Freshwater Wetlands : A Guide to Common Indicator Plants of the Northeast
Port City Press. Baltimore, MD. Woody Plants of Maryland. Conservation International. Conservation Experts Sourcebook. Delaware Native Plant Society. Delaware Native Plants for Landscaping and Restoration. Magee, Dennis W. University of Massachusetts Press. Natural Resources Group. City of New York Parks and Recreation.
Pennsylvania Department of Agriculture.
- Institute for Wetland & Environmental Education & Research!
- Valuing Agroforestry Systems: Methods and Applications (Advances in Agroforestry)?
- Hydrophytic Vegetation.
- Wetland Resource Guide!
- View Freshwater Wetlands A Guide To Common Indicator Plants Of The Northeast 1981.
- Grasses of the Northeast?
Giant Hogweed: An attractive but dangerous noxious weed -- Have you seen this plant? Randall, J. Invasive Plants: Weeds of the Global Garden. Brooklyn Botanic Garden Handbook No. Rhoads, Ann F. University of Pennsylvania Press. Even broken branches buried in the ground can sprout new shoots e.
Crawford , reported that the European alder developed a bush form polycormic growth form in frequently flooded wetlands, in contrast to a pole form on well-drained sites. Flooding stimulates basal buds to develop forming multiple trunks. The advantage of this adaptation is improved ventilation above the flood level as there is more lenticel-containing bark at the bottom of the stems.
This adaptation may also occur with other adaptations e. Sprouting may occur in other species as speckled alder A. In Jean Lafitte National Park LA , red maple had two different growth forms—a single-stemmed canopy tree on the natural levees and a multistemmed tree in the frequently flooded backswamp Denslow and Battaglia, McLeod et al. They believed that this mechanism allowed for an increase in the area of stem tissue for potential gas exchange with the atmosphere the same purpose of stem hypertrophy.
Saw palmetto Serenoa repens is a southern palm that grows mostly on dry sandy sites such as pine flatwoods, longleaf pine—scrub oak ridges, sand pine—oak scrubs, and coastal dunes. Yet it is also common in seasonally wet pine flatwoods Godfrey and Wooten, Wells listed it as one of the community dominants of southeastern shrub bogs. On dry soils, the saw palmetto sends up its palm leaves from a horizontal, usually underground, rhizome. On seasonally flooded sites, however, it develops an upright, often branched stem Figure 3.
Godfrey and Wooten recognized this different growth form and included this species in their book on aquatic and wetland plants of the Southeast. Colonization of flooded soils, if done through reproduction, requires that seeds be adapted to aquatic conditions. For those species using hydrochory, floatable seeds are important for dispersal, and as expected, seed floatability differs among species.
In a study of some common freshwater tidal species, Parker and Leck found that the floatability of seeds from two smartweeds Polygonum arifolium and P. A study of seed buoyancy and germination of 55 wetland species provides some interesting insights van den Broek et al. Seeds from plants in more aquatic habitats i. Species with higher buoyancy seed may have lower longevity than the others, suggesting a trade-off between dispersal and seed persistence.
The former may have longer or flatter seeds that are not likely to be buried as round seeds.
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The seeds of some plants may have structures to aid floatation e. In the Amazon, during the flood season, nonbuoyant seeds drop to the bottom of the submerged ground where they await the drawdown phase for germination Junk et al. Most seeds have a limited ability to germinate under anaerobic conditions and many wetland plants, especially those incapable of germinating underwater, delay germination until the flood-water recedes and the likelihood of more flooding has passed Crawford, The combination of changes in light and fluctuating temperatures from reduced flood levels stimulates germination in many wetland species, including water horehound Lycopus europaeus , purple loosestrife L.
Flooding can stimulate annual species, like those colonizing mudflats in summer, to break dormancy. Crawford provides several examples of the physiological problems of seed germination in a variety of seasonal flooding circumstances and different strategies for responding to these issues. The seeds of most plants lose viability when inundated for long periods. In contrast, seeds of marsh and aquatic species have prolonged dormancy and remain viable for many years Leck, Scientists claim to have germinated a year-old lotus seed from China The Boston Globe , November 14, , p.
