Investigating Vegetation and Small Mammals in the Cloud Peak Wilderness Area of the Bighorn Mountains in Wyoming
In the summer of 2000, I had the opportunity to spend three weekscamping and performing fieldwork in the Cloud Peak Wilderness Area of the Bighorn Mountains of Wyoming. Accompanying mewere 16 of my fellow students from State College Area High School in Pennsylvania, as well as 17 students from James Gillespie High School in Edinburgh, Scotland (Figure 1). The purpose of the expedition, organized and headed by StateCollege Area High earth science teacher Dr. Thomas Arnold and Edinburgh geography teacher Mr. George Meldrum, was toconduct various studies of the region, including a heat-budget determination, a lake water analysis, and a mapping ofthe valley. My research focused on the vegetation and small mammals present in the riparian area of Oliver Creek. As amember of the "Bio Group" (Figure 2), I studied the changes in vegetation with increasing distance from the streamacross three habitats, and determined the types and diversity of small mammals present in those three habitats.
Additionally, I collected and analyzed soil samples in the three habitats, monitored air conditions, and determined thetypes of macroinvertebrates found in Oliver Creek. The Bio Group was assisted in these tasks by field biologist Julie Roth, a graduate student at the University of Nevada. This expedition provided me with a unique opportunity to directlystudy the biology of a wilderness area while interacting with a diverse and international group of students who are asinterested in science as I am. Furthermore, since I had never gone camping before, this research endeavor meant that Ialso had to meet the challenges of learning to properly pitch a tent, sleep on the hard ground, and prepare meals on anoutdoor cookstove.
We set up base camp at the Hettinger Rest Area in the Bighorn NationalForest near Buffalo, Wyoming. Our research site, located at an elevation of 8,750 feet in the Cloud Peak Wilderness Area, was about a 10-minute drive away, followed by a 2.5-mile uphill climb from the main campsite (Figures 3 and 4).
Each morning, regardless of what day of the week it was or what the weather was like, we trudged up the mountain at ninein the morning and returned either at 4 pm or 6:30 pm, depending on the research conducted on that day. The sound ofbanging pots and pans roused us from our slumbers every morning no later than 7 am. Breakfast was always the same:oatmeal. While we tried to spice it up with brown sugar, raisins, or honey, it always had the same thick and bland taste. The first few days of our expedition were somewhat bleak; it rained every day. It was so cold that we went tosleep wearing multiple layers of clothes. The Scots were delayed in their arrival, and we were trying to comprehend the reality of eating oatmeal every day for the next three weeks. However, once the days became sunnier and everyone arrivedso that we could begin our research, we began to enjoy the trip immensely. Everyone in my group joined in the excitementof actually holding a chipmunk prior to weighing it, or finally locating an unknown forb in a field guide. In the evenings, we all gathered around the campfire and shared our discoveries as well as our misfortunes.
The first part of the Bio Group's research dealt with the vegetationof the Oliver Creek drainage basin (Figure 5). The study site consisted of meadowland and a recovering burn area on thenorth side of Oliver Creek, and forested land on the creek's south side. To determine how the vegetation changed withincreasing distance from the stream, a straight-line transect was set up perpendicular to the eastwardly-flowing creek.This transect began at 4416'19"N, 10700'46"W on the north side of the stream and at 4416'19"N, 10700'45"W on thestream's south side. White flags were positioned every 10m from the stream along the transect, for 150m on the creek'snorth side and for 110m on the creek's south side (Figure 6). The meadow extended for a distance of about 60m, while theremaining land on the north side was an area experiencing regrowth after a 1988 burn event. Mature forest was found onthe south side of the creek. At each white flag, we laid out a 1m2 vegetation sampling quadrat, using meter sticks.
