About two thirds of Tibetan Plateau (TP) is covered by alpine grassland, which includes two primary ecosystem types, alpine meadow in the east and alpine steppe in the west. The unique environmental condition and plant communities make Tibetan alpine grassland often ecologically fragile, and thus, more vulnerable to climate change than other low-elevation ecosystems.
Ecosystem water use efficiency (WUE) is a key index depicting the relationship between carbon gain and water loss, serving as an indicator of plant capacity to adapt to the changing climate. However, it remains poorly understood that how WUE varied across Tibetan alpine grassland under a warming climate.
On July 13, a new study published in Journal of Geophysical Research: Atmospheres by a research group from Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences found that the alpine grassland’s WUE strongly increased during 1982-2016. Interestingly, the significantly increasing WUE mainly occurred in the alpine meadow, while in the alpine steppe WUE remained almost stable.
“The obvious increases in greenness and atmospheric CO2 concentration are the two main reasons for the enhancement of WUE in alpine meadow,” explained Dr. MA Ning, the lead author of this study.
“Although alpine steppe also became greener, the negative effect of wetting counteracted the positive effect of greening on WUE trend. Moreover the CO2 fertilization effect in alpine steppe is much smaller because of low biomass.”
The results suggested divergent responses of WUE to ongoing environmental changes among different terrestrial ecosystems in TP.
“Such differences are tightly related not only to external climate forcings but also to vegetation intrinsic properties,” said Prof. ZHANG Yongqiang, the corresponding author.
(a) The spatial pattern of trends in WUE of the alpine grassland during 1982-2016; (b) the anomaly of WUE averaged across alpine grassland and across its two ecosystems during 1982-2016; (c) the dominate driver of WUE trend across the alpine grassland of Tibetan Plateau. (Image by MA Ning)
Contrasting trends in water use efficiency of the alpine grassland in Tibetan Plateau