Soil physicochemical properties and vegetation structure along an elevation gradient and implications for the response of alpine plant development to climate change on the northern slopes of the Qilian Mountains.

Elevation is one of key factors to affect changes in the environment, particularly changes in conditions of light, water and heat. Studying the soil physicochemical properties and vegetation structure along an elevation gradient is important for understanding the responses of alpine plants and their growing environment to climate change. In this study, we studied plant coverage, plant height, species richness, soil water-holding capacity, soil organic carbon (SOC) and total nitrogen (N) on the northern slopes of the Qilian Mountains at elevations from 2124 to 3665 m. The following conclusions were drawn: (1) With the increase of elevation, plant coverage and species richness first increased and then decreased, with the maximum values being at 3177 m. Plant height was significantly and negatively correlated with elevation (<italic>r</italic>=-0.97, <italic>P</italic><0.01), and the ratio of decrease with elevation was 0.82 cm·100 m^-1. (2) Both soil water-holding capacity and soil porosity increased on the northern slopes of the Qilian Mountains with the increase of elevation. The soil saturated water content at the 0-40 cm depth first increased and then stabilized with a further increase of elevation, and the average ratio of increase was 2.44 mm·100 m^-1. With the increase of elevation, the average bulk density at the 0-40 cm depth first decreased and then stabilized at 0.89 g/cm³. (3) With the increase of elevation, the average SOC content at the 0-40 cm depths first increased and then decreased, and the average total N content at the 0-40 cm depth first increased and then stabilized. The correlation between average SOC content and average total N content reached significant level. According to the results of this study, the distribution of plants showed a mono-peak curve with increasing elevation on the northern slopes of the Qilian Mountains. The limiting factor for plant growth at the high elevation areas was not soil physicochemical properties, and therefore, global warming will likely facilitate the development of plant at high elevation areas in the Qilian Mountains. [ABSTRACT FROM AUTHOR]