While some wetland plants are noted for their persistent in seed banks, others are short-lived e. Seed banks in the soil are important for wetland restoration efforts as they may harbor species that are not present in the existing aboveground community.
In studying California vernal pools, Faist et al. When favorable conditions occur, seeds in the banks can germinate. Seed banks in drained wetlands in agricultural regions may, however, have limited native species Seabloom and van der Valk, ; Nabity and Hoagland, Seeds need some level of oxygen to germinate, with few exceptions, two being rice O. Rice is undoubtedly the most studied wetland plant due to its economic importance—the staple for millions of people around the globe—with particular emphasis on its tolerance of flooding and waterlogging Colmer et al.
Only certain genotypes of rice can actually do this fast enough to do this under field conditions Ismail et al. Miro and Ismail review some major physiological processes involved in rice tolerance of flooding during germination, while Baskin and Baskin provide a treatise on seed ecology, germination, and dormancy, with some attention to aquatic species. Many wetland plants can germinate underwater. Among these exceptional species, Hook a listed several wetland plants including Peltandra virginica, Alisma plantago-aquatica, T.
The latter rely on natural drawdown conditions in wetlands for germination, so characteristic southern deepwater swamp species like baldcypress and water gum regenerate at low water accompanying extended droughts. Rapid growth of seedlings allows these species to get their foliage above water, thereby enhancing survival of the species. A germination study of six helophytes I. Typha spp. This experiment also investigated seedling growth after flooding and dewatering—growth of Phragmites and Phalaris ceased upon flooding but resumed upon drainage, and growth of Typha and Scirpus was unaffected by flooding, while Iris seedlings grew slowly when submerged but responded quickly upon drainage.
Interestingly, seedlings of all species survived 7 weeks of inundation Coops and van der Velde, The seeds of wetland species that germinate in fall may have physiological adaptations that prevent their germination in spring during high water conditions. Work by Kramer identified that soil wetness during the first year or two was critical for seedling survival of shallow-rooted species, specifically baldcypress and yellow birch Betula alleghaniensis.
Experimental studies of germination and seedling survival in lodgepole pine and ponderosa pine P. The conclusion was that the predominance of lodgepole pine a FAC species in Oregon over ponderosa pine a FACU species on wet soils must be related to other factors—possibly the former is a better competitor in sites with grasses and forbs. Tolerance of saturated conditions may change with age, as in loblolly pine; tolerance to oxygen deficiency was found to increase with age Grable, , Leyton and Rousseau, , as reported in Hu and Linnartz, Flooding stimulates ethylene production in many aquatic plants, which then promotes shoot elongation, allowing some of them to get their shoots or leaf tips above the flood level and thereby continue exchange of gases mainly through stomata , photosynthesis, and other life processes Ku et al.
In some species, adventitious root formation may begin after emergence Van der Sman et al. While many aquatic and marsh plants have this adaptive response to flooding, some terrestrial species, including corn Z. Stem growth can be extremely rapid. This can happen in less than 20 min Jackson, Variations in plant responsiveness of stem elongation help explain plant distribution at different levels on floodplains Blom et al. McKevlin et al. This species is a dominant species of semipermanently flooded and intermittently exposed wetlands, yet does not germinate underwater.
Instead it germinates during drawdowns late in the growing season or during dry years. This late germination also may require rapid stem growth to guarantee that the terminal shoot is above the winter flood level. In a study of the response of dallisgrass Paspalum dilatatum and narrowleaf trefoil Lotus tenuis to flooding with or without defoliation, Striker et al.
Dallisgrass grew taller when flooded for 15 days compared to nonflooded plants, while there was no noticeable height difference in the trefoil. The flooded dallisgrass also produced more tillers above the water level, which according to some sources increases the possibility of oxygen capture Laan et al. Many of these species are more common on the latter sites but have populations that tolerate varying degrees of soil wetness. Unfortunately, due to the lack of distinctive morphological differences, individuals of these wetland populations can only be recognized as hydrophytes when associated with more typical hydrophytic species or after identification of hydric soils i.
