[Responses of plant growth of different life-forms to precipitation changes in desert steppe]

Under the background of global climate change, precipitation changes will have profound impacts on plant community dynamics. Through field experiment with precipitation manipulation in a desert steppe of western Loess Plateau, we examined the responses of species richness, density, coverage, height and aboveground biomass of different plant life-forms to precipitation changes. The results showed significant effects of precipitation on richness, density and coverage of annual herbs in the third year of manipulation experiment (2015), with lowest values in the decreased precipitation treatments. The height of annual herbs was more sensitive to precipitation changes, and was lowest in the -40% precipitation treatment during three years. The magnitudes of negative response of growth and aboveground biomass of annual herbs to decreased precipitation were larger than that to increased precipitation. Richness, density and coverage of perennial herbs in the decreased precipitation were significantly lower than those in the +40% precipitation in the 3rd year, but were insignificantly different from the control. The height of perennial herbs was lowest in the -40% precipitation treatment during three years. The magnitudes of negative response of richness, coverage and height of perennial herbs to decreased precipitation were larger than positive response to increased precipitation, while the positive response of aboveground biomass to the +40% precipitation treatment was stronger. The positive responses of richness, density, coverage and aboveground biomass of shrub to ±20% precipitation treatments were most obvious, which might be related to the relatively concentrated distribution of shrub in these treatments. The precipitation reduction inhibited the growth of herbaceous plants, particularly on the annual herbs, whereas increasing precipitation promoted perennial herbaceous growth and biomass accumulation to some extent. The annual herbaceous growth and biomass fluctuated with interannual variation of precipitation. Shrubs were relatively less affected by precipitation changes. Precipitation changes would have significant effects on plant community composition and function of desert steppe in western Loess Plateau.