Functional ecology of hardwood trees under chronic drought

I compared the interrelationships among traits affecting interspecific variation in the growth of seedlings of 22 hardwood tree species subjected to chronic intermittent drought. Leaf traits were the most responsive to contrasting water regimes; canopy architecture, hydraulic conductivity and leaf phenology were less affected. Relative growth rate (RGR) under drought, however, was most closely related to variation in canopy duration: species in leaf longer had greater RGR. Secondarily, maintaining higher stomatal conductance (g) under drought further enhanced RGR. Higher g is associated with a higher photosynthetic rate (A), but the relationship between A and g varied with internal CO$ sb2$ concentration (c$ sb{ rm i}$), foliar nitrogen and specific leaf mass. Species with weaker homeostatic control over c$ rm sb{i}$ had higher water use efficiency. While photosynthetic characteristics were related primarily to species' shade tolerance, water use efficiency was most closely related to habitat moisture preference