In the s and the early s, it was used to define aquatic plants that were plants growing in water Schouw, , as reported in Warming, or plants with perennating buds beneath the water Raunkiaer, , According to this system, hydrophytes plants with perennating rhizomes or winter buds and helophytes plants with buds at the bottom of the water or in the underlying soil were the two types of cryptophytes plants with dormant parts below ground , while other wetland plants were included in other life-forms, such as phanerophytes trees and shrubs Smith, Warming was probably the first ecologist to arrange plant communities by the degree of soil wetness.
He recognized aquatic plants water plants that spend their entire life submerged or with leaves floating at the surface and terrestrial plants that are mostly exposed to air, including marsh plants. The first of the groupings was for soil that was very wet and two classes were listed: class 1, hydrophytes formations in water , and class 2, helophytes formations in marsh.
The distinction between hydrophytes and helophytes had ecological merit in that the truly aquatic plants hydrophytes were separated from those that grew on anaerobic saturated soils helophytes. Following the lead of Warming, Clements also used soil wetness to separate plants into different groupings. For this reason, they pass, on the one hand, into dry land plants, and, on the other hand, into amphibious plants.
Various xerophytes and hydrophytes have, moreover, often found themselves in conditions that changed them to mesophytes. The lists included many typical upland species that had wetland ecotypes or broad ecological amplitudes and were typically adapted for life in wetlands. This concept is not bound to the species level in plant taxonomy, but allows, for example, wetland variants of mostly dry-site species to be classified as hydrophytes. Tiner provides a detailed review of the concept of a hydrophyte as applied to wetland delineation.
In , the U. It recognizes that recurrent, prolonged wetness during periods of plant growth has a major influence on plant colonization, survival, and reproduction. The definition excludes plant species that only colonize wetlands during dry periods i. Growing period focuses on the growth of root, shoot, and other plant parts by native species. While a couple of thousand species grow exclusively in U.
Some of the latter occur mostly but not always in wetlands, whereas others display no particular affinity for wetlands and still others are actually more common in uplands. When the plants are growing under wetland hydrologic conditions, they are hydrophytes regardless of where the majority of individuals of their species occur.
The best plant indicators of wetland are clearly those species with the highest affinity for wetlands see Table 3. Source: Tiner, R. The affinity of certain species may vary with latitude or, in mountainous areas, with altitude. For example, in the Northeast, Labrador tea Ledum groenlandicum is restricted to wetlands, mainly bogs. Yet in Labrador and Newfoundland, this species also occurs in dry heaths and woods Ryan, Mountain holly Nemopanthus mucronata , an exclusive wetland species in most of its U.
Presumably the combination of low evapotranspiration, cold climate, moderate frequency of fogs, and cool, moist air maritime influence creates favorable conditions on drier soils. The colder climates, especially along the coast, may permit some excellent wetland indicator plants to be less reliable indicators locally. Most plants growing in wetlands have a broad ecological amplitude and are tolerant or adaptable to many environmental conditions e.
Such species are not particularly useful indicators of any environment, unless they possess morphological adaptations developed in response to prolonged flooding or waterlogging. A flood tolerance study of red maple A. As mentioned earlier, red maple was reported to have a highly adaptable root system Kramer, It is a good example of a species demonstrating ecological plasticity. Another example of a plastic species is water smartweed Polygonum amphibium —plants growing on land dry soil have hairy, rough stems and leaves, yet those in water possess stems and leaves that are quite smooth throughout Weaver and Clements, While many species are quite adaptable, some have populations of individuals that are better adapted to one set of environmental conditions than other populations of the same species.
While the definition of species is useful for taxonomic reasons and to discuss ecological relationships, it is not without problems. Merrell commented that up to half of all species of flowering plants are believed to be allopolyploids—the product of hybridization between species plus complications due to asexuality, introgression, geographic variation, and combinations of these factors. Recognizing the varied responses to different habitats, Clements et al.