Within each quadrat, the percentage of cover was determined by means of the point-intercept method of using knittingneedles on a meter stick frame (Elzinga). Vegetative species present were identified using guides such as Earl Jensen'sFlowers of Wyoming's Big Horn Mountains and Big Horn Basin and Classification of Riparian Communities on the BighornNational Forest, published by the USDA Forest Service. It was interesting to look at the Western vegetation, whichdiffered from what I was used to seeing in Pennsylvania. Although I am well acquainted with many Eastern species oftrees, shrubs, and plants, I encountered many plants, such as pussytoes (Antennaria), with which I was not familiar.Figures 7 and 8 show two of the plants that grew next to Oliver Creek, lupine (Lupinus) and sedge (Carex).
The second focus of our research efforts was a determination of thetypes and diversity of small mammals present in each habitat. This aspect of our studies was the most fun, since we gotto hold the mammals in order to weigh and measure them (Figure 9). (Note that all of the mammals were safely releasedafter trapping.) To conduct this part of the study, small-mammal trapping grids were set up in the same three habitatsin which the vegetation transect was laid out. We did not place the trapping grids exactly along the vegetationtransect, since our movements in assessing the vegetation could have distracted the mammals. Consequently, the mammaltrapping grids were set up in different representative areas of the habitats. Each trapping grid consisted of 30 trapsspaced 10m apart. The burn area and forest trapping grids were set up as 5x6 sampling rectangles, while the meadow wasset up as a 4x7 trapping grid, with the two remaining traps positioned as extensions of the middle rows. Bait made ofpeanut butter and oats was placed in each of the aluminum traps; cotton wool was also added to keep the mammals warm incase of overnight capture. The traps were then covered with litter and brush to disguise them and to provide insulationagainst temperature extremes (Figure 10). The small mammals that we caught were carefully handled while they weremeasured for mass, total length, tail length, ear length, and hind foot length (Figure 11). Gender and reproductive condition were also noted. The animals that were captured were marked in case they were trapped again. We placed nailpolish markings on their ears and also clipped a small amount of hair from a particular location that was noted on thedata chart. We checked the traps twice daily -- at approximately 10 am and again at about 5 pm, each time resetting themfor the next trapping session. The vegetation work was done in the afternoon between trap checks. Because of our longtrapping day, the biology group stayed overnight at our high camp on the mountain in order to be able to check the trapson time in the morning on the five days that mammal counts were made.
In addition to the main vegetation and small mammal studies, soilsamples were collected in the three habitats, temperature variations of the air were monitored, and a macroinvertebratesampling of the creek was performed. The purpose of the soil sampling was to provide a better idea of the conditions inwhich the vegetation grew. Soil sampling was performed at each of the vegetation quadrats. On-site measurements includedsoil moisture content, pH, and infiltration rates. Collected soil samples were sent for further analysis forconductivity and phosphorus, potassium, and magnesium content to Pennsylvania State University. The thermistor study wasset up to provide hourly air-temperature monitoring of the valley. Five thermistor poles were set up on the north sideof Oliver Creek at 30m intervals along the vegetation transect (Figure 12). Each pole had six probes, placed at 1mintervals, from ground level to a height of 5m. Temperature readings were recorded hourly over a three-day study period.
Since we were working in a riparian zone, we identified the macroinvertebrates present at three stream locations -- ariffle, a run, and a pool just downstream of our vegetation transect -- and calculated the Pollution Tolerance Index (PTI)for each location (Figure 13). As the stream's substrate was made up of various-sized boulders and cobbles, 20 rockswere selected for examination at each location, and the number and type of macroinvertebrates present were recorded. Theaverage rock circumferences and lengths were also measured.
The data that we obtained during our expedition is presented in theaccompanying graphs and tables. Figures 14A and 14B show the percent coverage of the three habitats by plants, litter,wood debris, rock, bare ground, and animal waste in relation to distance from Oliver Creek. Figures 15A and 15B are kitediagrams that break down the plant cover into forbs, grasses, sedges, shrubs, mosses and lichens, and conifers, whilethe specific types of plants found and their frequency of occurrence are listed in Table 1 (tables included at the endof the essay). Frequency of occurrence is obtained by dividing the number of quadrats that a plant occurs in by thetotal number of quadrats in a particular habitat -- seven in the meadow, nine in the burn area, and 12 in the forested area -- and then multiplying by 100%. Note that the vegetation quadrats did not include large-diameter trees in order toget a representative picture of the non-canopy vegetation in the forested and burn areas. An indication of the size ofthe trees in the wooded areas is given by Figure 16, which shows the mean circumference of the five closest trees within3m of the vegetation quadrats. There were no notable trees in the meadow; although willows were found, they were sosmall that they were designated as shrubs. The burn area showed the greatest plant-species richness, with 80% of theobserved types located there. The meadow had the lowest richness, with only 12 of the 30 observed types of plants.
