Overgrazing decreases soil organic carbon stocks the most under dry climates and low soil pH: A meta-analysis shows

Dlamini, P and Chivenge, P and Chaplot, V (2016) Overgrazing decreases soil organic carbon stocks the most under dry climates and low soil pH: A meta-analysis shows. Agriculture, Ecosystems & Environment, 221. pp. 258-269. ISSN 01678809

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Grasslands occupy about 40% of the world’s land surface and store approximately 10% of the global soil organic carbon (SOC) stock. This SOC pool, in which a larger proportion is held in the topsoil (0–0.3 m), is strongly influenced by grassland management. Despite this, it is not yet fully understood how grassland SOC stocks respond to degradation, particularly for the different environmental conditions found globally. The objective of this review was to elucidate the impact of grassland degradation on changes in SOC stocks and the main environmental controls, worldwide, as a prerequisite for rehabilitation. A comprehensive meta-analysis was conducted using 55 studies with 628 soil profiles under temperate, humid, sub-humid, tropical and semi-arid conditions, to compare SOC stocks in the topsoil of non-degraded and degraded grassland soils. Grassland degradation significantly reduced SOC stocks by 16% in dry climates (<600 mm) compared to 8% in wet climates (>1000 mm) and Asia was the most affected continent (−23.7%). Moreover, the depletion of SOC stock induced by degradation was more pronounced in sandy (<20% clay) soils with a high SOC depletion of 10% compared to 1% in clayey (≥32% clay) soils. Furthermore, grassland degradation significantly reduced SOC by 14% in acidic soils (pH ≤ 5), while SOC changes were negligible for higher pH. Assuming that 30% of grasslands worldwide are degraded, the amount of SOC likely to be lost would be 4.05 Gt C, with a 95% confidence between 1.8 and 6.3 Gt C (i.e. from 1.2 to 4.2% of the whole grassland soil stock). These results by pointing to greater SOC losses from grasslands under dry climates and sandy acidic soils allow identification of grassland soils for which SOC stocks are the most vulnerable, while also informing on rehabilitation measures.

Item Type: Article
Divisions: Research Program : East & Southern Africa
CRP: CGIAR Research Program on Dryland Systems
Uncontrolled Keywords: SOC stocks, Spatial variation, Controlling factors, Grasslands, Grassland degradation
Subjects: Others > Soil
Others > Climate Change
Depositing User: Mr Ramesh K
Date Deposited: 08 Jan 2017 13:26
Last Modified: 08 Jan 2017 13:26
URI: http://oar.icrisat.org/id/eprint/9847
Official URL: http://dx.doi.org/10.1016/j.agee.2016.01.026
Acknowledgement: UNSPECIFIED
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