Changes in soil properties and vegetation following exclosure and grazing in degraded Alxa desert steppe of Inner Mongolia, China

Abstract

Livestock grazing is recognized as one of the main causes of vegetation and soil degradation and desertification in arid and semiarid northern China. In this paper, soil properties and plant characteristics in a typical degraded area in desert steppe of Alxa were studied. The study focused on the effects of grazing on soil properties and vegetation changes under three management regimes: continuous year-long livestock grazing (FG), grazing excluded for 2 years (2EX) and grazing excluded for 6 years (6EX). Results showed that exclosure enhanced soil organic carbon (SOC) and total N accumulation, and decreased pH and bulk density. Soil organic carbon and total N in the 0–20 cm soil increased significantly with exclosure period, with 22% higher SOC, and 14% higher N in 6EX as compared with FG. Data indicated a considerable difference in soil particle size distribution between the exclosure and grazed area, and soil coarse sand fraction (>0.25 mm) in the grazed area was 16–26% higher than that in the exclosure. Plant cover was ranked according to 6EX > 2EX > FG, with a high of 46% (6EX) to a low of 31% (FG). Plant biomass was similarly ranked and vegetation diversity increased with increasing exclosure period. The results suggested that while continuous overgrazing in the erosion-prone desert steppe was detrimental to soil and vegetation, this can be reversed and significant increases in soil fertility, vegetation diversity, cover and biomass can be achieved with the implementation of protecting practices.