also through ammonia (NH 3), nitrous oxide (N 2O) and methane (CH 4) emissions which can be significant from improved grassland systems, where slurry and dirty water is regularly spread on land.

The soil biota play a myriad of indirect roles in regulating services, principally in relation to carbon and nutrient cycling, soil structural integrity and dynamics, biotic regulation and mutualism (e.g. Bardgett, 2005; Shennan, 2008). Such biota play a relatively small role in regulating services in any form of intensively-managed systems, particularly those geared to production, where industrially-derived substitution is adopted, such as via inorganic

48

fertilisers, synthetic biocides and ploughing; this distorts the natural balance of the ecosystem and may compromise the output of other environmental services (Kibblewhite et al ., 2008). This phenomenon predominates in high-production arable systems, and intensively managed grassland. Since these constitute only a relatively small proportion of organo-mineral soils, the biotic delivery of regulating services is relatively important in the majority of organo- mineral soils. In relation to C cycling, this relates to the primary energy sources, stores and flows in soil systems and how these fuel biotic action and interaction; this is the fundament of soil organic matter dynamics and all the properties this imparts (e.g. Janzen et al ., 1997; Magdoff and Weil, 2004; Osler and Sommerkorn, 2007). Organo-mineral soils, by virtue of the greater concentrations of C that they carry play specific roles in relation to C cycling and the biota are significant modulators of such processes in this respect. There is generally a positive association between with the C content of soils and the below ground (predominantly microbial) biomass, hence organo-mineral soils generally support a commensurately high microbial biomass. The soil biota play a pivotal role in modulating the losses of C from soil in that soil OM is essentially the primary energy source for all heterotrophic organisms, and assimilation of OM is associated with respiration, which results in loss of C from the system via respiration. Any actions, such as those associated with climate change or via management, which increase the availability of OM to organisms will result in such respiratory losses of C. Biotic action can also increase concentrations of dissolved organic C (DOC) in the soil solution which can then be prone to leaching. For example, Cole et al . (2002) demonstrated how increases in surface temperatures in an organo-mineral soil resulted in a migration of enchytraeid worms from surface zones deeper into the soil fabric, with a concomitant increase in perturbation of the matrix and substantial release of DOC. Accelerated or more extreme freeze:thaw and wet:dry cycles also generally increase the availability of otherwise physically-protected OM such that subsequent microbial action leads to C losses.

In grassland, heathland and woodland systems subject to low management, nutrient inputs are predominantly derived from natural sources (in contrast to production systems where large quantities are imported) and associated biotic cycling processes are fundamental to system functioning. These are particularly significant with respect to mutualistic associations between plants and the soil microbiota such as mycorrhiza, microbially-associated N-fixation, and looser associations such as via plant growth promoting rhizobacteria (e.g. Lavelle et al ., 1995; Rengel, 2002). Mycorrhizae, which involve a close mutualistic association between plants roots and various types of fungi, play very significant roles in governing vegetation structure in unmanaged grasslands, heathlands and both deciduous and coniferous forest systems, affecting nutrient (particularly P) uptake, water relations and resistance to pathogen attack. As such, mycorrhizae are of certain importance in organo-mineral soil systems.

3.3.3 Supporting services All the systems considered here produce organic material and therefore are significant primary production systems, with the more intensive agricultural systems and forest systems having the highest levels of productivity, and the low nutrient, low input systems of acid and bracken grassland the lowest. For all other supporting services there is generally a similar

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divide between intensive agricultural and less intensive/natural systems as for regulating services. Intensive agricultural production perturbs nutrient cycling, potentially creating a very leaky system in which nutrients are lost both into water sources e.g. NO 3 leaching (Galloway et al ., 2003) and into the air, e.g. N 2O & NH 3 emissions (Bouwman et al ., 1997). Associated high nutrient inputs affect the community structure both above and below ground (Jangid et al ., 2008) subsequently impacting on nutrient cycling capabilities, whereas systems with lower nutrient inputs cycle nutrients more efficiently. Similarly, intense systems are more subject to soil degradation and loss as described above, whereas less intense systems tend to create and accumulate soil and associated organic matter. Water cycling tends to be perturbed by intensive agricultural systems, due to rapid fluctuations between bare soils and high biomass crops. Forests can also disrupt hydrological cycling by increasing evapotranspiration, although this disruption occurs over longer periods. In terms of supporting biodiversity, in general less-managed systems carry greater levels of biodiversity, which is related to the provision of refugia; wherever there is soil and vegetation, refugia are provided to varying degrees, with unmanaged systems generally providing the greatest variety and diversity of such features. As explained above, belowground microbial diversity (per se ) is high in all systems. However, both aboveground and soil community structures vary between different systems and these carry different characteristic communities, supporting more specific forms of biodiversity associated with each land-cover type.

3.3.4 Cultural services Assessment of cultural ecosystem services is difficult because it is often a highly subjective matter and difficult to quantify. However, in many places land use practices have largely remained the same over long periods of time and therefore play an important role in forming part of our cultural heritage. Similarly, for many people, these land uses are an important aspect of the aesthetics of the countryside. Less intensive, more natural systems, especially forests are increasingly used for recreation purposes such as hiking and cycling, and consequently are also important for tourism. Forests also have high importance for many people with regard to other cultural services such as spiritual and religious purposes, while distinct landscape types in which people have lived for many years, such as intensive agricultural landscapes, can provide a sense of place. Soil biota play a modest direct cultural service role since they are largely invisible, however some subterranean fauna are particularly associated with soil systems, such as earthworms and moles, and as such arguably play a key cultural role in terms of a modest awareness of soil systems and their importance to society.

3.3.5 Summary of key points 1) Intensive agricultural systems (e.g. arable, horticultural or improved grassland systems) on organo-mineral soils generally deliver different combinations of ecosystem services to those delivered by less intensive or semi-natural systems. 2) Many of the ecosystem services delivered on organo-mineral soils by intensive agricultural systems (extremely important for our food and fibre production), are done so in a negative way (disbenefits), while the less intensive and semi-natural systems deliver services generally in a positive way.

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3) Woodland (especially deciduous) delivers the highest number of ecosystem services of all the significant land cover types occurring on organo-mineral soils, and generally to a higher degree than other systems.

Table 16 . Assessment of ecosystem services of organo-mineral soils in England and Wales by environmental zone (EZ) Environmental zone EZ1 EZ2 EZ3 EZ8 EZ9 Ecosystem services E. Low . Eng. W. Low . Eng. Up. Eng. Low . Wales Up. Wales Provisioning services Food ● ● ● ● ●

Fibre (thatch, wool, sedge) ● ● ● ● ● Fuel ● ● Genetic resources ● ●

Refugia ● ● ● ● ● Biochemicals/pharmaceutical ● Ornamentals ● Water provision ● ●●

Regulating services

Global climate ● ● ●● ● ●

Regional climate ● ● ●● ● ● Local climate ● ● ● Flood hazard regulation ● ● ●● ● ●

Erosion control ● ● ●● ● ●● Disease Pest regulation

Pollination services ● ● Toxic hazard regulation

Noise regulation ●

Soil quality ● ● ●● ● ● Air quality ● ● ●● ● ● Water quality ● ● ●● ● ●

Supporting services

Primary production ● ● ● ● ● Nutrient cycling ● ● ●● ● ● Soil formation ● ● ●● ● ● Water cycling ● ● ●● ● ●●

Cultural

Recreation ● ● ● Tourism ● ● Cultural heritage ● ● ● ● ● Education ● ● ●

Community development ● ●

Spiritual ● Religion

Aesthetics ● ● ● ● ●

Inspirational ● ● Sense of place ● ● ● High Medium Low None Negative influence Positive influence ● ● ● ● ●

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In some cases ecosystem services in different significant land cover types are both positive and negative, and this is indicated by recording the most significant value of each in the relevant matrix square, hence the occasional appearance of two dots.

3.4 Assessment of ecosystem services of organo-mineral soils by environmental zone

3.4.1 Approach The significant land cover type distribution among the five EZs considered varies greatly, ranging from a single dominant land cover type in EZ2 and EZ8 of improved pasture, to five different land cover types in EZ9 (Table 15). This range of ecosystem types is reflected in the ecosystem services delivered in each EZ (Table 16). Here we consider the ecosystem services delivered by each of the EZs.

3.4.2 Provisioning services by EZ The range of significant provisioning services delivered by EZ2 and EZ8 is limited because of their dominance by improved pasture, which is limited to food production, some fibre production and provision of refugia. However, EZ3 also has a significant amount of improved grassland, meaning it delivers these services, but the broader range of land-cover types means it can also deliver a wider range of ecosystem services, in particular the provision of refugia, genetic resources and water provision. The focus of land use in EZ1 is arable and horticultural production, and these intense systems means a wide range of provisioning services are delivered, most notably food and ornamentals. However, EZ9, the uplands of Wales, provide the widest range of provisioning services, but unlike the other EZs, food supply is not the most significant. Fibre, fuel and refugia are the most important provisioning services, and consequently, when considering this zone with regard to economic value in terms of productivity, it would be likely to rank the lowest, highlighting the importance for holistic assessment of ecosystem services.

3.4.3 Regulating services by EZ The range of distributions of land cover types across the EZs is strongly reflected in the delivery of regulating services, with EZ2 and EZ8 delivering a wide range of negative services (dis-benefits), as does EZ1, although here the dis-benefits are generally to a higher degree. This is because these EZs are dominated by intensive production systems, which generally conflict with environmental quality (Pilgrim et al ., 2010). Of particular importance are the effects on global climate, which is a reflection of greenhouse gas emissions from degradation of soil organic matter (also reflected by the highly negative delivery of soil quality), denitrification, and methane emissions from livestock within the range of systems dominant in these zones. Generally a wide range of positive benefits is delivered by EZ9, in particular pollination services and soil quality.

3.4.4 Supporting services by EZ All supporting services are delivered in each EZ, but like the regulating services, in the intensive agricultural dominated zones (EZ1, 2 and 8), these are generally highly negative, with the exception of primary production which is high across all EZs. In EZ3 the range of

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land cover types means that nutrient cycling, soil formation and water cycling are all delivered in both positive and negative ways, while the low intensity land covers which dominate in EZ9 mean that all supporting services are to some extent delivered to a high positive degree, with the exception of water cycling, which is disrupted to some extent by the presence of a significant area of coniferous forest.

3.4.5 Cultural services by EZ All the cultural services delivered by each EZ are positive, but again largely reflects the number of significant land cover types within them. Only two services, cultural heritage and aesthetics are delivered by EZ2 and EZ8 reflecting the single significant land use. Nearly all cultural services are delivered by EZ9, with particular emphasis on recreation, tourism and cultural heritage. The aesthetic service of the land uses within all EZs is all delivered to a high degree, reflecting the way in which dominant land cover types affect the way the landscape look, and help define the character of a region.

