"Grain for Green" driven land use change and carbon sequestration on the Loess Plateau, China.

Land-use change is widely considered to be a major factor affecting soil carbon (C) sequestration (ΔC_s). This paper studied changes to soil C stocks (C_s) following the conversion of farmland to forest, shrub and grassland across the key area for implementing China's "Grain for Green" — the Loess Plateau. The results are based on a synthesis of 44 recent publications (including 424 observations at 70 sites) which has allowed us to further refine our understanding of the mechanisms driving the increase in C_s following farmland conversion. This synthesis suggests that the ΔC_s potential of the Loess Plateau could reach 0.59 Tg yr^-1 based on an estimated annual average ΔC_s rate of 0.29 Mg ha^-1 yr^-1. In the region's different rainfall zones both the main contributing factors and C_s dynamics varied. Across the entire Loess Plateau, C_s showed first an increasing (<5 yr) then a decreasing (6-10 yr) tendency only to increase (>10 yr) yet again. In addition, the ΔC_s rates depended primarily on restoration age. This synthesis demonstrates that both the initial s C_s and the average annual temperature have a significant effect on ΔC_s while the effect of land-use conversion type, rainfall zone, and average annual precipitation were minimal. [ABSTRACT FROM AUTHOR]