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
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\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, cinatum/Gaultheria allon (fume/Acci/Gafi), and,(7) ripariao ( Fig. 3). The first six are equivalent o associationsand communitiesof the H. J. Andrews ExperimentalForest (Dyrness el al., 1974) and span most of the low-elevationmoisrure gradienr for the western Cascades.The riparian community is in fact a complex of stream_associated vegetation types currently under study (A. Campbell,pers. comm.). Each of the com_ munities or habitat types (HT) is describedbelow and its distribution on \x/s-10 is shown io Figure 3. The vegearion map does not show ecoronesbetween communities,although thev are preseor at least to some degree.Observed ecotones between major u"g",u,io"otyp". wele generally narrow, particulady betvreenthe environmentally more exffeme com_ mul;lties (T:he/Cacb and the Ttbe/Acci/poma communities) and any adjacenrcom- munity. Io somecases the ecotolleswete severalmeters wide as in the gradual transitions berweensetal and climax commuoities on the samehabitar rype. Ecotonesberween the T:be/Rhma/Gash ard, the Tsbe/Rhma/Bene habrtat.yp., -. ,r,or. subtle than those
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Mapping and Description of a \flestern Cascadelflatershed 205 betweeneither of these two communities arrd,the Tthe/Cach or the Tshe/Acci/pomu communiry. Mapping at small scale,the ecotonescould easily be drawn on S/S-10 maps, they but would be of lirle use in the context of intended usesof the rrrap. Basically, \75-10 was a mixrufe of old-growth and second_growthstands occurring on a mosaic of substrates. This variability in soil depth, slope, and aspecrexplains io part the mixing of climax communidessuch as rhe Trle/ Cach,Tshe/Rhma/Beie, T:he/ Rhma/Ga$, and the T the/ Acci/pomu associatiots wirh seral foresr stancls such as the Ptme/Acci/Ga$, Psme/Acci,/ Bene, and po.ions of the riparian communities.Fire his- tory has undoubtedly played an important role in the formation ancl developmeot of plant communitieswithin \75-10, as have bark beetlesand rvindthrow. Slope and aspectaffect plant community developmentthrough their effect on stand history; for example,fires, which are known ro be e continual sourceof disturbancein N7S-10,tend to be both more liLely and more intense on southedy aspects.Fires also havea greaterrotal effect on steepslopes than on gentle slopes.past disturbance,erosion, and deposirionyield differencesin soil depth and quality. The result is a watershedwith a mosaic of different age classedforests having complex historic involvemeocro specres distribution and structure. A completelisting of \fS-10 treesincludes 2g1j stems ) 15 cm
206 Hawk the vegetation stratification of the watershed.Peculiarities exist in that Pseadotnga menzieti,i, is reproducing in faidy large numbets ovel a wider range of the hypothesized moisrure gradient (Dyrness e, al., 1)74) than is rypical. This apparent aoomaly is probably the result of sampling, since study plots were placed (where reproductive size classeswere all estimated) within habitat types in order to sample the variation in the caoopy cove! of each rype. Therefore, open staods wete sampled in each habitat type. It was the open stands which included large portions of the Ptet/d'ott Ba menzietii rc' productive size classes.
TABLE 2. Coniier reproaiuciion within iour habilal t}?es o; Watershed 10 (stems pe! nar.
species lsrgr Thula Pinus C{loceilrua Eabiiai lype heteroDhyla plicd{ hmhorlhnr alecrrreng % ol ws-10 Area (ha) Seed. Sapl. Seed. SaDl. Seeat. Sapl. Seed. Sapl. Seed. Sapl.l
Tstrsa heterophylh/ Casirnopsis ehrtsoDlrylla 426 241 190 113 31 103 3!r.2 4.02 Tstrsa heierolhylltt/ Rloalodenihon macrorhyllum/ Grulihe a shallon 5? 419 305 209 ttl 31.17 3.19 Tsuga Ieterorhylla/ lihododandron Innerophylum/ BcrD€ris nerYosn 33 140 306 280 93 17.t3 1.?9 Tsuga hetcrorlhtlla/ ..!.cer chclnalr / Polystichtrm munitum 33 217 2E3 17 12.00 L.24 lseed:seeaUincs< l mtall; sapl.:saplinss > 1mtall and < 15 cm dbh.
