Meta-analysis of 21st century studies shows that deforestation induces profound changes in soil characteristics, particularly soil organic carbon accumulation

Deforestation is one of the most serious environmental problems facing humankind. It continues to escalate rapidly across many regions of the world, thereby deteriorating the forest soil quality. This has prompted a large number of field-based studies aimed at understanding the impacts of deforestation on soil properties. However, the lack of comprehensive meta-analyses that utilized these studies has limited our deeper understanding of how different soil properties, including the soil organic carbon (SOC) pool, respond to deforestation. To address this critical knowledge gap, we conducted a meta-analysis of 144 studies to explore the impacts of deforestation on soil chemical, physical, and biological properties, with special emphasis on the long-term changes in SOC, such as concentrations, stocks, and sequestration. The results revealed that deforestation significantly decreased soil organic matter, electrical conductivity, and base saturation by 52%, 50%, and 98%, respectively. While deforestation increased soil total nitrogen content and decreased available phosphorus content by 51% and 99%, respectively, it resulted in slight decreases in some chemical properties, including soil pH (1%) and base cations (1%–13%). Deforestation significantly increased bulk density by 27% and soil erosion by 47%, but significantly decreased soil aggregate stability by 39% and saturated hydraulic conductivity by 63%. Soil microbial biomass C and N concentrations and enzyme activities were significantly decreased as a consequence of deforestation. Soil biological properties were much more affected by deforestation than soil physical and chemical properties. Regarding the SOC, the land use conversion from forest to pasture significantly increased SOC concentrations, stocks, and sequestration rates (11%–13%), whereas the land use conversions from forest to both plantation and cropland significantly decreased SOC concentrations, stocks, and sequestration rates (10%–43%). This observed decline in SOC accumulations decreased with increasing years after deforestation. The SOC dynamics following deforestation were predominantly regulated by microbial biomass concentrations, dehydrogenase activity, soil erosion, saturated hydraulic conductivity, aggregate stability, as well as concentrations of total organic carbon, total nitrogen, total phosphorus and organic matter. The present meta-analytical study provides compelling evidence that deforestation can induce profound changes in soil characteristics, including soil C contents, and has significant implications for soil health sustainability and climate change mitigation.