3.4.6 Summary of key points 1) The greater the range of significant land cover types, the greater the range of ecosystem services delivered by the EZ. In this case EZ9 has 5 dominant land cover types and delivers 29 different ecosystem services, compared to EZ2 and EZ8, which have only one land cover type and deliver a total of 16 ecosystem services. 2) Nearly all the ecosystem services delivered in EZ9 are done so in a positive way, while approximately one third of the ecosystem services delivered in EZ1 and almost two thirds of those in EZ2 and EZ8 are done so in a negative way. 3) In the EZs dominated by intensive agriculture (EZ1, EZ2 and EZ8) provisioning and cultural services generally are positive, while regulating and supporting services are negative.

3.5. Assessment of ecosystem services of organo-mineral soils by soil type

3.5.1 Approach The method of assessment used here identifies only a few differences between the ecosystem services delivered by different organo-mineral soil types (Table 17). All three soil types have significant areas of between 7-8 different land cover types (Table 13), meaning that a wide range of ecosystem services are delivered. While the type of intensive agriculture varies across the three soil types, and consequently the precise products will as well, the range of ecosystem services delivered is similar. The range and degree of ecosystem services delivered by soil types 2 and 3 are identical, and some distinct trends across all soil types are apparent, such as nearly all provisioning services are provided to a medium or high positive degree, while regulating services and supporting services tend to be delivered equally both positively and negatively. The main differences identified between soil types is that soil type 1 delivers refugia to a higher degree than soil type 2 and 3, but unlike the latter, does not provide the services of biochemical/pharmaceuticals and ornamentals. The delivery of supporting services is identical across all soil types, as is that for cultural services with the exception that soil type 1 delivers slightly more spiritual and religious services, mainly as a result of the presence of significant amounts of deciduous woodland.

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Table 17. Assessment of ecosystem services of organo-mineral soils in England and Wales by soil type.

Ecosystem services Soil type Soil 1 Soil 2 Soil 3 Provisioning services Well drained Podzols Gley soils

Food ● ● ● Fibre (thatch, wool, sedge) ● ● ● Fuel ● ● ● Genetic resources ● ● ● Refugia ● ● ● Biochemicals/pharmaceutical ● ● Ornamentals ● ●

Water provision ●● ●● ●●

Regulating services

Global climate ●● ●● ●●

Regional climate ●● ●● ●● Local climate ● ● ● Flood hazard regulation ●● ●● ●●

Erosion control ●● ●● ●● Disease Pest regulation

Pollination services ● ● ● Toxic hazard regulation

Noise regulation ● ● ●

Soil quality ●● ●● ●● Air quality ●● ●● ●● Water quality ●● ●● ●●

Supporting services

Primary production ● ● ● Nutrient cycling ●● ●● ●● Soil formation ●● ●● ●● Water cycling ●● ●● ●●

Cultural

Recreation ● ● ● Tourism ● ● ● Cultural heritage ● ● ● Education ● ● ●

Community development ● ● ●

Spiritual ● ● ●

Religion ●

Aesthetics ● ● ●

Inspirational ● ● ● Sense of place ● ● ● High Medium Low None Negative influence Positive influence ● ● ● ● ● In some cases ecosystem services in different significant land cover types are both positive and negative, and this is indicated by recording the most significant value of each in the relevant matrix square, hence the occasional appearance of two dots.

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3.5.2 Summary of key points 1) There is little variation in the range of services delivered by the dominant land cover types on the different soil types. 2) The range and degree of services delivered by soil types 2 and 3 are identical 3) Nearly all provisioning and cultural services delivered by all three soil types are positive, while regulating and supporting services are delivered both positively and negatively.

3.6 Impacts of climate change on ecosystem services from organo-mineral soils

3.6.1 Approach Here we provide a general synopsis of how predicted climate change is likely to affect the services delivered by organo-mineral soils in England and Wales. The changes in ecosystem functions are based on the prediction that the UK is likely to experience warmer, wetter winters and hotter drier summers (Defra, 2009). Project SP1601 reports that there is great uncertainty over how climate change will affect soils and therefore only generalisations can be made, but the key effects of these changes as reported in SP1601 are likely to be as follows: 1) Drier summers may increase soil hydrophobicity resulting in increased erosion, increased flood risk and short term storage from crops. 2) Wetter winters may result in reduced access times to agricultural land, increasing the risk of inappropriate management. The consequences of this are likely to be associated with soil structural degradation, in particular compaction. The effects of compaction are complex, but principally result in: i) reduced N mineralisation, so an impact on N cycling ii) increased nitrous oxide emission iii) increased surface runoff, resulting in soil erosion and flooding iv) reduction in refugia due to degraded soil structure

Based on these conclusions, it is likely that intensive agricultural land is likely to be most affected by climate change rather than that which is less intensively managed. For example, organo-mineral soils used for arable, horticultural and improved grassland production are likely to experience reductions in food and fuel production, although there is considerable uncertainty over this, due to potential advances in agronomy and crop science, as well as the natural response to predicted increased concentrations of CO 2 in the atmosphere. What does appear likely is that soil structural degradation of intensive agricultural soils associated with climate change is likely to result in increased production of greenhouse gases, increased soil erosion, increased flood risk, degradation of soil and water quality. If, so such any negative impact these systems already may have on the supporting services of nutrient cycling, soil formation and water cycling would be exacerbated. In general terms, these impacts are likely to be less severe on the less intensive agricultural systems. However, any increase in soil and organic matter (oxidation) loss could induce deleterious feedback impacts on global climate

(e.g. additional release of CO 2) with flood risks also likely to increase due to changes in soil hydrophobicity. The response of different environmental zones to climate change with regard to ecosystem service delivery is likely to reflect their significant land uses in terms of intensive versus less intensive land use. Consequently, it is likely that EZs 1, 2 and 8 will

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experience the most wide ranging and severe impacts to ecosystem services, while the less intensive systems in EZs 3 and 9, although experiencing impacts such as global climate, will be less affected.

3.6.2 Summary of key points 1) Intensive agricultural land is likely to be impacted more than less intensive land. 2) Most impacts are likely to be detrimental or negative. 3) There is great uncertainty over these impacts because of the lack of information on how soil biota and plants will respond and interact under climate change.

3.7 Comparison of ecosystem services delivered by organo-mineral soils with organic soils and mineral soils As their name suggests, organo-mineral soils comprise some of the qualities of both mineral soils and organic soils. Similarly the ecosystem services they provide is an amalgam of the services provided by organic and mineral soils. Logically it can be assumed that services dependent on upon a soil’s primary properties (e.g. carbon storage capacity in relation to organic matter content, or crop production in relation to manageability of land) will be performed to a higher degree by soils with extremes of these properties. It will also be related to their landscape position, and a detailed assessment of how the delivery of ecosystem services by organo-mineral soils compares with those of mineral and organic soils is beyond the scope of this report, although some broad qualitative assumptions can be drawn based on organo-mineral soil properties in comparison with organic and mineral soils. Below in Table 18, the delivery of ecosystem functions by the three different soil types is compared in relative terms. This table takes into account the distribution of land uses on the three soil types, with the very general assumptions that mineral soils are predominantly used for arable and horticultural use, organo-mineral soils are generally of mixed use (including much forest), and organic soils comprise mainly rough grassland, heath and montane land cover. It also considers the assessments of ecosystem services delivered by organo-mineral soils earlier in this section. The term ‘low’, ‘medium’ and ’high’ are used to indicate in relative terms the qualitative degree to which the different ecosystem services are delivered by each soil type. In some cases the service is performed but in a negative way and this is indicated by the classification appearing in red i.e. if ‘high’ appears in red, it means that the particular function in question is performed to a high a degree, but that it is in a negative way.

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Table 18 Qualitative comparison of ecosystem services delivered by organic, organo-mineral and mineral soils in England and Wales.

Ecosystem services Organic soil Organo-mineral soil Mineral soil

Provisioning services Food low medium high

Fibre (thatch, wool, sedge) medium medium low Fuel medium medium low Genetic resources high medium low Biochemicals/pharmaceutical low low medium Ornamentals low low medium Water provision high medium low

Regulating services Global climate high medium high Regional climate medium medium medium Local climate medium low low Flood hazard regulation high medium medium Erosion control medium medium high Disease low low low Pest regulation low low low Pollination services high medium low Toxic hazard regulation low low low Noise regulation low low low Soil quality high medium high Air quality high high low Water quality high medium high

Supporting services Primary production low medium high Nutrient cycling medium high high Soil formation medium high high Water cycling medium medium medium

Cultural Recreation medium high low Tourism medium high low Cultural heritage high high medium Education medium medium low Community development low medium low Spiritual low medium low Religion low medium low Aesthetics high high high Inspirational low low low Sense of place low medium medium

One of the key features of this table are that relative to the organic and organo-mineral soils, mineral soils are the greatest primary producers, mainly as a result of arable and horticultural production. However, mineral soils also contribute to several of the supporting and regulating services in a negative way, where in general terms, organic and organo-mineral soils are positive providers of regulating services. There are several caveats to this, such as in

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situations where forestry dominates land use on organo-mineral soils, where it is likely that the function of water provision would be performed in a negative way, but overall this is probably outweighed by the fact that many of the soils will be in upland areas receiving high rainfall, and therefore storing water which feeds streams and rivers. As mentioned above, typically the degree to which ecosystem services are assessed as being delivered by organo- mineral soils generally lies somewhere between that of the extremes of organic and mineral soils. Key areas where they do appear to have higher delivery than the other two soil types is in the delivery of some cultural (e.g. recreation and tourism) and supporting (e.g. soil formation and nutrient cycling) services. However, it is quite possible that overall the delivery and value of services from organo-mineral soils could be greater than that from either organic or mineral soils alone.

This is a very tentative assessment of the relative degree to which organic, organo-mineral and mineral soils deliver ecosystem services, and a more thorough assessment, beyond the scope of this one is required. One way to address the issue of relative degree of delivery of ecosystem services by different soils could be by expounding the suggestion by Haygarth and Ritz (2009) that there is a need to map natural soil services and functions (i.e. what functions they would perform without management intervention) in the UK, with a move towards integrated maps combining current land use and natural functioning. While potentially a large task, involving the combination of existing datasets such as The Countryside Survey, the National Soil Map and datasets such as land use capability maps like that in Figure 16 and carbon carbon sequestration maps (e.g. Jones et al ., 2005), this would enable the quantitative estimation of ecosystem services across a range of soil types, and could form the basis of a future Defra project.

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Figure 16 Land use capability map of England and Wales with respect to suitability for growing winter cereals (Source: National Soil Resources Institute, Cranfield).

