Response of vegetation and soils to desertification of alpine meadow in the upper basin of the Yellow River, China.

Alpine meadow plays important roles in the animal production and conservation of water resources in the upper basin of Yellow River. In recent decades, desertification of this alpine meadow has resulted in changes in vegetation and soil features, as well as threatening the ecosystem functions and security. A field study was conducted to explain the response of vegetation pattern and soil features to desertification of alpine meadows. Results of vegetation studies indicated that hygrophytes were gradually replaced by mesophytes, xerophytes, and some annual psammophilous plants, and that cover and herbaceous biomass decreased along with the progressive desertification. Vegetation height increased in the slightly desertified stage, and then decreased in the very severe stage. Species diversity decreased, suggesting that desertification of alpine meadow contributed to species loss. This study also indicated that soil features gradually declined with increasing desertification of alpine meadow with soil texture becoming coarser and water content decreasing gradually. Soil bulk density (0-20 cm layer) increased with increasing desertification, but in the deeper soil (20-40 cm layer) decreased from original vegetation to the moderately desertified stage, and then increased after the severely desertified stage. The difference between the topsoil and the deeper soil in both soil bulk density and soil moisture was greatest at the moderately desertified stage. Soil organic matter dramatically reduced with progressive desertification. Soil nutrients (total N, P and K) decreased greatly due to desertification. Soil pH (0-20 cm and 20-40 cm) showed no significant differences among desertification stages. Overall, desertification of alpine meadow decreased plant diversity, reduced dominance of palatable species and changed soil physical and chemical properties. Correlation analysis indicated that vegetation change has been regulated by soil texture, soil organic matter and soil water. [ABSTRACT FROM AUTHOR]