Nutrient Cycling, Litter Accumulation, and Decomposition in Seasonally Flooded Tree Islands of the Southern Everglades

Abstract

Freshwater flow is the subject of great interest concerning Everglades restoration. Restoring freshwater flow to the system will not only increase flow, but may also increase nutrient inputs to downstream communities. The southern Everglades is one of the first regions to undergo hydrologic restoration, and is thus a good test for predicting the effect of large-scale Everglades restoration. In this study, part of an ongoing, long-term experiment, we characterized pool sizes and fluxes of phosphorus, nitrogen, and the primary organic matter cycles through southern Everglades tree islands. Our goal is to utilize this base ecosystem model to quantify the affects of increased freshwater flow through hydrologic restoration of the southern Everglades. In seasonally flooded tree islands, leaf litterfall contributes the greatest proportion of organic matter, and approximately 60% is accumulated on the forest floor. Our modeling effort shows that P and N are also largely retained within the tree island system, with limited remineralization to soil porewater. However, preliminary decomposition estimates show that 40% of cocoplum leaf litter undergoes decomposition within 18 months. Large accumulation and low remineralization would suggest that decomposition rates must be influenced by surface water flowing through tree islands seasonally. We estimated that a relatively large proportion of tree island litterfall is available for marsh ecosystem processes through decomposition, and will likely have a greater influence if loading of available nutrients increases with increasing freshwater flow through the southern Everglades.