Modeling grazing effects on soil-water budget under Leymus chinensis and Stipa grandis vegetation in Inner Mongolia, China.

摘要

To better understand the effects of different grazing intensities on soil-water dynamics and its budget in Inner Mongalia, China, five sites, under two representative vegetation types, Leymus chinensis (LC) and Stipa grandis (SG), were investigated: ungrazed sites since 1979, LCUG79 and SGUG79, a winter grazed site (LCWG), a continuously grazed site (SGCG) defined as a moderate grazing intensity, and a heavily grazed site (LCHG). Soil, plant, and meteorological data were collected for use in modeling soil-water content and its budget during growing seasons from 2008 to 2009 using the HYDRUS-1D. The soil-water content in 2010 was simulated using annually averaged values of initial and boundary conditions. Our results showed that grazing reduced total pores and saturated hydraulic conductivity but ungrazed sites benefited from natural recovery. Greater transpiration was observed at the SGCG site when compared with the LCWG and LCHG sites. At the two ungrazed sites, transpiration was greater in the SG region as compared with the LC region. Rainfall reduced the difference between potential and actual evapotranspiration through increasing plant-available water. The simulation of soil water in 2010 using annually averaged parameters was determined to be an acceptable alternative to actual on-site observation. Our data suggest that selection of an appropriate grazing intensity may be possible via simulation modeling for use in making land management decision, especially in the absence of on-site observations as often is the case from such remote regions.