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Indicator Symbol - Indicator Category - Definition (USFWS 1988) <br />OBL - Obligate Wetland Plants - Plants occur almost always (estimated probability >99 percent) in wetlands <br />• under natural conditions, but which may also occur rarely (estimated probability <1 percent) in non- <br />wetlands. <br />FACW - Facultative Wetland Plants - Plants occur usually (estimated probability 67 percent to 99 percent) in <br />wetlands, but also occur (estimated probability 1 percent to 33 percent) in non - wetlands. <br />FAC - Facultative Plants - Plants with a similar likelihood (estimated probability 34 percent to 66 percent) of <br />occurring in both wetlands and non - wetlands. <br />FACU - Facultative Upland Plants - Plants that occur sometimes (estimated probability 1 percent to 33 percent) in <br />wetlands, but occur more often (estimated probability 67 percent to 99 percent) in non - wetlands. <br />UPL - Obligate Upland Plants - Plants that occur rarely (estimated probability <1 percent) in wetlands, but occur <br />almost always (estimated probability >99 percent) in non - wetlands under natural conditions. <br />Categories were originally developed and defined by the USFWS National Wetlands Inventory and subsequently <br />O nodified by the National Plant List Panel. Per the Corps of Engineers Wetland Delineation Manual: Arid West and <br />Western Mountains, Valleys and Coast Regional Supplements, Plus ( +) and minus ( —) modifiers are not used. FAC —, <br />FAC, and FAC+ plants are all considered to be FAC. Plant species listed as NI (reviewed but given no regional indicator) <br />or NO (no known occurrence in the region at the time the list was compiled), were assigned the indicator status of the <br />species in the nearest adjacent region. Species were not used to calculate a hydrophytic vegetation indicator if the species <br />was listed but no adjacent regional indicator was assigned. In addition, if a species was not listed on the wetland plant list, <br />it was assumed to be an upland (UPL) species. <br />The presence of hydrophytic vegetation was assessed based on guidelines appearing in the Corps of Engineers Wetland <br />Delineation Manual: Arid West Region and Western Mountains, Valleys and Coast Region. An assessment of dominance <br />by hydrophytic vegetation (Dominance Test, Indicator 1) was performed for each sample. The "50/20 rule" was used to <br />select dominant species from each stratum of the community. This test was performed as follows: Dominant species for <br />each stratum (i.e. tree, sapling /shrub, herb, and woody vine) were identified for each sample and ranked in descending <br />order of abundance (cover) starting with the most abundant species. Of the identified dominant species, those <br />communities with greater than 50% of the dominant species rated as OBL, FACW, or FAC were identified as having <br />hydrophytic vegetation. <br />• <br />The Prevalence Index approach to assessing hydrophytic vegetation was also used if the vegetation community failed to <br />have greater than 50% of the dominant species rated as OBL, FACW, or FAC. The Prevalence Index is a weighted <br />