This clearly reveals the possibility for less habitat specificity than the nonscientist might expect from a given plant species. At the species level, plants do not have exactly the same environmental requirements and individual populations may differ in their tolerance of degrees of waterlogging or flooding. For some plant species, subspecies or varieties that are found in different habitats or with a restricted distribution are morphologically distinguishable Table 3. In some cases, these varieties have been assigned a different indicator status on national and regional wetland plant lists see following section for discussion , especially when their habitats are wetter than the typical species.
Their recognizable morphological differences make them particularly useful for identifying wetlands. Yet, it must be understood that ecotypes are typically more distinctive physiologically than morphologically Daubenmire, In other words, their differences are not visible, but require scientific study of physiological responses.
Sources: Range in wetland indicator status in its U. Habitat data from Fernald, M. Van Nostrand Co. Department of Agriculture, Washington, DC, Since the original version of this book was published, certain subspecies have been recognized as separate species: Andropogon virginicus glaucopis is now A. Numerous studies have found different responses to flooding within species that occur in wetlands. Keeley recorded different responses to flooding by seedlings from three distinct populations of black gum swamp, floodplain, and upland phenotypes. Floodplain seedlings did as well as the upland seedlings under drained conditions and produced a flood-tolerant type under flooded conditions.
This study demonstrated the existence of wetland ecotypes in black gum. Wetland ecotypes can evolve due to differences in environmental conditions that reproductively isolate wet-site individuals from dry-site individuals. Timing of flowering may be different, thereby limiting cross-fertilization. In their study of ecotypic variation in western white pine Pinus monticola , Squillace and Bingham found that seedbed moisture served as an ecological barrier to gene flow from contiguous populations. Genetically distinct populations can be created wherever there is a steep gradient in microhabitats, even when gene flow is strong Liu and Godt, In the case of western white pine, seedlings from dry-site populations failed to survive wet conditions, while wet-site seedlings could not grow in dry beds Squillace and Bingham, Examination of the physiological responses of eight red maple provenances four each from wet and dry sites to soil water availability led researchers to conclude that red maple A.
Cultivars of nursery plants and cropped species may be more tolerant to flooding than others. Anella and Whitlow subjected fully leafed-out saplings of 7 red maple cultivars, 4 Freeman maple A. The James River saplings and cultivars rated as high tolerance had longer hypertrophied lenticels than the other cultivars.
The authors were surprised at the poor development of adventitious roots, especially in the James River saplings as their other work found extensive adventitious roots in such saplings. In summarizing literature on plant adaptations to saltwater flooding, Wainwright mentioned the presence of salt-tolerant ecotypes of creeping bentgrass Agrostis stolonifera , red fescue Festuca rubra , and several other typically nonsaline species in salt marshes.
Individuals of these two species from salt marsh populations did not grow as vigorously as individuals from inland populations when grown under freshwater conditions Hannon and Bradshaw, ; Tiku and Snaydon, Intraspecific variation in salt tolerance has also been detected in many common salt marsh plants S. Salt hay grass occurs in dunes, interdunal swales, salt marshes, and brackish marshes, and these stocks showed different responses to salinity Silander and Antonovics, ; Pezeshki and DeLaune, Different populations of species have shown unlike responses to flooding and waterlogging.
Lessmann et al. Lynn and Waldren compared the flood response of creeping buttercup Ranunculus repens seedlings from two different habitats turlough, wet; ruderal, damp : there was no difference in aerenchyma formation or in response to saturation, but submergence produced leaf decay and blackening of root tissue in the ruderal seedlings but not in those from the turlough.
An interesting side note for the experiment was that the ruderal seedlings extended their petioles upward when submerged, while no such response was made by the turlough seedlings; in their natural habitat the latter are often covered by many feet several meters of water for months e.
