Final report to - Sierra Forest Legacy

1012VOLUME II, CHAPTER 36TABLE 36.1Ecological attributes of riparian areas.General Attribute Specific Attributes ReferencesMoisture availability Shallow water table supports phreatophytes California State Lands Commission 1993Evapotranspiration, shading increase humidityMoist environments for amphibians, reptiles Reynolds et al. 1993; Jennings 1996Structural complexityVegetation provides cover for wildlife, birdsMultiple plant canopies create multiple niches Krzysik 1990Seasonal changes in deciduous vegetation Reynolds et al. 1993Periodic disturbance Floods disrupt existing organisms, providing Resh et al. 1988; Sparks et al. 1990;opportunities for pioneer speciesJunk et al.1989Linear nature Edge effect: terrestrial-aquatic ecotone Schimer and Zalewski 1992Riparian zones serve as wildlife migration corridors Thomas et al. 1979Food resources Diverse vegetation yields diverse foods Cross 1988Diverse habitat harbors diverse prey Raedeke et al. 1988Open water available for wildlifeMicroclimate Shaded, cool, moist in summer Raedeke et al. 1988Protected in winter: overwintering habitatInfluences on aquatic habitat Shading moderates water temperatures Brown 1969Shading moderates algal growthPlant materials and insects fall into stream, adding Cummins et al. 1989;chemical energy and nitrogen Knight and Bottorff 1984Riparian zone “buffers” stream from upland Erman and Mahoney 1983;Mahoney and Erman 1984Riparian vegetation stabilizes stream banks Kondolf and Curry 1986and San Francisco Bay (Gilbert 1917; Mount 1995). Along theYuba River above Marysville, the “debris plain” built of thesesediments exceeds 64 km 2 (40 mi 2 ) in area.A later phase of mining involved dredgers. These reworkedthe natural floodplains or hydraulic mining debris and leftbehind elongated mounds of tailings, which are still largelyunvegetated because their surfaces consist of open cobbles inwhich plants cannot become established. The dredgers requiredextensive, deep, relatively flat deposits to work, so theywere concentrated in the lower Central Valley reaches of westernSierra Nevada rivers.Gravel mining for construction aggregate from river channelsand floodplains results in the direct removal of riparianvegetation for the creation of process yards, haul roads, andpits. Indirect effects of in-channel extraction typically includechannel incision, which propagates both upstream and downstream,lowering the alluvial water table and inducing channelinstability.Gravel mining for construction aggregate is the largestmining industry in the state (see Diggles et al. 1996). Morethan 100 million metric tons are produced annually, virtuallyall from river channels and floodplains. Large gravel depos-TABLE 36.2Selected geomorphic and hydrologic processes in riparian areas.Process Physical Effect Ecological Consequence ReferenceFloodingInundation Soil anoxia Selects for plants tolerant of anoxia Walters et al. 1980; Gill 1970Saturation of soilIncreases soil moistureHigh-velocity flow Scour of seedlings Prevents establishment of woodyvegetation in channelPhysical damage to plants Selects for tolerant plants Sigafoos 1964Bank erosion and undercutting of Creates new habitats for colonizationmature vegetationDeposition Burial of plants Selects for tolerant plants Sigafoos 1964Sand-gravel bar depositionSelects for plants capable ofcolonizing sandy substratesFine-grained overbank deposition Provides silty substratesStream-GroundwaterInteractionsDrainage from hill slope Maintains high water table Supports vegetation independent of streamflowBank storage Recharges alluvial water table Supports vegetation Kondolf et al. 1987aMaintains base flowProvides water downstream