Coordination of leaf, stem and root traits in determining seedling mortality in a subtropical forest

Plant traits from different organs are thought to be coordinated to achieve main vital functions. However, evidence on how the coordination of traits affect plant vital rates (e.g. mortality rates) is rare due to the poor representation of root traits, which play important roles in water and soil nutrients uptake. In this study, we collected plant traits from 13,733 seedlings of 57 species across 10-year monitoring in a subtropical forest in Southern China, asking whether traits from root and aboveground organs are coordinated, and whether they have consistent effects on seedling mortality (e.g. all fast resource-acquisitive traits reduce mortality). We performed phylogenetic principal component analysis (PPCA) to test trait coordination and used generalized linear mixed models (GLMMs) to examine trait-mortality relationships. We found that some of the root and aboveground traits were highly correlated. PPCA of traits separated species to the strategy of resource acquisition or conservation, supporting the plant economics spectrum. Traits from root, stem and leaf showed coordinated effects on seeding mortality, in which species with conservative traits tended to have lower mortality rates than species with acquisitive traits. Root traits, such as root nitrogen content, tissue density and specific root length significantly related to seedling mortality. We concluded that traits from different organs were coordinated describing an acquisitive-conservative continuum of strategies and have consistent effects on seedling mortality, providing the first evidence for the plant economics spectrum and for the root trait-mortality relationships in subtropical seedling communities. Our results emphasized that besides aboveground traits, key root traits significantly impact seedling mortality. Integrating root traits is necessary to gain further understanding in the relationships between plant performance and traits.