Effects of Climate and Grazing on Surface Soil in Grassland

Abstract

Primary productivity and nutrient cycling in grasslands can be accelerated or decelerated by grazing by large mammals, and climate is one of the most important factors to determine the direction of the ecosystem response to grazing. In Mongolian grasslands, livestock grazing is common, and there is a latitudinal gradient in the degree of aridity. The degree of aridity increases from north to south, and the type of grassland changes from forest steppe to steppe, and further to desert steppe. To examine the effects of livestock grazing and climate, and their interaction in Mongolian grasslands, we compared the chemical properties of the surface soils (0–10 cm) at the inside and outside of the fence in the three types of grasslands. The soil chemical environment deteriorated with the greater degree of aridity [e.g., soil pH increased and total nitrogen (N) concentration decreased], while the effects of grazing were not prominent. Laboratory rates of net soil N transformations, an index of N cycling, were slower in steppe and desert steppe than in forest steppe, and livestock grazing decelerated net soil N transformations, especially under drier incubation conditions. These results suggested that livestock grazing decelerated nutrient cycling, irrespective of the degree of aridity, in Mongolian grasslands.KeywordsClimateGrassland soilGrazingNet N transformations