Sustainable Land Management through Soil Organic Carbon Management and Sequestration The GEFSOC Modelling System Mohamed Sessay Eleanor Milne

Overview of Presentation Background Why assess SOC stocks and change Regional Approaches GEFSOC Project: Aims and Objectives Methodology: GEFSOC Project Approach Final Output

Background Importance of Soil Organic Carbon Soils represent largest terrestrial stock of C, holding between 1400 x10 15 g (Post et al 1982) and 1500 x g C (Batjes, 1996) Approximately 2x the amount in atmosphere and 3x amount in terrestrial vegetation Majority of C is held in form of soil organic carbon (SOC) (Batjes & Sombreck, 1997)

Changes in terrestrial SOC stocks (both increase and decrease) can be of global significance and may either mitigate or worsen climate change SOC is vital for ecosystem functions with major influence on : - Soil structure, Water holding capacity - CEC - Ability to form complexes with metal ion - Fertility (to store nutrients) - Above and below ground biodiversity

Why Assess SOC Stocks and Changes? Knowledge of SOC stocks and changes would help us device plans for: Appropriate management of soils to increase SOC levels to increase productivity and sustainability of agricultural systems The sustainable management of ecosystems The mitigation of GHG emissions The likely impact of climate change on soils/ecosystems in the future (Jones et al 2004)

The Kyoto Protocol The Kyoto Protocol - CO 2 emissions can be offset against removal of C from the atmosphere 1 st commitment period 2008 – 2012 Article 3.3, forestry activities Article 3.4, management of agricultural soils Changes before 2008? UNFCCC -Inventories of CO 2 emissions from LUC

Why assess SOC Stocks and Changes? Native Ecosystem Agriculture SOC decline Rothamsted long term experiments Versailles long term experiments SOC is sensitive to changes in land use

Why assess SOC Stocks and Changes? Knowledge of SOC stocks and changes would help us device plans for: Appropriate management of soils to increase SOC levels to increase productivity and sustainability of agricultural systems The sustainable management of ecosystems The mitigation of GHG emissions The likely impact of climate change on soils/ecosystems in the future (Jones et al 2004)

Important Areas Globally Rates of land use change greatest in the tropics Feed 70% of the population (Lal and Sanchez 1992) Increasing demand for land will be met by converting forest and pasture – C release ~ 26% of global SOC stocks are in the tropics (Batjes 1996) Relatively little information on soils and how they react to land use change The Tropics

Important Areas Globally Low SOC stocks per unit area Occupy ~47% of land surface (Lal 2003) Many areas are degraded with the potential for rehabilitation Drylands

Problem of Scale Plot Scale Many studies, site specific, limited value Global Scale Regional and National Scale Allows consideration of varying land use policy, relevant to resource management Informative, limited affect on policy at ground level

A generically applicable systems for estimating SOC stocks at national or regional scale is necessary to: Increase the accuracy of global estimates of SOC stocks and changes Understand the consequences of land use change for the global C cycle Understand the GHG mitigation potential of changes in land use/land management Identify geographic areas with potential for C release or sequestration Allow countries in tropical and arid areas to take advantage of opportunities presented through global carbon trading, (CDMs)

Regional Approaches Approaches used estimate changes in SOM/SOC include IPCC inventory method:- Series of factors (climate, soil type, history, tillage & productivity) 20 year period Identifies changes between first and last year of the 20 year period Simple accounting method Soil C stock is a function of soil C under native vegetation and changes in land use or land management

Regional Approaches Statistical approaches: Regression based approaches (Gupta and Rao 1994, Smith et al 2000, 2001) Regression approaches based on spatial soil databases (Kern and Johnson 1993, Kotto-Same et al 1997) Local variability in soil conditions

Process Based Modelling Approach 3.Dynamic SOM models linked to spatial data bases Spatial Databases Simulation model Active SOM Slow SOM Passive SOM Residues Plant Growth CO 2 Spatial Results

Aims of GEFSOC Project –To improve national assessment methodologies relating to land use options and UNFCC requirements and to support core activities of the GEF IEM OP and IPCC by developing and demonstrating a generic tool that quantifies impact of land use/management and climate change scenarios on carbon sequestration in soils at the national and regional scale

Specific Research Objectives Identify and use long term experimental data sets to systematically evaluate and refine modelling techniques to quantify carbon sequestration potential in tropical soils Define, collate and format national-scale soils, climate and land use data sets to use them in development of a coupled modelling- GIS tool to estimate soil carbon stocks Demonstrate this tool by estimating current soil organic carbon stocks at the national and regional scale (using The Brazil Amazon, The Indo-Gangetic Plains, India, Jordan and Kenya as case studies) and to compare these estimates with the existing techniques of combining soil mapping units and interpolating point data Quantify the impact of defined changes in land use on carbon sequestration in soils with a view to assisting in the formulation of improved policies to optimise resource use in the four case study countries Brazil, India, Jordan and Kenya

Case Studies Brazilian Amazon Jordan Kenya Indogangetic Plains, India

Methodology

GEFSOC Project Approach Two soil organic carbon models were chosen Roth-C (developed in the UK) is a SOM model that accounts for the effects of soil type, climate, moisture content and plant cover on turnover of organic C in soils. Uses monthly time-step to calculate total SOC and microbial biomass content Century (developed in the United States) is a general ecosystem model which stimulates the dynamic of C, N, P and S in different plant/soil systems. Has plant productivity, water movement and nitrogen leaching sub models

Evaluated under many conditions (including forestry, grasslands and arable in the tropics) Two of the most widely used SOM models Good performance in comparison of 9 models (Powlson et al 1996, Smith et al 1997) Used in regional applications Model GIS linkage Roth C Century

Rothamsted Carbon Model (Roth C) Decay BIO HUM CO 2 BIO HUM CO 2 Decay Organic Inputs DPM RPM Inert Organic Matter DPM = decomposable plant material RPM = resistant plant material BIO = microbial biomass HUM = humus Colman and Jenkinson (1996)

Century Ecosystem Model (Century) Parton et al (1987)

Stage 1. Model Evaluation

Stage 2. National Data

Stage 3: Model/GIS coupling Graphical user interfaceProgram modulesIPCC

Stage 4: Current Stocks Current land use Global level information + Landscape level

Stage 5. Future Stocks

Regional carbon stocks: current and future SOC stocks in the 0-20cm soil layer for the year 1990 SOC stocks (t C ha -1 )

Regional carbon stocks: current and future SOC stocks (t C ha -1 ) SOC stocks in the 0-20cm soil layer for the year 2030

The Final Output A transferable system for estimating SOC stocks and changes in a range of soils and climatic conditions (The GEFSOC Modeling System), designed to help in formulating national and sub-national land management and carbon sequestration policy by: (i) Quantifying current soil organic carbon stocks at national and sub-national level and (ii) Analyzing the impacts of land management options on carbon storage, GHG emissions and sequestration possibilities

Website Reference The GEFSOC Modelling System can be downloaded free of charge via the project website soc-uk soc-uk And the UNEP website And is accompanied by a use manual

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