Climate and soil properties limit the positive effects of land use reversion on carbon storage in Eastern Australia

S.M.F. Rabbi, Matthew Tighe, Manuel Delgado-Baquerizo, Annette Cowie, Fiona Robertson, Ram Dalal, Kathryn Page, Doug Crawford, Brian R. Wilson, Graeme Schwenke, Malem Mcleod, Warwick Badgery, Yash P. Dang, Mike Bell, Garry O’Leary, De Li Liu, Jeff Baldock

Australia's "Direct Action" climate change policy relies on purchasing greenhouse gas abatement from projects undertaking approved abatement activities. Management of soil organic carbon (SOC) in agricultural soils is an approved activity, based on the expectation that land use change can deliver significant changes in SOC. However, there are concerns that climate, topography and soil texture will limit changes in SOC stocks. This work analyses data from 1482 sites surveyed across the major agricultural regions of Eastern Australia to determine the relative importance of land use vs. other drivers of SOC. Variation in land use explained only 1.4% of the total variation in SOC, with aridity and soil texture the main regulators of SOC stock under different land uses. Results suggest the greatest potential for increasing SOC stocks in Eastern Australian agricultural regions lies in converting from cropping to pasture on heavy textured soils in the humid regions.