Dominance of rock exposure and soil depth in leaf trait networks outweighs soil quality in karst limestone and dolomite habitats

Abstract

Leaf trait networks (LTNs) visualize the intricate linkages reflecting plant trait-functional coordination. Typical karst vegetation, developed from lithological dolomite and limestone, generally exhibits differential communities, possibly due to habitat rock exposure, soil depth, and soil physicochemical properties variations, leading to a shift from plant trait variation to functional linkages. However, how soil and habitat quality affect the differentiation of leaf trait networks remains unclear. LTNs were constructed for typical dolomite and limestone habitats by analyzing twenty-one woody plant leaf traits across fifty-six forest subplots in karst mountains. The differences between dolomite and limestone LTNs were compared using network parameters. The network association of soil and habitat quality was analyzed using redundancy analysis (RDA), Mantle's test, and a random forest model. The limestone LTN exhibited significantly higher edge density with lower diameter and average path length when compared to the dolomite LTN. It indicates LTN differentiation, with the limestone network displaying a more compact architecture and higher connectivity than the dolomite network. The specific leaf phosphorus and leaf nitrogen contents of dolomite LTN, as well as the leaf mass and leaf carbon contents of limestone LTN, significantly contributed to network degree and closeness, serving as crucial node traits regulating LTN connectedness. Additionally, both habitat LTNs significantly correlated with soil nitrogen and phosphorus, stoichiometric ratios, pH, and organic carbon, as well as soil depth and rock exposure rates, with soil depth and rock exposure showing greater relative importance. Soil depth and rock exposure dominate trait network differentiation, with the limestone habitat exhibiting a more compact network architecture than the dolomite habitat.