Impacts of environmental factors on spatial distribution of soil moisture of grassland in Yunwu Mountain
云雾山自然保护区环境因素对土壤水分空间分布的影响

This article analyzed the effect of topography attributes, vegetation type, rainfall and enclosing on the soil moisture in grassland of the Yunwu Mountain. Results showed that the environmental attributes play controlling roles in the spatial distribution of grassland soil moisture. However, the contribution of these environmental indices varies with soil depth. The dominant controls on spatial variability of the time-averaged soil moisture changed from aspect, hill-slope position, community types and enclosing in the soil depth of 0-100cm to relative elevation, hill-slope position, aspect and enclosing for deeper soil layer of 100-300cm. The dynamic behavior of influences of different environmental indices on the layer-averaged soil moisture depends on several factors. In general, the correlation of soil moisture with slope gradient, elevation, slope position and enclosing showed a more significant increase following a greater amount of antecedent precipitation. It was observed that the influence of community types on soil moisture corresponds to the difference in community coverage and transpiration, with a stronger influence in May and July when have a greater difference in vegetation. The influence of aspect depends on solar irradiation, and is significant in July having intense solar irradiation. Being enclosed for a long time, the grassland coverage gradually increased, and water holding ability is boosted up, thus vegetation accommodation ability and redistribution ability for soil water are improved. Therefore, naturally enclosed grassland controls effectively soil water transport from air to vegetation and to soil, thus improves grassland hydrologic cycle.