The Sawmill Slough Preserve contains at least eight different natural communities, in congruence with definitions according to the Florida Natural Areas Inventory (FNAI). This diversity of ecosystems, within such a relatively small area, greatly influences the natural biodiversity of flora and fauna.
High Pine and Scrub
- Sandhill: xeric upland consisting of deep sand substrate; frequent fire (1-3 years); savannah of widely spaced longleaf pine and/or turkey oak with wiregrass understory.
- Wet Flatwoods: seasonally inundated flatland with sand substrate; frequent fire (2-4 years for grassy composition, 5-10 years for shrubby composition); closed to open pine canopy with grassy or shrubby understory; slash pine, pond pine, gallberry, fetterbush, sweetbay, cabbage palm, wiregrass, toothache grass.
- Mesic Flatwoods: mesic flatland with sand substrate; frequent fire (2-4 years); open pine canopy with low shrubs and herbs; longleaf pine and/or slash pine, saw palmetto, gallberry, live oak, wiregrass.
Freshwater Non-Forested Wetlands
- Wet Prairie: saturated and occasionally inundated flatland with sand/clayey sand substrate; frequent fire (2-3 years); treeless, dense herbaceous community with few shrubs; wiregrass, maidencane; cutthroat grass, wiry beaksedges, pipewort, toothache grass, pitcher plants, yellow-eyed grass.
Freshwater Forested Wetlands
- Dome Swamp: seasonally inundated with still water in shallow isolated depression in sand/marl/limestone substrate with peat accumulation toward center; occurring within a fire-maintained community; occasional/rare fire; forested canopy often tallest in center; cypress, tupelo.
- Bottomland Forest: occasionally inundated flatland with sand/clay/organic substrate; usually connected or adjacent to a riverine community; rare or no fire; dense canopy of mixed hardwoods, deciduous or mixed deciduous/evergreen; tuliptree, sweetbay, water oak, sweetgum, diamond-leaved oak, red maple, loblolly pine, spruce pine, white cedar.
- Blackwater Stream: perennial or intermittent/seasonal watercourse characterized by tea-colored water with a high content of particulate/dissolved organic matter derived from drainage through swamps and marshes; generally lacks alluvial floodplain.
- Seepage Stream:upper perennial or intermittent/seasonal watercourse with clear to lightly colored water derived from shallow groundwater seepage.