Trade-offs between water transport capacity and drought resistance in neotropical canopy liana and tree species

Abstract

In tropical forest canopies, it is critical for upper shoots to efficiently provide water to leaves for physiological function while safely preventing loss of hydraulic conductivity due to cavitation during periods of soil water deficit or high evaporative demand. We compared hydraulic physiology of upper canopy trees and lianas in a seasonally dry tropical forest to test whether trade-offs between safety and efficiency of water transport shape differences in hydraulic function between these two major tropical woody growth forms. We found that lianas showed greater maximum stem-specific hydraulic conductivity than trees, but lost hydraulic conductivity at less negative water potentials than trees, resulting in a negative correlation and trade-off between safety and efficiency of water transport. Lianas also exhibited greater diurnal changes in leaf water potential than trees. The magnitude of diurnal water potential change was negatively correlated with sapwood capacitance, indicating that lianas are highly reliant on conducting capability to maintain leaf water status, whereas trees relied more on stored water in stems to maintain leaf water status. Leaf nitrogen concentration was related to maximum leaf-specific hydraulic conductivity only for lianas suggesting that greater water transport capacity is more tied to leaf processes in lianas compared to trees. Our results are consistent with a trade-off between safety and efficiency of water transport and may have implications for increasing liana abundance in neotropical forests.

Coordination and trade‐offs among hydraulic safety, efficiency and drought avoidance traits in Amazonian rainforest canopy tree species

“…We show for the first time that Amazonian tree species vary along an axis of hydraulic strategy variation with low wood density, high xylem efficiency and high capacitance at one end of the spectrum, and low turgor loss point at the other. This stands in contrast to findings in many other vegetation types that show hydraulic strategy variation along the safety vs efficiency spectrum (Pockman & Sperry, ; Martínez‐Vilalta et al ., ; Wheeler et al ., ; De Guzman et al ., ). The lack of a safety vs efficiency trade‐off among the Amazonian trees that we studied is noteworthy, and supports the idea of diminishing selection on xylem cavitation resistance as moisture availability increases (Fig.…”

Wood allocation trade‐offs between fiber wall, fiber lumen, and axial parenchyma drive drought resistance in neotropical trees

“…Increasing wood density results in a decline of sapwood capacitance and therefore minimum branch xylem water potential. As a result, high wood density trees show a stronger desiccation of the leaves and stem during drought (Borchert, ; De Guzman et al, ; Meinzer, Woodruff, et al, ; Sterck et al, ). For this reason, embolism resistance has to increase with increasing wood density to maintain a wide enough hydraulic safety margin (Figure ).…”

The hydraulic efficiency–safety trade‐off differs between lianas and trees

“…De Guzman et al. () found a trade‐off between hydraulic efficiency and safety among six liana and six tree species in a seasonally dry tropical forest in Panama, which appeared similar for lianas and trees (Santiago et al. ).…”

“…, De Guzman et al. ). If, for lianas, hydraulic efficiency is not constrained by hydraulic safety (i.e., no trade‐off), then lianas could have high conductivity and remain photosynthetically active without being very vulnerable in dry conditions, which could then contribute to explaining why lianas tend to become relatively more abundant toward seasonal forests (Schnitzer ).…”