Native Habitat Inventory Final Report 2004 - St. Lucie County

“Edge is the place where plant communities meet or where successional stages or
vegetative conditions within plant communities come together” (Thomas 1979). The
edge is attractive to generalist species but most rare species are habitat specialists and are
attracted to a narrow habitat, such as interior forest. Edges increase access to core
habitats for feral animals, invasive exotic species, and human-related activities (e.g., offroad
vehicles). Thus a high percentage of edge is generally undesirable in natural areas.
The edge calculation provided makes two assumptions. First, that the entire perimeter of
a site is non-natural. Second, that the effect of the edge extends 230 feet interiorly. Edge
extends interiorly 2-3 times the canopy height of the tallest vegetation at maturity (Harris
1984). The south Florida slash pine is 115 feet tall at maturity thus twice that height is
230 feet. The south Florida slash pine was chosen because it is a common element in
many of the forest ecosystems. In some ecosystems (e.g., prairies and marshes) this will
exaggerate the amount of edge.
The data collected and the results of these analyzes are summarized in the Site Data
Summaries and Ranks section.
Conversion of FLUCCS to FNAI
Site Inventories and Reclassification
The 30 sites (40,142 acres) that were selected for this project were chosen based on their
potentially high quality natural areas. Each site was inventoried and all natural areas
were mapped and reclassified into FNAI Natural Communities (10.2 percent of the
county was sampled (40,142 of 391,700 acres)). Four sites (sites 4, 9, 43, and 44) were
inventoried via helicopter.
Intersection with FLUCCS
The FNAI Natural Community maps for all the sites were intersected with the 1995
FLUCCS coverage for the these sites, using ArcGIS 8.3. This generated a map and table
that had both the FLUCCS and the FNAI classification for all sites (4371 polygons).
From this table, areas that are developed were excluded from further analysis since no
FNAI Natural Community type would apply. The data was then sorted and summarized
by FLUCCS type (37 types). Then for each of these 37 FLUCCS types the FNAI
classification was sorted and summarized. Then the data was divided into FLUCCS
categories that were potentially natural and FLUCCS categories that were natural (Tables
13 and 14).
The Natural and Potentially Natural FLUCCS designations are grouped separately
because of their different relationship between FLUCCS and FNAI Types. The
boundaries of Potentially Natural FLUCCS type are often determined by human
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