This is issue 24: Willows and Moose: A Study of Grazing Pressure, Slough Creek Exclosure, Montana, 1961-1986https://scholarworks.umt.edu/montana_forestry_notes/1019/thumbnail.jp

Chadde, Steve

Kay, Charles

English

University of Montana

University of Montana ScholarWorks at University of Montana Montana Forestry Notes and Research Note, 1964-1992 University of Montana Publications 7-1-1988 Research Note, July 1988 Steve Chadde Charles Kay Follow this and additional works at: https://scholarworks.umt.edu/montana_forestry_notes Let us know how access to this document benefits you. Recommended Citation Chadde, Steve and Kay, Charles, "Research Note, July 1988" (1988). Montana Forestry Notes and Research Note, 1964-1992. 20. https://scholarworks.umt.edu/montana_forestry_notes/20 This Newsletter is brought to you for free and open access by the University of Montana Publications at ScholarWorks at University of Montana. It has been accepted for inclusion in Montana Forestry Notes and Research Note, 1964-1992 by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact scholarworks@mso.umt.edu. Number Twenty-Four, July 1988Montana Forest and Conservation Experiment Station School of Forestry, University of MontanaMissoula, Montana 59812Willows and Moose: A Study of Grazing Pressure,Slough Creek Exclosure, Montana, 1961-1986Steve Chadde** Research assistant, Montana Forest and Conservation Experiment Station, School of Forestry, University of Montana, Missoula; research funded by the Montana Riparian Association.**PhD candidate, Department of Fisheries and Wildlife, Utah State Univer­sity, Logan; research funded by the Rob and Bessie Welder Wildlife Foun­dation, Sinton, TX (Contribution No. 316).Charles Kay**ABSTRACTThe Slough Creek Exclosure was constructed in October 1961 in the Gallatin National Forest to determine the response of willows (Salix spp.) protected from browsing. The objective of this study was to compare vegetational changes inside and outside the exclosure after 25 years. The exclosure was visited and resampled in August 1986. Four existing line-intercept transects were sampled, and six new 30.5-meter transects were established and sampled outside of the exclosure. The willow species in the area were identified for the first time. Willow height and canopy coverage inside the ex­closure have increased steadily since 1961, while willows outside the exclosure have shown little change. Recommendations include periodic resampling of exclosure transects and use of historic photographs of the Slough Creek drainage to evaluate vegetation changes.INTRODUCTIONAn exclosure adjacent to Slough Creek, located in the Gallatin National Forest, Montana, was constructed by the U.S. Forest Ser­vice in 1961. Its purpose was to provide a reference area to study the response of browse plants, particularly willows, after they were protected from use by big game animals (Joy 1962). Because winter snow accumulation normally precludes use as elk winter range, winter browsing is generally limited to moose. However, elk oc­casionally use the area in late fall and early spring and, during years of low snowfall, in the winter (Puchlerz 1987). The objective of this study was to compare the vegetational changes in the exclosure, after 25 years of protection, with adjacent areas subject to browsing.According to available historical records, moose were not ob­served in the northern range of Yellowstone National Park until about 1913 (Houston 1982). Early explorers in the Yellowstone area rarely saw moose; except for the observations of the Hender­son party (1870), all recorded sightings were confined to the area south of Yellowstone Lake (Doane 1876, Norris 1880, Norris 1881). In addition, there have been no moose remains found in any of the archeological sites in the Yellowstone region (Wright 1979, Houston 1982, Wright 1984, Wright and Reeve 1981). During the early 1900s, Shiras (1913) “discovered” the Shiras subspecies of moose along the headwaters of the Yellowstone River above Yellowstone Lake. Since then, moose have extended their range into northern Yellowstone Park (Houston 1982) and the surrounding area (Stevens 1971, McDowell and Moy 1942).FIGURE 1Slough Creek Exclosure with Transect and Camera Point LocationsFew moose were observed in the upper Slough Creek drainage in the early 1920s. Local flora at the time included willows with shoots up to 5 centimeters in diameter, and willow clumps reached heights of 3 to 4.5 meters. South into Yellowstone Park, “willows along Slough Creek were taller than a moose’s back in most of the area (McDowell and Moy 1942). Increasing numbers of moose were seen along Slough Creek between 1930 and 1940. By the mid-1940s, tall live willows had all but disappeared, and fewer moose were observed in the