2018 ESA Annual Meeting (August 5 -- 10)

PS 14-30 - Short-term physiological responses of Puerto Rican dry forest after Hurricane Maria

Tuesday, August 7, 2018
ESA Exhibit Hall, New Orleans Ernest N. Morial Convention Center
Tristan Allerton, Skip J. Van Bloem and Stefanie L. Whitmire, Baruch Institute of Coastal Ecology and Forest Science, Clemson University, Georgetown, SC
Background/Question/Methods

Predicting future carbon and water cycling in forests depends on understanding mechanisms of tree mortality and how functional and compositional dynamics in forests respond to large-scale physical disturbances that may intensify with climate change. Capitalizing on the recent occurrence of Hurricane Maria, we conducted a field campaign in Guánica dry forest in SW Puerto Rico during the immediate months following the event to study functional responses of tropical dry forest trees to loss of aboveground biomass via snapping, uprooting, and massive defoliation. The study was based upon two alternate hypotheses predicting how dry forest trees might respond at the leaf-level to canopy damage from Hurricane Maria: (1) Rapid defoliation during storms prevents the usual drawdown of nutrients that occurs prior to senescence and is subsequently recycled in the construction of new leaves. As a result, leaves produced post-hurricane are of lower quality and less efficient relative to pre-hurricane leaves resulting in reduced resource acquisition rates or (2) the high phenotypic plasticity that exists among dry forest species allows trees to produce post-hurricane leaves characterized by more “acquisitive” traits in order to exploit higher resource conditions. We sampled the first leaves produced following Maria, and compared them to leaves collected pre-hurricane. A number of important physiological and morphological functional traits were measured including stomatal conductance, water use efficiency (C13 isotope discrimination), leaf nutrients (N, P and C), chlorophyll content, stomatal density, specific leaf area, and leaf size.

Results/Conclusions

Preliminary results indicate significant differences between pre- and post-hurricane leaf traits of Puerto Rican tropical dry forest trees. Seven of the 13 dominant species sampled displayed higher maximum rates of stomatal conductance six weeks following the hurricane compared to pre-hurricane conductance rates. Furthermore, specific leaf area was also found to have increased among many of the same species post-hurricane, suggesting that some species may be capable of exploiting the temporarily resource-rich environment. Interestingly however, chlorophyll concentrations and leaf area were consistently lower in new leaves relative to leaves produced under normal conditions. Therefore, although leaves from many of our species show higher rates of resource acquisition, leaf quality may be compromised. These results suggest differences in physiological and morphological responses to hurricane-related defoliation and snapping that affect the post hurricane forest function and which may be related to subsequent growth and mortality.