Tuolumne River Report - U.S. Fish and Wildlife Service

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TUOLUMNE RIVER TECHNICAL ADVISORY COMMITTEEHABITAT RESTORATION PLAN FOR THE LOWER TUOLUMNE RIVER CORRIDORCHAPTER 2To avoid problems associated with these classificationsystems, the Restoration Plan uses the“plant series” classification system based onSawyer and Keeler-Wolf (1995). This systemaccommodates the natural patchiness along theTuolumne River. Plant series consist of repeatingpatches of vegetation, usually comprised ofmultiple species, but always having one or twospecies that dominate. Series are stratified intocanopy, shrub, and ground layers, with the seriesname determined by the species of greatestrelative abundance within the highest strata(Sawyer and Keeler-Wolf 1995). The list of plantspecies comprising the stand defines the compositionof a particular plant series.Individual riparian plant species typically havefour life-cycle stages: initiation, establishment,maturity, and senescence (Figure 2-25). Thesestages are defined as follows:1. Initiation begins after a seed lands onexposed, moist substrate and germinates; thisstage continues through the first growingseason.2. Establishment begins after the firstgrowing season and continues until theplant has enough resources to begin sexualreproduction.3. Maturity begins when a plant first flowersand produces seeds.4. Senescence follows maturity, when seedproduction and reproductive capacity decline.The morphology of riparian stands is a result ofhydrologic, climatic, and fluvial processesinteracting with the life history of individualspecies. Over time, these processes vary mortalityrates at each life stage, resulting in variable anddynamic riparian stands. For example, a particularyear may exhibit high seedling mortalityassociated with a high flow scouring flood, whilelater, more moderate floods may encourageseedling survival on certain bank surfaces.2.4.1.1 Fluvial processes and riparian lifehistoryRiparian stands of the pre-1850 Tuolumne Rivercorridor were created and maintained by complexinteractions between the physiologic tolerances ofeach plant species and the dominant physicalprocesses, which includes:• hydrologic: magnitude and timing of flowinundation, and groundwater table fluctuation;• fluvial geomorphic: channel morphology (scourchannels, sloughs, floodplain/terrace elevations),channel migration and avulsion, finesediment deposition on floodplains andterraces, point bar scour, and woody debristransport.Hydrological processesAnnual streamflow patterns and riparian plantlifecycles interact to produce a dynamic relationshipbetween (1) mortality caused by surface orgroundwater inundation or dessication and (2)survival when adequate soil moisture conditionscorrespond to seed availability. High flows thatexceed the bankfull stage inundate floodplainsand recharge groundwater tables in floodplains,oxbow lakes, and sloughs. Historically, the timingof spring snowmelt floods coincided with seedreleasetiming of most woody riparian species(May-July), so when floodplain, oxbow, andslough surfaces were moist, airborne seeds landedand germinated on these surfaces. Point barsurfaces, generally at lower elevations thanfloodplains, were inundated during seed dispersal,which prevented germination.Occasionally, long duration spring snowmeltfloods had deleterious effects on certain riparianplants. Plants typically breath through their roots,but when roots are underwater they becomedeprived of oxygen, causing considerable stress tothe plant. Plants respond to inundation, coldtemperatures, and short photo period by goinginto dormancy. This increases their survival.Fremont cottonwood and white alder haveevolved pores in their bark called lenticels, whichincrease gas exchange to the plant during longterminundation, increasing their resistance.Fremont cottonwoods and white alders tend tobreak dormancy earlier than willows, and thislonger growth period benefit gives them anadvantage over willows. Under natural conditions,the longer growing season for cottonwoodsand alders, combined with willows being moresusceptible to scour mortality because theytypically grow closer to the main channel,resulted in a more equal distribution of species.Loss of winter scouring floods and long-durationinundation snowmelt floods has favored willowspecies (particularly narrow-leaf willow) andreduced natural regeneration of cottonwoods,reducing riparian species diversity and complexity.46
LINKING PHYSICAL PROCESSES AND SALMON LIFE HISTORYSpring snowmelt floods rose and fell gradually.After the peak, river water levels declined graduallythrough summer months (Figures 2-4 to 2-8,and 2-10). In some years oxbow lakes and sloughsdried up completely, requiring plant roots to followreceding moisture down into the soil column. Someplant species evolved rapidly growing roots tofollow the dwindling sub-surface soil moisture(Segelquist et al. 1993). During summer months,soil moisture gradients caused by varying elevationsrelative to the groundwater table createdstrong selective pressures on vegetation. Thesegradients, combined with local soil differences,caused distinctive zonation patterns in riparianCHAPTER 2Figure 2-25. A generalized riparian hardwood life cycle showing life stage, and mortality agents that affect lifestages.47
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Habitat Restoration Plan for theLow
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TUOLUMNE RIVER TECHNICAL ADVISORY C
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CHAPTER 3100Elevation (ft)110105100
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CHAPTER 3104Elevation (ft)195190185
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CHAPTER 3108Table 3-8. Wy 1970-1997
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134Relative elevation (ft)140130120
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CHAPTER 3136Relative elevation (ft)
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ADAPTIVE MANAGEMENT5. ADAPTIVE MANA
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ADAPTIVE MANAGEMENTmonitoring progr
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ADAPTIVE MANAGEMENTWILDLIFE POPULAT
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ADAPTIVE MANAGEMENT• Distribution
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REFERENCESREFERENCESAlderdice, D. F
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REFERENCESKjelson, M. A., P. F. Raq
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REFERENCESTID (Turlock Irrigation D
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APPENDIX AAPPENDIX AANNUAL HYDROGRA
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APPENDIX BAPPENDIX BTUOLUMNE RIVER
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VEGETATION SERIESNATURAL DIVERSITY
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VEGETATION SERIESNATURAL DIVERSITY
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Nature Conservancy Heritage Program
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215Scientific Name Common Name Loca
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APPENDIX BAPPENDIX B217
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Tuolumne River Report - U.S. Fish and Wildlife Service

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