Foresters have long recognized different site types to maximize timber production from variable sites. Forestry researchers often use wet-site and dry-site seed sources when studying the responses of seedlings to anaerobic conditions as Topa and McLeod a did when evaluating such responses in loblolly pine and other pines. Gill noted several examples of intraspecific and intravarietal differences in possessing the ability to produce adventitious roots.
Several researchers observed that flood tolerance varied in Eucalyptus among ecotypes and provenances Karschon and Zohar, ; Ladiges and Kelso, , as reported in Kozlowski, a. Sahrawat et al. When seaside goldenrod Solidago sempervirens from a Florida population was grown in New York, it grew poorly, while the New York populations clearly had no trouble growing there Clausen and Hiesey, Yellow monkeyflower Mimulus guttatus has many ecological races related to climatic, altitudinal, and other factors.
Even when the distributions of habitats overlap, the races may remain separate due to ecological conditions, with only minor hybridization Clausen et al. Many species seem to exhibit ecological plasticity—the ability to successfully colonize a wide range of habitats, even within a single geographic region. These are highly adaptive and opportunistic species. An example is pitch pine, the characteristic plant of the New Jersey Pine Barrens, predominating both wetlands and uplands.
It grows across a broad continuum of soil moisture from the driest sites e. They admitted that genetic effects are confounded by environmental effects and that genetic variation can occur at several levels in a species—among individuals within stands, among stands within regions, and among physiographic regions. Persimmon Diospyros virginiana occurs in permanently flooded sites on the Delmarva Peninsula Delaware, Maryland, Virginia and on sand dunes. It coexists with buttonbush C. Titus also found this species growing in a Florida hardwood swamp at low elevations, with its mean elevation between that of baldcypress and American elm U.
It is likely that a wetland ecotype for persimmon exists. On the West Coast, lodgepole pine occupies a similarly broad range of habitats Fowells, , with varietal habitat preferences. The shrubby coastal form var. The inland variety var. The evolution from land to water a terrestrial existence to an aquatic one by vascular plants may have happened over times Jackson et al. Cattails and bur reeds evolved from terrestrial plants Cronquist, Curiously, some terrestrial monocots were derived from aquatic ancestors only to return to a watery life as hydrophytes Crawford, The first trees on Earth grew in Carboniferous swamps about million years ago, so these swamps are the ancestors of terrestrial vegetation Kangas, Interestingly, Jackson et al.
Evolution is still occurring and land plants are continuing to adapt to life in wetlands and water. Traditionally, plant ecologists have attempted to use certain plants as indicators of specific environmental conditions e. In seeking to identify wetlands, there are many species that can serve as useful indicators for various wetland types especially the seasonally flooded and wetter types.
However, given the transitional nature of many wetlands or portions of wetlands e. Species in the drier-end wetlands are not likely to be reliable indicators of either wetlands or uplands, so plants may not be useful for identifying wetland boundaries under these conditions. Barbour et al. This may not be a realistic objective for two reasons. First, plants respond to a complex of climatic, edaphic, and biotic factors, and the impact of single factors is difficult to isolate.
While many botanists and ecologists would like to use the Linnaean species to determine precise limits of wetlands, it must be understood that most wetlands, especially the drier-end ones, cannot be simply identified by plant species alone. The existence of wetland ecotypes of species that are typically on drier sites has confounded the situation. Moreover, unless morphological adaptations are present, the only way to recognize these hydrophytic ecotypes is through verifying the presence of undrained hydric soils.
Since the beginning of plant ecology as a modern science, botanists have found certain plant species and communities to be characteristic of wetlands. They have been interested in describing plant communities and explaining the reasons for their establishment. They were not concerned about determining the exact boundaries between the communities as they collected data from representative sites or sites that typified the overall plant community. Typically, a plant ecologist would not select a sample plot in the interface between two communities unless he or she was interested in this transitional area.
Certain aspects of wetlands have baffled plant ecologists for some time as witnessed by the following quotations: … there is no sharp limit between marsh-plants and land-plants. The vascular species of this group [amphibious plants] are closely related to mesophytes and are the least specialized of water plants.
