Model simulations using the Rothamsted Carbon Model (RothC) to those using the default soil related coefficient (SRC) method were compared for a number of land use transitions, corresponding to those used in the GHGEI. This has shown that the SRC method tends to overestimate the loss of Soil carbon in scenarios where soil C is in decline, and overestimates the gain in soil carbon where soil C is increasing.

A prototype version of the Rothamsted carbon model for use with land use change scenarios was developed. A review of soil carbon cycling in peat soils was conducted, and possible developments of the RothC model, or other alternative models for simulating C cycling in peat soils were investigated. Testing of RothC predictions has been completed for a number of sites where grassland has been converted to arable land use (Morrow Plots, Illinois; SATWAGL, Australia;Waite Rotation, Australia), and shown a good reproduction of observed results in general.

A prototype interface for running the RothC model with spatial databases has been developed, allowing it to access soil, meteorological and land use information output from geographic information systems.

We have been unable to provide figures for the GHGEI due to lack of data provision

Other - ancillary datasets have been collected for use in the project as follows:
Climatic data:
long-term averaged and observed regional datasets (1961-1990)
Hadley Centre climate model predictions for use in future predictions

Land use/management information:
MAFF Agricultural Census information.

A sample soils dataset for an area of Derbyshire has been provided by NSRI (formerly SSLRC). This has been used to investigate C inputs to soil required to maintain measured SOC stocks for the 0-30cm, 30-100cm and 0-100cm layers, predicted by RothC. We also used these data to investigate the effects of using the dominant soil type to represent each 1km grid square versus using each component soil type, for the 0-30cm, 30-100cm and 0-100cm layers for a) calculating SOC stocks for the region and b) predicting SOC changes with RothC for a number of hypothetical land use change scenarios.

The use of dominant versus component soils data to calculate SOC stocks for the region showed that using only dominant soils information leads to significant errors in estimated SOC stocks. Using the RothC model for highly organic soils could also lead to significant errors in SOC stocks. Estimates of C inputs to soil provided by RothC suggested that the model may be inadequate for simulating SOC dynamics in highly organic and/or waterlogged soils. The use of dominant or component soils data in conjunction with the RothC model in predicting SOC changes under hypothetical land use change scenarios for the region also suggests that using dominant soil properties could lead to significant errors in predicted SOC fluxes.

Preliminary investigation of methods for uncertainty analysis has focused on the methodologies proposed by the IPCC, namely Monte Carlo analysis and error propagation equations. Analysis of climatic data from the CRU has suggested that the probability density functions (PDF's) of monthly temperature and rainfall for the UK are not normally distributed but strongly skewed, and the nature of the PDF's may vary between months. Analysis of soil C content data from the National Soils Inventory has also suggested a non-normal, skewed distribution. Further preliminary investigation of uncertainty in model outputs at the site and regional scale has been conducted and has been submitted for publication.

A prototype interface for running the RothC model with spatial databases has been developed, allowing it to access soil, meteorological and land use information output from geographic information systems, and to output results in a format compatible with GIS systems. We have developed test GIS datasets for this prototype using climatic data for the UK from CRU and soils data from the National Soils Inventory.

The Rothamsted Carbon model has been further evaluated for different land management, climate and soil type combinations at a number of long term experiments in Europe (see publications list). The prototype GIS-model interface has also been applied to Hungarian datasets for a number of carbon sequestration scenarios. A working document, 'Allocating the spatial location and timing of land-use change' has been written and provided for comment by the steering group.

We have built a collaboration with the Climate Research Unit at the University of East Anglia (Dr David Viner), who will provide and format relevant current/historic and future (scenario) climatic data: delivery of these datasets is expected soon.

We have been unable to provide figures for the GHGEI due to lack of data provision on soils, land use and land use change.

Project meetings were held as follows:

January 10th 2002 - University of Aberdeen
Pete Smith, Pete Falloon, Ronnie Milne
Discussion of spatial location and timing of land use change and combination of land use change with soils data

11th December 2001 - NSRI
Pete Smith, Pete Falloon, Ian Bradley and others
Discussion of soils data for the project

26th November 2001 - CEH Bush
Pete Smith, Pete Falloon, Ronnie Milne and others
DETR Inventory project meeting

26th June 2001 - Rothamsted Research Rothamsted
Pete Smith, Ian Bradley, Pete Falloon, Ronnie Milne
Discussion of soils and land use data

21st May 2001 - Rothamsted Research Rothamsted
Pete Smith, Pete Falloon, Ian Bradley
Discussion of soils data

18th May 2001 - CEH Bush
Pete Smith, Pete Falloon, Ronnie Milne and others
DETR Inventory project meeting

In the first instance, the RothCUK system has been tested with a subset of the preliminary 1km soils and land use datasets to investigate 1) fitting C inputs to measured SOC data, and 2) using default C input values to predict equilibrium SOC stocks, using the dominant soil type and component land use data for the 0-30cm and 30-100cm layers of each 1km square. These runs concentrated on arable, grassland and semi-natural land uses since woodland soils data were not available for the test area. RothC output data from these runs have been analysed, which has 1) allowed calculation of average C input values for different land uses in the 0-30cm and 30-100cm layers, 2) shown that using default C input values for each land use and soil layer does not allow accurate prediction of measured SOC stocks, and 3) shown that the RothC model may be inappropriate for certain soil types (notably organic soils). C inputs fitted to measured SOC values were well correlated with mean annual rainfall for grassland soils, but less so for arable soils. Since net primary production is strongly related to mean annual rainfall, better prediction of C input values for the RothC model may be achieved by linking RothC to a plant production model, which would also allow prediction of management effects on above and below ground C cycling.

