A Study of the Effectiveness of Rocky Mountain National Park Elk and Vegetation Management Techniques

Transcription

1 A Study of the Effectiveness of Rocky Mountain National Park Elk and Vegetation Management Techniques Matthew Arellano, Nicole Brunner, Stephen Geuder, and Kimberly Shoppell Environmental Field Studies, Fall 2011, Metropolitan State College of Denver Abstract: Rocky Mountain National Park (RMNP) located in Colorado supports a vide array of wildlife, including several ungulate species. Elk (Cervus elaphus) are native to RMNP, however by the late 1800s they were extirpated from the area. In the early 1900 s they were reintroduced and in the absence of significant predation or hunting the elk population flourished. A natural regulation policy that involved no active management within the park was instituted in 1969, with the belief that hunting in adjacent areas would control the elk population. In the ensuing years elk numbers increased and an observed change in vegetation occurred, particularly a decline in willow and aspen production. In response to the concern over the condition of the vegetation, in 2008 the Elk and Vegetation Management Plan (EVMP) was instituted within RMNP, conservation efforts include fencing, elk redistribution, vegetation restoration, and culling. In the current study twenty random plots were selected within fenced areas (exclosures) and unfenced areas within the core elk winter range. New growth, height, circumference and willow plot density data were gathered for all willow species in the plot. Average and total measurements from each plot were compared. Total measurements of individual plants show that in the fenced areas new growth, height, circumference, and plot density is greater than in the unfenced areas. Observations were noted on the health of the plant and the percentage of off-take (consumption), which showed by far healthier plants with more saplings within the fenced areas. Compelling evidence suggests that browsing in the unfenced areas does affect willow species ability to thrive and reproduce; therefore maintaining the fenced areas does allow the plant communities to rebound. Evidence supports the idea that some factors of the EVMP are effective. However, there is no notable improvement in willow quality in the unfenced areas suggesting culling is not an effective management tool, and fenced areas may not be a long-term solution due to the need for ungulate consumption as a natural and necessary component to a healthy ecosystem. Keywords: Elk Management, Rocky Mountain National Park, Willow, Elk Browsing, Riparian Areas, National Park Management. 1

2 Contents Introduction... 3 Literature Review... 5 Objectives... 8 Study Area... 9 Methods Results Discussion Conclusions References Acknowledgements

3 Introduction Rocky Mountain National Park (RMNP) is located in the North-central region of Colorado and is host to various populations of wildlife, as well as several ungulate species including Rocky Mountain elk (Cervus, elaphus) which are native to Rocky Mountain National Park. In the late 1800 s elk were extirpated from the park (Zeigenfuss et al. 2011) In the 1930s, The National Park Service became concerned about the deteriorating vegetation due to increasing elk populations. In 1944, rangers started to use lethal reduction (killing elk by shooting), as well as trapping and transplanting in order to control the elk population in the park. Since the US National Park Service adopted a policy of natural regulation (i.e., no capture or cull) in the 1960s, elk populations in Yellowstone National Park and RMNP have increased dramatically (Coughenour and Singer 1996). In the absence of both significant predation and hunting, the elk populations in the park have flourished. Research has shown that the elk herd in RMNP and the Estes Valley is larger, less migratory, and more concentrated than it would be under natural conditions. As a result, montane riparian willow (Salix spp.) and aspen (Populus tremuloides) stands are declining, depriving other wildlife of essential habitat (Zeigenfuss and Singer, 1999). Recent Research studies indicate that the RMNP and Estes Valley have reached their estimated maximum carrying capacity of elk (Zeigenfuss et al. 1999) and park managers have seen significant impact on the condition and spatial extent of riparian willow communities throughout the park (Peinetti et al. 2002), and there is very little new willow establishment or recruitment into larger size classes, suggesting that the long term persistence of these communities is threatened. Riparian vegetation comprises a small amount of area along rivers and streams. These areas are vulnerable to any number of periodic disturbances including flooding, river migration, channel meanders, fire, wind, plant disease insect outbreak, beaver dams, as well as herbivory by large 3

