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Small aspen stands are disappearing from the landscape in the Southwest, so it is important to understand their contribution to the avian community. We sampled birds in 53 small, isolated aspen stands and 53 paired plots within the ponderosa pine forest in northern Arizona, during the 1996 and 1997 breeding seasons. Bird species richness and abundance were higher in aspen than in pine. However, bird species richness and abundance did not vary with size of the aspen patch or isolation index. In addition, direct ordination of species distributions with habitat factors suggested no distinct avian communities. This suggests that aspen stands do not harbor separate populations, but rather are locations where the regional...
In western North America, quaking aspen (Populus tremuloides) is the most common hardwood in montane landscapes. Fire suppression, grazing and wildlife management practices, and climate patterns of the past century are all potential threats to aspen coverage in this region. If aspen-dependent species are losing habitat, this raises concerns about their long-term viability. Though lichens have a rich history as air pollution indicators, we believe that they may also be useful as a metric of community diversity associated with habitat change. We established 47 plots in the Bear River Range of northern Utah and southern Idaho to evaluate the effects of forest succession on epiphytic macrolichen communities. Plots were...
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Aspen exhibits a variety of ecological roles. In southern Colorado, the 1880 landscape mosaic contained a range of stand ages, of which half were >70 years old and half were younger. Pure aspen stands in southern Colorado are widespread and may result from previous short fire intervals that eliminated local conifer seed sources. Aspen regeneration in northern Yellowstone Park is controlled by ungulate browsing pressure and fire, so it has been limited since 1920. However, an episode of aspen seedling establishment occurred after the 1988 fires. We urgently need additional detailed, local case studies of aspen ecology to inform management decisions. Published in Sustaining Aspen in Western Landscapes: Symposium Proceedings,...
Phellinus tremulae is an important fungal decay agent common to aspen and a critical component to the cavity-nesting previous termbirdnext term complex found in western aspen stands. Little information exists on the conditions that facilitate infection and spread of P. tremulae in aspen forests. I used Forest Inventory and Analysis (FIA) data to explore the relationships of several tree and stand characteristics to the presence and frequency of P. tremulae in aspen measured across several western states of the United States. Results suggest a strong relationship between tree age, tree diameter, and compacted crown ratio with infection frequency in trees while stand purity, canopy cover and stand age had a positive...
Sudden aspen decline (SAD), affecting Populus tremuloides, was first observed in Colorado in 2004. By 2008 it affected at least 220,000 ha, an estimated 17% of the aspen cover type in the state. In southwestern Colorado, we examined site and stand features in paired healthy and damaged plots to assess the effects of SAD on aspen and to identify factors associated with decline. Root mortality increased significantly with recent crown loss. Consequently, density of regeneration did not increase as the overstory deteriorated, and regeneration that originated since 2002 decreased significantly in stands with moderate to severe SAD. However, mortality of regeneration did not increase with that of the overstory. Remeasurement...
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This dataset represents actual and predicted suitable habitat for Populus tremuloides (quaking aspen, species code 746) in the Eastern United States as measured by importance value based on data obtained from the Forest Inventory and Analysis (FIA) project, current climate conditions, and future climate projections. This summary unit of this dataset is a 20 by 20 kilometer cell. The actual importance value (IV) was calculated based on the number of stems and basal area of a given tree species relative to other tree species on a plot using about 100,000 FIA plots (representing nearly 3 million tree records) in the 37 states within the United States east of the 100th meridian. These importance values were summarized...
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Aim The recent concern that quaking aspen (Populus tremuloides Michx.) has been declining in parts of western North America due to fire suppression is largely based on trends during the latter part of the 20th century. The aim of the current study was to compare the extent of aspen in the modern landscape with its extent in the late 19th century prior to fire suppression, and to assess the effects of elevation, late-19th century fires, and pre-fire forest composition on the successional status of aspen. Location North-west Colorado, USA. Methods We used a georeferenced 1898 map and modern maps to examine trends in aspen dominance since the late 19th century in a 348,586 ha area of White River and Routt National...
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FY2011Aspen populations are in decline across western North America due to altered fire regimes, herbivory, drought, pathogens, and competition with conifers. Aspen stands typically support higher avian biodiversity than surrounding habitats, and maintaining current distributions of several avian species is likely tied to persistence of aspen on the landscape. We are examining effects of climate change on aspen and associated avian communities in isolated mountain ranges of the northern Great Basin, by coupling empirical models of avian-habitat relationships with spatially-explicit landscape simulations of vegetation and disturbance dynamics (using LANDIS-II) under various climate change scenarios. We are addressing...
We used data from 142 stands in Colorado and Wyoming, USA, to test the expectations of a model of growth dominance and stand development. Growth dominance relates the distribution of growth rates of individual trees within a stand to tree sizes. Stands with large trees that account for a greater share of stand growth than of stand mass exhibit strong growth dominance. Stands with large trees that contribute less to stand growth than to stand mass show reverse growth dominance. The four-phase model predicts that forests move from a period of little dominance (Phase 1), with trees accounting for similar contributions to stand growth and stand mass. Phase 2 is a period of strong growth dominance, where larger trees...
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Aspen is an environmentally, economically, and socially important species in the western U.S. It is typically the most abundant deciduous tree species in mountainous landscapes of the western U.S., providing food and habitat for a variety of wildlife, including black bear, deer, elk, moose, and numerous bird species. Aspen woodlands also provide high quality forage for livestock and draw tourists to the region to view the golden vistas that form in the fall. However, aspen is currently declining across large portions of the West and it’s estimated that approximately 40% of western aspen will be without suitable climate conditions within 50 years. In the northern and central Rocky Mountains, it’s thought that reduced...


    map background search result map search result map Aspen's ecological role in the West Influences of infrequent fire, elevation and pre-fire vegetation on the persistence of quaking aspen (Populus tremuloides Michx.) in the Flat Tops area, Colorado, USA Projecting the Effects of Climate Change on Aspen in the Central and Northern Rocky Mountains Eastern United States Climate Change Tree Atlas - Suitable habitat for Populus tremuloides (quaking aspen) as measured by importance value (IV) Quantifying vulnerability of quaking aspen woodlands and associate bird communities to global climate change in the northern Great Basin Influences of infrequent fire, elevation and pre-fire vegetation on the persistence of quaking aspen (Populus tremuloides Michx.) in the Flat Tops area, Colorado, USA Aspen's ecological role in the West Quantifying vulnerability of quaking aspen woodlands and associate bird communities to global climate change in the northern Great Basin Projecting the Effects of Climate Change on Aspen in the Central and Northern Rocky Mountains Eastern United States Climate Change Tree Atlas - Suitable habitat for Populus tremuloides (quaking aspen) as measured by importance value (IV)