3.8 Concluding remarks and summary The assessment provided here provides a semi-quantitative indication of the key ecosystem services delivered by organo-mineral soils in England and Wales, based on specific, spatially significant land cover types occurring in each EZ. An indication of how these ecosystem services are distributed with regard to soil type and EZ is also provided. For more detailed, quantified information, greater analysis of the spatial data is required incorporating weighted mean data analysis, but is beyond the scope of what is possible here. Overall summary of key points: 1) Organo-mineral soils generally deliver a wide range of ecosystem services. 2) Intensive agricultural systems (e.g. arable, horticultural or improved grassland systems) on organo-mineral soils generally deliver different combinations of ecosystem services to those delivered by less intensive or semi-natural systems. 3) Intensive agricultural systems on organo-mineral soils are important for the delivery of provisioning services, but have a detrimental effect on the environment. 4) Woodland (especially deciduous) delivers the highest number of ecosystem services of all the significant land cover types occurring on organo-mineral soils, and generally to a higher degree than other systems. 5) There is little variation in the range of services delivered by the dominant land cover types on the three different types of organo-mineral soils identified. 6) The range and degree of services delivered by organo-mineral soil types 2 and 3 are identical.

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7) Nearly all provisioning and cultural services delivered by all three organo-mineral soil types are positive, while regulating and supporting services are delivered both positively and negatively. 8) The greater the range of dominant land cover types occurring on organo-mineral soils, the greater the range of ecosystem services delivered by the EZ. In this case EZ9 has 5 dominant land cover types and delivers 29 different ecosystem services, compared to EZ2 and EZ8, which have only one land cover type and deliver a total of 16 ecosystem services. Upland regions of England, and especially Wales, deliver a wider range of positive ecosystem services from organo-mineral soils. 9) Nearly all the ecosystem services delivered by organo-mineral soils in EZ9 are done so in a positive way, while approximately one third of the ecosystem services delivered in EZ1 and almost two thirds of those in EZ2 and EZ8 are done so in a negative way. 10) In the EZs dominated by intensive agriculture (EZ1, EZ2 and EZ8), provisioning and cultural services from organo-mineral soils generally are delivered in a positive way, while regulating and supporting services are delivered in a negative way. 11) Intensive agricultural land on organo-mineral soils is likely to be impacted more by predicted climate change than less intensively managed land and most impacts are likely to be detrimental or negative. 12) There is great uncertainty over the impacts that will occur to organo-mineral soils as a result of climate change because of the lack of information on how soil biota and plants will respond and interact.

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Section 4. Best practices for managing carbon in organo-mineral soils

Anne Bhogal (ADAS)

4.1 Introduction

Land-use and its management can have a great influence on the turnover, loss or retention of carbon (C) in soils (Lal, 2004). Various methods for maintaining or increasing soil C storage have been identified for both mineral (e.g. Sousanna, et al ., 2004; Freibauer et al., 2004; Dawson & Smith, 2007; Smith et al , 2008; Bhogal et al ., 2009) and peat soils (e.g. SEERAD, 2007; Holden et al., 2007; Worrall et al., 2010), with general agreement over best practices. However, studies have either focused on lowland mineral soils or upland deep peats, with a paucity of studies specific to organo-mineral soils. The effect of changes in land-use or management practices on the C content of organo-mineral soils, therefore has to be either inferred from studies on mineral (or peat) soils, or derived from first principles on the behaviour of C in soils. Indeed in the absence of data, Smith et al . (2010) assumed that per- area greenhouse gas (GHG) mitigation potentials for land-use change on organo-mineral soils were the same as those for mineral soils.

The aim of this section was to review and synthesise research on soil C management (in mineral and organic soils), and to identify potential best practice options for retaining C in organo-mineral soils.

4.2 Carbon turnover and storage in soils

Figure 17 shows the key input and loss processes of a soil C budget. Soil C can only be increased by either increasing inputs (e.g. crop residues, organic manures) or decreasing losses (i.e. reducing oxidative losses to CO 2, or particulate and dissolved OC following erosion) via improved management. Notably, protection of existing soil C should remain a priority.

Figure 17 Key elements of the soil carbon budget

CO 2 CO 2 CH Rainfall 4 LIVESTOCK

VEGETATION OC (roots/residues/ma nures)

SOIL ORGANIC CARBON DOC/POC

SURFACE & GROUND WATERS

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There are a number of limitations to soil C storage: 1. The quantity of C that can be stored in any soil is finite. After a change in management practice, soil C levels increase (or decrease) towards an equilibrium value (after c. 100 years or more) that is characteristic of the soil type, land use and climate (Johnston & Poulton, 2005). The relatively ‘high’ annual rate of soil C accumulation (C storage) in the early years after a change in land-use or management cannot be maintained indefinitely and the annual rate of increase will decline (eventually to zero) as a new equilibrium is reached. It is therefore unlikely that the initial rate of increase in soil C following a change in land-use/management practice will be sustained over the longer term (>50 years), as a new equilibrium level is reached. 2. Carbon storage is reversible. Maintaining a soil at an increased soil C level, due to a change in management practice, is dependent on continuing that practice indefinitely. Indeed, soil C is lost more rapidly than it accumulates (Freibauer et al., 2004). 3. The soil C and N cycles are intimately linked. Increased soil C may affect the release of

other greenhouse gases (GHG) (e.g. nitrous oxide (N2O) and methane (CH 4)) or diffuse water pollution (nitrate (NO 3) and phosphorus (P)) i.e. there is a risk of ‘pollution swapping’ where the reduction of one form of pollution increases another. 4.3 Approaches

The land-cover associated with organo-mineral soils has been classified into 6 broad classes (Figures 18 a,b; further detail on the distribution between soil classes and environmental zones is provided in section 2). Notably, organo-mineral soils are estimated to cover an area of 1,165,665ha in England and 426,211ha in Wales. Soil C management practices will largely be specific to individual land-uses, however, the basic principles are the same; to increase inputs and/or reduce losses.

Figure 18 Distribution of broad land-cover classes associated with organo-mineral soils in England and Wales. a) England (1,165,665ha of organo-mineral soils) b) Wales (426,211ha of organo-mineral soils)

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Best practice measures for soil C management under each of the key land-cover classes have been identified from the literature and are summarised in Table 19, with further detail for the four major land use categories (grassland, cropland, forestry and heath) provided in the following sections. Each section gives a description and rationale for the method, details of other potential ecosystem service benefits and ‘potential pollution swapping’ that could occur following adoption of the method, and using expert judgement likely uptake (practicality). The table of practices (Table 15) was circulated to stakeholders in order to assess and prioritise the likelihood of their acceptance and uptake, and to identify any ‘gaps’. Where possible, an estimate of potential C stored following adoption of the method has been given. The rates of C storage have largely been obtained from global meta-analyses/reviews on mineral soils (e.g. Dawson & Smith, 2007), so should be treated with caution when applying them to organo-mineral soils in England and Wales. Also, they only represent the initial rate of soil C increase achievable (after 20-30 years), as soil C accumulation rates will slow and eventually cease when a new equilibrium is reached (estimated to be after 50-100 years; Johnston & Poulton, 2005). Table 19 Potential best practices for retaining carbon in organo-mineral soils Land-use a & method Benefit to soil C Likely uptake Environmental -1 -1 b c (t CO 2e ha yr ) (practicality) impact Semi-natural grassland 1. Reduce stocking density 1.3 d +

2. Establish woodlands/forestry 0.4 e +
Improved grassland 3. Increase water table 5.1-15 f +
4. Reduce stocking density 1.3 d +

5. Organic material additions 0.3-5.5 g +++
6. Establish woodlands/forestry 0.4 e +
Cropland 7. Establish grassland 1.1-7.0 g +

8. Establish woodlands/forestry 1.1-2.2 e,g +

9. Rotational grass 0.4-1.7 h +
10. Reduced tillage 0.6-1.1 i ++
11. Organic material additions 0.3-5.5 g,i +++
Forestry 12. Increase rotation length nd j ++
13. Site management nd j +++
Heath 14. Do not burn nd j ++

15. Reduce stocking density nd j +

aLess than 3% of organic-mineral soils in England and Wales are also associated with wetland communities; due to the low land area and limited management options we have not explored this area any further. bLikely uptake: +++ high; ++medium; +low

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cEnvironmental impact (diffuse pollution, biodiversity, erosion, GHG emissions):

Highly beneficial (impact over large area);
medium/low benefit;
potential benefit but also a risk of “pollution swapping”; see text for more detail. dConnant et al. (2001); this is considered to be the initial rate of increase (<20 years) eSoussana et al. (2004) estimated over 90 years; additional C stored in woodland vegetation -1 -1 estimated at 0.3-5.6 t CO 2e ha yr depending on tree species, harvest frequency and climatic conditions. fFreibauer et al . (2004); >50% uncertainty gDawson & Smith (2007); Bhogal et al. (2008) -assumes same rate as applications to cropland, which may not necessarily be the case. hSmith et al. (2010) iBhogal et al . (2008) jnd: no data. Benefit to soil C assumed due to reduction in soil disturbance and erosion.

4.4 Best Practices for retaining carbon in organo-mineral soils

4.4.1 Best practices for organo-mineral soils under grassland

The largest area of organo-mineral soils in both England and Wales is under grassland (c.50% and 65% of the total organo-mineral soil area, respectively), the majority of which is unimproved rough or acidic (semi-natural) grassland in upland regions, although there are also significant areas of improved grassland in lowland regions (see section 2). Temperate -1 -1 grasslands are believed to be net C sinks, with estimates ranging from 0.1-4 t CO 2e ha yr (Sousanna et al., 2004). Indeed, organo-mineral soils have been suggested to store most carbon and emit less GHG where the underlying natural grassland vegetation is managed with minimal disturbance and light grazing, where appropriate (SEERAD, 2007). A key requirement for the maintenance of C in organo-mineral soils under grassland is to avoid conversion to arable or ley/arable cropping. These practices result in the increased oxidation of organic matter, and can increase particulate organic C (POC) losses through soil erosion and dissolved organic C (DOC) losses in surface runoff and drainflow. Indeed, Dawson & Smith (2007) estimated that the conversion of permanent grassland to tillage cropping would -1 -1 result in C losses in the range 2.2-6.2 t CO 2e ha yr (albeit with >50% level of uncertainty), -1 -1 and Smith et al. (2010) even higher C loss rates (8.4-10.6 tCO 2e ha yr ) based on results from ley-arable experiments at Rothamsted (Johnston, 1973). The ploughing out of grasslands also increases direct emissions of N 2O (following mineralisation of organic matter), nitrate leaching losses and can result in increased sediment losses. Moreover, the conversion of grassland to arable land has been suggested to be the most damaging practice for reducing C stocks and enhancing GHG emissions, particularly on soils with high C contents (Holden et al ., 2007).