Tsuga heterophylla/Caslanopsischrysophylla associations (Tshe/Cach) This communiry is the most widespreadone on \)/S-10 (Table 3, Fig. 3) . It is generally located on both north and south bounding ridges of I7S-10. \Testerly aod southedy asPectsare most commoir The overstorylree straflrm here is typically quite open rela- tive to other forest rypes common to the area-Over 43 percett of the 0-cover classin \flS-10 occursin the Tshe/Cach habitat type. Most of the Tshe/Cach habitat tyPe occurs beoeatha very sparseprimary tree canopy with 92.1 percen! of the communiry haviog lessthan 50 perceot cover in this layer. The canopy of the understorytree stratum is very dense,reflecting the oPen over- story. Here 31.7 percent of the open uodeistory tree sffarLrmof N7S-10is in the Tthe/ Cach habitat type. However, a much greater amount of the Tshe/Cacb habitat type occurswith a deosetunderstory tree cover- The T$e/Cach habitat type in WS-10 contains 1138 trees ) 15 cm dbh. Of these, 39 percentarc Castanopsitchr:ophylla,but only eight of them exceed30 cm dbh. Thirty- rhree perceo! of the trees arc Pteulolnga menziesii; the speciesis well representedin the larger size classas well as reproductive classes.It is the dominant tree speciesand its abundancein the reproductive size classesinsr:res its presencein late seral stages. Tuga heterophyLlais another commoo understoryconifer. A good iodicator of rhe xeric narureof this habitat type ls Pinus lambertiana,Eighty- rwo percenrof the treesof this speciesoccur vrithin the T e/Cacb habitat type of $7S-
Mapping and Descriptionof a Western CascadeN7atershed 207 10. Someare over 120 cm dbh, ahhough most are considerablysmaller. Other less im, portant trees in this habitat type include Tb*.ja plicata, Calocedrusdecurtens, Acer macro, phyllum, Taxu breaiJolia, Cornas w.ttallii, ar'd Arbutut menziesii, Principal understory plant species and rheir cover values are shown in Table 3. The shrub stratum is dominated by Rhod,odend.toamacrophyLlum followed in importance by Acer circinatatn in the tall shrubs and Gaubheria $allon followed by Berberis nervosa in the low shrub layer. The herb layer is poorly developedand is dominated by Xero- phyllum tenax,Li,nnaea borealis is also a common species.Moss cover is low, but 9 to 12 speciesare commonly present. ^IheT$e/Cach habitar type is similar to both the Prme,Tthe/Cococaard the Psme/
TABI-E :1. Percent cover oi important plant species wjthin Watershed 10 Habiiar TyDes (from an alyiic plots) and the riparian zone (Ders. comm_, A. Campbell)_ (i-<0.5% cover mea sureal; +:present in lrlois ; M:maiure ; R=reprod.),
Tshe/Cach Tsh€/Iihma-cast Tsho/Rhma-Bene rsh€/Acct/pomu Ripadan
}I 18 2{, 22 11 + P' 2il E 6 +
M 15 16 43 R 5 18 13 11 + Thuja }I 19 11 1 R, 32+
macrophyllum M -4 420 + R t3 1t+
lambertiana trt l1 1, R 42 1
crysophylla M 40 1 2- Trll Ahrub layer Acer circinaium 13 30 29 1$
49 23 t25 Cornus nuliallii E12 168 + 1J1 1i+ Taxus brevilolia 77 810 Corylus cornuta 24 Ios. Shrub Lryer Gaullheria shallon 45 25 183 + Berbeds nervosa 64 146 + II€rb Laycr Xerophyllum tenax 13 I t Polysiichum munitum 1 5 3 27 + Linnaea borealis 4 4 4 + Syniheris renilormis t 1 I + Copiis laciniala i 4 4 + Viola sempervirens t 1 + Trillilrm ovaium i + Vancouveria hexandra I + WhipDlea modesla I 1 + O).rlis oregana - + Aralia calilornica l + Adiantum pealatum + Blechnum spicant +
208 Hawk Hodi habitat type of Dyrnesset al. (l)14) in its physiographiclocation, but the extreme developmentof the shrub layer distinguishestheTthe/Cacb habitat type
Tsugaheterophylla/Rhododendron macrophyllum/Gaullhe.ia shallon association (Tshe/Rhme/Gash) This habitat type occupiesonly about 10 Percent of I(S-10 (Table 3, Fig. 3). It is typically patchy in disribution and locatedmidway berweeoridgetops and major drain- ages.It is a mote mesic habitat rype than the Tshe/Caci habitat type (7obel et al., 1976) . The overstory tree stratum is commonly more dense thao that of the Tthe/Cacb habitat type. Again, the understorytlee stratum is commooly denserthan the overstory strarum with ody 21.1 percent occurring with less than 25 Pelceot cover. The habitat type containsao averageof 292 ffees large! than 15 cm dbh per ha. Of these,45 percent are Pseud.otsugamenziesii, which is found in nearly all size classes.The bimodal dis- tribution o{ Pteudotswgamenziesii it this habitat type is similar to that found for WS- 10 as a whole (Table 1). Tree density here is greater than in any other habitat tyPe mapped. The understory ffee stratum is dense and composedof conifers and hardwoods. Ca$anapJit chrltophylla doesnot play as inportant a role in the toral canoPycover io the T she/ Rbma,/ GasZ habitat type as it does in the Tshe/ Cach habitat type. It is largely replacedby pole and sapling size classesol Tsuga heterophylla.Floristically, the T:he/ Rhma-Ga:h habitat type is similar to the Tsbe/Cach habitat type. The moderatelyweli developedtree layers do not prevent the developmentof a fairly dense tall and low shrub layer (Table 3). Rbododenc on macrophyllum dominates the tall shrubs with Acer circinatatn a common associate.Gaubheria shallox ar'd Berberit nerttosa domiaate the low shrubs.The herb layer is poorly developed.Linnaea borealiq Xetophyllum tenax, Cbitnapbilaunbellata, ar'd Pollsticbam manirum are the most commoo species,but even theseare found in small amounts.