area. By the early 1960s, tall willows had almost completely disappeared along Slough Creek, and pro­gressively fewer moose were sighted each year (Joy 1962).Most observers suspected that repeated browsing by moose was responsible for the change in the extent and structure of a once- common riparian community. Researchers hypothesized that the former Yellowstone Park policy of feeding ungulates during the winter, combined with predator control, may have encouraged un­naturally large increases in the moose population (Joy 1962); after die supplemental feeding program ended in the early 1930s, brows­ing pressure on willows became excessive.Between 1961 and 1978, the moose population in the Slough Creek drainage was considered relatively stable (Erickson 1979). Swenson (1985) reported that moose populations have been increas­ing since 1978 due to conservative harvests of the animalsMETHODSThe Slough Creek exclosure is approximately 22 kilometers upstream from Yellowstone Park’s Slough Creek campground. The site was described and sampled in 1962 through 1965 and partially sampled in 1979 (Erickson 1979).In 1963, four line transects were established in the exclosure (Figure 1). Two transects (A and B) were inside the fenced area, bearing diagonally from comer to corner. Outside the exclosure, a transect (N-l) began at the northeast comer post; the other (S- 2) began at the southwest comer post. In 1986, six new transects (N-2, N-3, N-4, S-2, S-3 and S-4), each 30.5 meters long, were established outside the exclosure.Willow species were identified along each transect line, and the length of each willow clump was recorded to the nearest inch. Un­til the 1986 survey, willows had not been identified beyond the generic level. The average heights of plants along the line were also measured. A list was made of species both in and adjacent to the exclosure; nomenclature followed Brunsfeld and Johnson (1985) for Salix spp. and Hitchcock and Cronquist (1973) for all other taxa.Camera points, monumented in 1962, were photographed again m 1986 (Figure 1). The position of camera point 2 was approx­imated because it apparently had been washed out by Slough Creek.A soil pit one meter deep was dug and examined inside the ex­closure; another was dug and examined in a similar topographic position about 15 meters north of the fenced area. Horizon develop­ment, soil texture, depth of rooting and evidence of mottling or gleying were recorded.RESULTSVegetationWithin the exclosure, the willow overstory completely covered the ground surface and intercepted 114 percent (sum of each species intersect distance) of the total transect length of 51.2 meters (Table 1). Salix geyeriana predominated, followed by S. boothii and S.FIGURE 2ASlough Creek Exclosure, Camera Point 1, October 4,1962FIGURE 2BSlough Creek Exclosure, Camera Point 1, August 20,1986drummondiana. Average willow heights varied from 2.3 meters for Salix boothii to approximately 3.1 meters for S. geyeriana and 5. drummondiana.Outside the exclosure, willows intercepted 36 percent of the total transect length of 232 meters (Table 2). Salix geyeriana and 5. boothii were dominant species; S. drummondiana and 5. wolfii, a low willow (about one meter), were present in lesser amounts.As indicated by both transect data (Table 3) and photographs (Figures 2 and 3), changes within the exclosure since 1961 have included large increases in willow canopy coverage and height. Out­side the exclosure, intercept and height values changed only slightly, with no apparent upward or downward trend.There were also composition shifts, as indicated by comparisons of present willow cover inside and outside the exclosure (Tables 1 and 2). Unfortunately, it was not possible to make long-term com­parisons of trends in individual willow species because of the lack of previous identification by earlier researchers.The exclosure and adjacent area supported habitat similar to the Salix geyeriana/Carex rostrata riparian plant association described for northern Yellowstone Park (Chadde et al. 1988). Dominance in this type is shared by Salix geyeriana, S. boothii and S. drum­mondiana, and these species form an often associated group of ecologically equivalent species (Brunsfeld and Johnson 1985, Youngblood et al. 1985, Hansen et al. 1987).Within the exclosure, understory coverage was sparse because of shade, but Carex rostrata and Calamagrostic canadensis were present as scattered individuals. Adjacent to the exclosure, Carex rostrata and C. aquatilis were common. Other common graminoids outside the exclosure included Agropyron caninum, Bromus dliatus, Phleum pratense, Poa pratensis and Stipa occidentalis. Common forbs included Achillea millefolium, Aster spp., Epilobium angustifolium, Geum macrophyllum and Taraxacum officinale. A