4.4.1.1 Semi-natural grassland options

Over 80% ( c.220,000ha) of grasslands on organo-mineral soils in Wales are semi-natural, the majority of which (>90%) are located in upland regions. Similarly in England, c.70% (c. 380,000ha) of the grasslands on organo-mineral soils are semi-natural. Best practices for

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retaining/enhancing soil C within these systems are detailed below and a summary of the relative benefits/disbenefits is given in Table 20.

1. Reduce stocking density/grazing

Principle : Overgrazing has been identified as one of the main reasons for the degradation of organic soils (Holden et al., 2007) and poaching can exacerbate the transport of sediment (and organic matter) to water courses, by exposing bare soils and increasing surface run-off (Bhogal et al ., 2009). Soil disturbance associated with intensive grazing can also increase soil C oxidation rates. A reduction in stocking and grazing density can therefore help minimise soil structural damage and erosion, thereby reducing losses of both dissolved and particulate C. Bardgett et al . (1993; 2001) measured higher topsoil C contents in semi-natural grasslands on organo-mineral soils managed by light grazing (1-2 ewe ha -1 yr -1) compared to un-grazed and heavily grazed (8-16 ewe ha -1 yr -1) grasslands, which had significantly lower soil C contents. Connant et al . (2001) reviewed the effect of grassland management on soil C and -1 -1 predicted C storage rate increases of 1.3 t CO 2e ha yr from improved grazing practices (based on regression analysis of results from 31 studies across the globe, including the study by Bardgett et al ., 1993). Jones & Emmett (2009) reported a GHG mitigation range of 0.18- -1 -1 5.5 t CO 2e ha yr for reduced grazing of semi-natural grasslands; this was an aggregate of all changes in GHG emissions (i.e. N 2O and CH 4 , as well as changes in soil C storage).

Other benefits or risks : A reduction in stocking rate and hence grazing intensity will reduce the amounts of excreta and manure produced per unit area and hence decrease N losses via

nitrate leaching (NO 3) and denitrification (N 2O and N 2), particularly from urine patches (Cuttle et al., 2007). Methane and ammonia emissions will also be reduced.

Likely uptake : Although this practice will be simple to adopt, its uptake is likely to be limited, due to the impact on farm income resulting from reduced stock numbers. However, simple management measures such as moving feeding troughs at regular intervals, fencing off rivers and streams from livestock, and avoiding grazing on wetter sites (particularly in winter) can all reduce the potential for poaching/soil erosion and associated soil C loss.

2. Establish permanent woodlands/forestry.

Principle : The permanent conversion of grassland to woodland/forestry has often been promoted as a mechanism for GHG mitigation (e.g. King et al ., 2005), largely because of the -1 - potential increase in C stored in the vegetation itself. An estimated 0.3 - 5.6 tCO 2e ha yr 1can be stored in woodland vegetation depending on the tree species, harvest frequency and climatic conditions (Liski et al ., 2002; Hooker & Compton, 2003). However, changes in soil -1 -1 C storage are thought to be small; currently estimated at 0.4 ± 0.07 tCO 2e ha yr (Soussana et al., 2004), with some soils reported to accumulate C (typically mineral soils, with low initial C contents that are converted to broad-leaved woodland), whereas others potentially lose C (typically following drainage of wet peaty soils) (Soussana et al., 2004; Reynolds, 2007). Worrall et al. (2010) demonstrated that although the afforestation of peat soils can potentially increase the overall C budget, this was largely due to a transfer in C from the soil to above ground biomass. UK studies on the conversion of ‘agricultural land’ to

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forestry/woodland were summarised by Reynolds et al. (2007), including the conversion of moorland on peat soils (Billet et al., 1990; Harrison et al., 1997; Jones et al ., 2000) and arable land on mineral soils (Jenkinson, 1971). Annual soil C accumulation rates ranged from -1 -1 0.77 to 2.7 tCO 2e ha yr . There were no studies on organo-mineral soils and Reynolds (2007) cautioned against inferring soil C accumulation rates from other soil types, particularly given the inherent problems of soil heterogeneity and vertical gradients in soil C and bulk density. Moreover, Reynolds (2007) concluded that given the increases in soil respiration, DOC and POC losses during site preparation, the conversion of semi-natural grassland to forestry/woodland on organo-mineral soils is likely to have a relatively small net effect on soil C storage. Moreover, Smith et al. (2010) assumed that the conversion of permanent grassland to forestry on mineral and organo-mineral soils would result in a loss of -1 -1 soil C (1.5-3.0 tCO 2e ha yr ), based on the global meta-analysis of Guo & Gifford (2002). In the absence of conclusive evidence for organo-mineral soils under UK climatic conditions, a small net gain in SOC is assumed (Sousanna et al ., 2004).

Other benefits or risks: There is likely to be increased oxidation of organic matter and DOC/POC losses as well as N losses, during forestry establishment as a result of site preparation (including drainage and cultivation where necessary). However, once established forests are very effective in reducing nitrate leaching losses (Cuttle et al., 2007). Gaseous emissions of N 2O and NH 3 would also decrease due to the absence of grazing animals and fertiliser N inputs (depending on the previous grassland management). However, the conversion of semi-natural grassland to forestry/woodland on ‘wet’ organo-mineral soils may result in increased N 2O emissions (Skiba, 2005). These semi-natural grassland soils typically have low N 2O emissions, as the wet anaerobic conditions result in denitrification to N 2 rather than N 2O. Here, conversion to forestry (which usually requires drainage) may result in -1 -1 increased N 2O emissions, estimated in the range 0.1-0.6 kg N 2O-N ha yr (49-292 kg CO 2e/ha/yr), depending on the soil nutrient status (Skiba, 2005).

Likely uptake: Uptake of large-scale forestry/woodland creation is an extreme change in land use that is unlikely to be adopted by farmers, without the provision of suitable financial incentives. However, the small-scale creation of farm woodland (and hedges), as described in various ES options (e.g. shelter belts, in field trees and field corner management options, new hedges), may be more attractive.

Table 20 Summary matrix of the relative benefits/disbenefits of best practices for semi- natural grassland

Method Benefit to soil C Likely uptake Environmental -1 -1 d e (t CO 2e ha yr ) (practicality) impact 1. Reduced stocking density 1.3 a +

2. Establish woodland/forestry 0.4 b +
a Connant et al. (2001); this is considered to be the initial rate of increase (<20 years) bSoussana et al. (2004) estimated over 90 years; additional C stored in woodland vegetation -1 -1 estimated at 0.3-5.6 t CO 2e ha yr depending on tree species, harvest frequency and climatic conditions.

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dLikely uptake: +++ high; ++medium; +low eEnvironmental impact (diffuse pollution, biodiversity, erosion, GHG emissions):

Highly beneficial (impact over large area);
potential benefit, but also a risk of “pollution swapping”. See text for more detail.

4.4.1.2 Improved grassland options The main areas of improved grassland on organo-mineral soils are in lowland eastern and western England, where poorly drained (gley) soils have been drained and fertilised. This covers an area of c. 106,000ha, with a further c. 56,000ha of improved grassland in upland England. There is very little (<50,000ha) improved grassland on organo-mineral soils in Wales. Best practices for retaining/enhancing soil C are detailed below and a summary of the relative benefits/disbenefits is given in Table 21.

1. Water table management

Principle : The drainage of ‘wet’ soils has typically led to increased rates of organic matter oxidation and the shrinkage and subsidence of peat (Holden et al ., 2007). Therefore, re- wetting soils and increasing the water table height by blocking drains or allowing the natural deterioration of drainage systems, has the potential to reduce soil C losses. However, there have been few studies on the effects of raising water tables on soil C contents and the C balance of organo-mineral soils under grassland. Studies undertaken on upland deep peats have indicated that soil respiration rates would decrease, but methane production would increase, with a 55% probability of a net positive effect on the C budget of upland peats

(Worrall et al., 2010). Rewetting Dutch peat grasslands reduced the production of CO 2 by 14% (Best & Jacobs, 1997) and Freibauer et al . (2004) suggested that introducing shallower - water tables on organic soils would potentially increase soil C storage by 5.1 to 15 t CO 2e ha 1 yr -1, (albeit with an uncertainty level >50%), due to avoided C losses from peat oxidation. POC & DOC losses are also likely to be reduced by blocking drains due to reduced hydrological connectivity.

Other benefits or risks : Drainage systems can accelerate the delivery of agricultural pollutants from land to watercourses, therefore blocking drains would reduce hydrological connectivity and the potential transfer of pollutants to watercourses. However, on sloping land surface run-off losses may increase. Cuttle et al . (2007) suggested that this practice was neutral for reducing nitrate leaching and for P and sediment losses. However, the presence of drains can change the pathways through which runoff travels, and can reduce yields of suspended solids and associated phosphorus from improved grasslands by up to 50% (Bol et al. , 2008). In contrast, the same report also showed that field drainage can result in the promotion of losses of slurry and associated nutrients and pathogens following spreading (see section 3 on

organic materials below). There is a risk of increased N 2O emissions depending on N inputs, and degree of soil wetness (i.e. anaerobic conditions); CH 4 emissions are also likely to increase (Best & Jacobs, 1997). Grassland productivity is likely to decrease and stocking rates will have to be reduced to avoid increase poaching problems when soils are wet, which can lead to increases in suspended solids and phosphorus losses (Bol et al. , 2008); there is also potentially an increased risk of animal disease (foot rot).

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Likely uptake : This method is relatively easy to implement with the natural deterioration of drains requiring no necessary action; drainage deterioration is compatible with the Higher Level Stewardship (HLS) Scheme. However, rewetting grasslands will inevitably limit the current use of this land, with a potential loss of farm income.

2. Reduce stocking density

Principles, benefits & risks, likely uptake : As for semi-natural grasslands.

3. Encourage use of organic material additions

Principles : Increases in soil C in mineral topsoils can be directly related to organic matter (C) inputs (Dick & Gregorich, 2004). The recycling of organic materials to land is generally considered to be the best practicable environmental option for utilising the properties of these materials. Around 90 million tonnes of livestock manures (Williams et al., 2000), 3-4 million tonnes of biosolids (treated sewage sludge; Chambers, 1998) and 1.3 million tonnes of compost (“Survey of the UK Organics Recycling Industry 2007/08”; WRAP, 2009) are applied annually (on a fresh weight basis) to agricultural land in the UK. Other materials, such as paper crumble and (anaerobic) digestate are also applied to small areas of land (Gibbs et al., 2005; Taylor et al., 2010). There is also increasing interest in the possibility of increasing soil C storage through the use of biochar (Sohi et al., 2010). Biochar is produced through the pyrolysis of organic materials (usually plant material) and is a very stable C source, with the potential to act as a long-term soil C store. However, there is very limited experimental evidence of the potential benefits of biochar to soil C storage, particularly under temperate climates (Powlson et al., 2011).

