Restoration of Aquatic Ecosystems Science, Technology, and Public Policy (1992) / Chapter Skim
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6 Wetlands
6 Wetlands
Pages 262-340
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From page 262... ...
in the agreement to mitigate damages to wetlands (memo of agreement between EPA and COE, 1990~. At present the area of protected wetlands may be reduced by modifying the delineation manual that is used to identify wetlands that are under the Clean Water Act of 1977 (P.L.
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From page 263... ...
Current wetland restoration technology is summarized, along with constraints on achieving restoration goals, problems encountered during restoration, opportunities for major restoration projects, programs for wetland restoration, and reasons for varying opinions on the success of wetland restoration. Conclusions, recommendations, and research needs complete the chapter; however, recommendations on wetlands policy and institutional changes pertaining to wetlands are included in Chapter 8.
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From page 264... ...
Initial colonists are unlikely to be the same species as those of the floodplain forest that eventually develops. Along the edges of continents, mud flats are formed by alluvial outwash and are gradually colonized by salt marsh grasses and succulents, which in turn trap sediments that raise the topography and attract additional plant and animal species.
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From page 265... ...
For individuals, wetlands provide recreational, educational, research, and aesthetic functions (see Table 6.1~. FOOD CHAIN SUPPORT Although wetlands within the conterminous United States constitute only about 5 percent of the land surface (more than 40 million hectares, or about 104 million acres; Tiner, 1984; Dahl, 1990)
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From page 266... ...
Source of open space and contribution to aesthetic values Both tidal and inland wetlands are areas of great diversity and beauty, and provide open space for recreational and visual enjoyment. Water quality improvement Wetlands contribute to improving water quality by removing excess nutrients and many chemical contaminants.
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From page 267... ...
Plant productivity of freshwater marshes is often phosphorus limited, whereas that of coastal marshes is often nitrogen limited; thus, these elements have been the focus of most assessments of nutrient dynamics. In coastal wetlands, the nitrogen dynamics are very important; both fixation and denitrification rates are linked to availability of organic matter in the soil.
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From page 268... ...
. Until food chain functions are well understood, restoration projects will be jeopardized by the inability to ensure the reestablishment of critical links.
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From page 269... ...
· Shallow water coupled with the presence of emergent vegetation leads to significant sediment-plant-water exchange. HUMAN VALUES As discussed above, wetlands play an active part in hydrologic functions, water quality improvement, and food chain support functions that serve human needs.
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From page 270... ...
King (1990) has begun an analysis of the cost effectiveness relationship for wetland restoration projects.
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From page 271... ...
An endangered plant that might be rescued by a marsh restoration project may some day be found to produce an important pharmacological chemical; restoration of a coastal wetland may prevent real estate damage should sea level rise at unexpected rates; wetland plants may become horticulturally or agriculturally important (Glenn et al., 1991~; a habitat-dependent bird may be shown to be effective in controlling mosquito and malarial outbreaks; the presence of open space may be shown to be essential to mental health. LOSS OF WETLANDS Trends in historical losses of wetlands in the United States were recently summarized in a report to Congress (Dahl, 1990~: At the time of Colonial America, the area that now constitutes the 50 United States contained an estimated 392 million acres (about 160 million hectares)
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From page 272... ...
settled a lawsuit filed by the Sierra Club and the League for Coastal Protection against three federal agencies. Wetland habitat had been damaged by construction of a wider freeway, a new freeway interchange, and a flood control channel.
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From page 273... ...
Hunt, Caltra~ns, personal comm~unication, June:1990) ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ : : ~ : : ~ her settlement of thefts lawsuit, Caltran~s began a monitoring: program to assess plant cover and faunas ~use.: ~ They also funded a Propagation research program to improve transplantation~ methods and To develop techniques Burl establishing the endangered salt marsh bird s beak, which:~is a h~emiparasitic annual Plant.
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From page 274... ...
