Long-term aspen dynamics, trophic cascades, and climate in northern Yellowstone National Park

2016 ◽  
Vol 46 (4) ◽  
pp. 548-556 ◽  
Author(s):  
Robert L. Beschta ◽  
Luke E. Painter ◽  
Taal Levi ◽  
William J. Ripple
Keyword(s):  
Populus Tremuloides ◽  
Cervus Elaphus ◽  
Yellowstone National Park ◽  
National Park ◽  
Average Density ◽  
Drought Severity ◽  
Quaking Aspen ◽  
Climatic Trend ◽  
Predator Prey

We report long-term patterns of quaking aspen (Populus tremuloides Michx.) recruitment for five ungulate exclosures in the northern ungulate winter range of Yellowstone National Park. Aspen recruitment was low (<3 aspen·ha−1·year−1) in the mid-1900s prior to exclosure construction due to herbivory by Rocky Mountain elk (Cervus elaphus Linnaeus, 1758) but increased more than 60-fold within 25 years after exclosure construction despite a drying climatic trend since 1940. Results support the hypothesis that long-term aspen decline in Yellowstone’s northern range during the latter half of the 20th century was caused by high levels of ungulate herbivory and not a drying climate. Gray wolves (Canis lupus Linnaeus, 1758) were reintroduced during 1995–1996. For the period 1995–2012, we summarized annual predator–prey ratios, ungulate biomass, and drought severity. The average density of young aspen increased from 4350 aspen·ha−1 in 1997–1998 to 8960 aspen·ha−1 in 2012; during the same time period, those >1 m in height increased over 30-fold (from 105 to 3194 aspen·ha−1). Increased heights of young aspen occurred primarily from 2007 to 2012, a period with relatively high predator–prey ratios, declining elk numbers, and decreasing browsing rates. Consistent with a re-established trophic cascade, aspen stands in Yellowstone’s northern range have increasingly begun to recover.

scholarly journals Distribution, Morphology, Survival, and Genetics of Aspen (Populus Tremuloides) Seedlings Following the 1988 Yellowstone Fires

1996 ◽  
Vol 20 ◽  
pp. 118-122
Author(s):  
Monica Turner ◽  
Rebecca Reed ◽  
William Romme ◽  
Gerald Tuskan
Keyword(s):  
Populus Tremuloides ◽  
Yellowstone National Park ◽  
National Park ◽  
Plant Competition ◽  
Mineral Soil ◽  
Rare Event ◽  
Weather Conditions ◽  
Elevational Gradient ◽  
Quaking Aspen ◽  
Burned Areas

An unexpected consequence of the 1988 Yellowstone fires was the widespread establishment of seedlings of quaking aspen (Populus tremuloides) in the burned forests, including areas outside the previous range of aspen (Kay 1993; Romme et al. 1997). Although aspen is the most widely distributed tree species in North America (Powells 1965), it is relatively uncommon and localized in distribution within Yellowstone National Park (Despain 1991). Most aspen stands in Yellowstone are found in the lower elevation landscapes in the northern portion of the park, and the species was absent - prior to 1988 -- across most of the high plateaus that dominate the southern and central park area. Aspen in the Rocky Mountain region reproduces primarily by means of vegetative root sprouting. Although viable seeds are regularly produced, establishment of seedlings in the wild is apparently a rare event due to the limited tolerance of aspen seedlings for desiccation or competition (e.g., Pearson 1914; McDonough 1985). In the immediate aftermath of the 1988 Yellowstone fires, there was a brief "window of opportunity" for aspen seedling establishment, as a result of abundant aspen seed production, moist weather conditions in spring and summer, and bare mineral soil and reduced plant competition within extensive burned areas (Jelinski and Cheliak 1992; Romme et al. 1997). We initiated this 3-year study in 1996 to address four questions about the aspen seedlings now growing in burned areas across the Yellowstone Plateau: (1) What are the broad-scale patterns of distribution and abundance of aspen seedlings across the subalpine plateaus of Yellowstone National Park? (2) What is the morphology and population structure -- e.g., proportions of genets (genetic individuals that developed from a single seed) and ramets (vegetative root sprouts produced by a genet) of various ages - in aspen seedling populations? (3) What are the mechanisms leading to eventual persistence or extirpation of seedling populations along an elevational gradient, particularly with respect to ungulate browsing and plant competition? (4) What is the genetic diversity and relatedness of the seedling populations along gradients of elevation and substrate?

scholarly journals Climate induced wolf prey selection in Yellowstone National Park, 1995-2015

2016 ◽  
Author(s):  
Douglas W Smith ◽  
Matthew Metz ◽  
Chris Wilmers ◽  
Daniel Stahler ◽  
Chris Geremia
Keyword(s):  
Yellowstone National Park ◽  
National Park ◽  
Prey Selection ◽  
Selective Advantage ◽  
Late Winter ◽  
Age Classes ◽  
Predator Prey ◽  
Wolf Predation ◽  
Management Objectives

