South-Central Interior Small Stream Forest

This system is found throughout the Interior Low Plateau, Southern Ridge and Valley and Cumberland Plateau, Western Allegheny Plateau, lower elevations of the Southern Blue Ridge, and parts of the Cumberlands. Examples occur along small streams and floodplains with low to moderately high gradients. There may be little to moderate floodplain development. Flooding and scouring both influence this system, and the nature of the landscape prevents the kind of floodplain development found on larger rivers. This system may contain cobble bars with adjacent wooded vegetation and rarely have any marsh development, except through occasional beaver impoundments. The vegetation is a mosaic of forests, woodlands, shrublands, and herbaceous communities. Canopy cover can vary within examples of this system, but typical tree species may include Platanus occidentalis, Acer rubrum var. trilobum, Betula nigra, Liquidambar styraciflua, and Quercus spp. Shrubs and herbaceous layers can vary in richness and cover. Some characteristic shrubs may include Hypericum densiflorum, Salix spp., and Alnus spp. Small seeps dominated by sedges (Carex spp.), cinnamon and royal ferns (Osmunda spp.), and other herbaceous species can often be found within this system, especially at the headwaters and terraces of streams.

There is wide variation in vegetation depending upon the frequency of the flooding cycle (more frequent flooding creates a better environment for forbs and shrubs, less frequent may create a better environment for the establishment of trees). Typical tree species may include Platanus occidentalis, Acer rubrum var. trilobum, Betula nigra, Liquidambar styraciflua, and Quercus spp. Shrubs and herbaceous layers can vary in richness and cover. Some characteristic shrubs may include Hypericum densiflorum, Salix spp., and Alnus spp. Small seeps dominated by sedges (Carex spp.), ferns (Osmunda spp.), and other herbaceous species can often be found within this system, especially at the headwaters and terraces of streams. These areas are not typically flooded or scoured but saturated.

This system is found along fairly high-energy streams and rivers with steep banks, this system is subject to frequent flooding and can be subject to scouring depending upon the substrate. Some associations do not flood but instead are saturated zones or patches near the streams.

Flooding and seed propagule dispersal caused by flooding events are the two most important processes affecting this system. The two processes vary widely depending upon size of stream, upstream land use and topography, presence or absence of invasive exotics that may displace native community types, etc.

Alteration of the hydrologic regime is one of the most common and serious threats to this system, whether through increased or decreased water input and timing of the input. Significantly increased water input can result from increased runoff from the watershed, typically due to parts of the watershed being covered with impervious surfaces, such as roads, parking lots, or other urban or infrastructure development, or from removal of natural vegetation. Increased water input leads to more frequent and heavier flooding which can increase scouring and channel down-cutting. More rapid runoff from the watershed also increases the "flashiness" of the hydrologic regime, with the stream rising more quickly and higher right after precipitation events or snowmelt and then falling to lower levels later because there is little water left to drain slowly into the stream. Significantly decreased water input can result from diversions within the watershed or lowering of the water table, for those streams that receive groundwater. Land-use changes in the watershed can affect this system. Conversion of nearby land for agriculture can lead to increased erosion and subsequent sedimentation within this system as well as runoff of pesticides, herbicides, and fertilizer (Stevens and Cummins 1999).

This system tends not to have broad floodplains and is often narrow and linear. Thus, it may be more accessible for logging along the margins or through entire stands than floodplains on larger rivers. Logging can destroy or alter the vegetation composition and structure of a site directly or, if done near this system, lead to increased sedimentation and less water retention within the watershed.

This system ranges from the Interior Low Plateau to the Southern Blue Ridge and north into the Western Allegheny Plateau and portions of the Cumberlands. There would be limited and peripheral presence in the Upper East Gulf Coastal Plain. It also is present on Crowley's Ridge, an anomalous and distinct upland topographic feature that is embedded within the Mississippi River Alluvial Plain.