Plant community stability results from shifts in species assemblages following whole community transplants across climates

摘要

Climate change will decrease precipitation and increase rainfall variability in eastern Mediterranean regions, with responses of plant communities largely uncertain. Here, we tested short-term responses of dryland plant communities to contrasting rainfall regimes using reciprocal transplants of soil and seed banks. We exposed three annual plant communities to very different climatic conditions along a steep rainfall gradient. We tested for the role of climate versus community origin on community response and resistance. In parallel, we asked whether origin-specific climatic adaptations predict compositional shifts across climates. Due to an extreme drought, all plants in the driest climate failed to reach maturity. For the remaining two community origins, the most dry-adapted species in each community increased in dry climate and the wet-adapted species increased in wet climate. Dry community origins showed large compositional shifts while maintaining stable plant density, biomass and species richness across climates. Conversely, wet communities showed smaller compositional shifts, but larger variation in biomass and richness. This asynchrony in species abundances in response to rainfall variability could maintain structural community stability. This, in combination with seed dormancy, has the ability to delay extinction in response to climate change. However, increasing occurrence of extreme droughts may, in the long-term, lead to loss of wet-adapted species.