Acclimation of tropical tree species to hurricane disturbance: ontogenetic differences
Shiyun Wen (1), Ned Fetcher (2, 3) and Jess K. Zimmerman (4)
1. Department of Electrical and Computer Engineering, University of Puerto Rico, Mayagüez, PR 00680, USA / 2. Department of Biology, University of Scranton, Scranton, PA 18510-4625, USA and Wilkes Institute for Environmental Science
and Sustainability, Wilkes University, Wilkes-Barre, PA 18766, USA / 3. Corresponding author () / 4. Institute for Tropical Ecosystem Studies (ITES), University of Puerto Rico, P.O. Box 21910, Río Piedras, PR 00931-1910, USA / Received January 22, 2007; accepted November 21, 2007; published online April 1, 2008
Summary
We investigated acclimation responses of seedlings and saplings of the pioneer species Cecropia schreberiana Miq. and three non-pioneer species, Dacryodes excelsa Vahl, Prestoea acuminata (Willdenow) H.E. Moore var. montana (Graham) Henderson and Galeano, and Sloanea berteriana Choisy ex DC, following a hurricane disturbance in a lower montane wet forest in Puerto Rico. Measurements were made, shortly
after passage of the hurricane, on leaves expanded before the hurricane (pre-hurricane leaves) and, at a later time, on recently
matured leaves that developed after the hurricane (post-hurricane leaves) from both seedlings and saplings at sites that were
severely damaged by the hurricane (disturbed sites) and at sites with little disturbance (undisturbed sites).
Pre-hurricane leaves of the non-pioneer species had relatively low light-saturated photosynthetic rates (Amax) and stomatal conductance (gs); neither Amax nor gs responded greatly to the increase in irradiance that resulted from the disturbance, and there were few significant differences
between seedlings and saplings. Pre-hurricane leaves of plants at undisturbed sites had low dark respiration rates per unit
area (Rd) and light compensation points (LCP), whereas pre-hurricane leaves of plants at disturbed sites had significantly higher
Rd and LCP.
Post-hurricane leaves of plants at disturbed sites had significantly higher Amax and Rd than plants at undisturbed sites. Compared with seedlings, saplings had higher Amax and Rd and showed greater acclimation to the increase in irradiance that followed the disturbance. Post-hurricane leaves of the
non-pioneer species had significantly lower Amax and were less responsive to changes in irradiance than the pioneer species C. schreberiana. Variation in Amax across light environments and stages was strongly related to differences in leaf mass per unit area (LMA), especially in
the non-pioneer species. As indicated by Vcmax or Jmax per unit nitrogen, light acclimation of Amax was determined by leaf morphology (LMA) for the non-pioneer species and by both leaf morphology and leaf biochemistry for
C. schreberiana. Ontogenetic changes in Amax were attributable to changes in leaf morphology. The ontogenetic component of variation in Amax across light environments and stages differed among species, ranging from 36 to 59% for the non-pioneer species (D. excelsa, 59.3%; P. acuminata var. montana, 44.7%; and S. berteriana, 36.3%) compared with only 17% in the pioneer species C. schreberiana.