Tsugaheterophylla/Rhododendron macrophyllum/Berberis nervosa association (Tshe/Rhma/Bene) This habitat rype occupies8.71 percent of \flS-10 (Table 1, Fig. 3). It is located pri- marily on northwest aspects,and ocors on a variety of slopes.It approximatesthe cli- matic clima-r habitat type at low to middle elwations (Dyrnessel al., 1974). On $fS-10 the Tshe/Rhma/Bene qpe has between 1 and 50 percent cover in the ovelstory tree canopy-However, the understory tlee sffatum is generally quite dense. TheTthe/ Rhma/Bene habi,tattype contains265 treesover 15 cm dbh per ha Of these, 47 percentarcTsuga heterophylla,Most of the Trzga is in small sizeclasses. Preutlotrltga menziesii ls the next most abundant tree and is the domioant uee as it makes up the total of larger size trees in this habitat type on \(S-10. Smaller size classesof Prcudo' tsuga menzietii ate also ptesent. The tall shrub stratum is generallyless developed than in the more open Tthe/Cach ald Tshe/Rhma'Gash habitat types. It is dominated by Rhod'odendronmactophylhtm atd. Acet circinatum. Vaccinium paniloliam is also common- Betbet'is netvou ar'd Ga*ltheria shallon dormtate a moderately developed low shrub Iayer. Linnaea botealit is the dominant herb (Table 3).
Mappiog and Description of a 'ifestern Cascade$Tatershed 209 T_suga_helerophylla/Acercilcinatum/polystichum munitum associations (Tshe/AccilPomu) This habitat type occupies11.0 perceor of S7S-10 ( Table 3, Fig. I ) , almosrall of *,hich is adjacent to the drainage systemin the lower portions of the warershed.Two small portions of VS,10, one on a bench and the other in a slight depression,have also been included in this habitat type although they probably more closely resernblea Tsuga betetophylla/Polyttichum munirum habitat type (Dyrnesser at., 1974). Cover in the oversroryrree layer here is generallymoderate. The Tthe/Acci/poma habitar rype contaios 258 trees over 15 cm dbh per ha in VS-10. Of these,44 percent are Ts*ga heteropbylla,Agaio, most of the Tsuga are io small sizes. Dominance of Prcutlotsugamenzie.cii in the overstory uee layer is still evideot. There ate, hovrever. fewerJarge rrees per ha in rhis habirarrype. The tall shrub layet is moderatelywell developed.Acer circinatum, the dominant, is parchy io distribution and low in statute.Rhododendron macrophyllum, an occasiooal associate,is also lessrobust than thet found in other upland comrnunities.The Iow shrub stratum is dominated by Berberit neruosa. The herb strarum is dominate P_seudolsugarenziesii/Acer circinalum/Berberisnervosa community (Psme/Acci/Bene) This community occupies8.8 percent of \fS-10 (Fig. 3). The prme/Acci/Bene com_ munity occursadjacent to the Tsbe/Rhma/Beaa community in almost all casesand rep, resentsa seral community within the Tthe/Rhma/Bene habitat type. The overstorytree layer of the Psme/Acci/Bene community is open and patchy in distribution. The over_ story tree layer is similar to that io the T$e/Rbtna/Bene community in that it has a small percenrageof the community occurring beneathcover classes0 ard I. The psme/ Acci/Bene community in \75-10 cootains an averageof 257 trees larger thal lj cm dbh per ha. Here 45 percent ate Tsuga, mostly of small size.There is also understory PJeulotJ./|gdmenzietii, evidenceof the open nature of the community. The overstory tlee sffatum is dominated by scattered old-growth pteadottr.ga menziesii with only a fyw Tnga heterophyllain the large size classes.Ttuga betero,phylladominates rhe un- derstorytree stratum with T huja plicata as a major associatein someareas. The rall sfuub strarumis dominaredby I cer circinatum.Rhod.od,entlron maoophyllum