Ecological analysis and simulation models of landscape patterns in mangrove forest development and soil characteristics along the Shark River estuary, Florida.

摘要

Landscape patterns of mangrove forest development following large-scale disturbances in relation to soil nutrient resources and toxic stresses were examined along the Shark River estuary, Florida. Patterns of forest structure were based on 34 years of growth since Hurricane Donna destroyed most of mangrove forests in 1960. Basal area, biomass increment and stature of forests at the downstream marine sites were higher than those at the upstream and intermediate sites. Pore water salinities in the mangrove soils were below hypersalinity and sulfide concentrations were generally lower than other reported values in mangrove soils. Total soil phosphorus, available phosphorus and nitrogen mineralization rates increased from the landward to seaward zones along the estuary. Soil properties in the downstream marine region included high availability of nutrient resources and low concentrations of stressors supporting a region of optimum growth of mangroves. However, phosphorus input from the Gulf of Mexico leads to a gradient of soil phosphorus resources along the estuary, which may determine the landscape development of mangrove wetlands in this land-margin ecosystem.; Simulation models were developed to investigate landscape patterns of mangrove forest development. A soil organic matter model (NUMAN) demonstrated that the landscape gradients of sediment characteristics are contributed by plant production, litter decomposition and export, and allochthonous input of inorganic materials. A forest dynamic model (FORMAN) used an individual-based approach to simulate mangrove forest development. The accurately simulated the recovery of mangrove forests along the gradient of soil nutrient availability. Simulated basal areas by species fit well with data from field surveys. MANGAL adequately tracked patterns of species-specific size-class distribution along the estuarine gradient. Simulated basal areas of mangrove species along gradients of soil nutrient resources and salinities illustrated a change in competitive balance among species that was time dependent. Laguncularia racemosa dominated in fertile soils with low salinity stress at early stages of recovery, but its abundance decreased while Avicennia germinans increased in dominance. The dominance of Rhizophora mangle was limited to regions with low nutrient availability and low salinity.