Environmental Engineering Reference
In-Depth Information
19.2.2.3 Vernal Pools
Vernal pools are seasonal, often isolated, depressions, usually containing water for only a few
months of the year. They may ill with the rising water table during the fall and winter or during
the spring snowmelt and rain, and are commonly dry during late summer and fall and may be dry
for sustained periods during drought conditions. The dry period eliminates ish and many preda-
tors, such as bullfrogs, which take more than a year to develop from tadpole to adult. While only
periodically “wet,” these pools also provide a critical habitat for a variety of plants and animals that
are adapted to reproduce in temporary wetlands (Brown and Jung 2005). These include a variety of
amphibians, some of which breed exclusively in vernal pools, and other organisms such as the fairy
shrimp that rely on these pools during their entire life cycle.
19.2.2.4 Wet Meadows
Wet meadows occur in poorly drained areas such as shallow basins, low-lying farmland, and
between shallow marshes and upland areas. They often look like grassland or a fallow ield except
that they are dominated by water-loving grasses and sedges. Generally, they are completely covered
with vegetation and only periodically and temporarily have standing water. Wet meadow soils are
commonly saturated and mucky. Wet meadows are common throughout the United States in areas
ranging from mountain valleys to Florida. In Florida, they occupy large areas called “lats,” which
are extensive in the northwest Everglades (McPherson et al. 1976; Figure 19.5).
An example is the saw grass marshes common in Florida where they make up about 70% of the
remaining Everglades (McPherson et al. 1976). Saw grass ( Cladium jamaicense ) is not a “true”
grass, but a member of the sedge family, characterized by sharp teeth along the edges of each blade.
Saw grass marshes are usually looded with water for most of the year and the period over which
they are looded determines the growth of the saw grass, with taller, thicker stands of saw grass
corresponding to more prolonged and deeper inundation.
19.2.2.5 Swamps
Swamps are wetlands dominated by woody plants, which include forested swamps, dominated by
trees, or brush swamps (Figure 19.6). Forested swamps commonly occur in the loodplains of riv-
ers, and are typically saturated for most of the year and periodically inundated. Common trees in
the northern United States include the red maple and pin oak ( Quercus palustris ). In the south, the
overcup oak ( Q. lyrata ) and cypress provide the characteristics of many forested swamps, more
FIGURE 19.5 Saw grass marsh. (From McPherson, B.F., Hendrix, C.Y., Klein, H., and Tyus, H.M., The
environment of South Florida, a summary report, Geological Survey Professional Paper 1011, 1976.)
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