The RothCUK system has also been used to make preliminary estimates of changes in CO2 emissions from soils under two SRES climate change scenarios, A1f1 and B1, for the period 1961-2099, relative to the 1961-1990 baseline climate. These initial scenarios showed that increased CO2 emissions would be expected from most arable soils after about 2050, with the greatest losses occuring from soils containing more organic matter. Further simulations are needed to make concrete conclusions, and linkage with plant C cycling models will be necessary for predicting the interaction of plant and soil C cycling under climate change.

C fluxes have been modelled with RothC under observed land use change (1990-2000) for four test squares from the Countryside Survey data. These outputs have been compared with the soil related coefficient/ Monte Carlo method currently used for the Land Use, Land Use Change and Forestry Emissions Inventory. RothC estimates of C fluxes for the various land use change options were generally within the range predicted by the Monte Carlo/Soil related coefficient method. We have more confidence in the RothC method since it accounts for local climate, land use and soil type, and thus can provide more specific estimates of local decomposition rate constants, and hence predicted C fluxes. Initial RothC runs in the four test squares assumed instantaneous land use changes, although later work concentrated on succession and intermediate land use changes. This is of importance when considering land use changes which take a considerable time to occur, for example natural woodland regeneration on arable land would not naturally occur as a direct transition from arable to woodland, but through arable to grassy weeds, to scrubland and finally woodland succession. This work showed that the long-term trajectory of carbon flux under land use change was not greatly affected by intermediate land uses, but in contrast, strong effects were observed in the short term (up to 10 years or so), which would be of great importance in inventory calculations and Kyoto Protocol reporting. Outputs of C input values from the CENTURY model (which incorporates above ground vegetation C dynamics) for woodland vegetation succession runs were also used to drive RothC runs, although the output C fluxes were similar to those using step changes in intermediate land uses with RothC C input values. The quality and quantity of C inputs during early land use change succession is important in determining the short-term trajectory of C fluxes. A set of suggested land use change scenarios for possible land use changes under the categories recognised by the 1km soils and land use database have been created for testing with the RothC model.

Comparisons were also made between soil C changes predicted for gradual and instantaneous land use changes using the RothC model and the soil related coefficient method over 10 year timescales for the test squares. Where applicable, intermediate land use changes (not just initial and final land uses) should be accounted for in further modelling, and future work would benefit from linkage with plant production models.

Version two of the 1km soils and land use database has been received from NSRI, and preliminary missing data checks on these datasets had begun. A collaboration with the Hadley Centre has been developed for prediction of climate change effects on soil carbon stocks. The aim of this work will be to include the RothC model in the HADCM3 climate model, which currently has a very simple soil carbon model, to enable more accurate prediction of changes in ecosystem carbon stocks and climate feedbacks under climatic and land use change. Collaboration with a GEF-funded project ‘Assessement of soil carbon stocks at national scale’ has also been initiated, which will promote work on inventory method development with the NREL group at Colorado State University (using the CENTURY model) in case study countries, and a BBSRC ISIS exchange grant has been obtained to harmonize approaches between Rothamsted Research and NREL. The project website has been updated, and reports and information can be downloaded.

Project reports have been written as follows:
'Minutes of project meeting 27-7-02'
'Summary of soil and land use data report September 2002'
'Minutes of a project meeting 17-10-02'
'Preliminary 1km Soil C modelling outputs for DEFRA CCO2421 January 2003'

Project meetings have been held as follows:
DEFRA LULUCF meeting 29th April 2003
DEFRA LULUCF meeting 27th May 2002
DEFRA LULUCF meeting 6th December 2002
Project data meeting at CEH Edinburgh 17th October 2002.

Publications from the project

Falloon P and Smith P (2003) Uncertainty associated with soil carbon model predictions is too large for Kyoto accounting. Soil Use and Management (in press)

Falloon P, Smith P, Powlson D (2003) Carbon sequestration in UK arable soils - the case for field margins. Soil Use and Management (in press).

Smith P & Falloon P (2003) Carbon sequestration in European croplands. Carbon in Forest Biomes (submitted).

Smith P & Falloon P (2003) Agricultural practice, soil carbon storage and CO2 emissions. The Carbon Balance of Forest Biomes -A symposium of the Society of Experimental Biology and the Physiological Ecology Group of the British Ecological Society (BES) at the University of Southampton 1st - 4th of April 2003, Abstracts.

