Trifolium Thompsonii Stand Conditions Following a Wildfire Event in the Entiat Mountains of Central Washington
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245 Trifolium thompsonii Stand Conditions Following a Wildfire Event in the Entiat Mountains of Central Washington George Scberer1, Richard Everett• and Ben Zamora2 'USDA-Forest Science lab, 113:3 Western Ave., Wenatchee, WA 98801 Tel. (.509) 662-4:JJ.5; Far (.509) 664-2742 2 Department ofNatural Resource Sciences, Washington StaJe University, Pullman, WA Abstract. TrifoUum thbmpsonii. (Thompson's clover) is of the Columbia River, about 6 km southeast of the listed as a threatened legume of the Eastern Cascades Thompson's Clover Research Narura! Area. where wildfire is lhedootinantdisturbanceagenL Previous These new sightings snggesi even wider range poten researchsuggesttdfiresupressionadverselyimpactspopo tials and pezhaps a different ecological amplitude than pre lations of!his species. Recent fires in partS ofThompson's clover range indicate that Thompson• s clover responds viously described {Kennison and Taylor 1919). Toe pur pose of this study was to clarify the habitat characieciscics favorable to fire distwbance. Four areas of Thompson's of Tri[olium thompsollii and seek evidence which might clover habitat were sampled for vegetacion composicion indicaie the successiooal role of this species among the and structure. Thompson's clover stands we,e evaluated different plant communities where it is found. 1be ob for species density and morphological expression. In areas jectives of this.research were: 1. to docwnent the vegeia ofrecentfire, Thompson'scloverindividualsw~signifi tive communities and sue factors associated with Trifo cantly taller (means of range 32-25 cm) and had gn,arer li.um thompsonii.; and 2. to compare moqihological fea pwnbe:s offlowerbeads (means of range 4 to 1 pee plant) tures and plant density of Tri[olium thbmpsonii popula than on sites wilh no =nt fue activity, suggesting a tions among these vegetative communities. Thompson's clover response to fire caused resource release. This infonnation combined with a species density· ranging 0.6 to 4.8 plants m·2 suggests that Thompson's Methods clover appea,:s to achieve opcimum stand conditions on sires wbtte perodic grass-shrub eliminaling fires occur. Study Area Re-establishment of historical fire effeas may be a key to improved management oflandscapes in fire.respon which Climate of the area is typical of eastem flank of the sive ~-pecies such as Thompson's clover are components. Cascade range. Swnmers aie warm and <Icy and winlel's are modmtly cold. Precipitation occurs mostly as snow between November and April. The nearest climaie Sia· Introduction cion at Wenatchee, WA., has a mean January temperature of -3 °C and a mean Joly temperature of 22 °C. Annual Trifolium thompsollii (Thompson's clover) is one of precipitation is about 220 mm. This species occurs at el 12 plant species listed as lhreaiened along the east slope evations of 345 to 1146 m (Canfield 1977). Using the of the Washington Cascades (WNHP 1994). Wilhin ics normal lapse rate of2 "C per 300 M lhe mean temperatw:e range it is adominantforb, fl!Slreported by J.W. Thomp on the study sites would be -8 °C for January and 17 °C son in 1933 on the slopes of Swakane canyoo at the edge for July. At these elevations winter snowpaclc may be ex of Pinus ponderosa forests and into the Artemisia pected to remain for op to 60 days longer in the spring; tridenllJla shrub sieppe adjacent to the western shores of delaying bud emergence for Trifolium · thbmpsonii and the Columbia River (Hitchcock et. -al. 1969). Work by other species (Gamon and Sprague 1988). _ Canfield (1977) and Tiedemann ct.al (1977) expanded .knowledge of this species and docwnented 10 additional Discurbance History stands, the largest located within the 80 ha Thompson's Clover Research Natural Area. Survey wcrl< reported by In general, fire bas bcai an historical ~ agent Gamon and Sprague (1988) further extended the Chelan in this region and was evident on a portion of the Trifo county occurrences of Tri[olium thompsonii IO canyons lium thompsonii study area Figure 1 shows lhe ~ near lheEntiatRlverandadded information ofa stand east of wildfite within the known ra:ngeofTrifolium lhcmpsollll 246 Scherer, G., Everett, R. and Zamora, B. since 1930 (WNF 1990, Canfield 1977). The most recent rain fearures were tabulated for comparison by plant com tireoccmrenc:ewasJuly 1983. I.andscapeswithln thisaiea munity (Table 2). DataonclensityofTrifoliwnrhompsonii were grazed by domestic sheep and caUle until 1965 and measwemenrs of morphoiogical f~ we.e tabu (Tiedemannet.al.1977). NolmownfireshaveOCCUI7Cdon lated by plant community and analysis of variance was the Douglas =mty study sites but !he area is presently used LO 1CSt for differences among the community types.. under seasonal grazing impact by domestic caale and portions of the area are cultivated for wheat crops (Gamon and Sprague 1988, E. Gotzwile. 