A meta-analysis reveals increases in soil organic carbon following the restoration and recovery of croplands in Southwest China

In China, the Grain for Green Program (GGP) is an ambitious project to
convert croplands into natural vegetation, but exactly how changes in
vegetation translate into changes in soil organic carbon remains less
clear. Here we conducted a meta-analysis using 734 observations to explore
the effects of land recovery on the soil organic carbon and nutrients in 4
provinces in Southwest China. Following GGP, the soil organic carbon
content (SOCc) and soil organic carbon storage (SOCs) increased by 33.73%
and 22.39%, respectively. Likewise, soil nitrogen increased, while
phosphorus decreased. Outcomes were heterogeneous, however, depending on
variation in soil and environmental characteristics. Both the regional
land use and cover change indicated by landscape type transfer matrix and
net primary production from 2000 to 2020 further confirmed that GGP
promoted the forest area (2.95%) and regional mean net primary production
(52.94%). Our findings suggest that GGP could enhance soil and vegetation
carbon sequestration in Southwest China and help to develop carbon neutral
strategy.