Unravelling leaf hydraulic responses to urbanization and the coordination with economic strategies of subtropical urban forests

Abstract

Urban plants’ functional traits largely reflect their resilience to environmental stresses, necessitating a deeper understanding of plant adaptive strategies for sustainable urban forestry. This study investigated the intraspecific variation and coordination of leaf economic and hydraulic traits in eight subtropical tree species along an urbanization gradient in Hefei, China. We observed that trees in urban site exhibited enhanced drought tolerance traits compared with rural site, including more negative water potential at 50 % loss of hydraulic conductivity and turgor loss point, alongside higher leaf hydraulic conductance and leaf vein density. Urban trees also displayed lower leaf mass per area and higher leaf photosynthesis rate, indicative of an acquisitive resource strategy, contrasting with rural trees’ conservative traits (e.g., thicker palisade tissue). Principal component analysis demonstrated divergent trait coordination: urban trees prioritized hydraulic safety and photosynthetic efficiency, while rural trees emphasized structural investment. We also discovered that urbanization weakens the linkage between hydraulic and economic trait spectra in plant leaves, triggering a shift from the "coordinated optimization" adaptation mode observed in rural ecosystems to a "modular adaptation" strategy in urban to balance hydraulic safety and resource allocation demands. Collectively, our results revealed that the economic strategies of leaves showed a trend from conservation to acquisition along urbanization gradients extending from rural to urban sites. Our findings also reveal that urbanization progression leads to a weakening of the correlation between leaf hydraulic and economic traits in plants, providing a mechanistic understanding of how trees adapt to urbanization habitats.