Landscape dynamics in the Everglades: Vegetation pattern and disturbance in Water Conservation Area 1

Water Conservation Area 1 is a 57,234 ha remnant of the Northern Everglades, presently used as both a flood control retention area and a wildlife refuge. It is a unique wetland ecosystem in which the dynamics of water, vegetation, fire, and peat are tightly linked. These interacting factors produce a landscape pattern that provides excellent habitat for wading birds and other Everglades wildlife.; This doctoral research focused on the landscape of Water Conservation Area 1 and the processes determining its pattern. Few ecological studies had been conducted in Water Conservation Area 1, so previous studies of the Everglades and the Okefenokee Swamp were reviewed for relevant data. The landscape was observed and described in the field. Aerial photography, satellite images, and a computer geographic information system (GIS) were used to quantify the landscape.; The GIS was also used to perform a spatial analysis of tree islands in Water Conservation Area 1. The analysis showed more small islands than large ones, and a steep increase in the sizes of islands above a certain size. Simple models built to generate island size and frequency distributions demonstrated mathematical functions that could create a size distribution similar to that found in Water Conservation Area 1. A conceptual model proposing an explanation for the tree islands' size distribution was developed. The theory proposed that tree islands grow in size over time, but fire reverses island growth. The ability of fire to limit island growth is reduced once islands reach some size threshold. Therefore, the growth rate of large islands is greater than that of small islands.; A spatial model of vegetation succession and fire was made to illustrate the conceptual model in two dimensions, using a map of the actual landscape. The GIS was used to construct and run the spatial model using a classified satellite image as input. The model produced maps of landscape pattern under different fire frequency and severity regimes. The landscape composition and heterogeneity of the maps were compared with the current landscape. The results illustrated the importance of fire in determining landscape pattern.