Effects of shrub encroachment in desert grassland on runoff and the induced nitrogen loss in southeast fringe of Tengger Desert

Abstract

Grassland degradation typically characterized by the invasion of shrubs and semi鄄shrubs is a critical issue in arid and semi鄄arid desert regions throughout the world, which was broadly believed to eventually result in vegetation cover loss and the induced severe change of ecohydrological processes. The aim of this paper was to understand the response of runoff generation and the induced nutrient loss to shrub encroachment in desert grassland in arid regions since they are much closely related in drylands. We took the grasslands and shrublands in the southeast fringe of Tengger Desert, north China, for the in situ case study. Simulated rainfall experiments were conducted on grassland plots (Grassland treatment, GT) , intershrub bare soil plots (Bare soil treatment, BT) as well as the plots consisting of both bare soil patch and shrub patch (Shrub treatment, ST) in shrubland. The time to pond and to generate runoff, and the volume of rainfall to start runoff, the time series of runoff and nitrogen concentration, runoff coefficients, total nitrogen loss, and average concentration of total nitrogen were investigated simultaneously. By using these data, we compared soil water infiltration, runoff generation and nitrogen production from different habitats and elucidated the influences of the replacement of grassland by shrubland on the