N;trogen-fixati-on rates were lower on the soil surface and were limited: by low concentrations of soil organic matter (Zale ko, 19&93. Soil nitrogen concentrations were lower in the constructed marsh, with less
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From page 275... ...
presented" a "functional equivalency index" based on 11 marsh attributes that indicated less than 60 percent equivalency when the marsh was 4 to 5 years of age. For each attribute, the mean value for the constructed marsh was expressed as a percentage of the mean value for the reference wetland (organic matter content, 51 percent; sediment inorganic nitrogen, 45 percent; sediment nitrogen total Kjeldahl nitrogen (TKN)
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From page 276... ...
Fish and Wildlife Service.
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From page 277... ...
. In most physical alterations of the habitat, the wetland ecosystem is obliterated, and there is little opportunity for restoration once the habitat has been flattened or replaced by urban development, reservoirs pacts, or marimbas.
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From page 278... ...
If an exotic plant gains a foothold in one disturbed system, its seeds are more likely to disperse to nearby wetlands, increasing chances of spread into less disturbed systems. Changes in hydrologic regimes, such as those brought on by ground water depletion from wells or by dams, levees, or drainage, can effectively eliminate wetland characteristics and the values associated with those characteristics.
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From page 279... ...
. Although the Clean Water Act and regulations for implementation of its Section 404 by both EPA (44 C.F.R.
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From page 280... ...
The method also focuses attention on the landscape level and bases planning on landscape ecology principles. Researchers used the Tensas River basin, an area of approximately 1 million hectares in northeastern Louisiana, as a case study to test this general approach to cumulative impact assessment and management (Gosselink et al., 1990a)
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From page 281... ...
Global warming will result in a rise in sea level, with the effect that existing coastal wetlands will be flooded, salt marshes will be lost and species will be unable to "migrate" inland because of urbanized or otherwise developed landscapes. Because the rate of rise will accelerate, not all species will be able to move inland fast enough to keep up with the rate of loss at lower elevations (Park et al., 1989)
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From page 282... ...
Because restoration sites may lack some of the resilience of natural marsh communities (i.e., persistent seed banks, highly organic soils to ameliorate changes in soil moisture, ability to resist exotic plant invasions) , constructed wetlands may be more susceptible to rising sea level than their model ecosystems.
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From page 283... ...
Wetlands in headwater areas, in oxbows, and in low-velocity channels have not been extensively restored, although rather largescale floodplain forest restoration programs are proposed for areas in the lower Mississippi. Many small-scale restoration projects have been undertaken as part of local greenway and stream restoration programs such as the Urban Streams program in California.
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From page 284... ...
In many cases, the technical problems of reconverting such agricultural lands to functioning wetland systems are not as challenging as those encountered in the urban context, where the physical components of natural wetlands have been severely altered by chemical pollution, fill, barriers to water movement, and vast changes in the watershed. Former wetlands now in agricultural use can typically be reestablished by cessation of planting crops or domestic animal foraging, breaking drainage tiles, filling in drainage ditches, and if feasible, removing flood control structures.
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From page 285... ...
In smallscale restorations of the lower Mississippi valley, forested wetlands are being reestablished themselves on the alluvial soils that retain moisture for long periods following precipitation, even where federal flood control levees and channels block riverine overbank flooding. However, these small-scale wetland restorations are not often subject to rigorous scientific evaluation.
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From page 286... ...
Federal Water Projects Federal agricultural and urban flood control, navigation, and irrigation projects have done extensive damage to wetland systems. One careful, economic study has shown that at least 30 percent of the loss of millions of acres of bottomland hardwood wetlands in the lower Mississippi valley from 1934 to 1984 was caused directly by federally funded COE and Soil Conservation Service flood control projects.
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From page 287... ...
101-646) , Congress has directed COE, EPA, and other federal agencies to work with the state of Louisiana to identify and construct wetland restoration projects.
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From page 288... ...
Although restoration of scattered wetlands in the prairie pothole region successfully reestablishes duck breeding, feeding, and nesting habitat, such opportunistic, small-scale restoration projects may have fewer benefits in other kinds of wetlands systems, such as broad floodplains of southern rivers. Furthermore, CRP contracts are for only 10 years, enough time for the establishment of herbaceous wetland species but not for the reestablishment of wetland forests.
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From page 289... ...
