Responses of root exudates to phosphorus-rich patches in a subtropical evergreen broad-leaved forest and their module affiliation in the trait network

Root exudation-related traits are crucial for a plant acquiring spatially heterogeneous soil phosphorus (P) resources. Integrating root exudation traits into root trait networks reveals plant foraging strategies and trait coordination in P-rich patches, thereby providing deeper insights into the adaptation mechanisms employed by species. We constructed root trait networks for seventeen AM-associated tree species from a subtropical evergreen broad-leaved forest, aiming to analyze the regulatory mechanisms of P patch availability on plant belowground strategies by incorporating root exudation traits, mycorrhizal traits, and traditional absorptive root traits. Results showed that the root exudation rate (RE) and root acid phosphatase activity exhibited significant interspecific variations and were accordingly assigned to the exploration and the chemical traits modules, respectively. P addition reduced the connectivity of the trait network (lowering edge density and average path length) and increased modularity, thereby indicating a shift from a highly integrated collaborative strategy to a more flexible modular strategy in plants. Notably, most traits did not show systematic responses across species to P addition, except for a significant decrease in RE and a significant increase in root length growth rate in P-rich patches. This divergency in trait responses shows that co-existing tree species adopt diverse P acquisition strategies. This study elucidates the belowground responses of plants to P heterogeneity by demonstrating the reorganization of root trait networks and the functional differentiation of exudation traits, offering a novel trait-modularity perspective on species coexistence in subtropical forests. • Root exudation rate and root acid phosphatase activity exhibited significant interspecific variations and were accordingly assigned to the exploration and the chemical traits modules, respectively. • P addition reduced the trait network connectivity but increased modularity, reflecting a shift from a highly integrated collaborative strategy to a more flexible modular strategy in plants. • Except for the reduced root exudation rate and enhanced root length growth rate, the responses of most belowground traits to P addition varied across species without exhibiting a consistent trend.