Bhogal et al. (2008) summarised results from UK experiments quantifying the effects of various organic material additions on the C content of mineral soils, largely under arable cultivation. At typical application rates (equivalent to 250 kg ha -1 total N), soil C -1 -1 -1 accumulation rates ranged from 2.3 tCO 2e ha yr for livestock manures to 5.1-5.5 tCO 2e ha yr -1for green compost and biosolids. Dawson & Smith (2007) also estimated soil C storage -1 -1 rates in the range 0.73-5.5 tCO 2e ha yr following the application of organic materials to croplands. However, lower C storage rates have been suggested for grassland soils, as in the absence of incorporation (cultivation), much of the C in the organic material is potentially decomposed on the soil surface and lost to the atmosphere as CO 2 (Powlson et al ., 2011), although the evidence for this is limited.

Other benefits or risks: The application of organic materials to grassland provides a valuable source of plant available nutrients (N, P, K, Mg and S), thereby reducing the need for manufactured fertiliser inputs. They also provide an excellent means of improving soil physical, chemical and biological conditions (Powlson et al., 2011). However, organic material applications also present a risk of environmental pollution, if not handled and

managed carefully. Applications need to be managed to limit losses via NH 3 volatilisation and N 2O emissions to air, and NO 3, P and microbial pathogens losses to water. Also, repeated applications can lead to significant soil P enrichment, and application of some organic materials potentially lead to a build-up in soil heavy metal concentrations.

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Likely uptake : The use of livestock manures on improved grasslands is likely to result in a financial saving for the farmer, so the likely uptake is high; depending on the availability and logistics of handling and transport. For other organic materials (e.g. composts and biosolids), local availability and legislative ‘barriers’ may limit uptake. Notably if farmland is in a Nitrate Vulnerable Zone (NVZ), the application of organic materials must comply with the NVZ Action Programme Rules which came into force in 2009 e.g. the 250 kg ha -1 total N field limit and closed spreading periods.

4. Establish woodlands/forestry

Principles, benefits & risks, likely uptake : As for semi-natural grasslands.

Table 21 Summary matrix of the relative benefits/disbenefits of best practices for improved grassland Method Benefit to soil C Likely uptake Environmental e f (t CO 2e/ha/yr) (practicality) impact 3. Increase water table 5.1-15 a +
4. Reduce stocking density 1.3 b +

5. Organic material additions 0.3-5.5 c +++
6. Establish woodlands/forestry 0.4 d +
a Freibauer et al . (2004); >50% uncertainty b Connant et al. (2001); this is considered to be the initial rate of increase (<20 years) c Dawson & Smith (2007); Bhogal et al. (2008), assumes same rate as applications to cropland, which may not necessarily be the case (see text). d Soussana et al. (2004) estimated over 90 years; additional C stored in woodland vegetation -1 -1 estimated at 0.3-5.6 t CO 2e ha yr depending on tree species, harvest frequency and climatic conditions. eLikely uptake: +++ high; ++medium; +low fEnvironmental impact (diffuse pollution, biodiversity, erosion, GHG emissions):

Highly beneficial (impact over large area);
potential benefit, but also a risk of “pollution swapping”. See text for more detail.

4.4.2 Best practices for organo-mineral soils under cropland

Approximately 20% of organo-mineral soils in England are cropped (c.215,000ha). The majority of these are located in lowland England on poorly drained (gley) soils (Section 2) under cereal and vegetable production. As a result, they are likely to be drained and will

typically be net sources of CO 2, due to organic matter (C) oxidation following drainage and cultivation. Only a very small proportion of organo-mineral soils in Wales are under cropland (c.1% or 4800ha). Best practices for retaining/enhancing soil C are detailed below and a summary of the relative benefits/disbenefits is given in Table 22.

1. Convert to permanent grassland (preferably with an increase in height of the water table)

Principles : Permanent cropping can increase soil C storage due to the avoidance of annual cultivations which stimulate the mineralisation of organic C leading to carbon losses as CO 2.

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Indeed, land-use change from arable to unfertilised grassland has been widely promoted as a mechanism for GHG mitigation (Freibauer et al., 2004; Smith et al., 2008; Ostle et al., 2009; Powlson et al ., 2011). Increases in soil C storage have been estimated to range between 1.9 -1 -1 and 7.0 t CO 2e ha yr (albeit with 110% uncertainty; Dawson & Smith, 2007). Freibauer et al. (2004) estimated that the potential increase in soil C storage following conversion to -1 -1 grassland was 5.1 t CO 2e ha yr (>50% uncertainty) and the restoration of wetlands on organic arable soils (due to avoiding C loss from organic matter oxidation) was 8.1-16.9 t -1 -1 CO 2e ha yr ; although the evidence for this was limited.

Other benefits or risks: Arable reversion to un-fertilised (ungrazed) grassland has beneficial effects through reduced gaseous emissions (N 2O, NH 3, CO 2) and diffuse water pollution (NO3, P and sediment), Bhogal et al. (2009). There is also a potential for change in biodiversity value. However, land taken out of production will result in a substantial loss of farm income and has implications for long-term food security.

Likely uptake : Conversion of arable land to unfertilised (ungrazed) grassland is an extreme change in land use. It is unlikely to be adopted without the provision of substantial financial incentives. The establishment of permanent in-field or riparian grass buffer strips (as in ELS/HLS schemes) will also increase soil C storage (e.g. Falloon et al., 2004), albeit on a much smaller scale, but is perhaps more achievable than large-scale conversion to permanent grassland.

2. Establish permanent woodlands/forestry

Principle : Unlike the permanent conversion of grassland to woodland/forestry, significant increases in soil C storage following conversion of cropland to woodland have been predicted due to both a decrease in organic matter (C) oxidation and an increase in litter C inputs. -1 -1 Increases in soil C storage have been estimated to range between 1.1 to 2.3 tCO 2e ha yr (Freibauer et al., 2004; Dawson & Smith, 2007), based on global meta-analysis data. Reynolds (2007) summarised UK studies on the conversion of ‘agricultural land’ to woodland/forestry, including the conversion of moorland on peat soils (Billet et al., 1990; Harrison et al., 1997; Jones et al ., 2000), and arable land on mineral soils (Jenkinson, 1971). -1 -1 Annual soil C accumulation rates ranged from 0.77 to 2.7 tCO 2e ha yr , although there were no studies on organo-mineral soils. Also, additional C will be stored in the vegetation itself -1 -1 and has been estimated to range between 0.3 and 5.6 tCO 2e ha yr depending on the tree species, harvest frequency and climatic conditions (Liski et al ., 2002; Hooker & Compton, 2003).

Other benefits or risks: Woodland/forestry creation on arable land has beneficial effects through reduced gaseous emissions (N 2O, NH 3, CO 2) and diffuse water pollution (NO 3, P and sediment), Bhogal et al., (2009). There is also a potential for change in biodiversity value. However, land taken out of production will result in a substantial loss of farm income and has implications for long-term food security.

Likely uptake: Uptake of large-scale woodland/forestry creation is an extreme change in land use that is unlikely to be adopted by farmers, without the provision of (substantial) financial

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incentives. However, small-scale creation of farm woodland/forestry and hedges, as described in various ES options (e.g. shelter belts, in field trees and field corner management options, new hedges), may be more attractive.

3. Introduce rotational grass

Principle: Introducing rotational grass or grass/clover leys (e.g. for 2 years or more in a 6 year rotation) has the potential to increase soil C levels, due to a reduction in the frequency of tillage operations. However, the benefits to soil C storage of introducing ley-arable cropping (compared with continuous tillage cropping) are questionable, with conflicting evidence. In particular, there is uncertainty about how much of the potential increase in soil C from a 2 year ley (or longer) will be maintained over the long-term. Results from the long-term ley- arable experiments at Rothamsted and Woburn demonstrated that the inclusion of 1-3 year grass leys within a continuous arable rotation, had little effect on soil C (Johnston & Poulton, 2005); the 1 year ley had no effect on soil C levels and the 3 year ley increased soil C levels by 13-28% (measured after 15-28 years) compared to continuous annual tillage cropping. Using these and results from two European studies, Smith et al. (1997) estimated a potential soil C storage rate increase of 1.02% yr -1 compared to annual tillage cropping, equivalent to -1 -1 1.76 tCO 2e ha yr (King et al., 2005). More recently, Smith et al. (2010) estimated that ley- arable grassland was up to 10 times less effective at storing C than permanent grassland, and -1 -1 reported a C storage rate increase of 0.4-1.7 tCO 2e ha yr , again based on data from the Rothamsted ley-arable experiments (i.e. on mineral soils).

Other benefits or risks: There is potential for increased nitrate leaching losses following ploughing out of the grass ley, although this is likely to be balanced by the N immobilised in accumulating soil organic matter reserves (and reduction in leaching) during the ley phase. Gaseous N emissions during the ley phase will depend upon its management (i.e. livestock grazing, fertiliser and organic material inputs).

Likely uptake: A change in land use to rotational cropping is unlikely to be adopted without financial incentives, as there is potential for a reduction in farm incomes and food production, dependent upon the management of the ley.

4. Adopt reduced/zero tillage

Principle: Reduced/zero tillage has been widely promoted as a potential means of increasing soil C levels due to less soil disturbance (and hence organic matter decomposition) and reduced soil erosion rates (Smith et al ., 2008). However, recent reviews of data comparing conventional tillage (i.e. ploughing) and reduced/zero tillage have shown little difference in the amount of soil C present in the profile, where account is taken of soil C variation with depth and differences in bulk density (Powlson et al., 2011). Many of the increases in soil C measured following reduced/zero tillage have been confined to the top 10-15 cm; where deeper soil samples have been taken apparent differences between tillage systems have usually disappeared (Baker et al., 2007; Machado et al., 2003). Bhogal et al. (2008) reviewed the extent to which reduced tillage practices could increase the C content of UK arable soils. Taking an average of soil C changes measured in 6 UK studies (all on mineral soils), Bhogal

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-1 -1 et al. (2008) estimated an initial C storage increase of 1.14 tCO 2e ha yr for zero tillage under UK conditions (up to c.20 years). Reduced tillage was estimated to have half the C -1 -1 storage potential of zero tillage (0.57 tCO 2e ha yr ).

