Effects of grazing exclusion on carbon sequestration and the associated vegetation and soil characteristics at a semi-arid desertified sandy site in Inner Mongolia, northern China.

摘要

China's Horqin Sandy Land is a region vulnerable to disturbance that has been subjected to serious desertification, mainly because of overgrazing. We investigated whether the establishment of grazing exclosures in areas with active sand dunes would benefit vegetation recovery and improve soil quality. The results showed that along the age sequence of grazing exclosure for 8, 13, and 26 yr, plant cover, species number, and above-ground biomass increased, the soil's water-holding capacity, fine particle content, organic C, total N, total P, available N and K, and electrical conductivity also increased, and the soil coarse sand content, pH, and bulk density in the top 20 cm of the soil decreased. However, the greatest improvements compared with the continuous grazing sites occurred in the 13- and 26-yr exclosures. Based on the area of heavily and severely desertified land in the study region and the results of the present study, the amount of C sequestered in the top 20 cm of the soil could reach 7.8 Mt after 26 yr of grazing exclusion. Our results confirm that grazing exclusion is a positive way to restore desertified ecosystems and has a high potential for sequestering soil C and improving soil quality in the semi-arid Horqin Sandy Land.