Effects of warming and clipping on plant and soil properties of an alpine meadow in the Qinghai-Tibetan Plateau, China

Climate warming and livestock grazing are known to have great influences on alpine ecosystems like those of the Qinghai-Tibetan Plateau (QTP) in China. However, it is lacking of studies on the effects of warming and grazing on plant and soil properties in these alpine ecosystems. In this study, we reported the related research from manipulative experiment in 2010-2012 in the QTP. The aim of this study was to investigate the individual and combined effects of warming and clipping on plant and soil properties in the alpine meadow ecosystem. Infrared radiators were used to simulate climate warming starting in July 2010, while clipping was performed once in October 2011 to simulate the local livestock grazing. The experiment was designed as a randomized block consisting of five replications and four treatments: control (CK), warming (W), clipping (C) and warming+clipping combination (WC). The plant and soil properties were investigated in the growing season of the alpine meadow in 2012. The results showed that W and WC treatments significantly decreased relative humidity at 20-cm height above ground as well as significantly increases air temperature at the same height, surface temperature, and soil temperature at the depth of 0-30 cm. However, the C treatment did not significantly decrease soil moisture and soil temperature at the depth of 0-60 cm. Relative to CK, vegetation height and species number increased significantly in W and WC treatment, respectively, while vegetation aboveground biomass decreased significantly in C treatment in the early growing season. However, vegetation cover, species diversity, belowground biomass and soil properties at the depth of 0-30 cm did not differ significantly in W, C and WC treatments. Soil moisture increased at the depth of 40-100 cm in W and WC treatments, while belowground biomass, soil activated carbon, organic carbon and total nitrogen increased in the 30-50 cm soil layer in W, C and WC treatments. Although the initial responses of plant and soil properties to experimental warming and clipping were slow and weak, the drought induced by the downward shift of soil moisture in the upper soil layers may induce plant belowground biomass to transfer to the deeper soil layers. This movement would modify the distributions of soil activated carbon, organic carbon and total nitrogen. However, long-term data collection is needed to further explain this interesting phenomenon.