Soil Building Processes in Created Everglades Tree Islands.

Tree islands are ecologically important in the Everglades because they add habitat as well as plant and animal diversity to the surrounding marshes (Loveless, 1959). Hydrologic changes have impacted the soils and the vegetation of the Everglades tree islands. Modifications in the duration, frequency, and depth of inundation of the Everglades’ tree islands are thought to have resulted in their loss in both numbers and extent.

Several studies have been conducted to define tree island vegetation, hydrologic processes, nutrient limitation, and the relationship between them and the underlying geologic composition of re-constructed tree islands (van der Valk et al., 2008; Stofella et al., 2010; Sullivan et al., 2011; Subedi et al., 2012). The tree islands in this study are part of a larger research project that has contributed to the determination of a number of environmental metrics important to the ecological functioning of healthy or restored tree islands including: biomass allocation, litter quality, litter production and decomposition rates affect by hydrologic conditions. This study examines how ecosystem processes of biomass, litter production and organic matter (OM) decomposition interact with water depth to alter the formation and conservation of tree islands. We hypothesized that soil building processes will increase soil elevation at shallower water depth and reduced inundation because it favors OM production.

Soil building processes in created Everglades tree islands were evaluated based on simultaneous measurements of vertical accretion from feldspar marker horizons and soil elevation change from Surface Elevation Tables (SET). Measurements were conducted in the Loxahatchee Impoundment Landscape Assessment (LILA) facility (Boynton Beach, Florida, USA), where macrocosms mimic Everglades ridge, slough and tree island landscape structure. Within a tree island, as predicted, the higher elevations (i.e. shallower water) had higher soil accretion (0.71 cm yr^-1), coinciding with the highest litter production and tree productivity, compared to the lower elevations (0.55 cm yr^-1).