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The ELUM Project: Ecosystem Land Use Modelling & Soil Carbon GHG Flux Trial
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Zoe Harris4, Niall P McNamara1,*, Rebecca Rowe1, Marta Dondini3, Jon Finch2, Mike Perks5, James
Morison5, Iain Donnison6, Kerrie Farrar6, Saran Sohi7, Phil Ineson8, Pete Smith3 & Gail Taylor4
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*Lead Investigator: Niall McNamara (nmcn@ceh.ac.uk).
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Keywords (5-10): Biomass, greenhouse gas, flux, bioenergy, sustainability, 2nd generation, modelling,
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soil carbon, land use change
Centre for Ecology & Hydrology, Lancaster, LA1 4AP, UK
Centre for Ecology & Hydrology, Wallingford, OX10 8BB, UK
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University of Aberdeen, Aberdeen, AB24 3FX, UK
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University of Southampton, Southampton, SO17 1BJ, UK
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Forest Research, Alice Holt Lodge, GU10 4LH, UK
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University of Aberystwyth, Aberystwyth, SY23 3DA, UK
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University of Edinburgh, Edinburgh, EH9 3JW, UK
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University of York, York, YO10 5DD, UK
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Author for correspondence: Gail Taylor (G.Taylor@soton.ac.uk)
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Abstract
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There is increasing interest in the use of non-food second-generation (2G) lignocellulosic feedstocks
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and a move away from food crops for bioenergy applications, but questions still remain on
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sustainability. Empirical data are needed to quantify the greenhouse gas (GHG) balance of land-use
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transition to lignocellulosic bioenergy cropping systems, to inform life cycle analyses and aid model
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validation.
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The aim of this project ‘Ecosystem Land Use Modelling & Soil Carbon GHG Flux Trial’ is to produce a
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framework for predicting the sustainability of bioenergy deployment across the UK. This £4m
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consortium project is commissioned and funded by the Energy Technologies Institute, UK.
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Introduction
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Although bioenergy is considered to be one of the key renewable energy technologies set for future
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expansion [1], concern still remains over its sustainability. In particular, the greenhouse gas savings
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that are possible in many bioenergy and biofuel chains have recently been questioned [2]. Although
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bioenergy may help meet national and international targets for emissions reductions, significant
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work is still required to establish robust sustainability criteria [3, 4]. Within the UK, much of the
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current bioenergy feedstocks are imported, and this may have wider implications for a range of
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ecosystem services that we are only just beginning to quantify [5].
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One of the main concerns surrounding commercial bioenergy deployment in the UK is the potential
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displacement of food production and disturbance of valuable landscapes and the ecosystem services
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they provide, including erosion and flood regulation, pest and disease control, pollination and
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habitat provisions and soil and water quality. If we are able to understand the effects of land-use
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change (LUC) to bioenergy cropping systems, in a UK specific context, more informed decisions can
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be made and more appropriate policies put in place to safeguard against use of unsuitable. The
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focus of the ‘Ecosystem Land Use Modelling & Soil Carbon GHG Flux Trial’ (ELUM) project is to assess
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the potential scale of a future UK bioenergy sector based on domestic production of 2G feedstocks.
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The ELUM project is a consortium of seven UK partners; the Centre for Ecology & Hydrology (CEH),
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University of Aberdeen, University of Southampton, Forest Research, Aberystwyth University,
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University of Edinburgh and University of York, and is commissioned and funded by the Energy
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Technologies Institute (ETI), a public–private partnership between global energy and engineering
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companies and the UK Government. The 3-year, £4m project is coordinated by CEH and consists of
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four work packages (Figure 1a): a data mining exercise, meta-analysis and extensive literature review;
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cataloguing of soil carbon and changes in soil carbon pools using a paired site approach across the
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UK; establishment of paired field sites to assess the effects of direct LUC to bioenergy; process-based
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modelling to determine the effects of LUC to bioenergy in the UK using inputs from the other work
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packages. The ultimate product of the project will be a user-friendly and freely available meta-model
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that can predict the impacts of LUC to bioenergy spatially across the UK out to 2050. The transitions
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of interest are those from a primary land use, including grassland/pasture, arable and forestry to
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second generation bioenergy crops, including Miscanthus, short rotation coppice (SRC) willow and
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short rotation forestry (SRF). The model can also consider transitions into arable from forest and
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grassland. The ELUM project is unique in that firstly, the majority of experimental work is located on
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commercial farms across the UK rather than in controlled plot-scale experiments and secondly, that
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model and experimental work are brought together under one project.
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Data mining exercise
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The preliminary focus of this project is nearing completion and was to assess the current state of
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knowledge that exists in the literature for the effects of LUC to bioenergy on soil carbon and GHG
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emissions. This work was undertaken by conducting a systematic search of the literature using three
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commonly used search engines, namely Google Scholar, Science Direct and Web of Science, coupled
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to a meta-analysis. Exclusion criteria were clearly defined to allow papers to be selected and
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included in review and meta-analysis if appropriate. The findings of the literature review and meta-
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analysis showed that there are significant gaps in our knowledge surrounding LUC to bioenergy [6].
