Network characteristics and driving factors of leaf trait networks along a gradient of rocky desertification.

Rocky desertification severely constrains ecosystem functioning and vegetation in karst landscapes. Understanding how soil environmental changes influence plant functional coordination is therefore critical for ecological restoration. Here, we investigated soil physicochemical properties and leaf functional traits across a rocky desertification gradient in a karst ecosystem of southwest China. Using leaf trait networks (LTNs) to evaluate changes in trait coordination and identify key regulatory traits under different desertification intensities. We found that severely desertified (SRD) habitats were characterized by alkaline soils with lower bulk density, soil organic carbon (SOC), and total phosphorus (TP), but relatively higher total nitrogen (TN), total potassium (TK), and calcium (Ca) than lightly and moderately decertified habitats. Along the rocky desertification gradient, LTNs exhibited progressively lower edge density but higher average path length, diameter, and modularity, indicating reduced overall trait integration together with stronger functional compartmentalization under increasing environmental stress. Hub traits also shifted systematically across desertification stages. In lightly rocky desertified habitats, leaf water content, leaf thickness, and leaf nitrogen concentration acted as central traits, whereas specific leaf P and chlorophyll became dominant in moderately desertified habitats. In SRD habitats, leaf thickness and leaf tissue density emerged as the major hub traits associated with structurally conservative strategies. Redundancy analysis further showed that soil nutrient availability, pH, bulk density, and calcium jointly regulated changes in network topology across desertification stages. Overall, our results demonstrate that rocky desertification drives stage-dependent reorganization of leaf trait coordination, reflecting a transition from resource-acquisitive to structurally conservative adaptive strategies as environmental constraints intensify.