Some of this acreage is former wetlands, cleared and drained for agricultural or other use. In general, these small wetland restoration projects provide very J useful opportunities to restore individual wetland parcels.
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From page 290... ...
Importance of Setting Goals for Functional Value To set goals for the functional values of wetlands, we must understand how each type of natural wetland performs (i.e., in support of food chains, hydrologic functions, and water quality improvement)
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From page 291... ...
General dewatering of the landscape through ditching even if not directly in streams or wetlands, ground water pumping, subsurface tile drainage systems, or other mechanisms can lead to surface dewatering of wetlands. As an example, installation of tile drainage systems to improve agricultural production in the prairie pothole region of the north-central United States (see case study, Appendix A)
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From page 292... ...
Research on introducing animal species to restored wetlands is extremely limited.
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From page 293... ...
The sections below discuss several constraints on achieving 100 percent success in returning wetland ecosystems to their ideal predisturbance conditions. The most important of these appears to be the degree of disturbance to the site and its landscape, as illustrated by restoration projects visited by the committee or reviewed by others.
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From page 294... ...
due to diking, filling, and anthropogenic sedimentation. Before gold mining and flood control came to the Sacramento River Valley, nearly 60 percent of the delta was flooded by ordinary tides, and high tides covered almost the entire Delta (Kahrl, 1979~.
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From page 295... ...
Numerous wetland restoration projects have been conducted on San Francisco Bay (Berger 19903 and on the West Coast r (losselyn and Buchholz, 19841. For a comparison of natural and restored eastern coastal marshes with respect to fish and wildlife habitat value, see Roberts (1989~.
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From page 296... ...
are the urban salt marshes of Southern California (see Box 6.1) and New Jersey (see Box 6.3~.
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From page 297... ...
. E~cological studies dating back to the late nineteenth century indicate that in the las phase of its natural succession, the Hartz Mountain project site may have been high brackish marsh dominated by salt hay (Spartina patens)
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Water quality in the Hackensack River appears to be far better than the sewerlike conditions reported 20
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From page 299... ...
Within San Diego Bay and in San Diego County as a whole, only about 10 percent of the natural salt marsh acreage has escaped urban development. The Hackensack Meadowlands site is a second example of restoration efforts undertaken in an extremely disturbed urban setting (see Box 6.3)
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From page 300... ...
s also an example of a site with intermediate restoration potentialthe effects of disturbance are not easily reversible, yet the site exists within a region that has large reserves of natural habitat. In this case, a 21-ha salt marsh was diked in 1961 and used for grazing, as fresh water gradually diluted the salts and allowed pasture vegetation to become established.
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From page 301... ...
Bottomland hardwood forests of the southeastern United States have undergone rapid reductions in area and changes in composition (Box 6.4~. The lower Mississippi River floodplain is an example of a large-scale disturbance in which the physical condition of the wetland area has been altered and cumulative impacts have occurred.
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From page 302... ...
A small number of restoration projects have come under the Conservation Reserve Program. Most of these projects began during the late 1980s.
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From page 303... ...
reviewed wetland restoration projects in the southeastern United States and stated that "a smooth cordgrass stand established on sand in an area where natural marshes are relatively young will likely be comparable to the natural marsh for most measurements in a few years." In contrast, Broome predicts that it will take several years to restore more mature marshes that have accumulated peat and have highly organic and nutrient-rich soils. Similarly, ecosystems dominated by short-lived plants might be more quickly restored than those dominated by long-lived perennials.
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From page 304... ...
Attempts to reestablish populations of this species to restored salt marsh habitats have not yet succeeded (B. Fink, San Diego State University, personal communication, June 1990~.
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From page 305... ...
documented the occurrence of a lapanese mussel, Musculista senhousia, in a San Diego Bay salt marsh restoration site. In the lower
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From page 306... ...
But with increased awareness of the scale and rate at which introduced species are being transported and released today, we may be able to develop more specific and enforceable controls on the movement and release of species for mariculture, for scientific research, or by ballast water. Such invaders may pose much greater problems for restoration sites than for natural systems, because disturbed substrates have few defenses against germinating seeds or settling larvae.
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From page 307... ...
