Response of Soil Respiration and Its Components to Warming and Dominant Species Removal along an Elevation Gradient in Alpine Meadow of the Qinghai-Tibetan Plateau

The Qinghai-Tibetan Plateau is experiencing unprecedented temperature rises and changes in plant community composition owing to global warming. Few studies focused on the combined effects of warming and changes in species composition on soil respiration (Rs). We conducted a 4-year experiment (2015-2018) to examine the influences of warming and dominant plant species removal on Rs and its autotrophic (Ra) and heterotrophic (Rh) components along an elevation gradient (3200, 3700, and 4000 m) for alpine meadow of the Qinghai-Tibetan Plateau. Results showed that warming positively affected Rs, and the stimulation of Rs gradually diminished at 3200 m but remained stable at 3700 and 4000 m as warming progressed. Warming did not influence Ra at all sites. Dominant species removal produced hysteretic behavior that decreased Ra (29%) at 3700 m but increased Ra (55%) at 4000 m in 2018. No significant effect of dominant species removal on Rh was observed. Significant interactive effects of warming and dominant species removal were detected only on Ra at 3700 and 4000 m. Accordingly, under future warming, soil organic matter decomposition at higher elevation will enhance positive feedback to atmospheric CO2 concentration more than that at lower elevation, thus accelerating soil organic carbon loss.