Species that resprout after fire undergo a reduction in height and leaf area after fire without a comparable reduction in the size of the root system, and this reduction is likely to be greater for larger-statured species. An increase in the root:shoot biomass ratio post-fire should lead to an increase in the efficiency of water transport. In burned and unburned sites, we selected stems of variable heights of ten species, including forbs, shrubs, and trees, that occur in the ecotone between long-leaf pine savannas and stream-head pocosins. We measured stomatal conductance, mid-day leaf water potential, leaf-specific whole-plant hydraulic conductance, height, and leaf area. We tested the hypotheses that leaf-specific whole-plant hydraulic conductance is higher in post-fire resprouts than unburned stems and that large-statured species have greater increases in leaf-specific whole-plant hydraulic conductance than small-statured species after fire.
Results/Conclusions
Leaf-specific whole-plant hydraulic conductance was higher in post-fire resprouts than in unburned stems. The increase in hydraulic conductance was manifested as an increase in stomatal conductance and not an increase in mid-day leaf water potential. The post-fire increases in stomatal conductance may allow resprouts to maintain high rates of photosynthesis. Large-statured species recovered a lower proportion of their pre-fire height and leaf area than small-statured species and had the greatest increases in hydraulic conductance after fire. For woody species, the percent reduction in stem height after fire was positively correlated with the percent increase in hydraulic conductance. Our results suggest that post-fire increases in hydraulic and stomatal conductance may be particularly important for large-statured species to recover carbohydrate reserves and aboveground biomass since they recover a lower proportion of their pre-fire size.