A Contemporary Approach to a Classic Model: Exploring the Influence of Local Interactions and Disturbance on Mangrove Forest Dynamics with a Spatially-Explicit Version of FORMAN
Master of Science (MS)
Oceanography and Coastal Sciences
The mangrove forest gap dynamic model, FORMAN, was the first individual-based model (IBM) to simulate the long-term successional dynamics of three Caribbean mangrove species, Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle. Assumptions under the spatially implicit approach of gap dynamic models limit their application to small-scale simulations. An expanded, spatially-explicit version of FORMAN was developed to allow for simulations of larger spatial grids, through the inclusion of localized soil conditions and neighborhood-based light resource competition. This expanded model was used to investigate the influence of localized interactions and disturbances of varying size on forest dynamics. A data-model comparison using field data from the Shark River Estuary in the Florida Coastal Everglades (FCE) tested the model’s ability to predict spatial relationships (inter-tree distances) based on tree size and species. The structure and function of the simulated mangrove forests were sensitive to complex interactions between localized soil and light competition based on neighboring trees. Under spatially varying soil conditions, neighborhood-based light competition limited tree growth (especially that of A. germinans and L. racemosa) in favorable soil zones, while allowing for sapling establishment in less optimal habitats. Forest recovery rates following disturbance were sensitive to both soil stress and disturbance size. L. racemosa experienced the greatest increase in annual productivity following disturbance, and exhibited a positive relationship between post-disturbance structure (biomass and basal area) and disturbance size. There was good agreement between the model and field data for frequencies of inter-tree distances and for the distribution of inter-tree distances when examined by size-class and by each species within sizes classes. However, there were no consistent differences or trends in inter-tree distance probability distributions observed across size-classes or for species within size-classes. The expanded FORMAN model, while still limited to the km2 scale in scope, is a very first step in increasing its spatial capability beyond the gap scale. This expansion potential is important in the context of climate change, as IBMs have been suggested as potentially useful tools in identifying and minimizing inaccuracies resulting from current methods of scaling biomass and productivity estimates from site to continental scales.
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Hurff, Kieley Shannon, "A Contemporary Approach to a Classic Model: Exploring the Influence of Local Interactions and Disturbance on Mangrove Forest Dynamics with a Spatially-Explicit Version of FORMAN" (2016). LSU Master's Theses. 4592.
Rose, Kenneth A