Plants common to all three areas included heartleaved arnica (Arnica cordifolia), fireweed (Epilobium angustifolium),grasses (Poa), and mosses. The majority of the quadrats on the north side of the stream (meadow/burn area) exhibited 50%or higher plant cover, while only five of the 12 studied quadrats on the forested south side showed a percentage plantcover greater than 50%.
Seven different species of mammals were captured during a five-daystudy period, as shown in Figure 17. Least chipmunks (Tamius minimus confines) were the dominant species in the burnarea and forest, while meadow voles (Microtus pennsylvanicus insperatus) were the most frequently caught species in themeadow. Table 2 lists the number of small mammal captures that occurred overnight and during the day in each of the three habitats. Both new captures (bold type) and recaptures (parentheses) are listed. The burn area had the highestnumber of small mammals caught, but the lowest richness, since only chipmunks were captured. The forest showed thegreatest species richness, with five types of mammals captured. There appears to be no direct correlation between plantand small-mammal species richness, as indicated in Figure 18. The burn area, which exhibited the greatest plant-speciesrichness, also had the lowest small-mammal species richness. Only two small mammal species were captured in more thanone habitat; least chipmunks in all three habitats and the red squirrel (Tamusciurus hudsonicus baileyi) in the forestand the meadow. Five of the seven observed species limited themselves to one environment. Use of the Simpson diversityindex, Ds =1-Spi2, where pi is the relative species abundance, to compare the small mammal communities in the threehabitats yielded values of Ds(burn)=0, Ds(meadow)=0.66, and Ds(forest)=0.65. The diversity indices of the meadow andforest are very comparable and are greater than that of the burn area, in which only one small mammal species was found.
The soil was acidic throughout the entire riparian zone, as indicatedby the graph in Figure 19, with the least acidic soil found in the burn area. Mean values of pH increased from 4.8 inthe forested area to 5.0 in the meadow to 5.7 in the burn area. As shown in Tables 3A and 3B, the soil analysis by the Agricultural Analytical Services Laboratory at Pennsylvania State University indicated that the meadow had the lowestsoil-nutrient levels, with only magnesium in the optimum plant-growth zone. Highest nutrient levels were found in theburn area, with the amounts of potassium and magnesium present increasing significantly at the meadow/burn areatransition.
As is seen in Figure 20, the region experienced measurable levels ofprecipitation only during the first part of the study; there was negligible precipitation after June 30. Since the smallmammal study began on June 29, on which only 0.3 mm of rain fell, rainfall was not a factor in the capture rate. Figure21 gives the air temperature results at ground level and at 5m from two thermistor poles located 120m apart, one placedin the meadow and the other in the burn area. The results indicate that the air at ground level in the meadow exhibitedgreater variations in temperature than did the air next to the ground in the burn area. At higher air column levels,both the meadow and the burn area showed comparable fluctuations in air temperature over a 24-hour time period as wellas a smaller level of variation than that which occurred in the air closer to the ground.
The quality of the water in Oliver Creek was assessed using the 22 specific-indicator organisms of the PollutionTolerance Index (PTI). Table 4 lists the indicator macroinvertebrates that were found in the three study areas.
Classification of the macroinvertebrates present in a riffle, run, and pool yielded cumulative index values of 20, 15,and 15, respectively. PTI values between 17 and 22 indicate good water quality, while numbers in the range 1116 suggestfair water quality.Much still remains to be done in order to finish the analysis of the data that were collected on the expedition, and notall of it, such as the data on the small mammals' weight and size and soil infiltration rates, have been included inthis essay. Additional statistical relationships need to be determined, comparisons between data acquired on this expedition and that obtained on any previous studies of the area and cited in the literature must be made, and studytechniques and methods must be examined for deficiencies. A follow-up expedition to the area would be especially useful, particularly to see how the regrowth in the burn area has progressed.
