Tree islands: the bellwether of Everglades ecosystem function and restoration success

Abstract

Everglades tree islands are patches of woody vegetation ranging in size from 0.1 to 70 ha embedded in a marsh matrix. Tree islands are an essential component of the tree island-ridge-slough topographic continuum and the trees provide a mechanism for the accumulation of phosphorus in the landscape, enhancing landscape biocomplexity. This article reviews the literature of tree island ecology and describes the predicted effects of five ecosystem restoration scenarios on tree islands. Elevations of the highest points on 404 islands across the Everglades were used to assess the effects of the scenarios at a landscape level, while the plant communities of nine islands were modeled to assess local effects. Evaluation of the restoration scenarios were based on three critical components needed to maintain and restore tree islands: hydrology that allows the survival of woody species, seasonally appropriate water flow to move nutrients off the heads of islands, and oligotrophy. All restoration options generally improved water conditions for tree growth, although flooding of islands in some areas was predicted to increase. Scenarios with the greatest amount of decompartmentalization and largest capacity to remove phosphorus from water entering the Everglades provided the best chance of delivering vigorous pulses of sheet flow in directions parallel to historic flows and maintaining oligotrophy. Tree islands are "bellwethers" of restoration actions because their maintenance on the landscape requires multiple ecosystem functions.

Hydrology shapes microbial communities and microbiome‐mediated growth of an Everglades tree island species

“…For example, these tree aggregations can contain up to a hundred times more phosphorus than the surrounding wetlands (Wetzel et al 2005). Phosphorous builds up on tree islands over long periods of time as resident trees tap into deeper water sources in the dry season through evapotranspiration(Wetzel et al 2017). Unfortunately, the number of tree islands has declined by 54% since 1940 alongside a 67% decrease in the total area they cover (Sklar & van der Valk 2002; Wetzel et al 2005).…”

Characterizing hydrologic effects on soil physicochemical variation within tree islands and marshes in the coastal Florida Everglades

“…The Greater Everglades Ecosystem (GEE) that occupies much of the south Florida peninsula is one of the largest freshwater wetland complexes within North America (Richardson, 2010). The GEE contains a diverse set of habitats, including graminoid prairies, mangrove swamps, and fragments of woody vegetation embedded within the marsh landscape known as tree islands (Davis, 1943; Loveless, 1959; Wetzel et al., 2017). The areal extent of each of these habitat types, defined by their dominant vegetation, is determined by the combination of ecogeomorphic regimes, internal processes, and disturbances (Loveless, 1959; Sklar et al., 2002).…”