Interspecific and intraspecific trait variability differentially affect community-weighted trait responses to and recovery from long-term drought

1. Plant traits are useful proxies of plant strategies and can influence community and ecosystem responses to climate extremes, such as severe drought. Few studies, however, have investigated both the immediate and lagged effects of drought on community-weighted mean (CWM) plant traits, with even less re- search on the relative roles of interspecific vs. intraspecific trait variability in such responses. 2. We experimentally reduced growing season precipitation by 66% in two cold semi arid grassland sites in northern China for four consecutive years to explore the drought resistance of CWM traits as well as their recovery 2 years follow- ing the drought. In addition, we isolated the effects of both interspecific and intraspecific trait variability on shifts in CWM traits. 3. At both sites, we observed significant effects of drought on interspecific and intraspecific trait variability which, in some cases, led to significant changes in CWM traits. For example, drought led to reduced CWM plant height and leaf phosphorous content, but increased leaf carbon content at both sites, with re- sponses primarily due to intraspecific trait shifts. Surprisingly, these CWM traits recovered completely 2 years after the extreme drought. Intraspecific trait vari- ability influenced CWM traits via both positive and negative covariation with interspecific trait variability during drought and recovery phases. 4. These findings highlight the important role of interspecific and intraspecific trait variability in driving the response and recovery of CWM traits following ex- treme, prolonged drought.