Glacier extinction homogenizes functional diversity

QuestionsThe disappearance of glaciers threatens biodiversity and the functioning of ecosystems. To date, questions remain about the response of functional diversity to glacier extinction and its potential for adaptation to climate change. How does glacier retreat and extinction affect plant functional diversity? How do mean and variation of plant traits change with glacier retreat and extinction? LocationFour glacier ecosystems in Italian Alps. Plant communities spanning 0 to ca 5,000 years on average after glacier retreat. MethodsWe quantify how glacier retreat affects functional diversity of plant communities analysing twelve functional traits of 117 plant species across 170 plots. First, we addressed the impact of glacier retreat on functional divergence and functional homogeneity, analysing both trait average and trait variation. Next, we explored how biodiversity (i.e., plant species richness) influenced functional diversity and how glacier retreat affected such relationship. Finally, we explored the effects of glacier retreat on mean and variation of single traits associated to carbon and nitrogen cycling and resource allocation. ResultsGlacier retreat homogenizes functional diversity by reducing trait variation and making communities more functionally similar. While biodiversity positively contributes to trait heterogeneity, glacier retreat erodes the support of species richness to functional diversity. We also show how glacier extinction has medium to large negative effects on the average and variation of key functional traits associated to carbon economy, but small positive effects on leaf nitrogen content. ConclusionsOur results demonstrate the pervasive impact of glacier extinction on the functioning of plant communities. We stress that functional diversity and trait variation should be the focus of adaptation and mitigation actions.