Process to Monitor and Manage Ungulate Browsing Pressure

Plant communities are monitored to prevent ungulate browsing from having an adverse effect on habitat. The monitoring process described in this paper applies to plant species capable of growing through the browse zone, and uses two measurements (percent intensely browsed and LD Index) to determine if browsing will prevent the height growth of a young plant. To determine the potential effect of browsing on habitat structure, two variables are compared: 1) Existing browsing pressure is the percent of young plants that browsing is predicted to prevent from growing to full height. 2) Threshold browsing pressure is the percent of young plants that must grow to full height to attain a specified habitat structure. The process includes specifying target conditions, data collection and analysis, and refinement based on that analysis. The process requires a long-term commitment, but a minimal investment of time each year. By repeating the process over a period of years, the effects of browsing are documented and steps in the process are refined

Stages of Habitat Structural Trend That are Related to Ungulate Browsing

To maintain their structural identity, communities of tall-growing trees and shrubs depend on the growth of young plants to replace mature individuals that die. Ungulate browsing influences that structure by permitting or preventing the height growth of young plants. The resulting changes in structure are indicted by the browsing-related architectures of plants that grow within the browse zone, i.e., those ? 2.5 m tall. Using examples from six National Wildlife Refuges, we describe six stages of structural trend and their management implications: 1) Structure is Stable, i.e., all plants have Uninterrupted-growthtype architecture; 2) Early Stage of Structural Decline most or all plants have Arrested- or Retrogressed-type architecture and there is no visible evidence of dieback; 3) Intermediate Stage of Structural Decline, i.e., all plants have Arrested- or Retrogressed-type architecture, dieback is apparent, and live stems extend throughout the lower half of the browse zone; 4) Advanced Stage of Decline, i.e., all plants have Arrested- or Retrogressed-type architecture and live stems are restricted to the lowest part of the browse zone; 5) Structure is Lost, i.e., no live plants; and 6) Recovery of Structural Diversity, i.e., there is evidence that the Early, Intermediate, or Advanced Stage of Decline existed, and that young Uninterrupted-growth type plants are growing into the browse zone. Three factors influence the rate-of-change from one stage to another: Susceptibility, Resistance, and Resilience. Because the stages are independent of species composition, they provide a means of comparing the effect of browsing in diverse habitats across a region

Effect of Browsing Following Wildfire in the Missouri Breaks

This study examined the effect of browsing on skunkbush (Rhus trilobata) and chokecherry (Prunus virginiana) following two wildfires in the Missouri Breaks region of Garfield County in east-central Montana, one fire in the 2003 the other in 2006. Study objectives included: 1) Determine the potential height to which skunkbush and chokecherry can grow under local conditions, and 2) Determine if browsing will prevent young plants from attaining that potential height. Because ungulates are attracted to recently burned areas it is important to monitor browse use and regulate browsing pressure to a benign level. We documented the effect of browsing by measurement of plant height and age, browsing level, and LD Index. The most rapid growth occurred in the first two years following the fires. It is predicted that browsing will not prevent skunkbush from growing to its potential height. Three lines of evidence indicate that browsing is likely to prevent many chokecherry plants from growing to potential height. In the first few years following wildfire, the potential effect of browsing is best documented by analysis of height and age relationships and by analysis of stem growth rate. After five years browsing level and LD Index are a more-precise means of documenting the effect of browsing

15th Wildland Shrub Symposium - Shrublands: Wildlands and Wildlife Habitats, 2008 June 17-19, Bozeman, MT

The 35 papers in this proceedings are divided into four sections; the first includes an introduction to the symposium theme of Shrublands as wildlands and wildlife habitat, along with keynote addresses discussing geographic affiliations of eastern Montana\u27s great Plains Flora and methodology for surveying mule deer winter range habitat use and condition. The next two sections cluster papers on wildlife habitat and ecological relationships. These sections provide a diverse sampling of topics examining the nature and impacts of intra- and inter-trophic relationships among plants and associated species of western North American shrublands. Papers in the final section present assessments of various sampling and monitoring methodologies applicable to shrublands

Aspen Recruitment in the Yellowstone Region Linked to Reduced Herbivory After Large Carnivore Restoration