4 ungulates (Peinetti et al. 2002). Elk feed on a wide variety of plant species in a wide variety of habitats. Grasses usually make up most of the diet. The high concentrations of elk have diminished the vegetation in communities that support large numbers of bird, butterfly, and plant species. National Park Service management policies are striving to maintain the natural components and processes of evolving park ecosystems (U.S. Department of Interior, 2007). These policies also acknowledge that any biological or physical processes have been altered in the past by human activities, may need to be restored to the original state or to the closest possible estimate of the natural conditions. Natural conditions are defined as the condition of resources that would occur on the absence of human influence over the environment. Natural regulation of elk populations involves either predators or food limitations. The use of these methods as a management tool in national parks remains controversial (Lubow et al. 2002). Under natural conditions uninfluenced by human activity, the elk population size would be controlled by a number of factors, including predators such as wolves, and grizzly bears, as well as hunting by native Americans, and the presence of competition such as bison. Empirical evidence for areas with intact wolf populations such as Yellowstone, and Banff National Parks, indicates that elk would be more wary and less sedentary, resulting in lower densities. Grizzly bears, which were native to the park but also extirpated, would also contribute to elk population; research shows that wolves more effectively limit elk populations in the presence of multiple predators. Hunting has also been prohibited inside the park, making it a sanctuary which has no doubt contributed to the increased elk population. The Elk and Vegetation Management Plan (EVMP) in RMNP was implemented in The purpose of this project is to reduce the impact of the elk on the vegetation within RMNP, as well as to restore to closest extent possible, the natural range of variability in the affected plant and animal 4

5 communities. In order achieve results this requires as dramatic reduction in elk populations by means of culling (lethal reduction), as well as redistribution. The park has also installed fenced areas or exclosures that keep large ungulates from consuming vegetation, giving plant communities the opportunity to thrive. In future years, the park will re-evaluate opportunities to use wolves as well as fertility control as additional potential management tools (EIS, 2009). The following study was designed to evaluate these current management techniques from a broad ecological perspective. Literature Review Ungulate Herbivory of Willows on Yellowstone s Northern Winter Range: Declines in willow (salix spp.) abundance, disturbance and stature in Yellowstone s northern winter range were dramatic. Willows typically grow beyond the height of browsing by large herbivores through very rapid vertical growth rates and large below ground storage of nutrients and energy (Bryant et al. 1983). Willows of reduced canopy size and height ie: suppressed willows, are observed throughout the greater Yellowstone area (Singer et al., 1994) Willow herbivory was sampled in 42 browsed willow communities during 3 summers (1988, 1989, 1990). 10 browsed willow communities were classified as suppressed, 11 as intermediate and 21 as tall. Suppressed and intermediate browsed stands were more prevalent at lower elevations and tall stands were more common at higher elevations. Suppressed height = plants < 80 cm, intermediate height = plants cm tall, and tall willows = 121+cm. Suppressed communities tend to be browsed at a uniform height, intermediate stands tend to a lesser extent, while tall stands were of diverse heights. Wolves, elk, and bison: reestablishing the landscape of fear in Yellowstone National Park, USA: 5

6 The elk (cervus elaphus) and bison (Bison bison) of Yellowstone National Park have lived absent wolves for the last 50 years. In the winter of 1994, wolves were reintroduced to the park. This is a 5-year study examining the foraging theory that elk and bison would respond to the threat of wolves by increasing their vigilance levels. This prediction is tested by comparing vigilance levels of elk and bison in areas that have wolves to areas in the park that are still absent wolves. Male elk and bison showed no response to the presence of wolves. Female elk and bison showed significantly higher levels of vigilance levels in areas with wolves than areas without wolves. This study suggests that these behavioral responses to the presence of wolves may have more far-reaching consequences for elk and bison ecology that the actual killing of individuals by wolves. Reduced Cottonwood recruitment following extirpation of wolves in Yellowstone s northern range: Cottonwoods are an important component of riparian environments in the winter range of the northern Yellowstone elk herd. These young plants are very palatable to elk. A study was conducted in five different riparian locations in the park. Three areas were accessible to the herds and the other had limited accessibility. Diameter was measured at breast height (dbh) and trunk core samples were taken to determine age. At the limited access sites cottonwood recruitment has been occurring during the last fifty years. This is an indication that climatic factors have not played a role in recruitment. At two sites there was an overall decline in cottonwood recruitment following the extirpation of wolves in the 1920 s. At the third site Bison ranching and culling activities allowed cottonwood recruitment to continue even after the loss of wolves but terminated after the curtailment of the management programs. This data from the five sites in Yellowstone, along with other studies, shows compelling evidence that the lack of wolves in northern Yellowstone has had a major impact on the recruitment of cottonwood and other 6