species list for the protected and adjacent unprotected areas is presented in Table 4.SoilsSoils within the exclosure were characterized by a 5-centimeter accumulation of organic matter, composed of decayed willow leaves and stems, and a 30-centimeter moist, sandy-loam horizon'. A medium-coarse sand was encountered at depths greater than 35 cen­timeters; woody roots were noted to a depth of about 40 centimeters.There was a discontinuous layer of organic matter, in addition to more bare ground, outside the exclosure. A sandy loam with a high percentage of fibrous roots was found from the soil surface to 8 centimeters below it; this soil continued from 8 to 25 cen­timeters, with an increase in clay. Soil deeper than 25 centimeters was a moist sand with few roots. No evidence of mottling or gley- ing, which indicates fluctuating or high water tables, was observed in the upper meter of either profile. However, these characteristics are rare in coarse-textured soils (Rowell 1981).DISCUSSIONThe response of willows inside the exclosure indicates that the tall-growing species (Salix boothii, S. drummondiana, S. geyeriana) along Slough Creek cannot reach heights above 1 to 1.5 meters because of repeated browsing by ungulates. With protection from browsing, willow canopy coverages increased considerably. On the other hand, species diversity decreased in the exclosure due to com­petition and shading. However, in a broader prospective, the riparian vegetation of upper Slough Creek typically occurs as a mosaic of willows interspersed among herbaceous communities. Under a regime of no browsing or lower intensity browsing, a more struc­turally diverse habitat, typified by scattered patches of tall willows, would develop in the area.Preferential browsing of Salix geyeriana may account for the dif­ferences in composition in and out of the exclosure. McMillan (1953) noted a preference by moose for Salix geyeriana over S. wolfii in willow communities in Yellowstone Park, and Gaffney (1941) ranked S. geyeriana as “valuable” winter browse for elk. However, since willows are very shade-intolerant (Argus 1973, Rawson 1974, Haeussler and Coates 1986), shade from the taller Salix geyeriana may be responsible for that species’ preponderance in the exclosure, compared with the slightly shorter Salix boothii and the lower growing Salix wolfii, which was absent from the ex­closure in 1986.The available evidence suggests that moose are a recent introduc­tion, via immigration, to the study area, and that they have effectedFIGURE 3ASlough Creek Exclosure, Camera Point 3, October 4,1962FIGURE 3BSlough Creek Exclosure, Camera Point 3, August 20,1986a marked change in riparian vegetation, particularly willows. By reducing the stature and cover of woody species, moose and elk may have altered the overall character of riparian communities along Slough Creek and other drainages of the northern Yellowstone area. However, additional studies are necessary to separate trends because of other potential causative factors such as the extended drought of the 1930s or fire suppression.RECOMMENDATIONS• The Slough Creek exclosure should be maintained and resam­pled at intervals. Long-term records from exclosures and per­manent plots provide valuable objective measures of vegetation change. Resampling every five to ten years should be adequate to detect significant vegetational trends.• Historic photographs of Slough Creek should be located, and the area should be rephotographed for comparison. This would pro­vide a useful evaluation of change in the drainage and verify the reliability of previous descriptions of the extent of tall willow communities.• Because of moose impacts on shrub-dominated riparian com­munities, additional study is needed on the current status and population dynamics of moose and on moose-habitat relationships in the northern Yellowstone area.LITERATURE CITEDArgus, G.W. 1973. The Genus Salix in Alaska and the Yukon. Publica­tions in Botany No. 2. National Museums of Canada, Ottawa, OntarioBrunsfeld, S.J. and F.D. Johnson. 1985. Field Guide to the Willows of East-Central Idaho. Bulletin 39. College of Forestry, Wildlife and Range Sciences, University of Idaho, MoscowChadde, S.W., P.L. Hansen and R.D. Pfister. 1988. Wetland Plant Communities of the Northern Range, Yellowstone National Park. Final Contract Report to the National Park Service, National Park Service Research Center, Laramie, WYDoane, G.C. 1876. Expedition of 1876-1877. Yellowstone National Park Library, Mammoth Hot Springs, WYErickson, G. 1979. Slough Creek Big Game Exclosure: A Reevaluation after 20 years. Unpublished Report. Montana Department of Fish, Wildlife and Parks, HelenaGaffney, W.S. 1941. The Effects of Winter Elk Browsing, South Fork of the Flathead River, Montana. Journal of Wildlife Management 5: 427-453Haeussler, S. and D. Coates. 