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VOLUME 7: Ecosystem Studies / Interdisciplinary ApproachResource Management and PlanningInformation Technology

San Francisco, CaliforniaNovember 26-30, 1979

Sponsored by:National Park Service

andAmerican Institute of Biological Sciences

U.S. Department cf the InteriorNational Park Service

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1980

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RELATIONSHIPS WITHIN THE VALLEY FLOOR ECOSYSTEMS

IN WESTERN OLYMPIC NATIONAL PARK: A SUMIIARY

Jerry F. Franklin, U. S. Forest Service

Frederick J. Swanson, U. S. Forest Service

James R. Sedell, Weyerhaeuser Company

The major findings of the South Fork Hoh River researchteam emphasize interrelationships among components ofthe Olympic valley-bottom ecosystems. Geomorphic struc-tures provide the basic template for both terrestrialand aquatic communities. Vegetation has significantreciprocal impacts on geomorphic processes, however,and is a major element in formation of the most produc-tive aquatic habitats. The South Fork pulse illustratesaccomplishments possible with intense, short-term inter-disciplinary research efforts and the valuable functionsNational Parks can perform as benchmark areas to comparewith exploited land systems.

Preceeding papers considered geomorphology (Swanson and Lien-kaemper 1980), forest communities (McKee et al. 1930; Lambert 1980),Roosevelt elk (Jenkins and Starkey 1980), and aquatic habitats andcommunities (Ward and Cummins 1980; Sedell et al. 1930). There issome tendency to lose sight of the entire valley-bottom ecosystemin these more component-oriented presentations, however. .

The objective in this paper is to Izeapitulate the majorfindings of the South Fork research pulse with an emphasis on inter-relationships among various components and processes. We also suggestbroader implications for pack management and point out how the parkis serving as a control or baseline site for interpreting man'simpacts on adjacent managed landscapes and establishing guidelinesfor improved management. National Parks provide the rare opportuni-ties to study natural, undisturbed valley bottom forests and riverecosystems.

GEOMORPHIC RESULTS

Landforms can be viewed as the template on which the terrestrialand aquatic communities of the valley-bottom ecosystems develop.

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While geological processes determine the initial conditions, biolo-gical processes are significant modifiers. Vegetation-geomorphicinteractions are particularly important in the cases of smallstreams and river bars and teri.:ces which are entirely the interplaybetween vegetation finviaf, processes.

Woody debris creates acme o f the most conspicuous vegetationinfluences :xi geomorphic processes. Fluvial processes mobilize largeamounts of woody debris, particularly by undercutting and uprootingtrees on f-)rested alluvial flats and higher terracas. Stabilizeddebris in the main river channel is important in g etting up gravelbars, protecting pioneering vegetation from high flows and frombuffeting by floated organic debris, and regulating flow into riverside channels, thereby creating the especially productive off-channelaquatic habitat. Woody debris in off-channel and tributary habitatsalso provides physical stability (Swanson 1980), a diversity of biolo-gical habitats, and an ecosystem energy base both by retaining fineallochtonous material and directly through decomposition (Cummins 1980).

Four major categories of aquatic habitat are identifiable inriver valleys: the main river channel with fast, turbid, silty water;river off-channel, such as side channels partially isolated from themain stream; terrace tributary, which is low gradient and generallycarries clear, slow-moving water; and valley wall tributary, typicallya high gradient stream with clear, fast water. Geomorphic, hydrolo-gic, and vegetation factors combine to determine the basic types andarrangements of aquatic habitats.

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AQUATIC RESULTS

Off-channel and terrace tributary habitats are of overwhelmingimportance for product ivity of aquatiz ecosystems of the South Forkand similar, broad, alluviated valleys in western Washington. Theserelatively protected sites have abundant, diverse food resources forboth invertebrates and fish. Coho and cutthroat trout use theseareas for rearing. Terrace tributaries provide important shelterwhen the main channel is in flood.

Glacial silt limits productivity of some parts of the mainchannel ecosystem, but not others. Primary production in fast waterareas of the channel is severely limited by the scouring action ofsilt and fine sand being transported in suspension much of the year.Silt deposition in the few quiet water sites of the main channelprevents potentially very productive areas. Spawning is not greatlyreduced by the fine sediment because hydraulic conditions preventexcessive accumulation in the major spawning sites where pools tailout into the heads of riffles.

Productivity of valley wall tributaries is limited by theextremes of high and low flows and the dense conifer overstory whichreduces primary production by shading. Limited pool area and thedifficulty of moving from pool to pool along these high gradientchannels constrain use of valley wall tributaries by fish.

Large organic debris is an important factor in shaping micro-habitats in each of these types of stream environments.

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TERRESTRIAL RESULTS

The forest communities are strongly related to landforu orgeomorphic surface. Alnus rubra stands dominate youthful fluvialdeposits and mature Picea sitchensis-Tsuga heterophylla forestsoccupy older, higher surfaces. In the study area different Picea-Tsuga cot unities are formed on upper and lower. terraces, althoughdominant trees on both terraces are approximately the same age andcannot be considered successionally related. The vegetation-landform model proposed for the main fork of the Hoh River (Fonda1974) does not fit the South Fork, which probably reflects histori-cal differences in timing and patterns of forest disturbances suchas floods.

