Heavy grazing is recognized as one of the main causes of vegetation and soil degradation and of desertification in the semiarid Horqin sandy grassland of northern China. The objective of this study was to determine the effects of continuous grazing and 13 years of livestock exclusion on soil light fraction and total organic carbon and nitrogen stores in desertified sandy grassland.
Results/Conclusions
Results show that: (1) Light fraction organic matter in the top 100 cm of the soil is 181% higher in the exclosure than at the continuous grazing site, which accounts for 0.148% and 0.053% of soil mass in the exclosure and grazing site respectively. There is a strong positive relationship between light fraction organic matter and total soil organic carbon, and total nitrogen. (2) Soil light fraction organic carbon store is 271.38 g·m-2 in the exclosure and 130% higher than at the grazing site, whereas light fraction nitrogen store is 20.36 g·m-2 and 164% higher. Total soil organic carbon store is 1155.86 g·m-2 in the exclosure and 58% higher than at the grazing site, whereas total soil nitrogen store is 125.99 g/m2 and 24% higher. (3) Light fraction organic carbon and nitrogen account for 23.48% and 16.16% of total soil organic carbon and nitrogen stores in the exclosure respectively, whereas 16.05% and 7.59% in grazing site. (4) The effects of exclosure on light fraction matter mainly focus on surface soil. Light fraction organic matter in the top 0-10 cm of the soil increases by 537%, and 10-20 cm by 216% in the exclosure compared to the grazing site. However, there is no significant difference from 20 cm down to 100 cm between two sites.