Freshwater Wetlands | University of Massachusetts Press
Many sedges and willows, etc. Today, there is great interest in both identification and delineation of wetlands due to passage of laws and promulgation of regulations to protect wetlands or to curtail unnecessary wetland destruction. Consequently, attention is focused on determining the boundaries of wetlands. For the first time in history, it is critical to know the limits of wetlands on individual parcels of land, since many activities e. Vegetation plays a major role in wetland identification and delineation, so it is important to know which plants or groups of plants plant communities are wetland indicators see Chapter 9 for examples of U.
To aid in using plants to identify wetlands, a national list of vascular plant species that occur in wetlands has been prepared and updated by the federal government. Initially prepared by the U. Army Corps of Engineers Lichvar et al. The list was originally developed for use in defining hydrophytes or plants that occurred in wetlands to help interpret the U.
In reviewing the scientific literature, thousands of species of plants were reported growing in U. Rather than compiling a simple list of these species, it was realized that the affinity for wetlands varies considerably among plant species and in some cases across regions. Consequently, species were assigned to one of four wetland indicator categories based on differences in expected frequency of occurrence in wetlands: 1 obligate wetland OBL , 2 facultative wetland FACW , 3 facultative FAC , and 4 facultative upland FACU. Plants not found in wetlands are considered upland plants UPL. The definitions of these categories have slightly changed over time.
Obligate wetland OBL. Draft lists were subject to peer review by wetland specialists and plant ecologists across the country. Since all reviewers did not concur with a single indicator status, pluses and minuses were also assigned to species within the three facultative categories e. The national list Reed, represented a compilation of regional lists. The regions were still quite broad and further subdivisions could make the list even more sensitive to species habitat requirements.
The proposed list Reed, was the first attempt to address some significant intraregional differences. The national list of wetland plants contained 6, species out of a total of approximately 22, vascular plant species that exist within all habitats in the United States and its territories and possessions Reed, Although the list is lengthy, it did not contain the majority of U. The majority of listed species, therefore, grow in both wetlands and nonwetlands to at least some extent, which is quite expected for habitats that are, in many ways, transitional between land and water.
In December , maintenance and updating of the list was transferred from the U. Fish and Wildlife Service to the Corps, given their extensive use of the list for regulatory purposes. EPA, and U. Fish and Wildlife Service December 12, With few exceptions, these plants herbaceous or woody are found in standing water or seasonally saturated soils 14 or more consecutive days near the surface.
These plants predominately occur with hydric soils, often in geomorphic settings where water saturates the soils or floods the soil surface at least seasonally. These plants can grow in hydric, mesic, or xeric habitats. The occurrence of these plants in different habitats represents responses to a variety of environmental variables other than just hydrology, such as shade tolerance, soil pH, and elevation, and they have a wide tolerance of soil moisture conditions.
These plants predominately occur on drier or more mesic sites in geomorphic settings where water rarely saturates the soils or floods the soil surface seasonally. These plants occupy mesic to xeric non-wetland habitats. They almost never occur in standing water or saturated soils. Typical growth forms include herbaceous, shrubs, woody vines, and trees. The regions of interest for the wetland plant lists were revised to correspond with the 10 ecologically based regions used for their recently published regional supplements to the Corps wetland delineation manual Figure 3.
This required further peer review of the lists and wetland ratings. The Corps also established a process for updating the list annually—one that allowed the public, in addition to state and federal agencies, to suggest additions, deletions, and modifications of the wetland ratings. The list contained species, up from in , in , and in Lichvar et al. While most states are adopting the state-relevant species and corresponding indicators from the national list for their programs, at least one state may take the state list one step further.
Scientists in California have expressed interest in dividing the state into more regions and further regionalizing the list of wetland plants for California San Francisco Estuary Institute, Interpretation of plants as wetland indicators varies according to the approach taken for wetland delineation. To date, the federal government has generally embraced a three-factor approach for identifying regulated wetlands Environmental Laboratory, , and regional supplements; Federal Interagency Committee for Wetland Delineation, This approach tends to define hydrophytic vegetation in broad terms including FAC-dominated communities because hydric soils and signs of wetland hydrology are usually required to help make the final wetland determination.