Other benefits or risks: There are many benefits of adopting reduced/zero tillage cultivation systems besides the possibility of increasing soil C levels. Reduced tillage is effective at protecting and therefore maintaining existing soil organic matter from decomposition, and can reduce nitrate leaching losses (compared with ploughing) as a result of less soil disturbance and N mineralisation. Also, reduced tillage protects soils against soil water/wind erosion, with reductions in surface run-off particularly effective when a mulch of crop residues is left on the surface. However, there is some evidence that N 2O emissions may increase due to an increase in topsoil wetness and/or reduced aeration as a result of less soil disturbance, particularly in wetter environments (Rochette, 2008).

5. Encourage use of organic materials

Principles : See improved grassland section. It has been suggested that there is greater potential for organic materials recycled to cropland to increase soil C than when they are applied to grassland (e.g. Freibauer, et al ., 2004; Powlson et al ., 2011); however, the evidence for this is limited. Most long-term studies in the UK have focused on organic material applications to mineral soils under arable cultivation (summarised by Bhogal et al ., 2008). In the absence of studies specific to organo-mineral soils under cropland, soil C accumulation rates have been assumed to be the same as for mineral soils (i.e. 0.73-5.5 tCO 2e ha -1 yr -1; Dawson & Smith, 2007).

Other benefits or risks: See improved grassland section – the same benefits and risks apply.

Likely uptake : As for improved grassland section – uptake is highly dependent on availability of materials (and transport/handling logistics), as well as potential legislative barriers.

Table 22 Summary matrix of the relative benefits/disbenefits of best practices for cropland Method Benefit to soil C Likely uptake Environmental -1 -1 e f (t CO 2e ha yr ) (practicality) impact 7. Establish grassland 1.1-7.0 a +

8. Establish woodland/forestry 1.1-2.2 a,b +

9. Rotational grass 0.4-1.7 c +
10. Reduced tillage 0.6-1.1 d ++
11. Organic material additions 0.3-5.5 a,d +++
aDawson & Smith (2007) b -1 -1 Additional C stored in woodland vegetation estimated at 0.3-5.6 t CO 2e ha yr depending on tree species, harvest frequency and climatic conditions. cSmith et al. (2010) dBhogal et al . (2008) eLikely uptake: +++ high; ++medium; +low

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fEnvironmental impact (diffuse pollution, biodiversity, erosion, GHG emissions):

Highly beneficial (impact over large area);
potential benefit, but also a risk of “pollution swapping”. See text for more detail. 4.4.3 Best practices for organo-mineral soils under forestry

Approximately 15% of organo-mineral soils in England and Wales support forestry (c. 240,000ha; Figure 4.2). In Wales, this is largely in upland regions on poorly drained podzols, supporting coniferous forest plantations. This is the case in England too, but there are also significant areas of broad-leaved woodlands on organo-mineral soils in lowland England. Most biogeochemical studies of forestry management have focused on conifer plantations and their impacts on water quality, with C measurements somewhat infrequent and relatively short-term (Reynolds, 2007). Jones & Emmett (2009) suggested that recent changes in forestry management may reduce soil C oxidation and erosion rates (due to less disturbance), but were lower in magnitude than C effects from afforestation of croplands and to a lesser extent grasslands.

Best practices for retaining/enhancing soil C are detailed below and a summary of the relative benefits/disbenefits is given in Table 23.

1. Increase rotation length

Principle : Increasing the forest rotation length has been suggested as a simple means of increasing C storage due to reduced soil disturbance (associated with harvesting) and reduced decomposition of forest products (Dewar & Cannell, 1992; Jones & Emmett, 2009). However, over the long-term forest harvesting has been reported to have little effect on soil C storage (Johnson & Curtis, 2001).

Other benefits or risks: There is an increased risk of wind-throw by delaying harvesting which potentially increases soil disturbance and can result in higher timber decay rates due to sub-optimally harvested wood products.

Likely uptake: This is a relatively simple practice to introduce, however, it will increase the length of time before a forest yields a financial return.

2. Site management

Principles : Good forestry management practices aim to reduce soil disturbance and erosion and include “continuous cover forestry” policies: which reduce the extent of clearfelling, diversify species, stand age and structure of plantations so that an uninterrupted woodland cover is maintained (i.e. mixed-age stand forestry; Mason et al., 1999); prevent highly degrading practices such as stump removal, brash bailing and biomass burning and; use minimum site preparation practices (Dawson & Smith, 2007). However, the impact of these practices on soil C storage, has not been evaluated.

Other benefits or risks : Practices that minimize soil disturbance and erosion will have beneficial effects in reducing sediment and nutrient losses to water courses.

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Likely uptake : These practices are relatively simple to introduce, with most already part of the Forestry Commission’s “Forest and Water” (2011) guidelines, which provide guidance to forest managers on how forests should be designed and operations planned, and to practitioners on how field operations should be carried out in order to protect and enhance the water environment.

Table 23 Summary matrix of the relative benefits/disbenefits of best practices for forestry Method Benefit to soil C Likely uptake Environmental -1 -1 a b c (t CO 2e ha yr ) (practicality) impact 12. Increase rotation length nd ++
13. Site management nd +++
a nd: no data. Benefit to soil C assumed due to reduction in soil disturbance and erosion. bLikely uptake: +++ high; ++medium; +low cEnvironmental impact (diffuse pollution, biodiversity, erosion, GHG emissions):

Highly beneficial (impact over large area);
medium/low benefit, see text for more detail.

4.4.4 Best practices for organo-mineral soils under wetland Less than 3% of organic-mineral soils in both England and Wales are associated with wetland communities (Figure 4.2) The majority of these are located in upland regions on poorly drained gley soils (Section 2), which are associated with high soil wetness, waterlogging and periodic inundation. In these situations, best practice is to leave the land undisturbed. Indeed, Jones & Emmett (2009) suggested that apart from manipulation of the drainage regime, there was little opportunity for influencing GHG emissions from wetlands (fens and bogs). The only option proposed was the permanent wetting of these soils by the blocking of any drains present, although the long-term benefit of this is uncertain, given the potential for increased methane emissions. Due to the low area of organo-mineral soils under wetlands and the limited management options available, we have not explored this area any further.

4.4.5 Best practices for organo-mineral soils under heath

Approximately 16% of organo-mineral soils in England and Wales support heath (ericaceous dwarf shrub) or montane (prostrate dwarf shrub, rush, sedge) communities (c.200,000ha; Figure 4.2). The majority of these are in upland regions (Section 2). Indeed, organo-mineral soils support a large proportion (>50%) of the heathlands in England and Wales. Here best practice management options aim to reduce soil C losses following disturbance and erosion associated with grazing/burning practices.

Best practices for retaining/enhancing soil C are detailed below and a summary of the relative benefits/disbenefits is given in Table 24.

1. Do not burn

Principles: Burning is a traditional management practice in upland regions for maintaining open shrub (heather) communities and preventing succession to scrub or woodland (SEERAD, 2007). However, if this is mis-managed or uncontrolled, all surface vegetation

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can be lost, exposing the underlying soil which is then susceptible to erosion. Indeed, SEERAD (2007) suggested that burning should not be practiced on soils with significant C stores or areas with a high risk of erosion (e.g. areas with extensive drainage gullies/ditches). Heather cutting is considered the preferred and more controllable option, but is restricted on stony, wet, steep and remote areas, and is typically more costly than burning (Holden et al., 2007). Alternatively, grazing can be used to control community succession. There have been a limited number of studies on the effects of burning on soil C. Adamson (2003; in SEERAD, 2007) reported lower soil C (organic matter) accumulation rates on peat soils that were burnt every 10 years, compared with those which had not been burnt at the Moorhouse National Nature Reserve in the Pennines.

Other benefits or risks: Decreased soil erosion losses due to the absence of burning will have beneficial effects for water quality (reduced sediment loads, DOC, POC and nutrient losses). However, if grazing is introduced as an alternative management practice there is the potential for increased nutrient inputs in urine and dung and associated implications for diffuse water pollution (NO 3, P) and gaseous emissions (NH 3, N 2O, CH 4); although stocking rates and associated nutrient loadings are likely to be low.

Likely uptake: This practice is simple to introduce, although alternative options for vegetation management are likely to be more costly. Note: many upland organo-mineral soils under heath are managed as grouse moors, and require a rotational burning scheme to ensure heather regeneration - cutting is not considered to be as effective.

2. Reduce stocking density/grazing

Principles, benefits & risks, likely uptake : The principles are the same as for semi-natural grasslands, however, the effects of reduced grazing on the soil C content of heathland soils has not been studied in detail. In Wales, an increase in sheep grazing from 1.2 sheep/ha to 5-6 sheep/ha in the 1950’s resulted in a reduction in the soil C content of peaty podzols from 24- 27% C in undisturbed heathland soils to 5% at heavily grazed sites (SEERAD, 2007).

Table 24 Summary matrix of the relative benefits/disbenefits of best practices for heathland

Method Benefit to soil C Likely uptake Environmental -1 -1 a b c (t CO 2e ha yr ) (practicality) impact 14. Do not burn nd ++

15. Reduce stocking density nd +

a nd: no data. Benefit to soil C assumed due to reduction in soil disturbance and erosion. bLikely uptake: +++ high; ++medium; +low cEnvironmental impact (diffuse pollution, biodiversity, erosion, GHG emissions):

Highly beneficial (impact over large area); see text for more detail.

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4.5 Designated areas

A large proportion of organo-mineral soils in England and Wales fall within designated areas; almost 25% of organo-mineral soils are in an SSSI (see section 2) and hence are subject to specific management prescriptions, largely for conservation/biodiversity objectives. Hence, the uptake of best practice options will be limited by the specific management prescriptions in place and objectives of the designated area. Although most of the management prescriptions will result in the maintenance/retention of soil C, there are some potential conflicts, for example, between maintaining a specific vegetation cover (by burning) and retaining soil C. Also, many of the land-use change options (e.g. afforestation or raising water tables) will not be permitted.

4.6 Conclusions

This review identified 15 potential best practice methods for retaining C in organo-mineral soils under a range of land-covers, and provided a quantitative comparison (where data was available) of their relative benefits to C storage, practicality (likely uptake) and environmental impact. Many of the methods were compatible with the way agricultural land management is currently regulated (via Cross Compliance measures) and incentivised (via Environmental Stewardship). Cross Compliance requires farmers to maintain soils in Good Agricultural and Environmental Conditions (GAEC) and comply with certain Statutory Management Rules in order to be eligible for the Single Payment Scheme (Anon., 2010). Preparation of a Soil Protection Review is a key requirement, identifying ways in which soils will be managed to maintain organic matter and structure and minimise erosion (e.g. best practice methods 1, 4, 5, 9, 10 & 11). Agri-environment schemes aim to deliver improvements in biodiversity, landscape, protection of the historic environment and natural resources. Under these schemes best practice methods involving land-use change would be best promoted by methods 2, 3, 6 & 7 & 8.

