Is land condition a useful indicator of soil organic carbon stock in Australia's northern grazing land?

Bray, S.G., Allen, D.E., Harms, B.P., Reid, D.J., Fraser, G.W., Dalal, R.C., Walsh, D., Phelps, D.G., and Gunther, R. (2016) Is land condition a useful indicator of soil organic carbon stock in Australia's northern grazing land? Rangeland Journal, 38 (3). pp. 229-243.

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The grazing lands of northern Australia contain a substantial soil organic carbon (SOC) stock due to the large land area. Manipulating SOC stocks through grazing management has been presented as an option to offset national greenhouse gas emissions from agriculture and other industries. However, research into the response of SOC stocks to a range of management activities has variously shown positive, negative or negligible change. This uncertainty in predicting change in SOC stocks represents high project risk for government and industry in relation to SOC sequestration programs. In this paper, we seek to address the uncertainty in SOC stock prediction by assessing relationships between SOC stocks and grazing land condition indicators. We reviewed the literature to identify land condition indicators for analysis and tested relationships between identified land condition indicators and SOC stock using data from a paired-site sampling experiment (10 sites). We subsequently collated SOC stock datasets at two scales (quadrat and paddock) from across northern Australia (329 sites) to compare with the findings of the paired-site sampling experiment with the aim of identifying the land condition indicators that had the strongest relationship with SOC stock. The land condition indicators most closely correlated with SOC stocks across datasets and analysis scales were tree basal area, tree canopy cover, ground cover, pasture biomass and the density of perennial grass tussocks. In combination with soil type, these indicators accounted for up to 42% of the variation in the residuals after climate effects were removed. However, we found that responses often interacted with soil type, adding complexity and increasing the uncertainty associated with predicting SOC stock change at any particular location. We recommend that caution be exercised when considering SOC offset projects in northern Australian grazing lands due to the risk of incorrectly predicting changes in SOC stocks with change in land condition indicators and management activities for a particular paddock or property. Despite the uncertainty for generating SOC sequestration income, undertaking management activities to improve land condition is likely to have desirable complementary benefits such as improving productivity and profitability as well as reducing adverse environmental impact.

Item ID: 75508
Item Type: Article (Research - C1)
ISSN: 1834-7541
Keywords: carbon sequestration, pasture management, soil organic matter, uncertainty
Copyright Information: © The State of Queensland (through the Department of Agriculture and Fisheries, and Department of Science, Information Technology and Innovation) [2016]
Date Deposited: 29 Aug 2022 21:34
FoR Codes: 30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3004 Crop and pasture production > 300499 Crop and pasture production not elsewhere classified @ 50%
41 ENVIRONMENTAL SCIENCES > 4106 Soil sciences > 410604 Soil chemistry and soil carbon sequestration (excl. carbon sequestration science) @ 50%
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