In these contexts, private or public landowners seeking permits for various types of development are required either to create, to enhance, or to restore wetlands on-site after damage or to restore wetlands at other sites to compensate for wetland damage at a development site. Few of the Clean Water Act, Section 404 mitigation projects have constituted wetland restoration as defined in this report, and COE and EPA the two agencies responsible for implementation of the Section 404 program do not have systematic information about the number of acres of wetlands restored or the effectiveness of particular restoration projects.
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From page 308... ...
Similarly, the responsible federal agencies do not have staff to assess the adequacy of restoration projects and do not monitor or require permitter monitoring of permit mitigation conditions for sufficient time periods (10 years or longer)
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From page 309... ...
when: projects a:re:part of :com::pensatory mitigation) and to provide for mid-course corrections if plans fail to achieve their intended results; and no attempt is made to relate individual, piecemeal restoration efforts to broader hydrologic and ecosystem management goals.
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From page 310... ...
Sixteen chapters, contributed by authors from around the nation, review the state of the art of restoring wetlands along the eastern, southern, and western coasts of the United States; in marsh, pothole, and wooded wetlands of the interior; and in riparian systems along the streams of the Midwest, West, and Southwest. In reviewing wetland restoration projects in the coastal plain of Florida, Lewis (1989)
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From page 311... ...
He also noted that in restoration projects, "endangered species" needs might not be met, because so few of their requirements are known. Reviews of seagrass ecosystems (Fonseca et al., 1988; Fonseca, 1989)
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From page 312... ...
Additional problems were noted for a highly urbanized wetland in San Diego Bay, where a combined freeway widening, new freeway interchange, and flood control project has been under way for six years. Such large, complicated projects are likely to experience problems with contaminated substrates and construction errors (see Box 6.6~.
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From page 313... ...
The nursery had not been mapped as an ecologically sensitive area, and biologists were not on-site the day it happened. Removal of Temporary Filly In constructing the temporary detour road, contractors laid down a fabric layer so that the integrity of marsh soils could be preserved.
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From page 314... ...
Most recently/ in November 1990, the direct tidal flows to San Diego Bay were terminated because the flood control channel was again under construction. None of the physical impacts of these tidal modifications has been assessed.
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From page 315... ...
The most common types of freshwater wetland restoration projects are impoundments to create waterfowl and wildlife habitat and the establishment of marshes on dredged spoils along major rivers. Although there is much literature describing waterfowl abundances, there are few critical studies of the success of these restoration efforts as persistent, naturally functioning ecosystems.
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From page 316... ...
· Photographs of vegetation growing at the site are presented at local or national meetings proclaiming the project a success, without measurable criteria or data to support these claims. CONTROVERSIES ABOUT THE SUCCESS OF RESTORATION PROJECTS Whether we can succeed in restoring wetlands is a controversial subject.
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From page 317... ...
The developer then asked $15 million for the site, claiming that the project could obtain a Section 404 permit from COE. A1though there were many legal and political factors, the issue of whether or not lost wetland functions could be replaced played a role in determining the property value.
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From page 318... ...
For restoration projects in general, examination of a few characteristics may indicate success, whereas detailed studies would reveal shortcomings. Although restoration sites that develop dense plant cover or support native plant species may be considered a success by some evaluators, others would require data on fish, invertebrate, bird, and mammal uses and would want to examine the site's long-term persistence before providing a stamp of approval.
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From page 319... ...
Duration of Evaluation Period A judgment of success shortly after site preparation and transplantation may not tell the whole story. Long-term success may increase or decrease, although so few examples of long-term evaluation are available that it is difficult to know why some restoration projects improve and others disintegrate.
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From page 320... ...
For example, the Russell Sage National Wildlife Refuge System near Monroe, Louisiana, is located in the midreaches of its watershed. Although reforestation of some original bottomland hardwood forest is possible, off-site liabilities related to watershed drainage and flood "management" limit the potential for restoration of a functional bottomland hardwood forest.
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From page 321... ...
As restoration proceeds, managers can reevaluate whether the degree of restoration achieved is acceptable or if new techniques should be introduced. For those situations in which unexpected benefits develop (e.g., nesting of the endangered California least tern on part of a San Diego Bay site intended for salt marsh; see Box 6.1)
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From page 322... ...