7 riparian woody browse species (Beschta 2005). With no hunters or predators elk are able to browse and deter the recruitment of cottonwood and other riparian woody species. Wildlife management in the National Parks: questions in search of answers. Ecological Applications: Animals are an important resource in National Parks. In the beginning of the 20 th century preservation and animal management programs were modeled on early English and American game preserves. It was assumed that these models could be maintained or enhanced through protection of these resources. Artificial feeding, control of predators, fire suppression, and the elimination of disease and pathogens were the primary methods used. (Wright 1999). By the mid 1930 s elk populations in Yellowstone had increased considerably because of the lack of predation and hunting. Culling programs were instituted and >15,000 elk were removed from the park between the mid 1930 s and mid 1960 s. In 1969 the program was discontinued due to public opposition from animal rights groups and hunters. Interaction of beaver and elk herbivory reduces standing crop of willow. Ecological Applications: Habitat in the RMNP study areas is suitable for elk, represented by mountain meadows or riparian environments with abundant willow and aspen populations. However elk browsing in the meadows has disturbed willow recruitment and beaver populations (Castor canadensis). Large animals such as elk will browse on shoot tissues from the tops of woody plants. (Baker, Ducharme and Mitchell). Willow growth is limited by elk eating the tops of the new plants. In response to browsing, willow species will respond by compensatory growth. The response or compensatory growth is defined by a positive response of plants to injury, and helps plants tolerate damage from abiotic and biotic interactions (Baker, Ducharme and Mitchell). Beaver and willows will have difficultly thriving in riparian 7

8 environments with heavily browsed usage by ungulates such as elk. (Baker, Ducharme and Mitchell 110). The interaction between elk and beaver create a feedback relationship that has lead to a beaver decline. Regulating overabundant ungulate populations: An example for elk in Rocky Mountain National Park: Bradford and Hobbs used simulation models to determine options for regulation of elk populations in RMNP. This model was important in evaluating elk populations for determining the effective technique that will be used in combination with the current habitat fenced enclosures. It is well known that the technique of culling can achieve population goals in a short time span. According to Bradford and Hobbs, Culling can reduce a population to a target within a single year (Bradford and Hobbs), this approach is good for fast results. However the idea of shooting elk in a National Park is not popular. Wildlife and park managers can use this resource along with fertility control to evaluate control methods for overpopulation of ungulates, in particular elk. Culling management achieves population objects in a short duration; we will focus on fertility control. There are two methods of fertility control; yearlong contraceptive and life time contraceptive. The life time contraceptive technology is still under development, where in yearlong method technology is available (Bradford and Hobbs). In the lifetime control method, there is an increased amount of contact with treatment animals, and possible risk of extinction. This can occur when animals continue to be treated, to a point when all females are infertile. In yearlong contraceptive there is an increased amount of treatment required, with no risk of extinction (Bradford and Hobbs). Objectives This study was designed to assess the effectiveness of the current elk and vegetation management techniques prescribed by the environmental impact statement that was completed by the National Park Service in December The specific study objectives were as follows: 8

9 Assess the impact of elk browsing on willow species in riparian habitat. Compare the health of the unbrowsed willow species within the enclosures to the health of the browsed willows outside the enclosures. Determine whether the use of fenced enclosures is ecologically beneficial. Explore the pros and cons to using fenced enclosures Evaluate whether the enclosures should continue to be used as an effective management technique for maintaining the health of willow species. Investigate the potential for changing management techniques to wolf reintroduction. Study Area The study was conducted in the core winter elk range in the northeastern portion of Rocky Mountain National Park near Estes Park, Colorado. The core winter elk range is a 10,000 hectare area in the park that is divided by glacial moraines into four major valleys: Horseshoe Park, Moraine Park, Beaver Meadows, and Hallowell Park. The elevation in this area is approximately 2,400 m with an average annual precipitation of 41 cm mostly in the form of wet spring snow (Zeigenfuss et al. 1999). Because the study concentrates on riparian willow communities, the specific study plots were located in (1) the Moraine Park area of the Big Thompson River drainage and (2) the Horseshoe Park area of the Fall River drainage. Elk typically travel to these areas in the morning and evenings to feed (Stevens 1980; Green and Bear 1990). Both of these areas have considerable populations of a variety of willow species including: salix monticola, S. geyeriana, and S. planifolia (Peinetti et al.1999). Each of the 40 randomly sampled plots was adjacent to a stream. Half of the sample plots were located within the elk management fences while the other half were located outside of the fenced areas. 9

