Effects of land-use change on soil total carbon pool: a meta-analysis

Abstract

Soil carbon is crucial for plant growth, agricultural productivity, and ecosystem functions as it provides essential nutrients and improves soil structure. Land-use change is widely recognized to have a profound effect on the soil carbon pool. However, there remains a lack of comprehensive understanding regarding the global response of soil total carbon, which includes both organic and inorganic carbon, to such changes. Here, we present a thorough assessment of the impact of land-use change on soil total carbon through a pairwise comparative meta-analysis of 1033 paired observations from 73 sites across six continents. These sites cover six major land-use changes: forest to cropland (FC), grassland to cropland (GC), cropland to forest (CF), cropland to grassland (CG), sandy land to forest (SF), and grassland to forest (GF). Contrary to expectations, FC and GC were not found to have a significant adverse effect on soil total carbon (lnRR₊₊ < 0.05). Similarly, restoration from CF and CG did not result in the anticipated significant increase in soil total carbon (lnRR₊₊ ∼0.08), largely due to the offsetting effects of organic and inorganic carbon. Afforestation in sandy land (SF) significantly increased soil total carbon, whereas its impact on grasslands (GF) was not significant. The effects of SF and FC on soil total carbon become more pronounced with higher precipitation levels. Conversely, the effect of CF on soil total carbon diminishes with rising temperatures. Additionally, the impact of GC and CG on total carbon increased with both the depth and duration of the change. These findings underscore the complexity of soil total carbon responses to various land-use changes and environmental factors, and highlight the necessity of incorporating soil total carbon assessments in carbon storage evaluations and land-use change modelling, particularly in the context of intensifying climate change and human activities.