Specific research objectives covered in the dissertation:

Chapter II provides a quantitative understanding of the dynamics of lightning-initiated gaps as they progress towards a closed canopy condition in the South Florida mangrove ecosystem. I accomplished this by comparing gaps at three stages of development among themselves and with surrounding intact forest. The two main objectives were to assess physical characteristics of gaps (gap size and shape, light environment, woody debris, soil strength and crab fauna) and quantify the vegetation at different stages of successional development at three regions of the Shark River.

The objective of Chapter III was to determine how survival (mortality), growth, and recruitment (both as density and specific rates) varied across three successional stages of mangrove forest development (newly initiated lightning gaps, closing gaps, and intact forest) for the four dominate life phases (propagules, seedlings, saplings, and adult) of the three mangrove species (Avicennia germinans, Laguncularia racemosa, Rhizophora mangle). In this way I was able to follow change in density of stems but also change in population structure at these different successional stages as gaps progress to closed canopy condition.

Chapter IV determines the impact of lightning strike disturbance on the soil elevation. I believed that this loss in soil surface elevation in a peat-dominated substrate might be a result of root death of lightning killed trees. Root mortality may lead to a decrease in the cohesiveness of the soil allowing the soil surface to erode, resulting in a decline in surface elevation. Additionally root mortality may lead to a collapse or subsidence of the peat layer, which would also result in a decline of the soil surface elevation. I determined the impact of lightning disturbance by monitoring soil elevation of both the shallow soil zone and the entire soil profile and measured amount of live and dead roots, soil strength (bulk density, torsion, and compaction) and accretion.

To understand the changes in soil elevation I needed to understand how hydrology affects the soil elevation pattern. It is possible to partition the change in soil elevation into its component processes of surface accretion, and subsurface expansion or compaction using the surface elevation table - marker horizon approach. In Chapter V, I studied the soil elevation dynamics in the lower Shark River drainage that extends over the entire soil profile and distinguishes between three depths within the soil profile; the 0-0.35 m, 0-4 m, and 0-6 m. My objective was to investigate the relationship among changes in soil surface elevation and changes in the hydrological parameters of river stage and groundwater piezometric head pressure at the site over the three depths. Additionally, I wanted to determine the relative contribution to soil elevation by each of the four components of the soil profile: surface (i.e., accretion), shallow zone (active root zone; 0 - 0.35 m), middle zone (0.35 - 4 m), and bottom zone (4 - 6 m).

Chapter VI provides an overall synthesis of the dissertation, in which the lightning successional process is described as well as changes in the life stage parameters. Finally, I discuss the role proposed Everglades hydrological restoration may play on the gap successional process.