Another approach used to identify wetlands for inventories and mapping projects—the primary indicators method PRIMET; Tiner, —focuses on plant and other indicators that are unique to wetlands for positive wetland identification. This type of approach has gained acceptance for regulatory purposes in some states. For example, state agencies that traditionally used vegetation to identify wetlands, mainly a predominance of FACW and OBL species as positive indicators of hydrophytic vegetation and wetlands, now recognize other plant communities as hydrophytic upon verification of hydrology or hydric soils see Chapter 6.
Most methods focus on dominant species i. Dominant species with certain morphological adaptations. The best vegetation indicators of wetlands are the genera, species, or subspecies varieties that are unique to wetlands—the obligate hydrophytes see Table 3.
Plant Indicators of Wetlands and Their Characteristic
Whenever these species are common or abundant in an area, the area should be easily recognized as a wetland by vegetation alone. The FACW species also are fairly reliable indicators as they are found mostly in wetlands. Since the Corps regional supplements are now the basis for determining hydrophytic vegetation for regulatory purposes across the United States, a table highlighting their indicators is provided Table 3. Five hydrophytic vegetation indicators are given; one addressing bryophytes pertains only to the Western Mountains, Valleys, and Coast Region see preceding table for brief description.
For wetland identification, the investigator starts with the first one on the list, then if it is not satisfied, goes to the next one, and so forth. The use of the prevalence index and the morphological adaptations indicators requires that hydric soils and sufficient wetland hydrology indicators are present see Chapter 6. Since they occur in wetlands with some frequency and may even dominate certain types, they have the potential to be hydrophytes Chapter 6.
Hydrophytic members of these species can be recognized in four ways: When associated with OBL and FACW species When they possess certain morphological adaptations After verification of undrained hydric soils By their occurrence in areas with documented wetland hydrology. FAC species, by definition, have essentially no affinity for wetlands or nonwetlands and, therefore, are not indicative of either.
This has led to the development of the so-called FAC-neutral rule for determining the presence of hydrophytic vegetation Environmental Laboratory, —a rule that is no longer used for that purpose Williams, , but instead is now used as a wetland hydrology indicator e. Army Corps of Engineers, While FAC species may not be reliable indicators of wetlands due to their equal occurrence in wetlands and uplands , they dominate many forested wetlands across the country.
Examples of some dominant hydrophytic FAC trees include red maple, black gum, sweet gum, eastern cottonwood, balsam fir A. FACU species plants that are typically found in nonwetlands are more contentious as wetland species, since by definition they occur more in uplands than in wetlands. Some species are quite common in wetlands and when growing under such conditions are hydrophytic.
He felt that the first two were examples of broad tolerances, while the latter two were freak occurrences. He also noted that white spruce Picea glauca ; FACU was a characteristic peatland species and that some rather large red pines P. Pitch pine P. Subalpine fir A. These types of plants demonstrate considerable ecological plasticity and create a serious perception problem when attempting to depict these plant species as hydrophytes or wetland plants.
While the general public may have some difficulty understanding that FACU species can be hydrophytes, wetland ecologists should not, recognizing the ecological amplitude of and the possibility of ecotypes for many species. Moreover, the problem with FACU species is an artifact of our attempt to use the species level to identify wetland indicators. The individual FACU plants growing in wetlands are well adapted to a wetland existence.
Individual plants are continually adapting to varied environmental conditions in the pursuit of life and survival of the species. For wetland identification purposes following the Corps regional supplements e. Army Corps of Engineers, , , FACU species can be recognized as hydrophytic when the plants grow on a site with verified hydric soils and sufficient signs of wetland hydrology. The May , offering of this course was approved for the following credits. We will reapply for similar credits the next time the course runs, but we cannot guarantee credit approval for future offerings.
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