Strengthening Hydrological Regulation of China's Wetland Greenness Under a Warmer Climate

Natural wetlands are permanently or seasonally inundated with water, and the growth of vegetation in these wetlands is assumed to be sensitive to a warming climate. China's natural wetlands are mostly found in cold, high‐latitude (>40°N in NE China) and high‐altitude (>4,000 m in average on the Tibetan Plateau (TP)) areas. Rapid warming of regional climate (>0.30°C decade−1since the 1960s) is thought to have promoted the growth of vegetation in these cold wetlands. However, using three independent greenness data sets, we show that the wetlands in the TP and NE China experienced significant browning between 1999 and 2007, rather than a straightforward increase in greening. The interannual variation in wetland greenness on the TP was regulated by both the temperature and the amount of solar radiation. In NE China, however, the effect of temperature and solar radiation was unable to explain the temporal variation in greenness and the changes were mostly regulated by the soil moisture content and drought. There was a decrease in the dependence of vegetation growth on temperature in NE China, but no significant change on the TP, which has experienced a warmer and wetter climate in recent decades. The effect of drought and the soil moisture content on the interannual variation in the greenness of wetlands consistently increased across the TP and NE China. Our results highlight the hydrological regulation of the growth of vegetation in a warmer climate, even in wetland environments. China's natural wetlands have experienced significant warming of 0.49°C decade−1China's natural wetlands experienced significant browning from 1999 to 2007The effect of drought and soil moisture content on the interannual variation in the greenness of wetlands increased