Even if my research efforts do not produce a significant scientificcontribution, my Wyoming expedition was a success. It provided me with an amazing opportunity to learn how fieldwork isactually conducted, to spend time in the wilderness examining and marveling at the natural world, and to interact withpeople from another continent whom I had never met before but who had the common bond of a love of science. This tripheld a lot of "firsts" for me: my first time camping, my first time holding a chipmunk, my first time going to thebathroom in the woods. I had to carefully measure distances for the vegetation quadrats, set up the 5m thermistor poles,carry traps up the side of a mountain, and make sure that I correctly recorded my findings. Although the trip wasserious while we were working, we also had time to have fun. I am left with many memories of the expedition. I rememberthe first day we spent with the Scots, and how we marveled over how they supposedly spoke the same language as we didyet used so many foreign words. Their use of "trainers" for sneakers, "minging" for disgusting, and "Philadelphia" forany type of cream cheese, prompted us to put together a Scottish-American dictionary. I remember spending the Fourth of July at an artists' residency, playing volleyball, eating at "Aunt Bea's Chuckwagon" (Figure 22), and watching fireworks light up the night sky. I remember stumbling out of the tent at high camp at four in the morning to take a thermistor reading and sitting in the hot afternoon sun determining sedge cover. I remember my first sighting of a moose along Oliver Creek and looking up into the clear Wyoming night sky to find Cassiopeia and Cygnus. I remember 34 students sitting around a campfire making s'mores and the way we slowly dismantled the camp on our last day in Wyoming. The three weeks that I spent in the mountains of Wyoming doing research as part of a scientific expedition allowed me to learnmore about our wilderness areas while interacting with a diverse group of people. This experience led me to therealization that I want to discover more about the natural world and go on many more scientific expeditions.
Alden, P., B. Cassie, J. Grassy, J. Kahl, A. Leventer, D. Mathews, and W. Zomlefer. National Audubon Society Field Guide to the Rocky Mountain States. New York: Alfred A. Knopf, 1998.Craighead, John, Frank Craighead, Jr., and Ray Davis. A Field Guide to Rocky Mountain Wildflowers. New York: Houghton Mifflin Co., 1963.
Despain, Don G. "Vegetation of the Big Horn Mountains, Wyoming, in Relation to Substrate and Climate." Ecological Monographs 43.3 (1973): 329355.Elzinga, Caryl, Daniel Salzer, and John Willoughby. Measuring and Monitoring Plant Populations. USDI Bureau of Land Management, BLM/RS/ST-98/0051730, 1998.
Girard, Michele, David Wheeler, and Stephanie Mills. Classification of Riparian Communities on the Bighorn National Forest, USDA Forest Service, R2-RR-97-02, 1997.Jensen, Earl R. Flowers of Wyoming's Big Horn Mountains and Big Horn Basin. Greybull, Wyoming: Chimney Rock Books, 1987.
Lofgren, Lawrence. "Alpine Flowering Plants of the Cloud Peak-Cliff Lake Area, Big Horn County, Wyoming." M.S. Thesis. Laramie, Wyoming: University of Wyoming, 1956.McComb, William C., Carol L. Chambers, and Michael Newton. "Small Mammal and Amphibian Communities and Habitat Associations in Red Alder Stands, Central Oregon Coast Range." Forest Research Laboratory. Res. Pap. 2762. Corvallis, Oregon: Oregon State University, 1992.
Mitchell, Mark and William Stapp. Field Manual for Water Quality Monitoring. 11th ed. Dubuque, Iowa: Kendall/Hunt Publishing Co., 1997.Wilson, Don, F., Russell Cole, James Nichols, R. Rudran, and Mercedes Foster, eds. Measuring and Monitoring Biological Diversity: Standard Methods for Mammals. Washington: Smithsonian Institution Press, 1996.
More About This Resource...
OriginYoung Naturalist Awards