Experimental Warming Aggravates Degradation‐Induced Topsoil Drought in Alpine Meadows of the Qinghai–Tibetan Plateau

Abstract Climatic warming is presumed to cause topsoil drought by increasing evapotranspiration and water infiltration, and by progressively inducing land degradation in alpine meadows of the Qinghai–Tibetan Plateau. However, how soil moisture and temperature patterns of degraded alpine meadows respond to climate warming remains unclear. A 6‐year continuous warming experiment was carried out in both degraded and undegraded alpine meadows in the source region of the Yangtze River. The goal was to identify the effects of climatic warming and land degradation on soil moisture ( θ ), soil surface temperature ( T sfc ), and soil temperature ( T s ). In the present study, land degradation significantly reduced θ by 4·5–6·1% at a depth of 0–100 cm ( p < 0·001) and increased the annual mean T sfc by 0·8 °C. Warming with an infrared heater (radiation output of 150 W m −2 ) significantly increased the annual mean T sfc by 2·5 °C ( p < 0·001) and significantly increased θ by 4·7% at a depth of 40–60 cm. Experimental warming in degraded land reversed the positive effects of the infrared heater and caused the yearly average θ to decrease significantly by 3·7–8·1% at a depth of 0–100 cm. Our research reveals that land degradation caused a significant water deficit near the soil surface. Experimental warming aggravated topsoil drought caused by land degradation, intensified the magnitude of degradation, and caused a positive feedback in the degraded alpine meadow ecosystem. Therefore, an immediate need exists to restore degraded alpine meadow grasslands in the Qinghai–Tibetan Plateau in anticipation of a warmer future. Copyright © 2017 John Wiley & Sons, Ltd.