Prey selection by wolves has been a fundamental and long-term topic of interest for wolf-prey studies. Virtually all studies conclude the selectivity of wolf predation and typically identify what made an individual vulnerable. Vulnerability, however, varies for multiple reasons and emerging research is discovering climate induced effects on prey forage altering condition and selective advantage of migration. We present data from a twenty year study of wolf-elk predation in Yellowstone National Park (YNP) which found bull elk killed more frequently in early winter after years with less snowfall compared to years with normal snowfall. Snowfall impacted summer forage, which impacted bull elk condition going into the autumn rut, which weakened elk prematurely post-rut causing them to be selected by wolves in early rather than late winter, and possibly caused more bulls to be killed overall. Bull elk ratios have declined over the last 20 years (from 40-60 to 10-15 bulls/100 cows; lower outside YNP), which has led to calls for a reduced human harvest on bulls which has been met with significant resistance. Understanding the interaction between climate, forage and wolf predation on bull elk (and other sex/age classes) will help guide management decisions and potentially sustain hunting of bulls in the long term as well as protect natural management objectives within YNP. Results will be of widespread value as they may suggest changing predator-prey dynamics across North America by making some otherwise healthy prey vulnerable to predation.

scholarly journals Landscape-Level Interactions Among Ungulates, Vegetation, and Large-Scale Fires in Northern Yellowstone National Park

1992 ◽  
Vol 16 ◽  
pp. 206-211
Author(s):  
Monica Turner ◽  
Yegang Wu ◽  
Scott Pearson ◽  
William Romme ◽  
Linda Wallace
Keyword(s):  
Populus Tremuloides ◽  
Cervus Elaphus ◽  
Yellowstone National Park ◽  
National Park ◽  
Large Scale ◽  
Field Studies ◽  
Bison Bison ◽  
Fire Size ◽  
Management Scenarios ◽  
Winter Range

The scale of the 1988 fires in Yellowstone National Park (YNP) raised numerous questions for the management of natural areas subject to large, infrequent disturbances. An important management issue in YNP involves the interaction of large-scale fire with the large assemblage of native ungulates and vegetation dynamics in the landscape. We used landscape modeling and field studies to address basic questions about the effects of fire scale and heterogeneity on resource utilization and survival of free-ranging elk (Cervus elaphus) and bison (Bison bison), and the production and regeneration of preferred forage grasses and aspen in northern Yellowstone Park. More specifically, we asked (1) how fire size interacts with winter severity to control ungulate feeding behavior and survival, both in the initial postfire winter, when fire reduces forage, and in later postfire winters, when fire augments forage; (2) how fire pattern (e.g., clumped vs. dispersed burn sites) modifies the effects of fire size; (3) which environmental factors, including fire, influence selection of feeding areas by wintering ungulates at a variety of scales, from a single feeding station to the entire northern winter range; and (4) how the size and spatial pattern of burning influence regeneration of aspen (Populus tremuloides), a preferred and heavily browsed species in YNP. We focus on elk and bison because these are by far the most numerous ungulates in the area (Houston 1982), and we have chosen to examine winter grazing and browsing for several reasons. Winter range conditions are the primary determinant of ungulate survival and reproduction in Yellowstone, and winter utilization of the vegetation by ungulates appears to be intense in some areas. Ungulates make distinct foraging choices in the winter as in the rest of the year, and burn patterns may influence those choices in ways that we represent as hypotheses described later. In addition, the activities of animals can be readily monitored in the winter, and the exact locations of feeding and bedding sites can be determined. Travel routes are easily monitored, and the ability to sight animals is high; therefore, group locations and sizes can be readily determined. This research complements ongoing studies in Yellowstone by expanding the spatial scale at which plant-herbivore dynamics are considered and by explicitly addressing the effects of spatial heterogeneity. We produced a spatially explicit simulation model of the winter range that predicts plant and ungulate dynamics under varying fire sizes, fire patterns, winter weather scenarios. The model and field studies will generate quantitative comparisons of the effects of large and small fires on ungulate survival and will thereby permit the simulation of the effects of alternative fire management scenarios.

scholarly journals Distribution, Morphology, Survival, and Genetics of Aspen (Populus tremuloides) Seedlings Following the 1988 Yellowstone Fires

1997 ◽  
Vol 21 ◽  
pp. 135-137
Author(s):  
Monica Turner ◽  
Rebecca Reed ◽  
William Romme ◽  
Gerald Tuskan
Keyword(s):  
Populus Tremuloides ◽  
Yellowstone National Park ◽  
National Park ◽  
Plant Competition ◽  
Mineral Soil ◽  
Rare Event ◽  
Weather Conditions ◽  
Elevational Gradient ◽  
Quaking Aspen ◽  
Burned Areas