10 Figure 1: Core Winter Elk Range of RMNP In Figure 1 the core winter elk range of Rocky Mountain National Park is outlined in red. The sample plots used for the study are designated by the purple points. Areas of willow ground cover are highlighted in light green. A hillshaded elevation map is used in the background to show the topography of the area. 10

11 Figure 2: Moraine Park Study Area Figure 3: Horseshoe Park Study Area 11

12 Figure 2 and Figure 3 show close-up views of the two specific study areas at Moraine and Horseshoe Park. The map designates the study plots that are fenced in using blue point features. The orange point features indicate study plots that are unfenced. Figure 4: Image of Elk enclosures Methods To determine the effectiveness of the elk management techniques, random sample plots were taken along riparian habitat in Moraine and Horseshoe Park. Willow species were chosen as the target species for the study because they are a main food source for Elk and an indicator of ecosystem health. The study focuses on the riparian ecosystem, for this reason, all sample plots were located adjacent to streams. Each sample plot was a 4-meter x 4-meter quadrat with one edge running along the stream bank. The data recorded for each quadrat are as follows: GPS coordinates Number of Willow plants 12

13 Measurements of Plants (Including Total Height, Circumference, and longest stem length) Percentage cover of willows (land cover of entire quadrat) Presence or absence of browsing for each willow plant Observations of other plant species Photographs and any other observations (e.g. beaver dams, animal tracks, or scat) Figure 5: Sample plot w/ willow plant circled in red 13

14 A total of 40 sample plots were used for this study. 20 of the plots were within the fenced elk enclosures and 20 were outside of the enclosures in unfenced areas. The measurements of the plants were analyzed using Minitab 16. A two-sample t-test was used to determine whether or not there was a statistically significant difference between the mean measurements (total height, circumference, new growth, and % cover) inside and outside of the fences. The t-test was conducted in two different ways: (1) Plant measurements were averaged for each test plot and (2) The measurements from each individual plant was used, providing a much larger sample size. Results The following tables show the descriptive statistics and t-test results based on the average measurements for each plot (sample size n = 20 fenced and 20 unfenced). Average New Growth in cm n Mean STD Range Minimum Median Maximum Variance Fenced Unfenced % CI for difference: (-42.5, 8.4) T-Value = p-value = DF = 27 Average Circumference in cm n Mean STD Range Minimum Median Maximum Variance Fenced Unfenced % CI for difference: (-225.6, 58.6) T-Value = p-value = DF = 23 14

15 Average Height in cm n Mean STD Range Minimum Median Maximum Variance Fenced Unfenced % CI for difference: (-105.4, 22.0) T-Value = p-value = DF = 22 When analyzing the data of the plot averages for height, circumference, and new growth all p- values were above the expected alpha p-value of.05. Therefore, no significant difference was found to exist between the means of the fenced and unfenced areas. Comparing the STD and range for fenced and unfenced areas reveals unfenced areas to have considerably more variance. Percentage Plot density of willows (below) also shows no statistically significant difference. Percentage Plot Density n Mean STD Range Minimum Median Maximum Variance Fenced Unfenced % CI for difference: (-7.01, 26.11) T-Value = 1.17 p-value = DF = 34 The following histograms show the results of analyzing each individual plant measurement (sample size n = 99 fenced and n = 103 unfenced). The p-values for these t-tests were all below alpha levels indicating a significant difference between fenced and unfenced areas. This shows that the previous results for plot averages were only statistically insignificant due to their smaller sample sizes. 15

16 Frequency Frequency Histogram of circumference Normal fenced unfenced fenced Mean StDev N unfenced Mean StDev N Panel variable: fenced/unfenced circumference 95% CI for difference: (10.70, 49.21) T-Value = 3.07 p-value = DF = 154 Histogram of new growth cm Normal fenced unfenced fenced Mean StDev N unfenced Mean StDev N Panel variable: fenced/unfenced new growth cm 95% CI for difference: (6.13, 22.75) T-Value = 3.43 p-value = DF =

