Botany and Wetlands Study Report - McMillen, LLC

Botany and Wetlands Study ReportSoutheast Alaska Power Agency3.7.1 Forested WetlandsForested wetlands occur on poorly or very poorly drained hydric mineral and organic soils.Forested wetlands are most common on broad glacial valley bottoms, gently sloping hill slopesor benches, but are also commonly found on steep terrain in areas overlaying volcanic geology.These wetlands provide important functions including wildlife habitat, water qualityimprovement, peak flow reduction and erosion control, organic matter production and export,and nutrient and carbon cycling (Cooke 2005). Forested wetlands may support the transfer ofwater to downslope resources, function as recharge areas for groundwater and streams, andprovide depositional areas for sediment and nutrients.Forested wetlands are wetlands dominated by vegetation greater than 20 feet in height. Theoverstory in forested wetlands in the analysis area is varied but typically consists of westernhemlock, western red cedar (Thuja plicata), Alaska yellow cedar, and red alder. The understory isoften dominated by skunk cabbage (Lysichitum americanum). Other shrub and herbaceousspecies occurring in the understory of forested wetlands in the analysis area include seepmonkeyflower (Mimulus guttatus), deer cabbage (Nephrophyllidium crista‐galli), fowlmannagrass (Glyceria elata [G. striata]), California black currant (Ribes bracteosum), andsalmonberry. In the analysis area, approximately 60.9 acres (43.4 percent) consists of forestedwetlands.3.7.2 Emergent Sedge WetlandsEmergent wetlands contain organic soils that are very poorly drained, moderately deep, and aredominated by sedges and grasses. They may include poor fens and rich bogs and there istypically some water flow through. Vegetation in these wetlands typically consist primarily ofvarious sedges and mosses with scattered shrubs. In the analysis area, emergent wetlands weretypically found along the margin of Swan Lake adjacent to open water. Species commonlyobserved in emergent wetlands in the analysis area include Sitka sedge (Carex aquatilis),smoothstem sedge (Carex laeviculmis), bluejoint reedgrass (Calamagrostis canadensis), marshcinquefoil (Comarum palustre [Potentilla palustris]), western water hemlock (Cicuta douglasii),scattered willows (Salix sp.), and occasionally small‐fruited bulrush (Scirpus microcarpus). Thesewetlands provide habitat for unique plants and animals, and contribute water to downsloperesources, provide carbon and nutrient cycling benefits for watershed function, and providewater storage for flood and erosion control (EPA 2011). In the analysis area, approximately 15acres (10.7 percent) consists of emergent wetlands. Emergent wetlands mapped in the analysisarea include types mapped as freshwater emergent sedge (emergent sedge/FW) and tall sedgefens. A few small emergent wetlands were observed outside the analysis area along existingroads and near existing facilities associated with dam operations.3.7.3 Moss MuskegsMoss muskegs are characterized by nutrient limiting acid peat bogs, dominated by sphagnummoss and peat deposits. Muskeg wetlands support a distinctive flora which are adapted to life inSwan Lake Hydroelectric Project January 2013FERC Project No. 2911 Page 16 Version: Agency Review