Glenn M. Hawk Department of Forest Science Oregon State University Corvallis, Oregon 97331 tggetationMapping and CommunityDescription of a Small WesternCascade Watershed Abstlact \Tatershed 10 is a 10.24 ha watershedp-reviously used as an intetrsivesrudy site by the Oregoo"rhe ConiferousForest, Biome..projecr of the tJS/lBp ilnternational Aiobgiiri p;gram,.'Through useoi.an.esrablrshed trail andgri-d sysrem as well asa sremmap ofdl treeigrearerthan'i5 cm cDn,+ Lqrndrvrdual map unrrs ot ptanrcommuniries were delimited. These nere grouped into seven pluflrcommunures a-od tour habrratrypes. I mapand describe sttuctural vegaatio! characteristics of lheiecommunirres lor rheenrire ware.\hed Introduclion Compreheosivestudies of ecosysremprocesses, such as nufiient and carbon flow and cycling, require thorough basic biological and physical descriptionso{ the system.The "state need for the basic suweys or descriptionsto provide variable" data essentialto ecosystemmodeling efforts is often unappreciated.Eveo lessunderstood is the potential use of vegetation or plant communities as a basis of stratifying a srudy area into en- "compartments." vironmentally and biologically homogeneous Such compartmenrsor subareascan be particulady useful when dealing with a diversetract such as a mountain watershed.Various processes,such as transpiration or photosynthesis,ian be simulated separately for each compartment, eliminatiog rhe less desirable approach of developing a single averagevalue for an entire, often highly diverse,watershed. The basic approachused in describing the plant commuoitiesand habitat types of ITatershed 10 (Y/S-10) and the resulting descriptioosare the subjectsof this paper. Iflatershed 10 was an intensive study sire for the Coniferous Foresr Biome project o{ the US/IBP and is the presentsite for postJogging perturbation studies.The basicvege- tation surveywas an esselrial element in determinationof standing crops and in indeo- rifying environmentallyhomogeneous areas within this diverse watershed. There are severalpurposes to this paper: first, to document rhe approachfor others facedwith similar tasks;second, to provide a historical record of the original vegetation of this watershedwhich had been clearcut in 1975 as part of further srudies;rhird, to provide quantitative characterizationof the composition and sffucrure of an extensive area of old-growth Douglas-fir (Prc&d,orragamenzieii) {orest; and finally, to alert in- terested scieotiststo the availability oe an accuratestem map ol a Iarge, conlinuous forest areatogether with the associatedstem data set. SludyArea \Tatershed 10 is a 10.24 ha watershedlocated adjacentto the sourhwesterl tip of the H. J. Andrews Experimental Forest (Fig. 1). Elevationsrange from 430 m o 670 m. Slopesaverage about 45 percent, but often exceed 100 percenr. Soils are classified as 200 NorrhwestScience. Vol. 51. No. J, 1979 I ,/l .) .t^-l ,/ I I t I ( ) ) HJ.A€xPFOR.[ l-\ f\--.- I -J WS.I I I -F--'. t*_ - -t (' L-_ _ -___i -*_Y::___.,JaJ,COqtr:-o5 MILES \Watershed Figure- 1- Lolarion of 10, H. J. Andrews Experimental Forest, cedtral western Cascades .f Oregon (Number:highway number of highways generally parallel to maior rivers). Mapping and Description of a l7esrern CascadeNTatershed 20I Typic Dystrochrepts.They typically range {rom gravelly silty clay loams to very gravelly clay loams,and are derived from volcanic tuff and brecciacolluvium parent materials. Climare is typical of westerl Otegor Cascadeswith 2300 mm annual precipitation (75 percent between Ocober aod March) and common snow accumulationof short duration. Two years of on-site climatic data show ao averagedaytime remperatureof 21"C for July and OoCfor January.Extremes range from 41"C in August to _20. C in December. Methodsand Terminology Throughout this paper sevetal classificatiol terms are used which need to have rheir origins and meaningsclarified. The classificationsystem presertly in use is the Habirat Type system.It is an ecologicalsystem which groups similar forest plots into natural and reasonablyconsisteot homogeneous unirs of climax forest. Habitat types are defioed by landform and environmentalvariables and named by vegetarionvariables. The lower echelonhierarchical units include the community,which is used as either a generalterm for discussingdifferent entitiesor a term which includesa group of standswhich ate not yet advancedenough to consider as climax. The climax forests are called associations. and each association occurs on a habitat typ of the same name The habitat type includes all land areascapable of supporting standsof any seral stagewhich demoostratethe po_ tential of developingto a single climax type. A classificationkey (Dyrness et at., t9i4) was used ro identify all map uoits in this