17 Frequency Histogram of total height cm Normal fenced unfenced fenced Mean StDev N 99 unfenced Mean StDev N Panel variable: fenced/unfenced total height cm 95% CI for difference: (10.70, 49.21) T-Value = 3.07 p-value = DF = 154 These three histograms also show more variance of plant size within the unfenced areas when compared to the fenced areas. Discussion Our results for the total number of individual plant measured showed a significant difference in height (p-value = 0.003) circumference (p-value = 0.044) and new growth i.e. length of longest supple branch from node (p-value = 0.001). Which means that willows within the fenced areas are taller, wider, and have longer branches that displayed new growth. We also found more variation in height (STD unfenced = 87.5, STD fenced= 45.3) and circumference (STD unfenced = 237, STD fenced = 135) of the plants outside the fenced areas. Our results didn t show any significant difference when the plot data was averaged for each category and analyzed, this is likely due to the smaller sample size. Our Plot density also showed no significant difference (p-value = 0.249) between the fenced and unfenced areas. While we did observe possible previous beaver activity and remnants of past dams no active beaver 17

18 dams was observed in Moraine park or Horseshoe park, along the portions of the riparian zone that our plots were established. Based on observations made during the data collections willow in unfenced areas were highly browsed (100%) and leafless with majority (90%) brittle woody stems. The willows found in the fenced exclosures appeared to be much healthier, with supple branches (95%) and vegetative growth intact (100%), as well as displaying considerable amounts of reproductive growth. From our results and observations we see a significant difference in plant quality. Willows outside of the fenced areas continue to show signs of severe damage. It appears that there has been no improvement in reducing elk impact on willow communities since the implementation of the EVMP. Thus implying that elk culling as a component of the EVMP is not an effective management tool in reducing the impact of elk on riparian willow communities within RMNP. There is very little evidence of new willow establishment or recruitment into larger size classes, suggesting that the long-term persistence of these communities continues to be threatened. The fenced areas do appear to be effective in allowing the willow communities to re-establish. However, fenced areas may not be a long-term solution due to the need for ungulate herbivory as a natural and necessary component to a healthy ecosystem. Large native ungulate herbivores can influence many aspects of plant structure, growth, and net primary productivity. Ungulate grazing and the action of their hooves can result in more bare ground, soil compaction, and higher sediment yields. Increases in bare ground could result in warmer and drier microclimates. A warmer soil could result in increased nitrogen mineralization. Ungulates can also influence the nitrogen cycle by changing litter quality, which could affect nitrogen mineralization rates, as well as directly adding nitrogen to the soils through their urine and feces (Hobbs 1996). Intensely grazed grasses and shrubs have more optimal root-to-shoot ratios, longer growing seasons, higher water conductance, and higher survival than their un-grazed counterparts (Welker and Menke 1990). Holland 18

19 and Deting (1991) observed that rates of photosynthesis and nitrogen uptake were higher on grazed sites. Ungulates can increase biodiversity as well as influence succession (Hobbs 1996). Thus we regard limited ungulate herbivory as a natural as well as necessary component of a healthy ecosystem. Although multiple factors may contribute to the decline of willow communities, including climate, hydrologic changes associated with declining beaver populations, and direct anthropogenic disturbances (Singer et al. 1998), elk herbivory appears to be the main contributor to plant size, health, and recruitment. Elk may not have a direct affect on willow density and distribution. However, they indirectly affect beaver populations. In a study done by Peinetti (2002) data was collected from 1937, 1946 and 1996 in order to determine the extent of changes in willow cover in eastern slope of RMNP including Moraine Park and Horseshoe Park. The study found that elk could have reduced canopy cover within a willow patch by suppressing growth, but the total area covered by willow in the valley would be primarily controlled by the amount of wet habitats suitable for riparian vegetation. However, elk could indirectly affect beaver by reducing the extent of tall willows. It is not clear the primary cause of beaver decline in RMNP, but it is likely the increased elk population contributed. (Peinetti et al. 2002) Willow declines in the presence of high elk densities have been documented in RMNP, Yellowstone National Park (YNP) (Singer et al. 1998) and National Elk Refuge (Smith and Robbins 1994). All of these areas have similar histories of human alterations of the landscape, wildlife, and hydrologic conditions. The climate has also become warmer and drier throughout the century, thus contributing to willow declines in YNP as well as RMNP (Singer et al. 1998). Beaver declines have also been documented in both of the parks on their major elk winter ranges (Peinetti et al. 2002). 19

