[MIS02-P02] Divergent responses of ecosystem water-use efficiency to extreme droughts over Northern Eurasia
Keywords:water-use efficiency, droughts, terrestrial ecosystems
In this study, we examine the impacts of extreme drought events on ecosystem WUE during 1948-2008, with a particular focus on distinguishing response of different biomes over Northern Eurasia. The responses of ecosystem WUE to extreme droughts differed among different regions. For northern high latitudes (north of 50°N), hot days and increasing solar radiation were usually concurrent with droughts, which to some extent eliminate the limitations of low temperature and insufficient light on photosynthesis. In this case, vegetation productivity was potentially enhanced, with higher ecosystem WUE during drought years than during normal years. By contrast, for biomes in relatively arid climate conditions, extreme drought years tended to aggravate the water stress for vegetation growth. Consequently, in these regions, vegetation photosynthesis was largely suppressed with significantly lower ecosystem WUE observed. Our results, therefore, highlight that background climate is a crucial factor determining drought impacts on terrestrial carbon-water interactions. Further increases in baseline aridity could therefore exacerbate the impact of punctuated droughts on terrestrial ecosystems.