Above- and below-ground response to soil water change in an alpine wetland ecosystem on the Qinghai-Tibetan Plateau, China

The reduction of soil water content induced by global warming is expected to affect plant communities worldwide. However, less is known about the consequences of global warming-induced decreases of soil water on alpine wetland ecosystems on the Qinghai-Tibetan Plateau. To determine the responses of a natural alpine wetland community to decreases in soil moisture, we conducted a gradient analysis of soil water using a sequence space-series variation. We used the sequence space-series variation of soil water contents to reflect potential time-series variations by examining the effects of spatial heterogeneity on soil water, as well as determining the changes that would occur in above- and below-ground properties of an alpine wetland community. We found that vegetation aboveground biomass, vegetation cover and height all significantly increased along soil moisture, but species richness decreased. Soil organic carbon, total nitrogen, available nitrogen, total phosphorus and available phosphorus all significantly increased along soil moisture, but soil pH, total potassium and available potassium significantly decreased. Species richness was significantly and negatively correlated to aboveground biomass, vegetation cover and height. Aboveground biomass, vegetation cover and height were all significantly and positively related to soil organic carbon, total N and P, and available N and P, but were negatively related to total K. Conversely, species richness was significantly and negatively related to soil organic carbon, total N and P, and available N and P, but positively related to total K. Our observations indicate that decreased soil water would potentially have a negative influence on the alpine wetland plant communities and soil properties.

► Above-ground vegetation properties increased with SWC, except for species richness.
► Species richness showed positive correlations to biomass, covers and height.
► SOC, N and P significantly increased with SWC, but pH value and K were decreased.
► Aboveground biomass, covers and height were positively related to SOC, N, P.
► Species richness was significant negatively related to SOC, N and P.