Applied Wetlands Science - Chapter 6

Zentner, John “Wetland Enhancement, Restoration, and Creation” Applied Wetlands Science and Technology Editor Donald M. Kent Boca Raton: CRC Press LLC,2001 CHAPTER 6 Wetland Enhancement, Restoration, and Creation John Zentner CONTENTS Site Selection and Analysis Topography Vegetation Association Mapping Site History and Current Status Hydrological Analysis Soil Analysis Cultural Constraints Adjacent Site Conditions The Use of Template Associations Small-Scale Experimental Construction Goal Setting Elements of a Goal Statement Goal-Setting Process Practicability Construction Design Geography Size and Shape Location Slope Adjacent Uses Hydrology Hydroperiod and Depth Water Supply Soil ©2001 CRC Press LLC Vegetation Succession Planting Design Plant Selection Stock Selection Planting Density Weed Control Cultural Issues Mosquitoes Water Quality Implementation Construction Sequencing Protective Flagging Weed Removal Salvaging Grading Planting Water Supply Fencing As Builts Maintenance Weed Control Erosion Control Herbivory Plant Care Irrigation System Maintenance Litter Removal General Maintenance Frequency Minimizing Maintenance Efforts Research Needs References Freshwater wetlands develop at elevations above open water aquatic habitats and below uplands. They are found in a wide range of hydrologic conditions, from permanently flooded (to a depth of 1 m) to seasonally saturated. Freshwater wetlands occur on a wide variety of soil types including both organic and mineral soils, as well as in nonsoil conditions. Most freshwater wetlands are either freshwater marshes or riparian woodlands. Freshwater marshes are dominated by herbaceous emergents and can be divided into three general categories reflective of hydrology (Figure 1). Wet meadows are temporarily or intermittently flooded and dominated by graminoids and Juncaceae. In the United States, seasonal marshes are seasonally flooded or saturated and dominated by Cyperaceae and Juncaceae. Perennial marshes are permanently or ©2001 CRC Press LLC UPLAND Hydrology Dominant Plants WET MEADOW Temporarily flooded or intermittently flooded Grasses, rushes SEASONAL MARSH Seasonally flooded or saturated Sedges, rushes PERENNIAL MARSH OPEN WATER Permanently flooded or semi-permanently flooded Cattail, bulrush, tules Figure 1 Freshwater marshes are dominated by herbaceous emergents and can be divided into three hydrological categories: perennial marsh, seasonal marsh, and wet meadow. ©2001 CRC Press LLC semipermanently flooded and dominated by tall emergents such as cattails (Typha latifolia) or bulrush (Scirpus acutus). Riparian woodlands are dominated by shrubs and trees and are characterized by impermanent and varying periods of inundation or root zone saturation during the growing season. Compared to freshwater marshes, riparian woodlands occur on relatively permeable and well-oxygenated substrates. As with freshwater marshes, riparian woodlands can be categorized by hydrological regime (Figure 2). High terrace woodlands are temporarily flooded and dominated by a variety of species, especially oaks (Quercus spp.), that are typified by heavy seeds with relatively longer viability. Mid-terrace woodlands are seasonally flooded and generally dominated by green ash (Fraxinus pennsylvanica), sycamore (Platanus occidentalis), and other species with medium weight seeds. And low terrace woodlands are semipermanently flooded and generally dominated by willows (Salix spp.), silver maple (Acer sac-charinum), and similar species with relatively light seeds of limited viability. These categories correspond to Categories V (higher hardwood wetlands), IV (medium hardwood wetlands), and III (lower hardwood wetlands), as described by Cowardin et al. (1979), Larson et al. (1981), and Clark and Benforado (1981). Coastal wetlands share many of the characteristics of freshwater wetlands and are generally defined as those wetlands that lie within the realm and effects, however minor, of tidal salt water. As such, coastal wetlands include saltmarsh, fresh and brackish tidal marsh, and, in tropical waters, mangrove. Saltmarsh is the most ubiquitous type of coastal wetland, occurring on all coasts where appropriate substrate and tidal regimes are present (Figure 3). Saltmarshes are distributed over a relatively broad salinity range, from the high intertidal zone to the oligohaline habitats upstream on tidal tributaries where salinity may never exceed 10 parts per thousand. In the United States, various species of cordgrass (Spartina spp.) are dominant, with rushes (Juncus spp.) also common. On the Pacific Coast, Spartina foliosa and pickleweed (Salicornia virginica) are common. On the Gulf Coast and in the southeast, other species of cordgrass (Spartina alterniflora, S. patens), saltgrass (Distichlis spicata), and black needlerush (Juncus roemerianus) are typical. Sawgrass (Cladium jamaicense) marshes, such as the Everglades, occur in more brackish water. On the Atlantic Coast and to the northeast, Spartina cyno-suroides, S. alterniflora, J. roemerianus, and some other species are common. Wax myrtle (Myrica cerifera) and groundsel tree (Baccharis halimifolia) are typical shrubs associated with salt marshes from the Gulf Coast to New England. Oligohaline (salinity of 0.5 to 5.0 ppt) and tidal freshwater marshes (salinity is less than 0.5 ppt) are herbaceous wetlands located in tidally influenced rivers or streams. The plant community exhibits a diverse mixture of true marine species and typical freshwater taxa that tolerate low salinities (Cowardin et al., 1979; Lewis, 1990). Mangrove forests are limited in distribution to subtropical and tropical zones (Figure 4). In the United States, they occur predominantly in southern Florida, sparsely along the Gulf Coast to the Laguna Madre of Texas, and extensively in Puerto Rico (Kuenzler, 1974). Many species of trees of different families are called mangroves, with black mangrove (Avicennia germinans), red mangrove (Rhizo-phora mangle), and white mangrove (Laguncularia racemosa) common to the ©2001 CRC Press LLC ... - tailieumienphi.vn