Smith, P. & Falloon, P. (2003). Agricultural practice, soil carbon storage and CO2 emissions. Comparative Bioshemistry and Physiology Part A 134: S180.

Falloon P and Smith P (2002) Simulating SOC dynamics in long-term experiments with RothC and CENTURY: model evaluation for a regional scale application. Soil Use and Management 18, 101-111.

Falloon P, Smith P, Szabó J & Pásztor L (2002) Comparison of approaches for estimating carbon sequestration at the regional scale. Soil Use and Management 18, 164-174.

Falloon P, Smith P, Powlson D. 2002. Carbon cycling and sequestration opportunities in temperate arable agriculture. Abstracts of BSSS Meeting, 'Soils as carbon sinks: opportunities and limitations', Friday 28 June 2002, London. BSSS Edinburgh.

Falloon P & Smith P (2002) Modelling soil carbon fluxes due to land use change for the national CO2 inventory: challenges and opportunities. Abstracts of Meeting "Trees and peat: sources or sinks of carbon? 5th November 2002, ECCM, Edinburgh.

Smith P, Goulding KW, Smith KA, Powlson DS, Smith JU, Falloon PD, and Coleman KC (2001) Enhancing the carbon sink in agricultural soils: including trace gas fluxes in estimates of carbon mitigation potential. Nutrient Cycling in Agroecosystems 60, 237-252 2001

Falloon PD Smith P Szabo J Pasztor L Smith JU Coleman K & Marshall S (2002). Comparing estimates of regional C sequestration potential using GIS, dynamic SOM models, and simple relationships. Chapter 13 In: Kimble JM, Lal R & Follett RF (eds). Agricultural Practices and Policies for Carbon Sequestration in Soil, Lewis Publishers, Boca Raton. pp141-154.

Gaunt J, Powlson D, Sohi S & Falloon P. (2002) Soil organic matter and how to change it. Abstracts of Meeting "The draft soil protection strategy: implications for the agricultural and environmental sectors". 12 March 2002, SCI, London.

Falloon P. & Smith P. (2002) Modelling soil C fluxes for the national CO2 inventory: opportunities and challenges.. Abstracts of Meeting "The draft soil protection strategy: implications for the agricultural and environmental sectors". 12 March 2002, SCI, London.

Powlson DS, Christian DG, Falloon P & Smith P (2001) Biofuel crops: their potential contribution to decreased fossil carbon emissions and additional environmental benefits. Aspects of Applied Biology 65, 289-294

Falloon P D, Smith P, Smith JU, Szabo J, Coleman K, and Marshall S (2001) SOM sustainability and agricultural management - predictions at the regional level. Chapter 2.1 in: Rees, R.M., Ball, B.C., Campbell, C.D. & Watson, C.A. (eds.) 'Sustainable Management of Soil Organic Matter' BSSS99 Conference Proceedings. CABI, Wallingford, UK. pp 54-59.

Smith P, Falloon PD, Powlson DS. & Smith JU. 2001.. Carbon Mitigation Options in Agriculture: Improving our Estimates for Kyoto. Chapter 4.13 in: Rees, R.M., Ball, B.C., Campbell, C.D. & Watson, C.A. (eds.) 'Sustainable Management of Soil Organic Matter' BSSS99 Conference Proceedings. CABI, Wallingford, UK. pp 324-329.

Smith P, Falloon P, Smith JU & Powlson DS. (eds) 2001. GCTE Task 3.3.1 Soil Organic Matter Network (SOMNET): 2001 Model and Experimental Metadata. GCTE Report, GCTE Focus 3 Office, Wallingford, UK.

Falloon P and Smith P (2001) Modelling SOM dynamics in arable and grassland soils. COST 627: Carbon storage in European grasslands. Meeting of WG3, WG4 and MC on 28-29 September 2001, Abstracts. Danish Institute of Agricultural Sciences, Research Centre Foulum, Denmark. p11.

Gaunt J, Sohi S, Falloon P, Powlson DS (2001) The potential contribution of dissolved organic carbon to C sequestration. Abstract in Proceedings: DOM 2001, Bayreuth 9-11 October 2001. University of Bayreuth.

Falloon P and Smith P (2001) Combining plant and soil C cycling models - consideration of methods. In: (R Milne, ed) UK emissions by sources and removals by sinks due to land use, land use change and forestry activities. Report, April 2001. DETR contract EPG1/1/160,. April 2001. Department of the Environment, Transport and the Regions, Global Atmosphere Division.

Falloon P and Smith P (2001) Modelling soil carbon fluxes and land use change for the National carbon dioxide inventory. Annual/Interim Project Report, Financial Year 2000-2001. DEFRA Contract CC0242.

Falloon P and Smith P (2001) Modelling soil carbon fluxes and land use change for the National carbon dioxide inventory. Review Report for Review of DEFRA's R&D on Greenhouse Gas Emissions and Control, 24 September 2001, Nobel House, London. DEFRA, London. pp177-183