Plant hydraulics coordinated with photosynthetic traits and climate

The coupling between water loss and carbon dioxide uptake drives the coordination of plant hydraulic and photosynthetic traits. Analysing multi-species measurements on a 3000 m elevation gradient, we found that hydraulic and leaf-economic traits were less plastic, and more closely associated with phylogeny, than photosynthetic traits. The two trait sets are linked by the sapwood-to-leaf area ratio (Huber value, v H ), shown here to be codetermined by sapwood hydraulic conductance ( K S ), leaf mass-per-area (LMA) and photosynthetic capacity ( V cmax ). Substantial hydraulic diversity was related to the trade-off between K S and v H . Leaf drought tolerance (inferred from turgor loss point, –π tlp ) increased with wood density, but the trade-off between hydraulic efficiency ( K S ) and –π tlp was weak. The least-cost optimality framework was extended to predict trait ( K S -dominated) and environmental (temperature-dominated) effects on v H . These results suggest an approach to include photosynthetic-hydraulic coordination in land-surface models; however, prediction of non-plastic trait distributions remains a challenge.