What determines soil organic carbon stocks in the grazing lands of north-eastern Australia?

Abstract

This study aimed to unravel the effects of climate, topography, soil, and grazing management on soil organic carbon (SOC) stocks in the grazing lands of north-eastern Australia. We sampled for SOC stocks at 98 sites from 18 grazing properties across Queensland, Australia. These samples covered four nominal grazing management classes (Continuous, Rotational, Cell, and Exclosure), eight broad soil types, and a strong tropical to subtropical climatic gradient. Temperature and vapour-pressure deficit explained >80% of the variability of SOC stocks at cumulative equivalent mineral masses nominally representing 0–0.1 and 0–0.3 m depths. Once detrended of climatic effects, SOC stocks were strongly influenced by total standing dry matter, soil type, and the dominant grass species. At 0–0.3 m depth only, there was a weak negative association between stocking rate and climate-detrended SOC stocks, and Cell grazing was associated with smaller SOC stocks than Continuous grazing and Exclosure. In future, collection of quantitative information on stocking intensity, frequency, and duration may help to improve understanding of the effect of grazing management on SOC stocks. Further exploration of the links between grazing management and above- and below-ground biomass, perhaps inferred through remote sensing and/or simulation modelling, may assist large-area mapping of SOC stocks in northern Australia.

Factors Controlling Soil Organic Carbon Stocks with Depth in Eastern Australia

“…Land use, as represented by LDI is shown to have a relatively low influence on SOC levels at this sub-continental scale, but it may be at least partly masked by the vegetation cover factor. Its influence appears to decline further with depth, similarly reported by others (Luo et al, 2010;Wilson et al, 2010Wilson et al, , 2011Allen et al, 2013;Badgery et al, 2013), Nevertheless the factor is still considered important in subsoils (Guo and Gifford, 2002;Wright et al, 2007;Meersmans et al, 2009;Follett et al, 2009;Vasques et al, 2010;Rumpel and Kögel-Knabner 2011). It has been suggested that SOC in deeper soil layers might reflect historic rather than current land use (Schulp and Veldkamp, 2008;Wilson and Lonergan, 2013).…”

“…At more local scales, where climate is more uniform and therefore less of an influence, topography can be shown to be a significant driving factor (McKenzie and Ryan, 1999;Allen et al, 2013;Davy and Koen, 2013).…”

Soil Restoration after seven Years of Exclosure Management in Northwestern Ethiopia

“…rainfall and temperature), vegetation cover and land management (e.g. livestock stocking rate) (Anderson et al, 2007;Pulido-Fernández et al, 2013), and soil properties (Piñeiro et al, 2009;Allen et al, 2013). For example, drier and cooler climate, the case in the Tigray region, Ethiopia (Mekuria et al, 2011) relatively slow decomposition and enhance accumulation of SOC.…”

Management of Grazing Intensity in the Semi‐Arid Rangelands of Southern Australia: Effects on Soil and Biodiversity

“…Overgrazing is recognized as an important factor in rangeland degradation, but there is a lack of unanimity for the effects of livestock grazing on soil C. Some recent studies show a decrease (Su et al, 2004;Zuo et al, 2008;Mofidi et al, 2012), no significant change (Sanjari et al, 2008;Allen et al, 2013;Lu et al, 2015) or an increase in soil C (Reeder & Schuman, 2002;Li et al, 2011). These inconsistencies are due to differences in plant species composition (Piñeiro et al, 2010), the legacy of previous management and interactions between these factors.…”