Effects of experimental warming on the root biomass of an alpine meadow on the Qinghai-Tibetan Plateau, China

The Qinghai-Tibetan Plateau( QTP) has been considered an ideal region in which to study the responses of terrestrial ecosystems to climate change. The alpine meadow,a typical vegetation type of the QTP,is extremely fragile and highly sensitive to climate change. Once destroyed,reestablishing these meadows in a short timeframe has proven to be very difficult; their loss would result either in landscape degradation or desertification. Therefore,an understanding of the dynamic changes to the alpine meadow vegetation of the QTP caused by climate change is extremely important and urgently needed. In previous research,we chose an alpine meadow in the QTP as our study area and established 20 experimental plots with a randomized block design,comprising five replicates and four treatments: a control,warming alone,clipping alone,and a combination of warming and clipping. In this study,we tested the control and the warming plots independently and sampled root biomass using a soil auger with an inner diameter of 7 cm. Samples were collected from soil layers of 0-10cm,10-20 cm,20-30 cm,30-40 cm,and 40-50 cm during the growing season,from May to September in 2012 and2013. This study explored variations in root biomass occurring in different months and at different soil depths during the growing season,as well as correlations between biomass and the moisture and temperature of the corresponding soil layers.The results show that( 1) root biomass tended to increase over time in 2012,peaking from July to September and with the mean being 3811 g / m~2 and 4468 g / m~2 in the control and warming treatments,respectively. However,root biomass decreased over time in 2013,peaking in May and June with an average value of 4175 g / m~2 and 4142 g / m~2 in the control and warming treatments,respectively. Total root biomass was larger in the warming treatments than in the control,with a mean difference of 293.97 g / m~2. Conversely,there were no significant differences in total root biomass between treatments in the various months. Warming treatments resulted in slightly increased root biomass,but the magnitude of the increase varied widely among months in the growing season,which resulted in differences in the increase in inter-annual root biomass.( 2) The root biomass was primarily distributed at depths of 0-10 cm,where 50.61% of all roots were localized.In the warming treatments,root biomass declined by 8.38% in the 0-10 cm soil layer,whereas it increased by 2.1% in the10-50 cm soi