Different responses of leaf and root traits to changes in soil nutrient availability do not converge into a community-level plant economics spectrum

Abstract

Spatial heterogeneity in soil can influence the distribution of plant communities because plants differ in their ability to acquire resources. In nutrient-poor soils, plants should bear traits that prioritize conservation of resources over growth, whereas the opposite is expected in nutrient-rich soils. A coordinated response to soil fertility, in which leaves and roots converge into the same strategy, would lead to a community-level plant economics spectrum (PEScom). Here, we examine how nutrient availability across different soil types shapes the functional structure of desert shrub communities and how much of this variation is explained by species turnover or intraspecific variability (ITV). We measured leaf and root traits of 16 shrub species in four sites with contrasting soil nutrient availability in the southern edge of the Atacama Desert. In leaves, changes in soil nutrient availability were associated with a leaf economics spectrum, shifting from communities with more acquisitive strategies to communities with more conservative strategies with increasing nutrient limitation. No such pattern of co-variation was observed for roots; thus, the relationship between above and below-ground traits did not fit the PEScom. Variation of leaf traits was mainly determined by species turnover, while for root traits it was determined equally by species turnover and ITV. The lack of a PEScom appears to be related to the co-limitation of multiple resources, which promotes different responses in root traits. We highlight the importance of incorporating leaf and root traits to understand how multiple resource limitation shapes plant ecological strategies.