An unexpected consequence of the 1988 Yellowstone fires was the widespread establishment of seedlings of quaking aspen (Populus tremuloides) in the burned forests, including areas outside the previous range of aspen (Kay 1993, Romme et al.1997). Although aspen is the most widely distributed tree species in North America (Powells 1965), it is relatively uncommon and localized in distribution within Yellowstone National Park (Despain 1991). Most aspen stands in Yellowstone are found in the lower elevation landscapes in the northern portion of the park, and the species was absent -- prior to 1988 -- across most of the high plateaus that dominate the southern and central park area. Aspen in the Rocky Mountain region reproduces primarily by means of vegetative root sprouting. Although viable seeds are regularly produced, establishment of seedlings in the wild is apparently a rare event due to the limited tolerance of aspen seedlings for desiccation or competition (e.g., Pearson 1914, McDonough 1985). In the immediate aftermath of the 1988 Yellowstone fires there was a brief "window of opportunity" for aspen seedling establishment, as a result of abundant aspen seed production, moist weather conditions in spring and summer, and bare mineral soil and reduced plant competition within extensive burned areas (Jelinski and Cheliak 1992, Romme et al. 1997). We initiated this 3-year study in 1996 to address four questions about the aspen seedlings now growing in burned areas across the Yellowstone Plateau: (1) What are the broad-scale patterns of distribution and abundance of aspen seedlings across the subalpine plateaus of Yellowstone National Park? (2) What is the morphology and population structure -- e.g., proportions of genets (genetic individuals that developed from a single seed) and ramets (vegetative root sprouts produced by a genet) of various ages -- in aspen seedling populations? (3) What are the mechanisms leading to eventual persistence or extirpation of seedling populations along an elevational gradient, particularly with respect to ungulate browsing and plant competition? (4) What is the genetic diversity and relatedness of the seedling populations along gradients of elevation and substrate? We completed our sampling for questions 2 and 4 in 1996 (see our 1996 annual report for details). In 1997 we continued our annual sampling related to questions 1 and 3.

scholarly journals Climate induced wolf prey selection in Yellowstone National Park, 1995-2015

2016 ◽  
Author(s):  
Douglas W Smith ◽  
Matthew Metz ◽  
Chris Wilmers ◽  
Daniel Stahler ◽  
Chris Geremia
Keyword(s):  
Yellowstone National Park ◽  
National Park ◽  
Prey Selection ◽  
Selective Advantage ◽  
Late Winter ◽  
Age Classes ◽  
Predator Prey ◽  
Wolf Predation ◽  
Management Objectives

Prey selection by wolves has been a fundamental and long-term topic of interest for wolf-prey studies. Virtually all studies conclude the selectivity of wolf predation and typically identify what made an individual vulnerable. Vulnerability, however, varies for multiple reasons and emerging research is discovering climate induced effects on prey forage altering condition and selective advantage of migration. We present data from a twenty year study of wolf-elk predation in Yellowstone National Park (YNP) which found bull elk killed more frequently in early winter after years with less snowfall compared to years with normal snowfall. Snowfall impacted summer forage, which impacted bull elk condition going into the autumn rut, which weakened elk prematurely post-rut causing them to be selected by wolves in early rather than late winter, and possibly caused more bulls to be killed overall. Bull elk ratios have declined over the last 20 years (from 40-60 to 10-15 bulls/100 cows; lower outside YNP), which has led to calls for a reduced human harvest on bulls which has been met with significant resistance. Understanding the interaction between climate, forage and wolf predation on bull elk (and other sex/age classes) will help guide management decisions and potentially sustain hunting of bulls in the long term as well as protect natural management objectives within YNP. Results will be of widespread value as they may suggest changing predator-prey dynamics across North America by making some otherwise healthy prey vulnerable to predation.

scholarly journals Distribution, Morphology, Survival, and Genetics of Aspen (Populus tremuloides) Seedlings Following the 1988 Yellowstone Fires

1998 ◽  
Vol 22 ◽  
pp. 53-55
Author(s):  
Monica Turner ◽  
Rebecca Reed ◽  
William Romme ◽  
Gerald Tuskan
Keyword(s):  
Populus Tremuloides ◽  
Yellowstone National Park ◽  
National Park ◽  
Plant Competition ◽  
Mineral Soil ◽  
Rare Event ◽  
Weather Conditions ◽  
Elevational Gradient ◽  
Quaking Aspen ◽  
Burned Areas

