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Abstract

In view of future changes in climate, it is important to better understand how different
plant functional groups (PFGs) respond to warmer and drier conditions, particularly
in temperate regions where an increase in both the frequency and severity of
drought is expected. The patterns and mechanisms of immediate and delayed
impacts of extreme drought on vegetation growth remain poorly quantified. Using
satellite measurements of vegetation greenness, in-situ tree-ring records, eddy-covariance
CO2 and water flux measurements, and meta-analyses of source water of
plant use among PFGs, we show that drought legacy effects on vegetation growth
differ markedly between forests, shrubs and grass across diverse bioclimatic conditions
over the temperate Northern Hemisphere. Deeprooted forests exhibit a
drought legacy response with reduced growth during up to 4 years after an extreme
drought, whereas shrubs and grass have drought legacy effects of approximately
2 years and 1 year, respectively. Statistical analyses partly attribute the differences
in drought legacy effects among PFGs to plant eco-hydrological properties (related
to traits), including plant water use and hydraulic responses. These results can be
used to improve the representation of drought response of different PFGs in land
surface models, and assess their biogeochemical and biophysical feedbacks in
response to a warmer and drier climate.