20 Possible weaknesses in our research could come from the willow stands in the open areas having a lack of leaves making it difficult to positively identify willow species. There may have been possible inconsistencies in the measurements taken due to various groups collecting data, particularly for new growth where it was often difficult to determine the branch to measure when they are primarily brittle in unfenced areas and also due to some confusion of what to identify in terms of new growth. Strengths in our research include our random sample plots along the riparian zones, as well as location and timing. Our two data collection sites within the core elk winter range, Moraine Park and Horseshoe Park have very high densities of elk especially in the months of October and November when rutting season takes place. Conclusions We found that willows within the fenced areas were larger, healthier and showed more signs of reproductive growth. There by suggesting elk are the primary component contributing to size and integrity of willow stands. We also conclude that the EVMP, since its implementation in 2009, has not had any noticeable impact on reducing the impact of elk on riparian willow communities. There are no noticeable signs of beaver re-establishment within Moraine and Horseshoe Park. From our research, it appears that in order to successfully revive a healthy and natural ecosystem there needs to be a toppredator introduced which will likely alter not only elk population but also elk behavior. With an intact predator base, elk would be more wary and less concentrated in certain areas thus making willow and aspen more abundant. After the grey wolves were reintroduced to Yellowstone in 1995, the results were immediately seen. Within two years the wolf population grew to 97, and their presence effected most realms of the park. The wolves had killed half the coyote population, which increased the number of coyote prey such as deer and ground squirrels. The mid-level predators such as foxes, hawks, owls and pine martens, then benefited from having larger prey populations, thus 20

21 increasing species diversity and balance. The coyote population that survived the wolf reintroduction began to prosper living on the edges of wolf habitats and benefiting from carcasses wolves had left behind. The carcasses not only benefited the coyotes, but also many scavengers and bears. The number of ravens doubled, and eagles increased fivefold. In addition, the wolves began to solve one of the growing problems in the park, the abundance of the elk population. Elk populations have decreased by half since the introduction of the wolves in A healthy fear of wolves also keeps elk from lingering at stream sides, where they are more vulnerable to predators. Thus allowing willows, cottonwoods, and other riparian vegetation to rebound which in turn helps to stabilize stream banks restoring natural water flow and healthy vegetation with intact canopies, which provide overhanging branches that shade the water and provide bird habitats. Beaver colonies in North Yellowstone have risen from one to twelve, since some stream banks have become lush with vegetation, especially willows (a key beaver food). Beaver dams create ponds and marshes, supporting fish, amphibians, birds, small mammals, and rich insect populations to feed them (Robbins, 2004). Our study indicates that wolf reintroduction would be a wise management decision, at least from an ecological perspective. Social, economic, and political pressures may not allow this to be possible though. So other alternatives may need to be considered, some of these may include: (1) a system of rotating fences allowing for seasonal browsing (2) Increased culling to limit elk browsing so that willow species return to a healthy state (3) Increased use of contraceptives and redistribution techniques or (4) Some combination of the above techniques. In future research there could be more samples taken, over longer periods of time. Possibly comparing willow quality in summer months to our samples taken during rutting season. 21

