Usually, People know the “karst” through Guilin’s scenic beauty. Karst is a distinctive topography, created by the action of acidic water on carbonate bedrock. Although karst scenic is beautiful, its environment is fragile and its soil is so little. Recent studies show that soil contains more carbon than does the atmosphere and vegetation of the Earth combined. Understanding the mechanisms controlling the accumulation of soil carbon is critical to predict patterns of global warming. Therefore, scientists in the Institute of Subtropical Agriculture, Chinese Academy of Sciences (ISA) believes understanding the relationships between soil organic carbon (SOC) and soil biotic and abiotic characteristics in different vegetation types is essential for carbon management. 

Since the 1990s, government policies have forced farmers to abandon fields in parts of the karst area where erosion losses were especially high. With the enforcement of the projects, such as “Grain-for-Green”, agricultural and rocky land gradually restored to grassland, shrubland, and forest, depending on the time since abandonment. Scientists guessed soil carbon sequestration may be affected by different factors in different vegetation types. Therefore, it is essential to identify the main drivers that control soil carbon sequestration to achieve effective soil carbon management at the regional or global scale. 

In order to verify their hypothesis, SOC was measured along a vegetation succession sere in a karst area in Southwest China, and other soil physicochemical properties, microbial biomass, enzyme activities, and litter characteristics were recorded. Redundancy analysis (RDA) was applied to determine the significant parameters on the portion of explained SOC variation and to test the contribution of individual significant parameters to the SOC variation for the different vegetation types. 

Scientists found that vegetation restoration is conducive to soil carbon sequestration in karst areas. SOC significantly increased along the vegetation succession. Besides, they considered that the factors controlling SOC accumulation differed along vegetation succession. Microbial biomass parameters (soil microbial biomass carbon content & soil microbial biomass nitrogen content) were the main factors contributing to SOC accumulation in all vegetation stages, while URE (urease activity) and SAC (saccharase activity) were only important controlling factors in the early-middle and middle-late stages, respectively. Litter nitrogen only played an important role in the shrubland. In addition, along succession, the interaction effect among significant factors became more and more prominent, indicating that positive interactions among plant communities, soil biotic processes, and the soil matrix were enhanced over vegetation succession. 

Based on these results, scientists suggest that managers should increase nitrogen import in the early and middle succession stages including legume species cultivation in the ecosystems, and prevent disruption of the physical structure of the soil and provide a suitable environment for microbe activity to enhance the soil carbon sequestration capacity, which may promote ecological restoration in the ecologically vulnerable karst landscape. 

This study was supported by the National Key Basic Research Program of China (2015CB452703), the Chinese Academy of Sciences through its Hundred Talent Program to LI Dejun, two grants from the National Natural Science Foundation of China (31270555 and 41471445), and a grant from the Western Light Program from the Chinese Academy of Sciences to ZHANG Wei. 

The study entitled “Factors controlling accumulation of soil organic carbon along vegetation succession in a typical karst region in Southwest China” has been published in the July issue of Science of Total Environment, details could be found at http://www.sciencedirect.com/science/article/pii/S0048969715003496.