is colrstant,but with low cover.Low shrubsare dominated by scatteredBerbetis ne,cota, though Cauhhetia shallon is also common. The herb stratum consists of a mixture of plants common to dry to mesic sites which iodicate that the communlty may occupy slighdy drier and warmer and more open sites than the climax Tthe/Rhma/Bene coi- muniry. This fact explainsin part why Acet circit at m dominatesthe typically lessmesic seral stage ol the Tsbe/Rhna/Bene habitat rype rarher that Rbodod.end,ronmacro- p hyllum. P-seudotsugamenziesii/Acer circinatum/Gaultheria shallon community (Psme/Accilcash) This community is the secondmost abundanrplaot community within VS-10 (Fig. 3). 210 Hawk It occurson a variety of slopesand aspects.The Psme/Acai/Ga$ communiry normally occursdownslope of the Tthe/Rhrna/Gatb or Tshe/Rhma/Bene commun.ities.Like the T$e/Cach community, the Ptme/Acci/Gasl community has a sparseoverstory tree layer cover.Over 81 percentof this commr:nityhas less thao a 25 percentovelstory cover' The understorytree layer of the Psme/Acci/Garl community is patchy. The total oPeo areain the overstoryhere is 30 percent of the cover class0 of WS-10. The understory0 cover classof this community accountsfor 51.1 percent of that classon VS-10. The Ptme/Acci/Gaslr community cortai,ts 222 uees over 1) cm dbh per ha. Tswga heterophlla ard Pseudotsugattenzietii have neady equal densities (38 percent and 36 percentof the rotal, respectively) . PJe dot; ga nenzieii domlnatesin total cover, how- ever. Smaller size classesare vrell stockedwith both Pteudotwga menziesii and Tsuga beterophylla, Acer cbcinatum domioatesthe tali shrub layer.This straaurnmay also contain small amouots of Rhododendranmacrophyllam. Gaubheria thalLon occttrs with high cover valuesand dominatesthe low shrub layer, occasionallysharing domioancelocally with Betbetit nentota.Mosses are moderatelywell developedin the more protectedareas but occut with low covervalues. RiparianCommunity The ripariao community is the most Iimited of the sevencommuoities in WS-10 (Fig 3). It occursmainly aloog the streamcourses at low elevatioosand adjaceotto the T$e/ Acci/Pomu community. The overstory and understory ttee strata generally have be- tweeo 25 and 50 perceotcover, providing an oPenappearance. Stem maps show a marked increasein the number of logs on rhe ground surfacewithin this ar,d the adlacen Tshe/ Acci/Pomu community comparedto other plant communities on $?S-10. The overstorytree stlatum of the riparian type is dominated by PvudorruS.l Tnen' ziesii and T:uga heterophllla. with local concentlatioosof Acer macrophyllum, Thuja pLicata,and Alnus tabru. The understory ffee stratum is dominated by Twga hetero' PhylLa. The tall shrub stratum containsAcer cfucinlrkm awl Vaccinium parttifoliatn; Arulia californica also occutsand is an indicator of the ripariao environment.The sparselow shrub layer has scatteredGa*ltheria shallon ar.d Berbetit nenosa The herb sttatum is composedof a large number of moisture-lovinggenera. Some small ateasof less common commuflities are iocluded in other majol com- muniries. Ooe of rhese occurred often enough to warrant mention, the XeropbylLam "Xete tendx open (Xete open) type. The opeo" areasocctlPy 0.73 percent of I7S-10, or nearly as much as the ripatian community. It usually occuls on open slopesor ridge- tops or near rock outcropswhere soil developmentis limited. The Xere open tyPe occurs most abundantly (91.1 perceot of it) within the T:he/Cach habitat type. HabitatTypes The sevencommunities have been combined into four habitat types (HT) for stratifi- cation of the physicalenvitonment aod vegetationduriog the