Historical climate supplements contemporary environment as a determinant of plant functional diversity across Europe

Background/Question/Methods

Predicting how climate change will drive shifts in functional diversity, and thereby in ecosystem functioning and the provisioning of ecosystem services, is a crucial issue for science. Broad-scale patterns in species richness and composition are often jointly determined by modern environment and long-term historical factors, but whether these effects penetrate to functional diversity is unknown. Combining distribution data and functional trait information for a total of 3232 plant species at the scale of ~50×50km grid cells, we quantified the geographic patterns in plant functional richness (F_Rich), evenness (F_Eve), and dispersion (F_Dis) across Europe, and assessed their relationships to contemporary environment and a key historical factor, namely Quaternary glacial-interglacial climate change. 

Results/Conclusions

European plants functional diversity consistently exhibit high values across metrics in areas as the Alps and the main known glacial refugia for non-boreal temperate trees in Southern Europe. All three functional diversity metrics exhibit geographic patterns that are simultaneously linked to both sets of factors. Contemporary productivity, topographic heterogeneity, and glacial-interglacial temperature instability determined F_Rich. Contemporary water balance, topographic and edaphic heterogeneity, as well as glacial-interglacial precipitation instability determined F_Eve. Current climate stress (extreme winter cold and temperature seasonality), and to a lesser extend glacial-interglacial temperature instability, determined F_Dis. We show that macro-scale functional diversity geographic patterns for European plants are indeed linked not just to contemporary environment, but also to Quaternary glacial-interglacial climate change, despite the last glaciation ending ~11,500 years ago.

These findings reinforce the idea that while current climate has strong effects on functional diversity, long-term climate variability poses important supplementary constraints. An important consequence is that we should expect future climate change to elicit not just short-term shifts in ecosystem functioning, but also long-term functional disequilibria. Hence, future climate change may elicit not just short-term shifts in ecosystem functioning, but potentially long-term functional disequilibria. Understanding the strength and generality of such long-term climate constraints on functional diversity will be paramount for predicting how ecosystem functions and services will be affected by future climatic conditions.