PS 8-80 - The effects of microhabitat variability on intra-annual tree seedling mortality in a montane tropical forest

Monday, August 8, 2011
Exhibit Hall 3, Austin Convention Center
Omar Gutiérrez del Arroyo Santiago, Departments of Biology and Environmental Sciences, University of Puerto Rico, Río Piedras, PR and Christopher J. Nytch, Environmental Sciences, University of Puerto Rico, Río Piedras, San Juan, PR

Microsite heterogeneity in tropical forests is believed to strongly influence tree community dynamics. Correlations have been shown relating species distributions with topography, substrate, and soil moisture availability. The objective of this study was to determine if there is a resulting short-term drought effect on intra-annual seedling mortality in the Luquillo Forest Dynamics Plot (LFDP) that can be linked to site-specific environmental variability. We hypothesized that topographical position and surface substrate influence soil moisture availability, with higher seedling mortality in plots exhibiting abundant rock cover, and lower seedling mortality in plots dominated by leaf litter and mineral soil. To test the localized effects of microhabitat variability on seedling viability, we conducted a census of 272 seedling plots in the LFDP and collected data on topographic position, percent soil moisture, and plot surface cover, in addition to assessing seedling mortality over a period of 3 months. 


Our findings indicated that soil moisture is likely driven in part by surface rock cover, although other factors, such as local drainage, may play a larger role in determining soil moisture availability. Decreased soil moisture, in turn, was positively correlated with augmented intra-annual mortality in some species. Given the expected increase in severity and duration of drought in the Caribbean in the next 100 years, these results provide insight into understanding the impact of short-term drought effects on tropical tree seedling mortality, which may improve the ability to predict directional trends in forest composition related to global climate change.

Copyright © . All rights reserved.
Banner photo by Flickr user greg westfall.