Soil carbon measurement and modelling
Overview
Soil carbon is both a source and a sink of greenhouse gases. Emissions typically occur after deforestation, while some land management practices, such as pasture improvement, may actually increase soil carbon. The Rothamsted soil carbon (RothC) model estimates the change in agricultural soil carbon levels over time, based on:
- pre-disturbance soil carbon contents to a depth of 30 cm
- clay content and soil type
- land use and management history
- residue inputs to soil carbon from a variety of cropping/grazing systems
- paired sites designed to compare impact of land use and management on soil carbon.
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Soil carbon estimation: Land management practices, climate and soil type affect soil carbon pools directly through residue and manure inputs, and indirectly by influencing decomposition rates.
The RothC model is calibrated and verified to Australian conditions, and correction factors provide comparability between historic soil carbon data from a variety of analytic laboratories typically using different methods.
Modelling change in forest soils after afforestation/reforestation has been investigated using the GRC-3 model.
Implementation
Implementation focussed on standardisation of soil sampling and analysis, and calibration and verification of the RothC model:
- development of an agreed soil sampling protocol
- analytic method corrections - a standardised methods correction for soil-carbon data ensures consistency in the analysis of soil samples from a range of sources and laboratories. The correction was derived by re-analysing archival soil samples via a dry combustion method, and comparing the results to known results from the original methods
- carbon conversion factors - enables use of data generated from a wide range of sources
- paired site sampling - compares impacts of different management regimes on similar soils.
- model development:
- agricultural soils - refinement of RothC soil change model including calibration and verification, incorporation of the residue inputs to soil carbon from a variety of cropping/grazing systems; and improvements derived from the analysis of paired sites
- forest soils - modelling change in soil carbon following afforestation and reforestation
Analysis and integration
Soil data are used within the FullCAM modelling framework to provide a 30-year dynamic perspective on the nature and extent of change in land systems across the continent over the period since 1970.
- Analytical methods and supplement (these link directly to bookmarks within a pdf document)
- FullCAM model
- Latest results
Technical reports
- Review of C:N Ratios in Vegetation, Litter and Soil under Australian Native Forests and Plantations - TR 45, 2005
- The Impact of Tillage on Changes in Soil Carbon with Special Emphasis on Australian Conditions - TR 43, 2005
- Emission Sources of Nitrous Oxide from Australian Agriculture and Mitigation Options - TR 35, 2003
- Paired Site Sampling for Soil Carbon Estimation - WA - TR 38, 2003
- Paired Site Sampling for Soil Carbon (and Nitrogen) Estimation - Qld - TR 37, 2003
- Integrated Soils Modelling for the NCAS - TR 36, 2003
- Paired Site Sampling for Soil Carbon Estimation - NSW - TR 34, 2003
- Modelling change in soil carbon following afforestation or reforestation: Preliminary simulations using GRC3, and sensitivity analysis - TR 29, April 2002
- Pre-Clearing Soil Carbon Levels in Australia - TR 12, 2002
- Change in Soil Carbon following Afforestation or Reforestation - TR 20, 2000
- Carbon Conversion Factors for Historical Soil Carbon Data - TR 15, 2000
- Sampling Measurement and Analytical Protocols for Soil Carbon Estimation - TR 14, 2000
- Estimation of Changes in Soil Carbon due to Changed Land Use - TR 2, 1999