Mature valley-bottom Picea sitchensis-Tsuga heterophylla forests contrast with those found elsewhere in the coastal Picea sitchensis zone of the Pacific Northwest (Franklin and Dyrness 1973).Stands, especially those on lower terraces, are open with relativelylow density of above-ground biomass and numerous openings of up toa hectare or more. Picea is reproducing successfully, earningrecognition as a climax tree species on these sites. While there?ative success of Picea and Tsuga reproduction appear to haveoscillated over the past century, there is no evidence that eitheris going to be replaced successionally. Crazing by Roosevelt elkis a factor that may favor survival of Picea reproduction over thatof Tsuga, but grazing is almost certainly not the sole cause ofvariation in reproductive success. Wind and floods appear to bethe major environmental factors disrupting these valley-bottomforests while wildfire appears to be inconsequential.

Coarse woody debris is an extremely important structural featureof the terrace forests. Woody debris occupies much of the forestfloor and contains large masses of carbon and nutrients. Reproduc-tion of trees on older terrace surfaces is confined almost exclu-sively to rotten logs and associated stumps and root wads. Logsvary significantly in their value as nurseries depending upon logspecies, decay state, and terrace level. Forest renewal is dependenton seedbeds of coarse woody debris.

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APPLICATIONS

The South Fork of the Hoh River appears to be the arch type ofthe western Olym7 s ic Mountain river valley ecosystem. Fluvial land-farms and proces:,es, mature Picea-Tsuga terrace forests, and valley-bottom aquarlc habitats al:e well represented. The valley habitatshave undergone minimal modification from adjacent mountain sideslopesand river tributaries in comparison with the other four major rivervalleys of the western Cl)Lpic Mountains. It therefore seems appro-priate to manage and utilize the South Fork valley as a primary sitefor research on Olympic rainforests and associated streams.

Recognition that off-channel and terrace tributary habitatsare aquatic hotspots and essential to anadromous fish in the Olympicriver valleys has implications for managers inside and outside thepark. Park managers should locate trails, road, and other develop-

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rents so as to have minimum impact on these features. Resourcemanagers outside the park should appreciate the importance ofproviding off-channel and terrace tributary habitats with at leastas much protection as the main channel. Rehabilitation of suchhabitats may be essential in areas where they have beer; destroyedby logging or road construction activities.

The significance of woody debris is further documented for bothscientists and resource managers. Debris can now be seen to playimportant roles in larger streams and rivers, roles which must beaccounted for by land managers in programs of riparian managementand stream cleanup. The role of woody debris as critical seedbed incoastal forest types has implications on lands managed for timberproduction as well as on lands reserved from development.

CONCLUSIONS

The South Fork study demonstrates the use of a National Park andBiosphere Reserve as a benchmark site for scientific research and acontrol area for adjacent manipulated landscapes. The only remainingnatural examples of river valleys in the coastal region are withinOlympic National Park. The knowledge gained in the pulse study hasextended our understanding of northwestern ecosystems to a distinctive 4variant (the rainforest) and a larger scale (river drainage).

Finally, the pulse in the South Fork of the Hoh River demonstratesthe numbers and types of data that can be gathered by an interdisci-plinary research team in a short time span. A successful project isb4 • sed on substantial logistical planning and a balance between carefuldriinition of objectives and ample opportunity to pursue promisingleads and for serendipitous discoveries.

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References Cited

Cummins, Kenneth. 1980. The multiple linkages of forests tostreams. In Richard Waring, ed. Proceedings 20th Annual Biology

Colloquium. Oregon State University Press. Corvallis, Oreg.In Press.

Fonda, R. W. 1974. Forest succession in relation to river terracedevelopment in Olympic National Park, Washington. Ecol. 55(5):927-942, illus. 4

Franklin, Jerry F., and C. T. Dryness. 1973. Natural vegetation of Oregon and Washington. USDA Forest Service General TechnicalReport PNW-8, 417 p., illus. Pacific Northwest Forest and RangeExperiment Station, Portland, Or..ag,

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Lambert, Robin Lee. 1980. The biomass, coverage, and decay ratesof dead boles in terrace forests, South Fork Hoh River, OlympicNational Park. American Institute of Biological Sciences. Second `';nnfereuce on Scientific Research in the National Parks.

McKee, Arthur, George LaRoi, and Jerry F. Franklin. 1980. Struc-ture, composition, and reproductive behavior of terrace forests,South Fork Hoh River, Olympic National Park. American Instituteof Biological Sciences. Second Conference on Scientific Researchin the National Parks.

Sedell, J. R., P. A. Bisson, and J. A. June. 1980. Ecology andhabitat requirements of fish populations in South Fork Hoh River,Olympic National Park. American Institute of Biological Sciences.Second Conference on Scientific Research in the National Parks.

Swanson, Frederick J. 1980. Erosion as an ecosystem process. InRichard Waring, ed. Proceedings 20th Annual Biology Colloquium.Oregon State University Press. Corvallis, Oreg. In Press.

Swanson, Frederick J., and George W. Lienkaemper. 1980. Inter-actions among fluvial processes, forest vegetation, and aquaticecosystems, South Fork Hob River, Olympic. National Park, Washington.American Institute of Biological Sciences. Second Conference on Scientific Research in the National Parks.

Jenkins, Kurt J., and Edward Starkey. 1980. Home range and habitatuse of non-migratory elk (Cervus elaphus roosevelti) in OlympicNational Park, Washington. American Institute of BiologicalSciences. Second Conference on Scientific Research in the Notional Parks.

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Ward, G. Milton, and Kenneth W. Cummins. 1980. Habitat and foodresources for invertebrate communities in South Fork Hoh River,Olympic National Park, Washington. American Institute of Biolo-gical Sciences. Second Conference on Scientific Research in the National Parks.