22 References Baker, Bruce W, et al. "Interaction of beaver and elk herbivory reduces standing crop of willow." Ecological Applications (2005): Beschta, Robert L Reduced Cottonwood recruitment following extirpation of wolves in Yellowstone s northern range. Ecology, 86(2): Bradford, John B and N. Thompson Hobbs. "Regulating overabundant ungulate populations: An example for elk in Rocky Mountain National Park, Colorado." Journal of Environmental Management (2008): Coughenour, M. B., and F. J. Singer Elk population processes in Yellowstone National Park under the policy of natural regulation. Ecological Applications 6: Hobbs, N.T Modification of ecosystems by ungulates. Journal of Wildlife Management 45: Environmental Impact Statement, Elk and Vegetation Management Plan. Rocky Mountain National Park. December 2007 Georgiadis, N.J., R.W. Ruess, S.J. McNaughton, and D. Western Ecological conditions that determine when grazing stimulates grass production. Oecologia 81: Green, R.A., and G.D. Bear Seasonal cycles and daily activity patterns of Rocky Mountain elk. Journal of Wildlife Management 54: Holland, E.A., and J.K., Detling Plant responses to herivory and belowground nitrogen cycling. Ecology 71: Laundre J. W., Hernandez L., and Altendorf K Wolves, elk, and bison: reestablishing the landscape of fear in Yellowstone National Park, U.S.A. NRC Research Press Web site at Lubow, B. C., F. J. Singer, T. L. Johnson, and D. C. Bowden Dynamics of interacting elk populations within and adjacent to Rocky Mountain National Park. Journal of Wildlife Management 66: Also in F. J. Singer, ed. Ecological evaluation of the abundance and effects of elk in Rocky Mountain National Park, Colorado, USGS Open File Report National Park Service, U.S. Department of Interior Elk and Vegetation Management Plan (EVMP) Enivironmrntal Impact Statement (EIS). Peinetti, H. R., M. A. Kalkhan, and M. B. Coughenour Long-term changes in willow spatial distribution on the elk winter range of Rocky Mountain National Park (USA). Landscape Ecology: 17: Also in F. J. Singer, ed. Ecological evaluation of the abundance and effects of elk in Rocky Mountain National Park, Colorado, USGS Open File Report

23 Robbins, J Lessons from the Wolf - Restoring the top predator to Yellowstone has altered the balance of the park's flora and fauna for more than expected. Scientific American. 290, no. 6: 76 Singer, F. J., L. C. Mack, and R. C. Cates Ungulate herbivory of willows on Yellowstone's northern winter range. Journal of Range Management 47: Singer, F. J., L. C. Zeigenfuss, R. G. Cates, and D. T. Barnett Elk, multiple factors, and persistence of willows in national parks. Wildlife Society Bulletin 26: Smith, B. L., and R. L. Robbins Migrations and management of the Jackson elk herd. Resource Publication, National Biological Survey. vol 199, pp.61 Lubow, B. C., F. J. Singer, T. L. Johnson, and D. C. Bowden Dynamics of interacting elk populations within and adjacent to Rocky Mountain National Park. Journal of Wildlife Management 66: Also in F. J. Singer, ed. Ecological evaluation of the abundance and effects of elk in Rocky Mountain National Park, Colorado, USGS Open File Report Tripler, C E, et al. "Soil nitrogen availability, plant luxury consumption, and herbivory by white-tailed deer." Oecologia (2002): Welker, J. M., and J.W. Menke The influence of simulated browsing on tissue relations, growth and survival of Quercus gouglasii seedlings under slow and rapid rates of soil drought. Functional Ecology. 4: Wright, R. Gerald Wildlife management in the National Parks: questions in search of answers. Ecological Applications, 9(1): Zeigenfuss, L. C., F. J. Singer, and D. Bowden Vegetation responses to natural regulation of elk in Rocky Mountain National Park. Biological Science Report USGS/BRD/BSR U.S. Government Printing Office, Denver, Colorado. Also in F. J. Singer, ed. Ecological evaluation of the abundance and effects of elk in Rocky Mountain National Park, Colorado, USGS Open File Report Zeigenfuss. L. C., F. J. Singer, S. A. Williams, and T. L. Johnson Factors influencing plant productivity in shrub communities on elk winter range of Rocky Mountain National Park: experiments on elk herbivory, water availability, and burning. In F. J. Singer, ed. Ecological evaluation of the abundance and effects of elk in Rocky Mountain National Park, Colorado, USGS Open File Report

24 Acknowledgements Data Collection: Matthew Arellano, Nicole Brunner, Stephen Geuder, and Kim Shoppell GIS/GPS: Stephen Geuder Photography: Nicole Brunner and Stephen Geuder Abstract: Kim Shoppell Literature Review: Matthew Arellano, Nicole Brunner, and Kim Shoppell Introduction: Nicole Brunner Objectives: Nicole Brunner and Stephen Geuder Study Area: Stephen Geuder Methods: Stephen Geuder Statistical Analysis: Nicole Brunner and Stephen Geuder Results: Kim Shoppell Discussion: Nicole Brunner Conclusion: Matthew Arellano and Nicole Brunner Poster: Matthew Arellano References: Matthew Arellano, Nicole Brunner, Stephen Geuder, and Kim Shoppell Special Thanks: Dr. Jason Janke 24

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