The importance of belowground processes in drylands: from an individual to a whole plant community perspective

Abstract

A plant trait-based approach and the identification of functional trade-offs are key tools in plant ecology to link plant form and function. In the last decades, increasing attention has been given to root traits to integrate them with leaf and stem traits and achieve a whole-individual perspective of plant functional strategies. The gap between aboveground and belowground data is still very high, hampering the development of a general framework and theory describing plant functioning and sources of phenotypic variation. In this context, in drylands, where soil water and nutrients represent the main constraints for plant survival and development, plant strategies related to both water and nutrient use are of special interest as they are directly connected to plant performance and community dynamics. A growing body of evidence points out that the spatial scale of the study strongly affects the observed patterns of trait coordination and functional trade-offs, because the processes that filter the traits shaping plant communities are spatial-scale dependent. Furthermore, evolutionary history exerts a strong effect on the functional characterization of the plant community, thus demanding its consideration when searching for plant functional trade-offs. Recently, increasing efforts have been carried out to characterize species distribution belowground, as a result of new straightforward techniques, such as DNA metabarcoding, which provide the necessary tools to investigate what for long has been coined the hidden part of plant communities. Given the importance of plant-plant and plant-soil (including both biotic and abiotic factors) interactions in arid environments, the assessment of both taxonomical and functional diversity patterns belowground will likely shed some light on the mechanistic aspects of community assembly and species coexistence.