Quaking aspen (Populus tremuloides) recruitment during the 1980s–90s was suppressed by Rocky Mountain elk (Cervus canadensis) herbivory on winter ranges in the Yellowstone region, and saplings (young aspen taller than 2 m) were rare. Following the 1995–96 reintroduction of gray wolves (Canis lupus), browsing decreased and sapling recruitment increased in Yellowstone National Park. We compared aspen data from inside the park to data collected in three winter ranges outside the park. For most areas, the percentage of young aspen browsed annually was 80–100% in 1997–98, decreasing to 30–60% in 2011–15. Sapling recruitment was inversely correlated with browsing intensity, and increased despite climate trends unfavorable for aspen. Browsing decreased with decreasing elk density, a relationship suggesting that densities greater than about 4 elk/km2 resulted in consistently strong browsing effects likely to suppress aspen recruitment. Changes in elk density and distribution were influenced by predators, as well as human hunters. Most evidence for trophic cascades involving large terrestrial mammals has been from protected areas within national parks. This study provides evidence of widespread changes in plant communities resulting from large carnivore restoration, extending outside a protected national park to areas with hunting, livestock grazing, and other human activities

The Prehistoric Bison of Yellowstone National Park

When Yellowstone National Park (YNP) was established in 1872, American bison (Bison bison) were living in the park's forests and mountains. A study conducted in the 1960s concluded that those were Mountain bison (Bison bison athabascae), a subspecies adapted to mountain habitat. It was assumed that those historical bison occupied their native habitat and had done so in prehistoric times. When archaeological evidence of YNP bison was discovered in the mid-1990s it seemed reasonable to assume that those bones were derived from a herd of native prehistoric bison. However, a review of archaeological, historical, genetic, and ecological evidence suggests a different history. Namely, herds of bison were absent before 1840. Sometime between 1840 and the mid-1850s, plains bison were driven into the mountain forest in and near YNP. In those forests, bison were relatively safe from horse-mounted, bow-and-arrow-armed Native American hunters. Archaeological evidence suggests that YNP's prehistoric bison were bulls that left herds on the low-elevation plains that surround the park; the bulls would have traveled up mountain drainages to the Yellowstone volcanic plateau. Bison played no significant role in the ecological processes that shaped YNP's prehistoric landscape. YNP's modern bison herd is causing significant changes in range condition.The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

How Perceptions About Naturalness Affect Science in Yellowstone National Park

This paper describes a history of science and management on the Northern Range of Yellowstone National Park (YNP). In 1983 YNP began to shape public perceptions about management issues. In this case study, YNP shaped public perceptions to cause an unnatural condition (the appearance of the Northern Range was due to the extermination of wolves) to be portrayed as a natural condition (the appearance was due to climate change). Perception shaping can adversely affect the quality of science and influence the role of science in resource management. Perception shaping can have devastating ecologic consequences.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

An increase in herbivory of cottonwood in Yellowstone National Park

This study examined an effect of elk (Cervus elaphus nelsoni) on narrowleaf cottonwood (Populus angustifolia) in northern Yellowstone National Park, where stands consist of old trees and younger, densely-branched bushes. The elk herd increased from a census of 3,172 in 1968 to a census of 18,913 in 1988. The purposes of this study were to: 1) document the height-growth of cottonwood bushes, 2) determine if the height of browsing corresponded with snow depth, and 3) determine if there has been a recent increase in cottonwood herbivory. In 5 stands of different age (ranging ca. 9-45 y old), I measured the height of live previous-year-growth and the height of the oldest stems killed by browsing. The tallest previous-year-growth was 80 cm; all stems taller than 29 cm had been browsed. Stems were killed by browsing closer to the ground in younger stands (respectively, 87, 62, 28, 14, and 9 cm; P lt 0.001). There was no change in mid-winter snow depth during the period 1950-1994. The 2 stands established since 1977 had relatively small variances in the height at which stems were killed by browsing (21 and 15 cm-2), a uniformity likely caused by intense herbivory since respective stand creation. The large variances in the height of browse-killed stems in older stands (745, 399, and 291 cm-2) were likely caused by an initial period of light-to-moderate herbivory followed by an increase in herbivory that killed the stem tips at the heights existing at the time. The bush growth-form apparently results from an increase in herbivory that occurred between 1968 and 1977, a period in which the elk winter census increased from 3,172 to 8,981. The weight of evidence suggests that EuroAmerican influences have caused the northern elk herd to increase in number since the establishment of the park. If herbivory does not decrease, cottonwood may be eliminated from Yellowstone's northern rang