1993, pm. comm.). Resulis F~ld Sampling Trifolium thompsonii occurred in three broad yegeta tive settings: forest patches, SLeppe-like parklands, and Sampling sites were selected by reviewing maps of semiarid shrub Stq)pe. The forest patches consisted of a known Trifolium rhompsonii locations from the multilayered community ofirees, shrubs, grasses and forbs Wenatchee National Forest Thompson's Clove. Manage dominated by Pseudotsuga menziesii occurring on mesic ment Guideline (Gamon and Sprague 1988). Criteria for IOpographic·seuings such as gullies and northerly slopes. sample site selection was: The appearance of distinct Steppe paddands were grass dominated landscapes with patches of Trifoiium thompsonii in the overall mosaic of occasional mature Pi.nus ponderosa . individuals. The vegeiation coverage and patch size greater than 50 M di shrub steppe was the extensive drought LOlerant tall sbrub ameter. bunchgrass (,Artemisia trkkn!alal Agropyron spiCIJlun:,) Vegetali.ve sampling was done by systematically plac vegelative associations typical of the central Columbia ing a 50cm x 20cm sampling frame in a4 X 5,20 frame basin. matrix at three positions (0, 30, SOM) along SO mew tape Wilhin these lhree settings four plant communities transect running trough Trijolium thompsonii patches. The were identified using cluster analysis of species compo polygonal cover class of each species eocoonreted in the sition and cover values wilhin stands. These four com P,lot frame was recorded (Daubenmire 1959). Taxonomic munity types probably represent various successional nomenclature follows Hitchcoclc and Cronquist (1973). stages of four plant associations as descn"bed by Franklin At the same time, soil surface condition was recorded at .and Dymess (1973) and Daubenmire (1970). They are 10 _pointS on Ille plot frame as either litter, bate ground, Psew:w1suga menz~sii/Calmagrosris rubescens (PSMEI plant basal area, crypwgamic crust, wood pieces, or rocks. CARU) of the forest setting, Pillus ponduosa/Agropy At each sampled community !he density of Trifoliwn ro" spicatum (PIPO/AGSP) and Artemisia rriderual.tJ rhompsor.ii was measured by counting individuals within · vaseyana/Agropyron spicaium (ARVA/AGSP) of I.be Len ll'vf plot frames in !he same 4 X 5 vegetation sam steppe setting and Artemis/a 1ridenta1a-1riden1ataJA,gr<> pling matrix. Frol)l each sampled community 10 ID 30 pyron spicarum (ARTR/ AGSP) of !he shrub Sleppe zone. Trifolium Ihompsonii individuals were randomly selected Physiognomic differences between the community types and measured for height, leaf number, shoot number, we.e distinctive and easily recognizable. These four com flowerhead number and root crown diameter. munity types are descn"bed below wilh refe.ence LO veg At each sampled community the following sire fac. etativecom_position and site fac!Or dala in Tables l and 2. tors we.e recorded: elevation, slope, aspect, slope posi tion, and a microterrain feature (flat, convex, concave). Planr Commwliry Descriptions The soil depth was measured and a soil sample ofthe up per 20cm was collected at each sample matrix and ana The PSME/CARU community occurred on noi:th fac lyzed for bulk density and% soil moisture. Toe soils dala iog steep slopes (40-60 %) at mid LO upper elevations (> we.e compared and suppleme.nied wilh SCS Soil survey HMO m) in Chelan county. This was the weucst and laboraLOry information available on the Study area (Beiler coolest environment wilh estimated annual precipitation 1969, 1978). ranging 508 LO 1016 mm and estimated annual iempera ture ofS-6 "C. Pseudo1suga menziesii was the overstory Anaiysis -dominant with Pinus ponderosa a codom.inant in some .sample units. Spiraea betulifolia and Pensremon Mean coverage and frequency values were calculat£d jnuicosus were prominent shrub layer componentS. 1be for all species in each sample unit and used IO consuuct a grass, Calmagrosris rubescens was a significant CCHlomi species list ofcover and a table of plant communities with nant of this communjty type. Balsamorhiza sagi1ra1a, species cove. and coosiancy (Table I). Dendograms pro AcMllia millefo/ium and Trijoliwn 1/wmpsonii were the duced by cluster analysis (Wilkinson 1992) we.e used IO most prominent forb species. Other imponant hcrbacrous identify relationships among Trifolium 1/rompsonii sam =ics were Festuca idalroensis, JJrornus tectorwn, Poa pling clusters based on species composition and cover. s~cundi, Collensia parvif/ora, Cryprhantha a/finis, Site fac!Or data on soil moisture, surface cover and ter- Epi/obium paniculara. In Ibis community fire recently • Trifolium tltompsclfii Stand Conditions FoUowing Wildfire • 247 Tablcl.Conmooymdmean~crofspecicoinfourTrifo/iJJmtliomp,,,niicommunityiypes.Tr-=%coverlessthanO.l. N=nnmbcr of sample unit&. Cot,,, """""""Y· = % canopy covcr. PSME P.ceo ARTR ARVA N=Z N=7 N"9 N=J Ca, Cov Ca, Cov ,... Ca, Cov Con Cov PWU p<>ltduMO 100 29.0 p p 0 0.0 Puw:louwga nvlfZiaii 100 0 0.0 32.0 0 0 0 • 0.0 Shrub 0 0.0 Arte,ni,io tr;,J,AJaJa-tr 0 0.0 14 Tr 77 8.S 0 o.o Nt~t4 trid,usl4J4-\t2 0 0.0 0 0.0 tripartiJa 0 0.0 67 1.2 ,1,..,,,.,.