For almost three decades we have been aware that dry tropical forests (DTFs) are potentially the most threatened of all tropical forests. Due to forest loss and degradation there has been a large decline in DFTs worldwide, and in the Mesoamerican region only 2% of DTFs are sufficiently intact to be considered worthy of conservation. This study will focus on the DTFs of Puerto Rico (Guanica Forest). We will use an Individual Based Model (IBM) which utilizes the processes of gap dynamics to simulate growth within a forest by simulating the growth of individual trees on a specific number of individual plots. There has been an absence of these models in tropical diverse forests. This project will use simulation modeling (IBMs) to predict the future of Puerto Rico’s intact and mature DTFs to various environmental changes. I parameterized an existing gap dynamic model with species specific and site specific parameters for the Puerto Rican forest. The species specific parameters included growth rates, mortality rates, seed and seedling survival, leaf area, bulk density of trees, tolerance levels to stresses, maximum age, height, and diameter, as well as allometric related features for growth, biomass estimates, and amount of carbon in the above ground biomass. Site specific parameters included temperature, precipitation, slope, soil moisture and soil chemistry values at different depths.
Results/Conclusions
Upon completion of the model simulations it was found that gap dynamics and individual birth, death, and growth processes do determine succession in dry tropical forests. Forest structure and traits in the modeled dry forest were successfully matched with the observed forest (Guanica), and also compared to the wet forest in Puerto Rico (Luquillo). It was re-confirmed that basal area, leaf area index, stand height, total biomass were lower in the dry forest then the wet forest. Growth, mortality, and ingrowth rates were also slower in the dry forest. These are all results that could make a dry forest more vulnerable to global change. Lastly, it was found that different environmental conditions (changes in precipitation, light attenuation, and temperature) will produce different responses in dry tropical forests. This project is also able to monitor long term changes in above and below-ground carbon levels, showing that carbon storage and NPP will decrease with increasing environmental disturbances. This work provides results to long term dynamics of tropical forest structure and composition.