modeling effort in VS-10 The habitat typesare: ( 1) T:he/Cach HT, coosistingof the areaoccupied by the Tshe/ CacDcommnnity; (.2) Tshe/Rhtna/Garl HT, consisringof the combinedareas occupied by the Tsbe/Acci/Gash a*f Tthe/Rhma/Gath commuoities; (3) Tthe/Rhrna/Bene HT, an area occupiedby the Tshe/Rhma/Bene aod the Psme/Acci/Bene communicies; Mapping aod Description of a Western CascadeWatershed 211 and (4) the Tsbe/Acci/Pomu HT, which combines the areasoccupied by the Tthe/ Acci/Pamu atd riparian communities (Fig. 1). The commuliries and habitat types representedin WS-10 are similar ro standsrep- reseotativeof their respectivetypes on other portions of the H. J. Andrews Experimental Foresrand other western Cascadesites in Central Oregon (Franklin et al., I97O; Frank- lin and Dyrness,1973; Dyrnesset al., 1974; Franklin el at., 1972). Summary \Tatershed 10 is a mosaic of mature and old-growth standsdominated l>y pseudotruga 'nenzietii. Communiries are those commoo to low elevationsitr the Twga beteropbylla Zone. They spanmost of the range or gradient in temperatureand moisture for this zone. Sevencommunities were identified and mappedduring this study: T the/ Caclt,Tshe/ Rhma/ Ga$, T t he/ Rhma/ Bene, T she / Ac ci/ Pomu, Psme / Acci/ Gasb, and p nne/ Acci/ Beze communities and the riparian vegetationtype. These communities are replesenra- tive of four major habitat types. Intensive stem and vegetationmapping has yielded numerousdata on the structure and composition of plant communities.These data provide a souod base for environ- mentally and biologically stratifying the watershedfor ecosystemmodeling projects. Acknowledgments The work reported here was supported by National ScienceFouqdadon Grant number DEB-74-207 44 A02 to the Coniferous ForesrBiome, EcosystemsAnalysis Studies.This is Coniferous Forest Biome contribution number 181. Office and laboratory spacewele supplied by the U.S. Forest Service,Forestry SciencesLaboratory, Corvallis. LiteratureCited Daubenmire,R. 1959.A canopycoverage method of vegetarionalanalysis. Northw. Sci.i3:43-64. 1968.Plant Communiries.A Textbookof PlantSynecology. Harper and Row, New York. 300 pp. Dyrness,C. T., J. F. Franklin,and 17. H. Mojr. 1974.A PreliminaryClassification of ForestCom- jn munities in the Cenrral Portion of the -NfiesternCascades Oregon.Univ. Vash., Seattle.US/ IBP Coniferourfor. Biomc.No. 4. t2J pp. Franklin,J. F.. and C.{. Dyrness.Io-J. Narural Vegerationof Oregonand \flashington.pac. Northwest lor. and RangeExp. Stn., Pordaod,Oreg. USDA For. Seiv. Geo. Tech. REp. pNV- 8,417 pp. , and W. H. Moir. 1970. A ReconnaissanceMethod for ForestSite Class! fication. Shinrin Richi 12( 1), Meguro Tokyo, Japan. 14 pp. !. C. Hall, C. T. Dyrness,and C_ Maser. 1972. Feieftl ResearchNatural Areas in Oregon and ITashington: a guidebook for scientistsand educators.USDA For. Serv..pacific For.and RangeExp. 5rn.,Po land,Oreg. Miqcellaneour paees. -Maner Fredriksen,R. L. 1976. Nitrogeo, Phosphorusand Particulaie Budsetsof F;ve Coniferous Forest Biosystemsin rhe $/estern CaicadeRange, Otegon_Oreg. State-Univ.,Corvaliis, ph.D. thesis.127 DD. Garrison, G. A;-J. M. Skovlin, and C. E. Poulton. 1976. Northwest plaot Names and Symbolsfot EcosystemInventory and Analysis.Pac. Norrhwesr For. and Range Exp. Stn., potrtind, Oreg. USDA for. Serv.Gen. Tech. Rep. PN\yy'-ao, 26J DD. Zobel,D. B.. W. A. McKee.G. M. Hawk.and C. T. ijyrnes. t0-6. Relarionshipsof environment to composition,srructure, and diversity of forest communitiesof the centtal westernCascades o( Oregon.Ecol. Mongr. 46:115-156. Receioed, December 24, 1977 Accepred fot publicati.on March 2, 1p78 212 Hawk