Based on what is known of restored salt marsh systems, suggestions have been made for southern California coastal wetlands (Zedler et al., 1988; PERL, 1990~. Here the committee provides general recommendations for functional assessment.
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From page 323... ...
may stagnate, or it may continue to gain functional values. The committee believes that the standards for assessing restoration projects should be high and that field sampling protocols should be able to withstand scientific peer review.
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From page 324... ...
For regions in which environmental conditions are highly variable from year to year, the time frame will probably be long. At least one project in San Francisco Bay has a 20-year monitoring requirement; this is appropriate for a wetland subject to highly variable inflows of fresh water.
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From page 325... ...
· Flood-peak reduction: Monitor water levels in relation to flow velocity. · Restoration tidal flows: Monitor water levels over tide cycles; determine amplitude; lags; monitor salinity of water and soil.
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From page 326... ...
Recommendations have been put forth for southern California (PERL, 1990) , where mitigation is driving many restoration projects and where several species are endangered due to past losses of habitat.
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From page 327... ...
Potential pitfalls are high foliar nitrogen concentrations that may stimulate excessive herbivory. Research is proceeding through the California Sea Grant Program and the National Oceanic and Atmospheric Administration's Coastal Ocean Program to develop this ecotechnology for coastal wetlands.
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From page 328... ...
sites as shell as funding opportunities: · The requirement for careful long-term monitoring of selected restoration projects will fill gaps in information on how ecosystem functions develop. An understanding of how early and late restoration conditions compare will lead to predictive power that will help in future projects.
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From page 329... ...
· The availability of restoration sites for experimental work would have great potential for answering research questions (Gross, 1987~. Determining the relationship between various plant and animal species is very approachable on sites where sin~le-snecies vegetative v .
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From page 330... ...
Research Needs and Techniques Traditional research on wetlands and ecosystem development should also be continued, using both natural and restored wetlands. Examples of this traditional research include the following topics mentioned by several EPA authors (modified from Kusler and Kentula, 1989~: · the hydrologic needs and requirements of wetland plants and animals, including minimum water depths, hydroperiod, velocity, dissolved nutrients, the role of large-scale but infrequent events such as floods, and the effects of long-term fluctuations in water levels; · the importance and functional significance of substrate to wetland plants and animals, and to chemical and biological functions; · characteristics of development rates for natural successional vegetation; · recolonization of restored sites by invertebrate and vertebrate fauna; · functions of wetlands, with special emphasis on habitat values for a broad range of species, food chain support, and water quality enhancement; · evaluation of the stability and persistence of wetland ecosystems; and · evaluation of the impact of sediment deposition or erosion, nutrient loading or removal, toxic runoff, pedestrian and off-road vehicle use, grazing, and other impacts on wetland structure and function.
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From page 331... ...
Cooke and Lefor (1990) sampled planted and natural salt marsh soils at Indian River marsh In Connecticut and observed that vesicular-arbuscular mycorrhizae (fungi that help plants take up nutrients)
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From page 332... ...
1976a. Abundance and production of macroinvertebrates from natural and artificially established salt marshes in North Carolina.
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From page 333... ...
1990. Research Needs: Salt Marsh Restoration, Rehabilitation, and Creation Technique for Caltrans Construction Projects.
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From page 334... ...
1990. Restoration of the Salmon River Salt Marshes: Retrospect and Prospect.
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From page 335... ...
1991. Nitrogen assessments in a constructed and a natural salt marsh of San Diego Bay, California.
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From page 336... ...
1979. Documentation, Chronology, and Future Projections of Bottomland Hardwood Habitat Losses in the Lower Mississippi Alluvial Plain.
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From page 337... ...
1989. Detritus Production and Epibenthic Communities of Natural Versus Constructed Salt Marshes.
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From page 338... ...
1984. Evaluation of artificial salt marshes in New Jersey.
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From page 339... ...
1988a. Restoring diversity in salt marshes: Can we do it?
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From page 340... ...
U.S. Fish and Wildlife Service, Washington, D.C.
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