The impacts of grassland vegetation degradation on soil hydrological and ecological effects in the source region of the Yellow River--A case study in Junmuchang region of Maqin country

As one of the special structure layers of grassland ecosystem, soil has significant hydrological and ecological effects. However, the soil interior hydrological and ecological effects will be affected by the grassland vegetation degradation. This research was carried out in the source region of the Yellow River, where grassland vegetation was in severe degradation, with the methods of choosing typical areas and quadrates to collect soil samples and doing experiments in laboratory. Some important results were obtained from this research which mainly contained four aspects as follows. (1) With the increasing of grassland degradation degrees, the capillary water holding capacity and saturated water content decreased in all soil layers as a whole. However, the capillary water holding capacity and saturated water content increased when the grassland degradation from middle degree to heavy degree in all soil layers. (2) With the increasing of grassland degradation degrees, the field water capacity first increased and then decreased in the 0∼10 cm layer and decreased in the means of “increasing-decreasing- increasing-decreasing” manners in the 10∼20 cm, but it gradually increased in the 20∼30 cm layers. (3) Soil saturated water content was mainly affected by the soil bulk density and total phosphorus, and the soil capillary water holding capacity was mainly affected by the soil bulk density, while the soil field water capacity was mainly affected by the total nitrogen. (4) Soil water retention was not a simple process of decreasing during the grassland degradation, but it was a changing process of differences. It was very important to protect the original grassland vegetation for the hydrological process in the river source regions and this research could provide the scientific basis for revealing the impacts of grassland vegetation degradation on soil hydrological and ecological effects in the region scale and displaying the effects of grassland vegetation degradation on river runoff forming and regulation.