Atmospheric and soil drought risks combined shape community assembly of trees in a tropical dry forest

By: Méndez-Toribio M., Ibarra-Manríquez G., Paz H., Lebrija-Trejos E.
Published in: Journal of Ecology
SDGs : SDG 06  |  Units:   | Time: 2020 |  Link
Description: Predicting plant community assembly is challenging in part because the influence of environmental conditions via plant f unctional strategies and the relevance of mechanisms of community assembly change across habitats and these changes remain poorly studied. To assess how environmental conditions drive species sorting in a tropical dry forest, we used the combined RLQ and Fourth-Corner methods to analyse changes in tree species assemblages among sites with distinct atmospheric and soil drought risks. We asked how variation in potential radiation, soil water availability and evapotranspiration interact with functional traits to explain the cross-site sorting of species lying along a continuum of drought coping strategies ranging from acquisitive to conservative resource-use. Environment and traits were tightly related. Opposing common expectations on the success of strategies in resource limited environments, drought tolerant conservative species with dense tissues and tardily deciduous leaves were favoured on sites with higher resource (soil water) availability. Drought avoiding acquisitive species with water storing tissues and thin, light leaves with short retention time periods were favoured in sites with drier soils. A decoupling of stressing conditions caused by soil and atmospheric aridity combined with differences in species adaptations to each of these factors can explain the apparent discrepancies. Synthesis. Drought stress gradients entailed shifts in community functional composition. We show that atmospheric and soil drought risks can be decoupled and jointly determine species distribution in relation to their functional strategies. By considering atmospheric drought stress, a key yet often overlooked factor in studies of community assembly, we offer a novel explanation to a seemingly contrasting pattern in tropical dry forests where species with acquisitive, rather than conservative strategies, predominate in the most resource-limited yet less water demanding environment. More generally, our results emphasize the need for detailed studies of the multiple habitat-dependent relationships between traits and environment to advance our predictive understanding of species distributions and community assembly. © 2020 British Ecological Society