An unexpected consequence of the 1988 Yellowstone fires was the widespread establishment of seedlings of quaking aspen (Populus tremuloides) in the burned forests, including areas outside the previous range of aspen (Kay 1993, Romme et al. 1997). Although aspen is the most widely distributed tree species in North America (Fowells 1965), it is relatively uncommon and localized in distribution within Yellowstone National Park (Despain 1991). Most aspen stands in Yellowstone are found in the lower elevation landscapes in the northern portion of the park, and the species was absent -- prior to 1988 -- across most of the high plateaus that dominate the southern and central park area. Aspen in the Rocky Mountain region reproduces primarily by means of vegetative root sprouting. Although viable seeds are regularly produced, establishment of seedlings in the wild is apparently a rare event due to the limited tolerance of aspen seedlings for desiccation or competition (e.g., Pearson 1914, McDonough 1985). In the immediate aftermath of the 1988 Yellowstone fires, there was a brief "window of opportunity" for aspen seedling establishment, as a result of abundant aspen seed production, moist weather conditions in spring and summer, and bare mineral soil and reduced plant competition within extensive burned areas (Jelinski and Cheliak 1992, Romme et al. 1997). We initiated this 3-year study in 1996 to address four questions about the aspen seedlings now growing in burned areas across the Yellowstone Plateau: (1) What are the broad-scale patterns of distribution and abundance of aspen seedlings across the subalpine plateaus of Yellowstone National Park? (2) What is the morphology and population structure -- e.g., proportions of genets (genetic individuals that developed from a single seed) and ramets (vegetative root sprouts produced by a genet) of various ages -- in aspen seedling populations? (3) What are the mechanisms leading to eventual persistence or extirpation of seedling populations along an elevational gradient, particularly with respect to ungulate browsing and plant competition? (4) What is the genetic diversity and relatedness of the seedling populations along gradients of elevation and substrate? We completed our sampling for questions 2 and 4 in 1996 (see our 1996 annual report for details). In 1997 and again in 1998 we continued our annual sampling related to questions 1 and 3.

ESTABLISHMENT, PERSISTENCE, AND GROWTH OF ASPEN (POPULUS TREMULOIDES) SEEDLINGS IN YELLOWSTONE NATIONAL PARK

Ecology ◽  
2005 ◽  
Vol 86 (2) ◽  
pp. 404-418 ◽  
Author(s):  
William H. Romme ◽  
Monica G. Turner ◽  
Gerald A. Tuskan ◽  
Rebecca A. Reed
Keyword(s):  
Populus Tremuloides ◽  
Yellowstone National Park ◽  
National Park

Threat of predation: do ungulates behave aggressively towards different members of a coyote pack?

1999 ◽  
Vol 77 (3) ◽  
pp. 499-503 ◽  
Author(s):  
Eric M Gese
Keyword(s):  
Body Size ◽  
Aggressive Behavior ◽  
Cervus Elaphus ◽  
Yellowstone National Park ◽  
National Park ◽  
Bison Bison ◽  
Antilocapra Americana ◽  
Wild Canids ◽  
Pronghorn Antelope ◽  
Large Groups

Wild ungulates have evolved a variety of antipredator strategies to deter or escape predation by carnivores. Among wild canids, the dominant pair of a pack often initiates attacks upon prey. Previous observations in Yellowstone National Park, Wyoming, showed that the alpha pair in a coyote (Canis latrans) pack most often leads attacks on ungulates during winter. We were interested in determining whether ungulates can distinguish (perhaps by body size or posture) which members of a coyote pack are the alpha individuals, and whether they initiate and direct aggressive behavior towards those members of the pack that pose the greatest threat of predation to themselves and (or) their offspring. During 2507 h of behavioral observations on 54 coyotes between January 1991 and June 1993, we observed 51 interactions between coyotes and adult elk (Cervus elaphus), bison (Bison bison), and pronghorn antelope (Antilocapra americana) in Yellowstone National Park. The interactions analyzed here are those in which the ungulate appeared to initiate aggressive behavior towards the coyote(s) and were not a response to an attack by the predators. We found that aggression by ungulates towards coyotes was highest during the summer months, when calves and fawns were present; female ungulates were more frequently aggressive than males. The frequency of aggression of adult ungulates towards small and large groups of coyotes was equal to the frequency of occurrence of these groups. Ungulates directed aggressive behavior more frequently towards alpha coyotes and were less aggressive towards beta coyotes and pups. Large ungulates, particularly elk and bison, appeared to perceive that alpha coyotes posed a greater threat to themselves and their offspring. The smaller ungulate, the pronghorn antelope, directed aggressive behavior equally towards all coyotes. Adult ungulates were probably responding to the larger body size of the alpha coyotes and the tendency of alpha coyotes to travel at the front of the pack.

Sign in / Sign up

Export Citation Format

Share Document