Biodiversity Guide - The Intertwine

egional conservation strategybiodiversity guideChapter 3 Major Habitat Types of the RegionColumbia SedgeMeadowsColumbia sedgemeadows areconsidered a criticallyimperiled habitat typein Oregon. Historicallyabundant, most sedgemeadows have beenlost as a result of filling,draining, agriculturaland grazing practices,and fire suppression.Remaining Columbiasedge meadows aremost threatened byinvasive plant species.Remnants occurat Metro’s Smith andBybee Wetlands NaturalArea in north Portland.WetlandsEsther LevWetlands are swamps, marshes, bogs, and othertransitional lands between terrestrial and aquaticsystems where the water table is usually at ornear the surface or the land is covered by shallowwater; wetlands can also exist in a slope ordepressional setting that is not associated withanother water body. Typically, wetland soils aresaturated with moisture, either permanently orseasonally, but each wetland is different. This isbecause of variations in soil, landscape, climate,water regime and chemistry, vegetation, andhuman disturbance. Wetlands may be coveredpartially or completely by shallow pools of waterthat is salty, brackish, or fresh.Wetlands are among the most importantecosystems on earth. These complex habitatsstore, clean, and filter water, prevent soil erosion,and control flooding. They provide habitat forthousands of species of birds, fish, and mammals.They are also, in effect, natural libraries thatcontain information on climate, history, adaptation,and evolution embedded in peat, muck, clay,and silt. Yet historically people did not recognizethe value of wetlands, regarding them as “wastelands,”barriers to development, and breedinggrounds for mosquitoes, insects, and disease.Consequently, many of the nation’s wetlands havebeen drained, filled, and paved over for otheruses.The greater Portland-Vancouver region hasretained a variety of different types of wetlands,from freshwater marshes to wet prairies. Thedescriptions below include examples of whereeach major wetland type can still be found in theregion. Such areas can serve as reference sites forwetland enhancement and restoration projects.Major Wetland Types in the GreaterPortland-Vancouver RegionAquatic BedsAquatic beds are composed mostly of submergedvegetation, the upper portions of which may floatat the surface. Aquatic beds occur in near-shoreareas along the coast, in estuaries, and in rivers,ponds, lakes, and sloughs on most topographicsurfaces throughout the state. Plants may berooted, suspended in the water column, or freefloating.They provide critical food and coverfor fish, amphibians, and invertebrates and areusually directly linked to riverine and emergentwetlands by hydrology, chemistry, and food webs.A large variety of invertebrates and vertebratesuse both aquatic beds and emergent wetlandsduring part of their life cycles. Since 1850, muchaquatic bed habitat has been lost to river channelization,siltation, and filling for agricultureor urban development. Examples of aquatic bedhabitat can be found at Sturgeon Lake, Smith andBybee Wetlands Natural Area, and the Vancouverlowlands.fensMost wetlands in Oregon that have been calledbogs are actually fens, because they are hydratedby mineral-rich surface water or groundwater,lack a domed peat profile, and have a pH generallyhigher than 5.5. However, many fens containlocalized hummocks or lawns of Sphagnum witha pH as low as 4, and these are classified as “poorfens.” Oregon’s fens occur in depressions on variouslandforms, particularly in troughs betweendunes and in headwall basins and floodplains.Fens can also occur around the edges or overthe surface of mid-slope slump or sag pondsin landslide areas. Fens are usually perenniallysaturated, but local areas of surface drying are notuncommon. Fens may include patches of shrubswamp and forested wetland occurring on peatsoils. Drainage, filling, peat mining, conversionto commercial cranberry or blueberry production,and plant succession have destroyed manyfens, and losses continue to occur despite wetlandregulations that were designed to protect them.The only known fen left in the Willamette Valleywas recently protected by Metro.Forested WetlandsSometimes called swamps, forested wetlandsoccur on seasonally or perennially wet flats,depressions, or stream terraces. Hydration occursvia precipitation, groundwater discharge, orinflowing streams. Forested wetlands sometimesare located within riparian zones but differ fromriparian wetlands in their higher water tablesand longer duration of surface water. Forestedwetlands typically are flooded for several weeksduring the growing season (seasonal flooding),and are differentiated from riparian stands thatmay have surface water for only a few days duringa temporary flood. Examples of forested wetlandscan be found at the Vancouver Lake lowlands, onSauvie Island, and along the Columbia River.Freshwater MarshesFreshwater marshes occur in depressions andaround the edges of lakes, ponds, rivers, andstreams where surface water is present for all ormost of the growing season and the soil is perenniallywet. (Freshwater tidal marshes are treatedseparately in the following section.) They arecharacterized by emergent herbaceous vegetationsuch as spikerush (Eleocharis spp.), sedges (Carexspp.), bulrushes (scirpus spp.), bur-reed (Sparganiumspp.), cattails (Typha spp.), and variousgrasses. Broadleaved herbs and shrubs may alsobe present. Freshwater marshes are particularlywell known as breeding or foraging sites for birds.Freshwater marshes are found throughout thestate, but many thousands of acres have beendiked, drained, and farmed. Ridgefield WildlifeRefuge Complex, Tualatin Wildlife Refuge,Fernhill Marsh, Wapato Lake, Jackson Bottom,and Shillapoo Lake offer examples of freshwatermarshes.Riparian WetlandsRiparian wetlands occur along rivers and streamsthroughout the state and are often intermixedwith upland portions of floodplains in a jumbleof units that are difficult or impossible to mapseparately. Riparian wetlands usually are associatedwith seasonal flooding of adjacent streamsand rivers, but they also can be hydrated byperennial or seasonal seepage, tributary streams,or flooding caused by tidal cycles. Vegetation inriparian wetlands can be forested, scrub-shrub,or herbaceous but is usually a mixture of alternatingpatches of all three different types. Historically,most riparian areas were grazed intensivelyby livestock and severely degraded as a resultof soil compaction, denudation, down cuttingof streams, and subsequent invasion by uplandor non-native invasive species. These impactsalso degraded streams and have impaired fishand other aquatic species. Over the last 20 years,extensive areas of riparian vegetation and hydrologyhave been restored by improved managementpractices. Examples of riparian wetlands canbe found along Multnomah Channel, ShillapooLake, and the Sandy, Clackamas, Columbia, andLewis rivers).Scrub-Shrub WetlandsScrub-shrub wetlands include areas dominatedby woody vegetation less than 6 meters (20 feet)tall. Characteristic species include true shrubs,young trees, and trees or shrubs that are small orstunted because of environmental conditions. Allwater regimes except subtidal are included. Willow,spirea, and red twig dogwood are commondominant shrub species found in scrub-shrubwetlands in the region. Examples of scrub-shrubwetlands can be found at Killin Wetland, BeggarsTick Marsh, Oaks Bottom Wildlife Refuge,38 39