Transition in multi-dimensional leaf traits and their controls on water use strategies of co-occurring species along a soil limiting-resource gradient

Water use efficiency is among the most important eco-physiological strategies for species adaptation to waterlimiting habitats. However, understanding of how co-occurring species adopt diverse water use strategies to cope with water- and resource-limited soil habitats via the adaptation of leaf functional traits remains limited. Here, leaf 813C and 818O were used as proxies for water use efficiency (WUE) and stomatal conductance (gs) across a soil limiting-resource gradient from a non-karst primary forest to karst communities including primary forest, secondary forest, shrubland, and grassland. Leaf apparent morphology, stomatal morphology, macro- and micro-nutrients and stoichiometry were measured. We found that there were significant differences in soil physical and chemical properties across five communities, forming a soil limiting-resource gradient. Cooccurring species in each community segregated along a continuous and wide range of WUE and gs, revealing a wide spectrum of stomatal regulation intensity and contrasting water use strategies. Multiple leaf functional traits separated into two principal components: leaf economics spectrum (LES) and leaf limiting-resource spectrum (LLRS). As the stress intensity of soil limiting-resource increases, the number of composition traits of LLRS increased and the dominant traits of LLRS shifted from leaf-thickness to macro-nutrients. The major driver of gs variability in each community was LES. Variability in WUE in forests was mainly determined by LES, in shrubland by LLRS, and in grassland by neither LES nor LLRS. Our study illustrated for the first time how soil limiting-resource induced changes in multi-dimensional leaf traits with effects on water use strategies of cooccurring species: the variability in WUE was mainly controlled by the leaf economic spectrum in mild soil limiting-resource habitats; however, that effect was replaced or offset by leaf limiting-resource spectrum in moderate or severe soil limiting-resource habitats.

Automated summary

The study reveals that co-occurring species adopt diverse water use strategies along a soil limiting-resource gradient, with WUE variability mainly controlled by the leaf economic spectrum in mild soil limiting-resource habitats but replaced or offset by the leaf limiting-resource spectrum in more severe habitats. Multiple leaf traits contribute to the adaptation of species to cope with water- and resource-limited soil habitats.