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Dryad

Data from: Positive effects of tree species diversity on productivity switch to negative after severe drought mortality in a temperate forest experiment

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Mar 06, 2024 version files 177.40 KB
Mar 13, 2024 version files 1.27 MB

Abstract

Synthesis of a large body of evidence from field experiments suggests more diverse plant communities are both more productive as well as more resistant to the effects of climatic extremes like drought. However, this view is strongly based on data from grasslands due to limited empirical evidence from tree diversity experiments. Here we report on the relationship between tree diversity and productivity over ten years in a field experiment established in 2005 that was then affected by the 2018 megadrought in central Europe. Across a number of years, tree species diversity and productivity were significantly positively related, however, the slope switched to negative in the year of the drought. Net diversity effects increased through time, with complementarity making greater continuations to the net diversity effect than selection effects. Complementarity was clearly positive (95 % credible interval) in three and five species mixtures before the drought (2012-2016) but was found to decrease in the year of the drought. Selection effects were clearly positive in 2016, and remained positive in 2018, the drought year in two, three, and five species mixtures. Survival of the Norway spruce (Picea abies) plummeted during drought and a negative relationship between species diversity and spruce survival was found. Our findings suggest that tree diversity per se may not buffer communities against the impacts of extreme drought and that tree species composition and the drought tolerance of tree species (i.e., species identity) will be important determinants of community productivity as the prevalence of drought increases.