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Section 5. Impact of changing land use and management on ecosystem services provided by organo-mineral soils (Martin S.A. Blackwell and Roland Bol, Rothamsted Research)

5.1 Approach The impacts on the services delivered by organo-mineral soils of the potential best practices for retaining carbon in organo-mineral soils (as determined in section 4 of this report) have been assessed. These assessments have been made by expert opinion and are generic and qualitative. The following five tables indicate the direction of change of a service based on the initial semi-quantitative assessment of the services (section 3), and are presented in the following five Tables 25-29. These assessments are generic in that the broad land cover type only has been assessed, e.g. semi-natural grassland, improved grassland, cropland, forest and heath. Where more than one specific land cover type occurs for each broad habitat, the general trend for best practices is indicated. This is deemed satisfactory because in nearly all cases the initial assessment of services was similar in qualitative terms across the specific habitats, although qualitatively there may be variations.

Individual tables are presented for the five broad land cover types listed above. The first column lists the various ecosystem services considered. The next column(s) contain dots indicating whether or not a service is considered to be performed by the land cover type under consideration, and the degree to which it is performed. The size of the dot represents the latter, with a small dot representing performance to a low degree, a medium dot representing performance to a medium degree and a large dot, to a high degree. The colour of the dot reflects whether the service is delivered in a positive (i.e. beneficial to humans – black dot) or a negative (i.e. a dis-benefit – red dot) manner. In some cases ecosystem services in different significant land cover types are both positive and negative, and this is indicated by recording the most significant value of each in the relevant matrix square, hence the occasional appearance of two dots. The columns after the ecosystem service assessment columns show how these services would change if individual best practices of most significance to each land cover type were implemented. The arrows indicate the direction of change of service as follows:

↑ - delivery of service is increasing ↓ - delivery of service decreases ↕ - delivery of service may either increase or decrease ↔ - No change ? – uncertain

If a service is delivered but in a negative way (indicated by a red dot) then the direction of the arrow represents whether that dis-benefit will increase or decrease, e.g. for improved grassland generally the water quality service is negative, but the raising of water levels is likely to result in improved water quality, therefore a downward arrow indicates that the negative aspect is likely to decrease. Assessments highlighted yellow indicate that there is extreme uncertainty with the assessment.

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5.2 Results

Table 25 Potential impact of changing to ‘best practice for retaining carbon in organo- mineral soils’ on overall ecosystem services for semi-natural grasslands

Ecosystem services Semi-improved grassland Best practice Rough Acid Bracken Reduced grazing Establish woodland Provisioning services

Food ● ● ↓ ↓ Fibre (thatch, wool, sedge) ● ● ● ↓ ↑ Fuel ↑ Genetic resources ● ● ● ↑ ↑? Refugia ● ● ● ↑ ↑ Biochemicals/pharmaceutical Ornamentals

Water provision ● ↔? ↓

Regulating services Global climate ● ● ● ↑ ↑ Regional climate ● ● ● ↑ ↑ Local climate ↑? Flood hazard regulation ● ● ● ? ↑ Erosion control ● ● ● ↑ ↑ Disease Pest regulation

Pollination services ● ● ● ↑ ↑ Toxic hazard regulation Noise regulation ↑ Soil quality ● ● ● ↑ ↑ Air quality ↑? Water quality ● ● ● ↕ ↑

Supporting services

Primary production ● ● ● ↑ ↑ Nutrient cycling ● ● ● ↑ ↑ Soil formation ● ● ● ↑ ↑ Water cycling ● ● ● ↕ ↑

Cultural Recreation ● ● ● ↑ ↑ Tourism ↑ Cultural heritage ● ● ● ↔ ↔ Education Community development Spiritual Religion

Aesthetics ● ● ● ↑ ↑ Inspirational Sense of place

High Medium Low None Negative influence Positive influence ● ● ● ● ●

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Table 26 Potential impact of changing to ‘best practice for retaining carbon in organo- mineral soils’ on overall ecosystem services for improved grassland

Ecosystem services Grassland Best practice Improved Increase water table Reduce stocking density Organic additions Establish woodlands Provisioning services

Food ● ↓ ↓ ↔? ↓ Fibre (thatch, wool, sedge) ● ↓ ↓ ↔ ↑ Fuel ↑ Genetic resources

Refugia ● ↑ ↑ ↑ ↑ Biochemicals/pharmaceutical Ornamentals Water provision ↑ ↔? ↔? ↓

Regulating services Global climate ● ↓ ↓ ↓ ↓ Regional climate ● ↓ ↓ ↓ ↓ Local climate ↑ ? ↔? ↑? Flood hazard regulation ● ↕ ↓ ↓? ↓

Erosion control ● ? ↓ ↓ ↓ Disease ↓ ↑? Pest regulation ↓ Pollination services ↑ ↑ ↑ Toxic hazard regulation Noise regulation ↑ Soil quality ● ↓ ↓ ↓ ↓ Air quality ● ↓ ↓ ↑ ↓? Water quality ● ↓ ↕ ↑ ↓

Supporting services

Primary production ● ↑? ↑ ↔? ↑ Nutrient cycling ● ↓ ↓ ↓ ↓ Soil formation ● ↓ ↓ ↓ ↓ Water cycling ● ↓ ↕ ↓ ↓

Cultural Recreation ↑ Tourism ↑ Cultural heritage ● ↑ ↔ ↔ ↔ Education Community development Spiritual Religion

Aesthetics ● ↑ ↑ ↔ ↑ Inspirational Sense of place

High Medium Low None Negative influence Positive influence ● ● ● ● ●

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Table 27 Potential impact of changing to ‘best practice for retaining carbon in organo- mineral soils’ on overall ecosystem services for cropland

Ecosystem services Cropland Best practice Arable Horticulture Establish grassland Establish woodland Rotational grass Reduced tillage Organic additions Provisioning services

Food ● ● ↓ ↓ ↓ ↔ ↔? Fibre (thatch, wool, sedge) ● ↔? ↑ ↔? ↔ ↔ Fuel ● ↓ ↔? ↓ ↔ Genetic resources ↑

Refugia ● ● ↑ ↑ ↑ ↑ ↑ Biochemicals/pharmaceutical ● ↓ ↓ ↓ ↔ ↔ Ornamentals ● ↓ ↓ ↓ ↔ ↔ Water provision ↓ ↔?

Regulating services

Global climate ● ● ↓ ↓ ↓ ↓ ↓ Regional climate ● ↔? ↔? ↔? ↔? ↔? Local climate ● ● ↑ ↔? ↑ ↔? ↔?

Flood hazard regulation ● ● ↓ ↓ ↓ ? ↓? Erosion control ● ● ↓ ↓ ↓ ↓ ↓ Disease ↑? Pest regulation Pollination services ↑ Toxic hazard regulation Noise regulation ↑ Soil quality ● ● ↓ ↓ ↓ ↓ ↓ Air quality ● ↕ ↓? ↓? ↔? ↑ Water quality ● ● ↓ ↓ ↔? ↔? ↑

Supporting services

Primary production ● ● ↓ ↑? ↓ ↔? ↑ Nutrient cycling ● ● ↓ ↓ ↓ ↓ ↓ Soil formation ● ● ↓ ↓ ↓ ↓ ↓ Water cycling ● ● ↓ ↓ ↓ ↔? ↓

Cultural

Recreation ● ↑ ↑ ↑ ↔? ↔?

Tourism ● ↔? ↑ ↔? ↔? ↔? Cultural heritage ● ● ↑ ↑ ↓ ↑ ↓

Education ● ↔? ↔? ↔? ↔? ↔?

Community development ● ↔? ↔? ↔? ↔? ↔? Spiritual Religion

Aesthetics ● ● ↔? ↔? ↔? ↔? ↔? Inspirational ● ↔? ↔? ↔? ↔? ↔? Sense of place ● ↔? ↔? ↔? ↔? ↔?

High Medium Low None Negative influence Positive influence ● ● ● ● ●

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Table 28 Potential impact of changing to ‘best practice for retaining carbon in organo- mineral soils’ on overall ecosystem services for forest

High Medium Low None Negative influence Positive influence

● ● ● ● ●

Ecosystem services Forest Best practice Deciduous Coniferous Increase rotation length Site management Provisioning services Food

Fibre (thatch, wool, sedge) ● ● ↓ ↓ Fuel ● ● ↓ ↓ Genetic resources ● ● ↔ ↔ Refugia ● ● ↔ ↔ Biochemicals/pharmaceutical Ornamentals

Water provision ● ● ↑ ↑

Regulating services Global climate ● ● ↑? ↑? Regional climate ● ● ↑? ↑? Local climate ● ● ↔ ↔ Flood hazard regulation ● ● ↑? ↑? Erosion control ● ● ↑?* ↑?* Disease Pest regulation

Pollination services ● ● ↔ ↔ Toxic hazard regulation

Noise regulation ● ● ↑ ↑ Soil quality ● ● ↑ ↑ Air quality ● ● ↔ ↔ Water quality ● ● ↔ ↔

Supporting services

Primary production ● ● ↓ ↓ Nutrient cycling ● ● ↑ ↑ Soil formation ● ● ↑ ↑ Water cycling ● ● ↑ ↑

Cultural

Recreation ● ● ↑ ↑ Tourism ● ● ↑ ↑ Cultural heritage ● ● ↑ ↑ Education ● ● ↔ ↔ Community development ● ● ↔ ↔ Spiritual ● ● ↔ ↔

Religion ●

Aesthetics ● ● ↑ ↑ Inspirational ● ● ↑ ↑ Sense of place ● ● ↑ ↑

* This refers to increase in erosion control in both cases - i.e. a reduction in the disbenefits.

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Table 29 Potential impact of changing to ‘best practice for retaining carbon in organo- mineral soils’ on overall ecosystem services for heathland

Ecosystem Services Heath/montane Best practice Dense Open Do not burn Reduce stocking density Provisioning services

Food ● ● ? ↓

Fibre (thatch, wool, sedge) ● ● ↔ ↓ Fuel Genetic resources ● ● ??

