A review of the evidence linking management and soil carbon sequestration in rangelands

Abstract

While the agronomic benefits of organic matter in soils have long been established, debate continues regarding the potential for increasing carbon storage in soils to help combat anthropogenic climate change. Of all the world’s biomes, rangelands have arguably the highest expectations, and the greatest uncertainty, for soil organic carbon (SOC) sequestration, i.e. removing carbon dioxide from the atmosphere via photosynthesis and securely storing the assimilated carbon in soil. Our review of evidence for persistent increases in SOC stocks following implementation of new management strategies showed significant methodological limitations and inconsistencies in reported outcomes. A major challenge is that detection and attribution of management impacts are difficult in low productivity, high diversity rangelands where 90% or more of sampled differences in SOC stocks may be determined by climate and soil factors. Caution is needed in interpreting results, but strategies with more consistent evidence for SOC sequestration include over-sowing forage legumes into grass pastures, conversion from cropping to permanent pasture and avoiding prolonged high grazing intensity. Our analysis did not find evidence for significant, persistent increases in SOC stocks with the implementation of other livestock management options (e.g. rotational grazing). We conclude from the available evidence that the potential for SOC sequestration in rangelands is likely modest. However, uncertainty is high, and we recommend research priorities to improve data and understanding of SOC in rangelands for production and environmental benefits.