Grazing effects on soil characteristics and vegetation of grassland in northern China

Abstract. Large areas of grassland in the agro-pastoral region of northern China were converted into cropland for grain production, and the remaining grasslands are being overgrazed and seriously degraded. The objective of this study was to evaluate how reductions in grazing intensity affect the soil and vegetation characteristics in grasslands of northern China. Soil heterogeneity and vegetation characteristics were evaluated for ungrazed (UG), moderate grazing (MG), and heavy grazing (HG) sites. Grazing increased diversity, but heavy grazing decreased aboveground biomass and increased the non-grass component. Vegetation biomass was greatest at the UG site (220 g m−2) followed by the MG (99 g m−2) and HG (27 g m−2) sites (P < 0.05). The non-grass proportion of total biomass increased with grazing intensity, which was 8, 16, and 48 % for UG, MG, and HG sites, respectively. Species richness at the MG and HG sites was significantly higher than at the UG site (P < 0.05) with 3.6, 5.5, and 5.7 for UG, MG, and HG sites, respectively. Over grazing homogenized soil characteristics at a 10 m scale. The ranges of spatial autocorrelation for soil organic C (SOC) and total N were both > 120 m at the HG site, which was considerably larger than that at the MG and UG sites with corresponding distances of 17.3 and 20.8 m for the MG site and 25.8 and 15.0 m for the UG site, respectively. Therefore, MG was recommended as the preferred management alternative for grasslands in northern China because of increased plant diversity without negative consequences related to decreased forage quality and forage quantity, and soil heterogeneity in northern China's grasslands.