Climate warming will probably have large impacts on carbon fluxes in high-altitude alpine grassland ecosystems. This is due to the rapid rise in air temperature and the large amounts of stored soil organic carbon. An infrared heater temperature enhancement system has been established since June 2006 in an alpine grassland ecosystem at the Haibei Alpine Grassland Ecosystem Research Station (latitude 37.61°N, longitude 101.31°E, and altitude 3203 m asl), Northwest Institute of Plateau Biology, Chinese Academy of Sciences. We tested the hypothesis that experimental warming increase soil respiration because of the high temperature sensitivity at high altitude ecosystems. Soil respiration was measured twice a month over the growing season of 2007 using the static chamber/gas chromatography method, and was monitored once per hour using eight-channel automated soil CO2 flux system (Li-8150, Li-Cor, Inc, Lincoln, Nebraska, USA) since 1st June 2008.
Results/Conclusions
The results showed that total growing season (June to September) soil respiration was 434 and 498 g C m-2 in control plots for 2008 and 2009, respectively. Experimental warming for about 2 degrees in 5 cm soil depth did not significantly affect total soil respiration in 2007 and 2008, but slightly decreased soil respiration in 2009. Across 2007 and 2008, with continuous monitoring of soil moisture, we found experimental warming significantly decreased soil volume water content. Thus, contrary to our hypothesis, experimental warming does not increase soil respiration at high altitude ecosystems on the Tibetan Plateau, probably because of the balance of the positive effect of temperature and the negative effect of warming-induced water deficit.