str_rdy.Several seral communiries identified in the key have more than one possibieseral direction so thar slope,aspect, and landform as vrell as adjacenrvegetation types wete used to determine habitat tvpe of setal com_ muniries.Seral derelopmenr of srand.in WarershedI0 was con,idereclequivalenc ro that described by Dyrnesset al. (19741 for the H. J. Andrews forest. A slope-corrected25 m x 25 m grid systemwas establishedas a refereflcesystem for the entire watershed.Aluminum corner stakeswith number tags were iostalleclat each grid corner.AI1 rreestems with a dbh rdiamererbreast high-1.37 m) ) 15 cm were mapped, and tagged wirh sequentialiy numbered aluminum taqs. Dar;lollecrion in- cluded tree species,dbh, location,and ooteson the uigo, and crown conclidon.Logs and stumps wete also mapped. Logs and stumps ate mapped within 2 m of rheir actual .lo_ cation(Fig.2). Vegetatioo mappiog rvas begun in eariy summer using a reconnaissancetechnique (Franklin, Dyrness, and Moir, 1970). Speciesand cover classesq,ere lisred for four strata within eachof the 411Ireconoaissaoce rnap units using an opeo legend mapping system.The size and shapeof each unit were determined by understory plant species aod given the community name in accordancewith Dyrness, Franklin, and Moir (1974). The four strata include: (1) oversmly canopy including marurc oversroryrrees dgwn o dbh of 15 (2) l ) cm, understorytree stratum including all size classes( 14.9 cm dbh of specieswhich typicaily attain tree staturein this region and commuoiry, (3) tall shrub stratum, and (4) low shrub strafum. Herbaceousspecies were noted aod inciuded in the map spnbol in instanceswhere it was felt to be an aid to the final classificationof the map unit. Cover $,as esrimatedusing Daubenmire (19)9) cover classes.The major planrs of each sffarurn were listed in order of rhei! cover ciomr[ance follo*'ed by a single digit indicative of the combined cover classof the stratum. Indi- vidual map units were identified aod drawn on slope-correctedfield maps rhloush the 2D2 Hawk - " i-Fp-"q,,l-1- i :t .' ffi"1| ""#,\u" <3'"/l';.[\\ jl T\zE='l?:";'' I L "ccz\- -} or" l, "*q -z:', o-=/ree - _ s/.eo_n ': = 51"-P '- "t--_-:t zs^ .- = /.",t Q.,T FigLrrc 2. S3m_plcsrem map and vegetation unit map of selected grid sections of \(atershed 10, H- l. Andr("5 FxDerimenlalFores(. use of the mappedand taggeduees and the coroef Post numbels of the grid sections' The area (in ha) of eachof the map uoits and the percentagesof cover wirhin them were calcr:latedwith the aid of an electronicgtid counting device rVS-10 In August 1973, 16 samPlePlots were establishedwithin to obtain prelogging data io a study of early successionwithin habitat types found in the watershed These successiooalstudy plots were placed within previously identified and mapped habitat typesin proportioo to the percentageof Watershed 10 areaoccupied by the rype. Initial mapping and data from rhese36 sampleplots have been usedas the basedata for \X/S-10 preh,ggingplant communrr y descriprions. The sampleplots were rectaogular,15 m x 10 m in dimension,slope-corrected, and oriented parallel to contour. Each plot was permaneotlylocated by placing metal corner postsreferenced to severaltree tags aod/or numberedgrid corner stakes.Data collecrion iocluded the following: (1) Trees: caoopy cover of mature trees ()15 cm dbh) esti- matedby species;total densityof cooifer sapliogs ( I 1 rn tall ( 15 cm dbh ) , speciesden- sity; density of conifer seedlings( )1 m tall) within rePreseotativesubsamples of each plot ( 15 m by 1 m strip abovethe top, middie, and bottom lines of eachplot : 4) m!); (2) Shrubs: cover and frequency estimated by line intercept along top, middle, and bottom lines of each plot; (l) Herbs: cover and frequencyof herb and moss species estimatedwithin 45 mictoplots (each 2 x 5 dm tectangles) spacedat 1 m intervals adjacentto and below the top aod middle plot lines and abovethe lower PIot line; (4 ) Other: cover of stone.lirter. and mineral soil estirnatedwithin eachof the 45 microplots; lisrs made of plant speciesin each ptot; Photo Poiots establishedand photos taken in summerand fall at eachplot ptior to logging; and 16 selectedspecies were measutedfor leaf areaindex aod biomassdata. Results The 414 map units were grouped into seven communities: (1') Tuga heterophylla/ Mapping aod Descriptionof a \Testern CascadeN/atershed 201 Castanopsi.rchrytophylla (T$e/Cacb), (2) Twga bererophjlta/Rbod,od.endronnzdcro- phyllum/Gaultheria shallon (.7$e/Rhma/ Gash), (3) Tvga ieterophytla/Rhododend.ron macrophyllum/ Berberisnenosa (T she/Rhma/Bene), (4) Tuga heterophylla/Acercit_ cinatatn/Polytichum muni.tunt. (T the/ Acci/pomu), (5) pseudotwga menziesii/Acet oircinatum/Berberit nerttov (Prme/ Acci/Bene), (6) pseudoxuga menzieii/Acer cir,