Treesearch

No other tree in the Rocky Mountain region is more highly valued for its amenities than aspen (Populus tremuloides). In Colorado, New Mexico, Arizona, and southern Utah, aspen covers entire mountain slopes and plateaus, sometimes forming the landscape matrix in which other cover types occur as patches. Northward aspen occurs in patches (figure 1), forming small groves that can be thought of as a keystone cover type - one that has more significant effects on species diversity and ecological processes than would be expected considering the comparatively small amount of land area that it...

Recognizing the historical abundance of major vegetation cover types is the foundation for estimating the magnitude and significance of conversion from one cover type to another and the proportion of existing cover types that are in properly functioning condition. Techniques to determine desired conditions are discussed. Existing situations for the need to treat ecosystems where aspen (Populus tremuloides Michx.) occur are prioritized: highest - mixed-conifer with aspen but where conifers comprise greater than 50% of the canopy; high - aspen/sagebrush transition; and moderate - aspen...

Populus tremuloides is distributed from drought-prone fringes of the Great Plains to extremely cold sites at arctic treeline. To occupy these conditions aspen appears to be more tolerant of stress than the other North American species of the genus Populus. Cold winters, cold soil conditions during the growing season, periodic drought, insect defoliation, and competition from conifers are typical stresses faced by aspen. Aspen is capable of high photosynthetic rates but has conservative use of water during high vapor pressure deficits. This paper examines photosynthesis, water relations,...

Effects of climate change at three aspen sites in Saskatchewan were explored using a climate-driven model that includes insect defoliation. A simulated warming of 4-5 °C caused complete mortality due to drought at all three sites. A simulated warming of 2-2.5 °C caused complete mortality of aspen at the parkland site, while aspen growth at two boreal sites showed little change from the present climate until after insect defoliation, when dieback was more severe under the warmer climate. The results suggest that future impacts of climate change on boreal aspen forests may not become evident...

A conifer release trial was established in a 45-year-old aspen overstory stand in Northeast British Columbia, Canada. Thinning occurred from 0 to 100% in increments of approximately 10% to yield a total of ten units. Treatment consisted of physically cutting aspen stems at the root collar or girdling at breast height (d.b.h.) for trees 10 cm d.b.h., respectively. The thinning treatment was conducted following standard brushing and weeding contracts common to the British Columbia Ministry of Forests. At this time no significant difference in diameter growth can be found between treatments....

Using a monograph provided by Warren (1926) and two sets of aspen increment cores collected in 1997 and 1998, we analyzed aspen overstory recruitment in Yellowstone National Park (YNP) over the past 200 years. We found that successful aspen overstory recruitment occurred on the northern range of YNP from the middle to late 1700s until the 1920s, after which it essentially ceased. We hypothesized why the browsing influence of Rocky Mountain elk (Cervus elaphus) may be different now than it was historically. At a landscape scale, elk hunting outside YNP may be a significant factor changing...

Aspen is notoriously difficult to age because of its light-colored wood and faint annual growth rings. Careful preparation and processing of aspen ring samples can overcome these problems, yield accurate age and growth estimates, and concisely date disturbance events present in the tree-ring record. Proper collection of aspen wood is essential in obtaining usable ring data. Mounting of increment cores and sawn disk samples to wood backings holds samples rigid for easy surfacing. Sequential use of planers, belt sanders, and an assortment of sanding material on the surface of aspen core and...

Vegetative regeneration of aspen can be initiated through manipulations that provide hormonal stimulation, proper growth environment, and sucker protection - the three elements of the aspen regeneration triangle. The correct course of action depends upon a careful evaluation of the size, vigor, age, and successional status of the existing clone. Soils and site productivity, competition from other plants, and the potential impact of browsing animals upon new regeneration should also be considered. Treatments may include doing nothing, commercial harvest, prescribed fire, mechanical root...

Changes in preburn aspen root biomass 8 years following prescribed fire were analyzed for five experimental sites distributed across a moisture gradient. Total root biomass decreased across all sites but was proportionately greater in xeric than mesic sites. Response of post-burn aspen suckers to ungulate browsing varied according to site and treatment. Browsing influenced the age class structure and height growth, but had no influence on stem density, in aspen occurring on more mesic sites. Aspen occurring on the more xeric sites responded differently, with the extreme case being the...

Quaking aspen regenerated from seed after a stand replacement wildfire in the Chiricahua Mountains of southeastern Arizona. The wildfire had created gaps in the canopy so that aspen were able to establish from seed. Seedlings were found at a mean density of 0.17 m-2, 30 m or more from the nearest potential seed trees. Six clumps of aspen seedlings contained 18-186 trees, occupying areas of 145-500 square meters at densities of 0.09-0.27 m-2. White-tailed deer (Odocoileus virginianus) browsed 14.3% of the seedlings. Occasional sexual reproduction of aspen may be a general trait of the...