1986. Autecological Characteristics of Selected Species that Compete with Conifers in British Columbia: A Literature Review. Land Management Report No. 33. Ministry of Forests, Victoria, British ColumbiaHansen, P.L., S.W. Chadde and R.D. Pfister. 1987. Riparian Dominance Types of Montana. Review Draft. Montana Riparian Associa­tion, School of Forestry, University of Montana, MissoulaHenderson, A.B. 1870. Narrative of a Prospecting Expedition to the East Fork and Clark’s Fork of Yellowstone, 1870. Yellowstone National Park Library, Mammoth Hot Springs, WYHitchcock, C.L. and A. Cronquist. 1973. Flora of the Pacific Northwest: An Illustrated Manual. University of Washington Press, SeattleHouston, D.B. 1982. The Northern Yellowstone Elk: Ecology and Manage­ment. MacMillan Publishing, NYJoy, C.R. 1962. Slough Creek Big Game Exclosure. Unpublished Report. USDA Forest Service, Gallatin National Forest, Bozeman, MTMcDowell, L. and M. Moy. 1942. Montana Moose Survey: Hellroaring- Buffalo-Slough Creek Unit. Montana Department of Fish and Game, HelenaMcMillan, J.F. 1953. Some Feeding Habits of Moose in Yellowstone Park. Ecology 34: 102-110Norris, P.W. 1880. Annual Report of the Superintendent of Yellowstone National Park. In; Annual Report of the Secretary of Interior for the Year Ended June 30,1880. Washington, DCTABLE 1Summary of 1986 willow data: Inside Slough Creek Exclosure. Total intercept length = 51 m.TABLE 4Species list for Slough Creek Exclosure site, 1986.Norris, P.W. 1881. Annual Report of the Superintendent of Yellowstone National Park. In: Annual Report of the Secretary of Interior for the Year Ended June 30, 1881, Vol. 2. Washington, DCPuchlerz, T. 1987. Personal Communication. Ranger, Gardiner Ranger District, Gallatin National Forest, MTRawson, J.W. 1974. Willows. In: Shrubs and Vines for Northeastern Wildlife (J.D. Gill and W.M. Healy, compilers). General Technical Report NE-9. USDA Forest Service, Northeastern Forest Experiment Station, Bromall, PARowell, D.L. 1981. Oxidation and Reduction. In: The Chemistry of Soil Processes (D.J. Greenland and M.W.B. Hayes, editors). John Wiley and Sons, NYShiras, G. 1913. Wild Animals That Took Their Own Pictures by Day and by Night. National Geographic 54: 763- 834Stevens, D. 1971. Shiras Moose. In: Game Management in Montana (T.W. Mussehl and F.W. Howell, editors). Montana Fish and Game Depart­ment, HelenaSwenson, J. 1985. Moose Survey in the Absaroka High Country. Memo to LeRoy Ellig, Bozeman, MT. Montana Department of Fish, Wildlife and Parks, HelenaWright, G.A. 1979. Homage to Gustavus Cheney Doane. In: First Con­ference on Scientific Research in the National Parks (R.M. Linn, editor). National Park Service, Washington, DCWright, G.A. 1984. People of the High Country: Jackson Hole Before the White Settlers. Peter Lang, NYWright, G.A. andS.A. Reeve. 1981. Prehistoric Resource Procurement and Climatic Change in Northwestern Wyoming. In: Quaternary Paleoclimate (W. Mahaney, editor)Inside OutsideExclosure ExclosureTreesPicea engelmannii x xPinus contorta xShrubsBetula glandulosa xLonicera involucrata x xPotent ilia fruticosa xRibes sp. x xSalix boothii x xSalix drummondiana x xSalix geyeriana x xSalix wolfii xForbsAchillea millefolium xAgoseris glauca xAntennaria sp. xAster sp. x xAstragalus sp. xCirsium arvense x xCirsium scopulorum xEpilobium angustifolium x xFragaria virginiana x xGalium boreale xGeum macrophyllum x xPotentilla gracilis xSenecio pseudaureus x xSolidago canadensis xTaraxacum officinale x xThalictrum fendleri xGraminoidsAgropyron caninum xBromus ciliatus x xCalamagrostis canadensis x xCarex aquatilis xCarex microptera x xCarex rostrata x xDanthonia intermedia xPhleum pratense xPoa pratensis xPoa sp. xStipa occidentalis x% of Total Intercept Avg. Height Species (m)Salix geyeriana 79 3.1Salix boothii 24 2.3Salix drummondiana 12 3.1Total 114'I. Value may be greater than 100% when individual species canopy coverages overlap.% of Total % of Willow Avg. Height Species Intercept Intercept (m)Salix geyeriana 15 42 0.9Salix boothii 15 42 0.9Salix drummondiana 3 9 1.0Salix wolfii 3 7 0.5Total 36 100Sample Date % of Total Intercept Avg. Height (m) Inside Exclosure8/22/63 46 1.28/27/64 55 1.210/7/65 47 1.28/14/79 —■ —8/20/86 114 3.0Outside Exclosure8/22/63 20 0.88/27/64 32 0.710/7/65 28 0.88/14/79 36 1.98/20/86 28 1.01. Transect not sampled in 1979.Montana Forest and Conservation Experiment Station UM School of ForestryMissoula, MT 59812Non-Profit Organization U.S. Postage PAID Permit No. 100 Missoula, MT 59812350 6.88 2767—CM Printing Sen ices

Research Note, July 1988

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Research Note, July 1988

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