Affiliation: | (1) Department of Botany, University of Florida, Gainesville, FL 32611, USA;(2) Department of Biology, University of Miami, Coral Gables, FL 33124, USA;(3) USDA Forest Service, Forestry Sciences Laboratory, Corvallis, OR 97331, USA;(4) Fairchild Tropical Gardens, Coral Gables, FL 33156, USA;(5) Department of Forest Science, Oregon State University, Corvallis, OR 97331, USA;(6) Present address: Department of Integrative Biology, University of California, 3060 Valley Life Sciences Building, Berkeley, CA 94720, USA |
Abstract: | We investigated how water transport capacity, wood density and wood anatomy were related to leaf photosynthetic traits in two lowland forests in Panama. Leaf-specific hydraulic conductivity (kL) of upper branches was positively correlated with maximum rates of net CO2 assimilation per unit leaf area (Aarea) and stomatal conductance (gs) across 20 species of canopy trees. Maximum kL showed stronger correlation with Aarea than initial kL suggesting that allocation to photosynthetic potential is proportional to maximum water transport capacity. Terminal branch kL was negatively correlated with Aarea/gs and positively correlated with photosynthesis per unit N, indicating a trade-off of efficient use of water against efficient use of N in photosynthesis as water transport efficiency varied. Specific hydraulic conductivity calculated from xylem anatomical characteristics (ktheoretical) was positively related to Aarea and kL, consistent with relationships among physiological measurements. Branch wood density was negatively correlated with wood water storage at saturation, kL, Aarea, net CO2 assimilation per unit leaf mass (Amass), and minimum leaf water potential measured on covered leaves, suggesting that wood density constrains physiological function to specific operating ranges. Kinetic and static indices of branch water transport capacity thus exhibit considerable co-ordination with allocation to potential carbon gain. Our results indicate that understanding tree hydraulic architecture provides added insights to comparisons of leaf level measurements among species, and links photosynthetic allocation patterns with branch hydraulic processes. |