Structural changes in steppe vegetation community according to grazing gradient in semiarid regions of Inner Mongolia, China

Abstract

The productivity of the semiarid grasslands in Inner Mongolia, China has been decreasing rapidly due to the vegetation degradation. Using vegetation as an index, this research analyzed the changes in the characteristics of the vegetation community along a profile from inhabitants to protected non-grazing areas, and evaluated the affects of grazing to the grasslands. With an increase in grazing intensity, the dominance of Aneurolepidium chinensis and Stapa grandis in primary communities have decreased, while the dominance of Artemisia frigida and Potentilla acaulis have increased. With the increase in grazing intensity, physical properties of surface soil changed, i.e., the soil hardness and capacity increased, and the soil porosity decreased. Such changes can be used as an index to evaluate grassland degradation. The growth and development of vegetation communities depend on their biological characters and environmental conditions. The height of plant and the biomass in a vegetation community decreased with the increase in grazing intensity, while the composition of the community remained unchanged. Effects on synusias depend on grazing intensities. In the sub-shrub synusia composed of diverse species, Artemisia frigida was the most grazing-resistant. In terms of the moisture ecological type of vegetation, arid-growth species dominated in the community, communities and were complemented by mid arid-growth type of vegetation according to grazing intensity. The mid-growth and arid mid-growth types of vegetation were affected by grazing intensity, i.e., an increase in grazing intensity caused decreases in the biomass and diversity of mid-growth and arid mid-growth types of diverse vegetation.