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Article Excerpt
ABSTRACT. To support the determination of hydrophytic vegetation in wetland delineations in Alaska, USA, a series of tests were conducted to develop a group of "test positive" species to be used in a "cryptogam indicator." In 2004, non-vascular cryptogam species (bryophytes, lichens, and fungi) from Interior and South-Central Alaska in the vicinities of Fairbanks and Anchorage were collected at a series of ten 50 x 50 cm plots along two 30 m transects in each of six upland and five wetland sites. Nineteen moss and liverwort species were selected from 86 species surveyed to test for wetland fidelity. In 2005, a plot-based analysis of frequency and cover data yielded a revised list of 17 bryophyte species that were specific to wetland communities dominated by black spruce, Picea mariana (P. Mill.) B.S.P. Fungi and lichens were found to be inadequate wetland indicators in the sampled locations because the lichen species were sparsely distributed and the fungi were too ephemeral. The cryptogam indicator was thus restricted to bryophytes. Also in 2005, bryophytes were analyzed for their presence on microtopographic positions within the landscape, including tops of hummocks and hollows at the bases of hummocks. Upland bryophyte species were found on hummock tops inside the wetland boundary, but were not abundant in the hollows (p < 0.05). The fidelity of the species selected for use in the cryptogam indicator was tested. It was determined that if more than 50% of all bryophyte cover present in hollows is composed of one or more of the 17 wetland bryophytes tested in 2005, then vascular vegetation can be considered to be hydrophytic (p < 0.001).
Key words: Alaska, wetlands, delineation, bryophytes, indicators, mosses, Alaskan wetland supplement, mushrooms, lichens,
cryptograms
RESUME. Afin d'etayer la presence de vegetation hydrophytique dans les delimitations de zones humides de l'Alaska, aux Etats-Unis, une serie de tests a ete effectuee dans le but d'aboutir a un groupe d'especes [much less than] de test positives [much greater than] a utiliser avec un [much less than] indicateur de sporophyte [much greater than] En 2004, des especes de sporophytes non vasculaires (bryophytes, lichens et champignons) de l'interieur et du centre-sud de I'Alaska, aux environs de Fairbanks et d'Anchorage, ont ete recueillies a une serie de dix parcelles de 50 sur 50 cm le long de deux transects de 30 m dans chacun de six sites montagnards et de cinq sites humides. Dix-neuf especes de mousse et d'hepatiques ont ete choisies a partir de 86 especes prelevees dans le but d'en determiner la fidelite aux zones humides. En 2005, une analyse de frequence de parcelles et des donnees de couverture ont permis d'obtenir la liste revisee de 17 especes de bryophytes propres aux zones humides dominees par l'epinette noire, Picea mariana (P. Mill.) B.S.P. Nous avons constate que les champignons et les lichens etaient des indicateurs de zones humides inadequats aux sites echantillonnes parce que les especes de lichen etaient reparties maigrement et que les champignons etaient trop ephemeres. Par consequent, Tindicateur de sporophytes a ete restreint aux bryophytes. Egalement en 2005, nous avons analyse les bryophytes afin d'en determiner la presence a des positions microtopographiques du paysage, ce qui comprenait le sommet de hummocks et les creux a la base de hummocks. Des especes de bryophytes montagnardes ont ete decelees aux sommets de hummocks a Tinterieur de la limite des zones humides, mais celles-ci n'abondaient pas dans les creux (p < 0.05). La fidelite des especes choisies afin d'etre utilisees dans Tindicateur de sporophytes a ete testee. Nous avons determine que si plus de 50 % de toute la couverture de bryophyte presente dans les creux est composee de Tune ou plusieurs des 17 bryophytes de zones humides testees en 2005, la vegetation vasculaire peut alors etre considered comme hydrophytique (p < 0,001).
Mots cles: Alaska, zones humides, delimitation, bryophytes, indicateurs, mousses, [much less than] Alaskan wetland supplement [much greater than], champignons, lichens, cryptogrammes
Traduit pour la revue Arctic par Nicole Giguere.
INTRODUCTION
The U.S. Army Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory, 1987), hereafter referred to as the 1987 Manual, uses three factors--hydrology, soils, and vegetation--to determine whether wetland conditions are present at any given site. To be considered a jurisdictional wetland under Sec. 404 of the Clean Water Act, a site must meet the criteria for all three parameters. For each factor, a series of field indicators is used as evidence to support particular criteria. In the case of vegetation, vascular plant species have been assigned wetland ratings corresponding to their frequency of occurrence in wetlands: Obligate (OBL) species occur at least 99% of the time in wetlands; Facultative Wetland (FACW) species, 67-99%; Facultative (FAC) species, 34-66%; Facultative Upland (FACU) species, 1-33%; and Upland (UPL) species, less than 1% (Reed, 1988). To meet the hydrophytic vegetation criterion at a particular site, estimated areal cover values for the vascular plants are used along with their wetland plant indicator status to determine whether or not the dominant plant species are hydrophytes. The basic rule for meeting the hydrophytic vegetation criterion is that more than 50% of the dominant vegetation must be rated as hydrophytic. Species rated as FAC, FACW, and OBL are considered hydrophytic. When the vascular vegetation fails the indicator test, the site is considered to have upland vegetation. In some instances, particularly in Alaska, using existing field indicators to determine whether or not the vegetation is hydrophytic can be problematic.
Regional working groups assign wetland plant indicator status ratings across ten broad regions that typically include multiple states (Tiner, 2006). The database supporting the National Wetland Plant List (U.S. Army Corps of Engineers, 2009) used by each regional working group lacks frequency data for most species. But frequencies of wetland species are well documented in the literature and by direct reports from expert field delineators and botanists working with wetland species in these regions. This reference information, along with the expertise of the working groups and input from others, is used to assign wetland indicator ratings for each species within a region. However, the resulting lists of species known to occur in wetlands do not assign wetland indicator status ratings to localized sub-regions or particular vegetation communities; they do not address variations in species habitat preferences or environmental settings; and they contain no standardized method of testing the accuracy of the assigned ratings for problematic species.
In Alaska, 60% of the vascular flora is rated as hydrophytic (Tiner, 2006). Hydrophytic vegetation determinations are therefore problematic because certain groups of widespread wetland plants occur in both wetlands and uplands, and the indicator status ratings used across the entire region are inadequate to capture differences in ecological distribution patterns. For example, species such as paper birch (Betula papyrifera Marsh) are rated as FACU species. But in some wetland types, Betula is the dominant genus in the stand. These cases represent locations where FACU species are expressing their ability to be hydrophytes 33% of the time (Tiner, 1991). FACU communities fail the hydrophytic vegetation criterion, but are problematic for wetland delineation if hydric soils and hydrology indicators are present. In contrast, black spruce Picea mariana (P. Mill.) B.S.P., an FACW species, is widespread throughout Interior and South-Central Alaska and is one of the most frequently delineated wetland vegetation types in Alaska (U.S. Army Corps of Engineers,...
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