Refugia ● ● ↑ ↑ Biochemicals/pharmaceutical Ornamentals Water provision ● ● ↑ ↔

Regulating services Global climate ● ● ↑ ↑ Regional climate ● ● ↑ ↔ Local climate ● ● ↑ ↔ Flood hazard regulation ● ● ↑ ↔ Erosion control ● ● ↑ ↑ Disease Pest regulation

Pollination services ● ● ↑ ↔ Toxic hazard regulation Noise regulation Soil quality ● ● ↑ ↔ Air quality ● ● ↑ ↔ Water quality ● ● ↑ ↔

Supporting services Primary production ● ● ↑ ↑ Nutrient cycling ● ● ↓ ↑ Soil formation ● ● ↑ ↑ Water cycling ● ● ↑ ↕

Cultural Recreation ● ● ↓ ↔ Tourism ● ● ↔ ↔ Cultural heritage ● ● ↓ ↔ Education ● ● ↔ ↔ Community development Spiritual Religion

Aesthetics ● ● ↔ ↔ Inspirational Sense of place ● ● ↔ ↔

High Medium Low None Negative influence Positive influence ● ● ● ● ●

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5.3 Summary

1) Potential impact of changing to ‘best practice for retaining carbon in organo-mineral soils’ on various ecosystem services varies considerably between land use types. 2) This complex picture of responses is currently only based on expert advice and opinion with current very little detailed project underpinning. The National Ecosystem Assessment may provide additional information when available. 3) The delivery of food and fibre production in more intensive agricultural was often at the detriment of many other ecosystem services, in line with findings of Pilgrim et al . (2010). 4) Woodland (especially deciduous) provided the greatest range and level of services of the land cover types considered here, but to the detriment of food production.

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Final conclusion

Despite having been able to complete all the key objectives of the project, we believe that that several knowledge gaps or uncertainties issues remain unresolved and require further attention: (1) Lack of field measurements (under UK conditions) of the potential C storage/saving benefits of implementation many of the proposed methods, (2) Variable impact responses of ecosystem services for the different land use cover types for implementing ‘best practice for retaining carbon in organo-mineral soils’ and (3) Uncertainty of how the timescale over which they are considered may influence which of the ‘best management options’ should be selected for implementation. Therefore, the overall evidence base to support any policy implementation remains weak. With the lack of actual field experimental underpinning, all assessments carried out in this project must to some extent be considered tentative, especially in light of the uncertainties with limited current data on the mechanisms behind C storage and dynamics of organo-mineral soils, which to a large extent is interpolated from studies on peat or mineral soils.

Acknowledgements

In addition to the main authors and contributors to individual chapters of the report as indicated at the start of each section, important contributions were also made by a number of other researchers and experts. This enabled us to verify that we have included all appropriate information and management options in relation to organo-mineral soils. We would like to thank Pete Smith (University of Aberdeen), Pete Falloon (Met Office), Cerys Jones (NFU), Adam Lockyear (FWAG), Julie Ingram (CCRI, University of Gloucester), Richard Evans (pers. comm.), Ian Ball (pers. comm.), Zoe Frogbrook (pers. comm.) and Emma Tilson (pers. comm.) for their kind input to this report. We would also like to thank Claire Hill at Defra for advice and guidance throughout the production of this report.

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ANNEX 1

Table A1. Areas (ha) of organo-mineral soils within Land Cover Classes of LCM2000 for England

Eastern Lowland England: Organo-mineral soil class Environmental Zone (1) 1 2 3 Areas Areas Cropland Areas (ha) (ha) (ha) 41: arable cereals 4612 939 54116 42: horticulture 8003 3146 84769 43: non-annual 355 425 3468 Total 12970 4510 142352 Grassland 51: improved grass 18578 4984 24513 52: setaside 778 417 5503 61: rough grass 1184 954 13100 71: calcareous grass 10138 588 14103 81: acid grass 2400 2690 4087 91: bracken 219 67 296 Total 33297 9700 61603 Heath/Montane 101: dense dwarf shrub heath 1407 5755 1198 102: open dwarf shrub heath 1057 3062 1664 151: montane habitats 0 0 0 Total 2464 8817 2862 Forest 11: broadleaved 13549 7909 13619 21: coniferous 10184 9234 4927 Total 23733 17143 18546 Wetland 111: fen, marsh & swamp 273 249 3168 121: bog 1 20 701 131: standing/inland water 102 55 540 Total 376 324 4409 Coastal 212: saltmarsh 0 22 783 181: supra-littoral rock 0 0 0 191: supra-littoral sediment 1 0 242 201: littoral rock 0 0 0 211: littoral sediment 1 2 172 Total 2 24 1197

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Organo-mineral soil class Western Lowland England:

Environmental Zone (2) 1 2 3 Cropland 41: arable cereals 2604 4119 7569 42: horticulture 4291 13050 15648 43: non-annual 104 216 645 Total 6999 17385 23862 Grassland 51: improved grasss 10521 14070 33809 52: setaside 369 282 1440 61: rough grass 1890 2719 12186 71: calcareous grass 1082 1241 6087 81: acid grass 4470 11334 3496 91: bracken 265 189 1262 Total 18598 29835 58280 Heath/Montane 101: dense dwarf shrub heath 814 4252 1858 102: open dwarf shrub heath 1191 2545 2311 151: montane habitats 0 0 0 Total 2005 6796 4170 Forest 11: broadleaved 5698 10616 8630 21: coniferous 4198 7927 5266 Total 9896 18543 13896 Wetland 111: fen, marsh & swamp 103 169 708 121: bog 60 226 336 131: standing/inland water 148 71 302 Total 311 466 1346 Coastal 212: saltmarsh 115 31 1111 181: supra-littoral rock 0 0 0 191: supra-littoral sediment 18 0 62 201: littoral rock 34 0 0 211: littoral sediment 140 36 1364 Total 308 67 2536

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Organo-mineral soil class Upland England:

Environmental Zone (3) 1 2 3 Cropland 41: arable cereals 155 168 693 42: horticulture 980 1039 2937 43: non-annual 24 0 53 Total 1159 1207 3683 Grassland 51: improved grass 7301 12234 36806 52: setaside 93 34 224 61: rough grass 16992 18198 110612 71: calcareous grass 8721 3306 10060 81: acid grass 29142 31971 31496 91: bracken 14562 4328 6284 Total 76812 70070 195482 Heath/Montane 101: dense dwarf shrub heath 5371 20768 31197 102: open dwarf shrub heath 8451 15541 29678 151: montane habitats 0 0 0 Total 13821 36309 60875 Forest 11: broadleaved 5823 8583 9216 21: coniferous 3799 9403 32645 Total 9622 17986 41861 Wetland 111: fen, marsh & swamp 12 11 2 121: bog 3151 5819 11342 131: standing/inland water 155 153 210 Total 3318 5983 11553 Coastal 212: saltmarsh 0 0 0 181: supra-littoral rock 0 0 0 191: supra-littoral sediment 0 0 0 201: littoral rock 0 0 0 211: littoral sediment 0 0 0 Total 0 0 0

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Table A2. Areas (ha) of organo-mineral soils within Land Cover Classes of LCM2000 for Wales

Organo-mineral soil class Lowland Wales

Environmental Zone (8) 1 2 3 Cropland 41: arable cereals 0 10 185 42: horticulture 1295 117 1369 43: non-annual 0 0 0 Total 1295 127 1554 Grassland 51: improved grass 8514 1079 17665 52: setaside 0 0 15 61: rough grass 1147 380 6057 71: calcareous grass 462 42 1641 81: acid grass 2153 1385 3393 91: bracken 183 156 349 Total 12460 3042 29121 Heath/Montane 101: dense dwarf shrub heath 326 109 447 102: open dwarf shrub heath 157 137 341 151: montane habitats 0 0 0 Total 483 246 788 Forest 11: broadleaved 660 184 4051 21: coniferous 621 784 2058 Total 1281 968 6110 Wetland 111: fen, marsh & swamp 0 5 66 121: bog 4 0 4 131: standing/inland water 41 35 13 Total 46 40 82 Coastal 212: saltmarsh 49 6 63 181: supra-littoral rock 0 0 0 191: supra-littoral sediment 50 0 66 201: littoral rock 10 0 1 211: littoral sediment 52 0 41 Total 162 6 171

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Organo-mineral soil class Upland Wales

Environmental Zone (8) 1 2 3 Cropland 41: arable cereals 6 48 103 42: horticulture 259 522 911 43: non-annual 0 0 0 Total 265 570 1015 Grassland 51: improved grass 5170 3576 11272 52: setaside 6 0 2 61: rough grass 3987 14802 37352 71: calcareous grass 853 2603 2898 81: acid grass 20676 81842 27669 91: bracken 1031 4186 4194 Total 31722 107009 83388 Heath/Montane 101: dense dwarf shrub heath 7399 16344 5394 102: open dwarf shrub heath 7560 14579 12782 151: montane habitats 0 0 0 Total 14958 30922 18176 Forest 11: broadleaved 1183 981 2728 21: coniferous 4443 33794 14986 Total 5625 34775 17713 Wetland 111: fen, marsh & swamp 109 284 251 121: bog 126 2690 230 131: standing/inland water 385 359 100 Total 620 3332 581 Coastal 212: saltmarsh 25 24 1 181: supra-littoral rock 0 0 0 191: supra-littoral sediment 0 0 3 201: littoral rock 0 0 0 211: littoral sediment 0 0 2 Total 25 24 5

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Table A3 Definitions of designated areas in England and Wales.

Less Favoured Area

An EC Designation which provides special measures to assist farming in the areas designated. The Less Favoured Areas consist of Severely Disadvantaged and Disadvantaged Areas. They are (mainly upland) areas where the natural characteristics (geology, altitude, climate, etc.) make it difficult for farmers to compete.

Environmentally Sensitive Area

Environmentally Sensitive Areas are one of a range of agri-environment schemes operating under the England Rural Development Programme. Incentives are offered to farmers to adopt agricultural practices which will safeguard and enhance parts of the country of particularly high landscape, wildlife or historic value.

Environmental Stewardship Agreements

Environmental Stewardship is a new agri-environment scheme which provides funding to farmers and other land managers in England who deliver effective environmental management on their land. Environmental stewardship has three elements: Entry Level Stewardship (ELS), Organic Entry Level Stewardship (OELS) & Higher Level Stewardship (HLS)

Special Areas of Conservation (SAC)

SACs are strictly protected sites designated under Article 3 of the EC Habitats Directive which requires the establishment of a European network of important high-quality conservation sites that will make a significant contribution to conserving the habitat types and species identified in Annexes I and II of the Directive (as amended).

Special Protection Areas (SPAs)

SPAs are strictly protected sites classified in accordance with Article 4 of the EC Birds Directive, which came into force in April 1979. They are classified for rare and vulnerable birds (as listed on Annex I of the Directive), and for regularly occurring migratory species.

National Nature Reserve

NNRs are nationally important examples of a type of habitat, established as a reserve to protect the most important areas of wildlife habitat and geological formations in the United Kingdom. They are protected by law in order to preserve the plants and animals that live there, or to preserve other features of the environment.

Site of Special Scientific Interest

SSSI is a conservation designation denoting a protected area in the United Kingdom. SSSIs are the basic building block of site-based nature conservation legislation and most other legal nature/geological conservation designations in Great Britain are based upon them.

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