Influence of experimental warming on heat and water fluxes of alpine meadows in the Qinghai-Tibet plateau

Abstract

In order to predict the response of alpine ecosystems to global warming and to provide the experimental data needed for Atmosphere Global Circulation Models (AGCMs) coupled with Land Surface Models (LSMs), a warming experiment using infrared heaters was conducted in the alpine meadow ecosystem of the Qinghai-Tibet Plateau. Five replicate blocks with three 2 x 2 m treatment plots in each block were randomly installed. The treatment plots were control plots (C) at ambient temperatures, moderately warmed plots (W1), and intensely warmed plots (W2), manipulated by using 130 W m-2 and 150 W m-2 infrared heaters, respectively. The results showed that when significant warming increased the daily mean soil surface temperature by 1-3 °C compared to temperatures in the control plots during the warm season (seasonal frozen soil thaw), the soil temperature gradients from depths of 0 to 100 cm significantly increased by 0.02-0.04 °C cm-1 during the day and 0.01-0.03 °C cm -1 at night. Volumetric soil liquid water content significantly decreased by 2.6-3.4% in shallow soil (5-15 cm) and significantly increased by 0.7-5.1% in deep soil (100 cm) compared to the control plots. Likewise, soil liquid water content gradients at depths between 10 and 20 cm significantly decreased by 0.2-0.3% cm-1 and significantly increased by 0.01-0.08% cm-1 at depths between 20 and 100 cm. Warming did not cause significant vapor water change in the atmosphere near the soil surface. Based on these results, it can be concluded that increasing soil temperatures accelerated the processes of ground heat flux, sensible heat, and latent heat, which caused significant change in soil water content and in its gradients.