Agricultural cultivation can usually decrease soil carbon stocks and potentially raise atmospheric CO2 concentrations. The worldwide concern of the potential contribution to the greenhouse gas effect can be modified by ecological restoration, such as vegetation restoration from cropland into grassland or forest. 

Vegetation restoration has been recognized as an effective strategy for substantial soil organic carbon (SOC) accumulation and for mitigating global climate change. Additionally, the individual effects of environmental factors are relevant in controlling SOC by redistributing soil particles and soil organic matter. 

However, the complex interactions between vegetation restoration types and environmental factors on SOC dynamics still remain poorly understood. 

Researchers from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences measured the effects of environmental factors under managed vegetation restoration (forage grassland and plantation forest) and natural vegetation restoration (natural grassland, shrubland, and secondary forest) on SOC in a karst catchment, southwest China. 

They found that compared with cropland, SOC was significant higher in natural vegetation restoration but not in managed vegetation restoration. 

"The average content of SOC was 1.89 times higher in natural vegetation restoration than in cropland," said Prof. WANG Kelin, a researcher in ISA. 

"In contrast to managed vegetation restoration, significant effect of natural vegetation restoration on SOC was encountered after about nine years of the abandonment of cropland. This result highlights that, in the short-term, natural vegetation restoration is more beneficial to SOC accumulation than managed vegetation restoration in the karst region." 

The team also found that the total variation in SOC explained by environmental factors (e.g. soil bulk density, rock outcrop ratio, soil depth, pH, and altitude) was higher in natural than in managed vegetation restoration, and this proportion increased along the successional gradient. 

The results suggested that environmental factors function as accurate predictors of SOC accumulation in naturally restored vegetation in karst regions. Both management and environmental factors were recommended for consideration when characterizing SOC in managed vegetation restoration. 

This work was supported by the National Key Research and Development Program of China, the National Key Basic Research Program of China, the National Natural Science Foundation of China, and the Chinese Academy of Sciences. 

The study entitled "EFFECTS OF ENVIRONMENTAL FACTORS ON SOIL ORGANIC CARBON UNDER NATURAL OR MANAGED VEGETATION RESTORATION" was published in Land Degradation & Development.