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There were particular data gaps for transitions to SRF and high levels of uncertainty around
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transitions from grasslands to non-food bioenergy crops, largely reflecting the importance of
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management activities such as fertiliser input and tillage. This work confirmed the need for further
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studies to generate datasets to fill these gaps, from which to derive evidence-based models; which
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are scheduled to take place as part of the ELUM project. A systematic review was also conducted
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into the effects of bioenergy cultivation on a wide range of ecosystem services, highlighting the
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levels of uncertainty which surround our understanding of these changes, with significant data gaps
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in most types of ecosystem service [5].
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This work is being undertaken by the University of Southampton.
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Field studies
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The empirical studies in this project take four approaches: the large-scale sampling of paired field
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sites (original land use versus bioenergy) across the entirety of the UK; the establishment of a
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network of six paired sites where transitions to bioenergy are assessed for GHG emissions and soil C
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changes; an experimental plot field trial assessing the potential of different Miscanthus genotypes as
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future bioenergy crops; the use of 13CO2 pulse labelling of vegetation to track shorter term carbon
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flow through the plant and soil system.
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Paired site approach A paired site approach is a method used to assess the effects of a treatment, in
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this case LUC to bioenergy crops, on a particular variable, soil carbon, over an extended duration of
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time. These ‘space-for-time’ replacements have been used in many ecological and environmental
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studies and are highly appropriate for measuring landscape-scale soil processes [7]. Fields where
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bioenergy crops of several different ages are cultivated were sampled to assess the changes in soil
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carbon over time. Critically, this technique overcomes the common challenge of repeated sampling
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of the establishment phase of perennial energy crops in the first few years, and thereby generates
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unique and meaningful data on the mature crop in different locations. The sampling gave good
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spatial coverage of the UK, with a total of 70 sites representing 117 sampled fields. A detailed soil
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analysis was conducted on over 10,000 soil samples on cores taken to depths of up to 1 m.
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Assessment of the soil carbon to depth below 30 cm is important as there have been several studies
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which have over- or under- estimated soil carbon due to insufficient sampling depths [8,9]. In
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addition, under SRF transitions laboratory experiments measured potential GHG fluxes under
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controlled temperature and moisture conditions, in combination with assessments of soil microbial
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populations. Physiochemical fractionation of soil samples is being undertaking to allow assessment
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of any changes in soil carbon pools and the likely direction of any future changes in soil carbon.
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The wealth of soil data from the paired site approach will provide an extensive data set for model
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testing and parameterisation, whilst the fractionation work will allow the assessment of model
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performance in modelling soil carbon portioning and residence times.
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This work is being undertaken by CEH, Forest Research, and the University of Edinburgh.
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A network of paired GHG sites A network of six paired experiments at four sites has been
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established across the UK (Figure 1b), with contrasting climate and soil types; Scotland, Wales,
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northern and southern England. These sites cover five transitions to bioenergy including, arable to
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SRC willow, arable to Miscanthus, grass to Miscanthus, grass to SRC willow and grass to SRF. These
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sites were all planted at commercial scale on commercial farms following typical cultivation practices,
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and are representative of the crop species that would be cultivated in that area, such as SRF in
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Scotland, as shown in Figure 1b. Over 24 months all sites undergo periodic monthly gas sampling to
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assess soil fluxes of carbon dioxide (CO2) by infra-red gas analyser and nitrous oxide (N2O) and
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methane (CH4) using the static chamber approach with subsequent sample analyses by gas
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chromatography. At selected field sites, higher temporal resolution measurements of soil respiration
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are being made using automated chambers. As well as soil fluxes, each site is equipped with state-
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of-the-art eddy covariance systems which allowes continuous measurements of whole crop
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ecosystem CO2 exchange at a scale of a few 100 m2 [10]. These instruments measure the ‘covariance’
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of wind turbulence, air temperature and CO2 concentration 20 times a second to calculate CO2 fluxes
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across the crops upwind at any moment. Automatic meteorological stations at the sites measured
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weather variables to enable determination of the relationship with GHG fluxes.
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These intensive measurements will not only produce a large amount of GHG flux data to allow us to
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understand the processes affected by LUC but will also feed into the modelling for parameterisation
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and validation.
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This work is being undertaken by CEH, University of Southampton, University of York, Forest Research
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and Aberystwyth University.
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Miscanthus genotyping The majority of Miscanthus planted commercially in the UK is the single
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clone Miscanthus x giganteus (Mxg). To determine the extent to which models based on Mxg will
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apply to future Miscanthus varieties under development, 15 diverse Miscanthus genotypes,
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including parental species M. sinensis, M. sacchariflorus, and their interspecific hybrids, were
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analysed to represent the morphological and physiological diversity present within the breeding
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population. Our aim is to understand the processes driving atmospheric CO2 capture and carbon
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sequestration by Miscanthus crops and to assess genotypic variation in carbon sequestration
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potential. Phenotype analysis, GHG sampling and soil sampling have been conducted across all
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genotypes and six have now been chosen for a more intensive analysis.
