The effects of vegetation communities on soil organic carbon stock in an enclosed desert-steppe region of northern China

Enclosure is an effective strategy for enhancing soil carbon sequestration in the desert steppe. Soil organic carbon (SOC) and its stock during changes in the plant community influence soil fertility and the global carbon cycle. We studied changes in SOC and its stock along with six plant community types in the desert steppe of Inner Mongolia, northern China. The goal of this study was to explore differences in SOC and its stock among plant communities while accounting for the effects of environmental factors. We collected 336 soil samples at four soil depths (0-5 cm, 5-10 cm, 10-20 cm, and 20-30 cm) and vegetation attributes from 84 plots in the enclosure. The results revealed that plant community type and soil depth were the most influential factors for root biomass, SOC, and SOC stock. Total root biomass varied from 229.21 to 731.71 g center dot m(-2) and was ranked as follows: Koeleria cristata > Leymus chinensis > Stipa krylovii >Allium mongolicum >Stipa breviflora > Convolvulus ammannii. Mean SOC and its stock of soils associated with K. cristata were 1.94 and 1.62 times higher than that measured for C. ammannii soils, respectively. Root biomass, SOC, and its stock gradually decreased with soil depth. Stratification ratios (SRs) of SOC increased with soil depth for different plant communities and showed better soil quality (except C. ammannii and A. mongolicum). Results from redundancy analysis (RDA) showed that root biomass, clay, coverage, and litter biomass had significant impacts on SOC and SOC stock. We conclude that the plant community had the greatest effect on improving SOC stock after enclosure, and plant root biomass contributed the most to SOC stock.