Effect of Enclosure Period on Soil Properties and Characteristics of Plant Community in Degraded Grassland

Artificial enclosure has been an important and practical measure widely used to restore vegetation in the ecologically degraded area. In this study, using a standard plot investigation method, we investigated the changes in biomass and species diversity of the plant communities in the desertified grassland located in Ningxia Autonomous Region, China, after enclosure for 0, 5, 15 and 25 years with fences made up of cement piles and barbed wires, with a complete exclusion of interferences from any activities including grazing. We also analysed the factors driving the changes in these parameters. The results showed that with the increase in the enclosure duration, the soil electrical conductivity and nutrient contents were significantly increased but the thickness of biological crust in the deserted area was not changed regularly and the soil pH values were changed only slightly. Furthermore, while no significant differences in plant biomass, species abundance and α-diversity were seen, significant difference in β-diversity was seen among different enclosure years. Principal component analysis showed the significant differences in species compositions in the deserted grassland among various enclosure years. The redundancy analysis revealed that the available nitrogen, available potassium, soil organic carbon and soil electrical conductivity were the major factors affecting the plant species compositions in the deserted area in the studied region. These findings can be of practical significance for formulating the measures to effectively curb the deterioration of ecological environment in grassland.