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This work is being undertaken by Aberystwyth University and CEH.
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adjacent SRC willow and Miscanthus plots in Lincolnshire and in diverse Miscanthus genotype plots
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at Aberystwyth. Crops were enclosed in large transparent tents and exposed to highly-enriched
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These experiments will allow us to understand carbon allocation within the plant, the flow of carbon
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in soils and transformations of plant inputs to soils by microbial groups [11].
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This work is being undertaken by CEH and Aberystwyth University.
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Modelling
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Detailed process modelling provides a mechanism to scale point values gained at the network of
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field sites, up to the whole UK, providing a resolution to 1 km2 for the GHG balance of the land-use
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transitions to non-food bioenergy crops. Based on the outputs of the process model, which models
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yield, and soil processes, a user-friendly meta-model is being developed with a graphical user
CO2 pulse labelling Large scale
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CO2-pulse chase experiments have been conducted under
CO2 with plants, soils and soil-atmosphere CO2 exchanges being sampled for months afterwards.
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interface (GUI) to allow users to undertake spatial estimations for GHG emissions from bioenergy
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cropping. The model is able to predict effects out to 2050 for the whole UK, with areas unsuitable for
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transitions removed, such as urban areas or protected green sites. The user will be able to select an
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area of land anywhere in the UK, define a LUC transition and see the effects of the change on GHG
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and soil carbon (derived from the ECOSSE model [12]), with the addition of estimated yields (input
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derived from ForestGrowth[13,14], Forest-GrowthSRC [15] and Miscanfor models[16]). The meta-
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model and GUI will be available for download from the CEH and project webpages, enabling use by
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the wider scientific community, policymakers, land planners, and those with a commercial interest in
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developing sustainable bioenergy feedstock crops.
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This work is being undertaken by the University of Aberdeen.
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Future perspectives
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The outcomes of the ELUM project include an increased understanding of the way in which
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transition to 2nd generation non-food crops impacts soil and crop processes related to GHG
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emissions. New data include GHG measurements and soil carbon stocks of relevance to national
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inventories. The meta-model and associated GUI will provide a valuable resource for the scientific
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community and a wide range of stakeholders including growers, land managers, energy companies
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and policy makers. The meta-model is due for public release at the end of the project in 2014.
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Overall the outcomes of the project should enable a better understanding and informed decision
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making around the deployment of sustainable bioenergy. For further information on the ELUM
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project please visit: www.elum.ac.uk.
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Executive summary
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An extensive literature review and meta-analysis highlighted significant gaps in our current
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understanding of the impacts of land use change to bioenergy cropping systems on GHG
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balance.
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Paired site comparisons of land-use transitions into bioenergy has occurred at 70 land-use
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transitions across the UK, assessing the longer term effects of established bioenergy
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plantations on soil carbon stock compared to their original land use.
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A network of new sites has been established across the UK to monitor GHG emissions and
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soil carbon changes occurring after/with a transition to bioenergy cropping systems,
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representing a world-leading infrastructure from which to assess long-term impacts of land-
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use change on GHG emissions.
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Plot experiments are being used to assess the mechanisms underpinning Miscanthus soil
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carbon sequestration and test if there is a difference in the carbon sequestration and yield
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potential of 15 Miscanthus genotypes representing the diversity within the UK Miscanthus
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breeding programme.
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Modelling efforts combine all aspects of the ELUM project and data collected to provide
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detailed effects of land use conversion for bioenergy in the UK. The final product will be a
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user-friendly model intended to provide an industry standard for land planners, industry and
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policymakers.
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Financial & competing interests disclosure
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Funding for this project was provided by the Energy Technologies Institute (ETI). The Centre for
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Ecology & Hydrology, Forest Research also directly funded elements of the ELUM project. The
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authors declare no other financial interests or conflicts.
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Acknowledgements
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The authors would like to thank all the members of the ELUM consortium project: Giorgio Alberti,
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Emily Bottoms, Ben Keane, Alice Massey, Jon McCalmont, Mark Pogson, Mat Tallis, Sirwan Yamulki,
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Carina Convery, Julia Drewer, Janet Dutch, Dafydd Elias, Jon Evans, Aidan Keith, Jonathan Oxley, Kim
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Parmar, Clare Peters, Rachel Marshall and Elena Vanguelova. We would also like to thank the Energy
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Technologies Institute (ETI) for commissioning and funding this project and for the allied research
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projects Carbo-BioCrop (www.carbobiocrop.ac.uk; an NERC funded project) and UKERC (funded as
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part of the flexible research fund of UKERC, NERC) for providing field sites and yield data respectively.
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Figure 1 – (a) An overview of the project structure, with key tasks, responsible organisations and
individuals, their linkage and outputs. (b) An overview of the network sites and the measurements
made: eddy covariance, static soil GHG emissions and dynamic CO2 soil respiration.
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