Paved urban environments can pose great threats to the physiological functioning and ecological services of street trees. In this context, assessment of leaf phenotypic plasticity is crucial for understanding the ecological strategy of tree species under impervious pavements. In this study, we measured a set of leaf economic traits, hydraulic traits of Cinnamomum camphora, and surrounding environmental factors in a street site (the soil was covered by the impervious pavement) and a park site (the soil was covered by grass) in Hefei, eastern China. Compared with the park site, trees in the street site had higher stomatal length (SL), leaf thickness (LT), maximum photochemical quantum yield of photosystem II (Y(II)), and lower stomatal density (SD), specific leaf area (SLA), the leaf water potential at 50% loss of hydraulic conductance (P₅₀), and leaf turgor loss point (TLP). Redundancy analysis showed that air relative humidity and volumetric soil water content caused these traits to be altered. Our results showed that C. camphora adapted to the street pavement environment through the coordination of leaf economic and leaf hydraulic traits, and adopted the slow investment return type in the leaf economic spectrum and high drought resistance to meet its actual physiological needs. This finding provides a new perspective for understanding the physiological strategies of street trees to adapt to urban pavement environments.

Ginkgo biloba is a dioecious heterophyllous tree species with two leaf types. Short shoots always bear many leaves, which are undivided or slightly bilobed, but long-shoot leaves are smaller and are deeply divided into two or more lobes. To clarify the functional difference between the two leaf types, we investigated the morphology, anatomy, gas exchange, and hydraulic traits of the two leaf types in male and female trees. Our results showed that long-shoot leaves possessed a lower specific leaf area (SLA), higher leaf thickness, gas exchange rates, and average tracheid number than short-shoot leaves. When compared to short-shoot leaves, long-shoot leaves in male trees had higher leaf hydraulic conductance (K_leaf) and leaf water potential of 50% loss in K_leaf (leaf P50), while female trees exhibited relatively higher K_leaf. When comparing sexual differences, male trees possessed higher leaf thickness, leaf dissection index, vein density (VD), and predawn leaf water potential and lower SLA, tracheid number, and midday leaf water potential, while no significant difference in leaf P50 was observed between the two sexes. Male trees exhibited greater leaf gas exchange rates, which were tightly associated with other functional traits, such as VD and K_leaf. We found strong shoot-based and sex-related heterogeneities in the leaf hydrology, anatomy, and economy of Ginkgo biloba. Moreover, male ginkgoes may perform better due to their greater leaf hydraulic efficiency and gas exchange rates.

The stresses imposed by impermeable paved grounds are known to result in poor health and drastically depressed benefits of street trees, but not all trees respond similarly. In this study, we investigated anatomical and chemical traits to evaluate the phenotypic plasticity of seven common street species. Analyses were performed on wood cores and leaves collected from street sites and a forest park site in Hefei, eastern China. We found significant increases in the vessel size of Sapium sebiferum (Ss) for the street trees, and the vessel frequency of Albizia julibrissin (Aj) and Koelreuteria bipinnata Franch. var. integrifoliola (Kb), indicating higher water transport efficiency and drought resistance under impervious pavements, respectively. The specific leaf area tended to be higher in Kb, Sapindus mukorossi (Sm) and Ss in the street site, while it was lower in Cinnamomum camphora (Cc) and Platanus acerifolia (Pa) for the street trees. Stomatal traits showed little change between the street site and the park site. Cc exhibited lower chlorophyll and carotenoid concentration in street trees. Ss and Cc showed high plasticity in terms of anatomical and chemical properties, respectively, while Acer buergerianum was unresponsive. These results provide a physiological basis for future street species selection in eastern China.

Key message: Evergreen and deciduous species in a subtropical urban forest of Eastern China exhibit pronounced differences in leaf traits, with evergreens species showing lower photosynthetic rate on a leaf mass basis and leaf nutrient contents, but higher leaf mass per area ratio, leaf thickness, leaf carbon content, and leaf carbon-to-nitrogen ratio, whereas deciduous species show the opposite pattern, reflecting distinct resource-use characteristics. In addition, leaf economic and hydraulic traits are coordinated, with higher vein density associated with higher scores along the leaf economics spectrum PCA axis, reflecting resource-acquisitive characteristics and highlighting vein density as a key trait linking water transport capacity to carbon economy. Context: Understanding how leaf economics and hydraulic traits vary and interact among different plant growth forms and leaf habits is essential for elucidating plant adaptability. However, the coupling of these two trait dimensions remains unclear within urban forest ecosystems where environmental conditions differ significantly from natural forests. Aims: This study aimed to investigate variation and coordination between leaf economics and hydraulic traits among woody species in a subtropical urban forest of Eastern China, focusing on differences between leaf habits and growth forms. Methods: We measured 10 leaf economic traits and 4 hydraulic traits across 53 woody species from a subtropical urban forest. Results: Evergreen species exhibited lower photosynthetic rate on a leaf mass basis, leaf nutrient contents, and higher leaf mass per area ratio, leaf thickness, leaf carbon content, and leaf carbon-to-nitrogen ratio, consistent with resource-conserving characteristics. Deciduous species showed higher values of these parameters, indicative of rapid resource acquisition. Shrubs displayed significantly higher phosphorous content in leaves than trees. Vein density was positively correlated with the leaf economic spectrum. Conclusion: These findings reveal a coordination between leaf hydraulic and economic traits. This coupling highlights the balance between water transport and resource acquisition characteristics.

Urban drought increasingly challenges the survival and performance of urban forests, consequently undermining their sustainability and productivity. Hydraulic-economic trait trade-offs are primary determinants of species drought tolerance, yet these trade-offs remain poorly understood in urban forests. In this study, we investigated the differentiation in hydraulic and economic traits in leaf and stem functional traits among 14 tree species with different xylem anatomical types, explored their correlations along the plant economic spectrum, and further systematically evaluated drought adaptation strategies, aiming to guide species selection and management in urban forests. We found that ring-porous trees exhibited trait values associated with faster water transport compared to diffuse-porous species. Specifically, ring-porous species had significantly higher xylem-specific conductivity, leaf-specific conductivity, and branch xylem vessel diameter. However, the hydraulic safety margin of diffuse-porous species was significantly lower than that of ring-porous species, accompanied by lower leaf and wood phosphorus content. These patterns support the hydraulic safety enhancement strategy in ring-porous species. Across the 14 studied tree species, ring-porous species occupied the fast-acquisitive end of the plant economics spectrum, while diffuse-porous species were positioned at the conservative end. We also discovered a significant negative correlation between hydraulic and economic functional trait principal components, demonstrating that hydraulic safety and carbon economy are synergistically integrated along a unified plant economics spectrum, from fast-growing but vulnerable species to slow-growing but resilient ones. Our study reveals that ring-porous and diffuse-porous species occupy opposite ends of the plant economics spectrum, employing divergent drought adaptation strategies. This clear functional differentiation provides a robust ecological rationale for diversifying urban forests. We propose that selecting a mixture of acquisitive and conservative species will create a more resilient urban ecosystem capable of withstanding a variety of environmental stresses, from seasonal droughts to heatwaves, thereby securing long-term stability and functionality.