نتایج جستجو برای: aspen dynamic
تعداد نتایج: 408689 فیلتر نتایج به سال:
The persistence of quaking aspen (Populus tremuloides Michx.) is of significant importance to land managers in the Rocky Mountain region. Fire suppression in the past century has been implicated as a mechanism influencing aspen population dynamics, as aspen are generally considered an early seral disturbance adapted species. The heterogeneity of aspen community assemblages and fire regimes make...
از آنجایی که ایران بعنوان دومین منبع گاز جهان شناخته شده است، اجرای طرح های تولیدی با ارزش افزوده بالا از لحاظ اقتصادی توجیه پذیر است. در همین راستا، شرکت ملی صنایع پتروشیمی در بخش آمونیاک و اوره طرح هایی را اجرا کرده است و پروژه های جدیدی را نیز در دست طراحی و راه اندازی دارد. تحقیقات بسیاری در زمینه ی بهینه سازی انرژی، بهینه سازی ترمودینامیکی و شبیه سازی در حالت پایا بر روی واحدهای تولید آمون...
The paucity of aspen (Populus tremuloides) regeneration in the western United States and on Yellowstone National Park’s (YNP) northern range has been of concern to managers and scientists for much of the 20th century, with the effects of ungulate browsing, climate fluctuation, and fire suppression being vigorously debated. We analyzed the interaction of fire and elk (Cervus elaphus) browsing in...
The analysis of current cervical collars (Aspen and Miami J collars) and cervical thoracic orthoses (CTOs) (Aspen 2-post and Aspen 4-post CTOs) in reducing cervical intervertebral and gross range of motion in flexion and extension was performed using 20 normal volunteer subjects. The gross sagittal motion of the head was measured relative to the horizon with the use of an optoelectronic motion ...
To investigate the extent and causes of recent quaking aspen (Populus tremuloides) recruitment in northern Yellowstone National Park, we measured browsing intensity and height of young aspen in 87 randomly selected aspen stands in 2012, and compared our results to similar data collected in 1997-1998. We also examined the relationship between aspen recovery and the distribution of Rocky Mountain...
Aspen has been declining in Jackson Hole for many years, a condition generally attributed to the fact that lightning fires have been aggressively suppressed since the early 1900s. It is also believed that burning will successfully regenerate aspen stands despite high elk numbers. To test this hypothesis, I evaluated 467 burned and 495 adjacent, unburned aspen stands at eight different locations...
Because firm conduct in Aspen Skiing stands at the outer boundaries of monopolization, it has received considerable scrutiny from antitrust scholars. The critical and somewhat puzzling determination of the relevant geographic market in this case—“the Aspen area”—however has received essentially no attention. In this paper, we report the results of archival and interview research to illuminate t...
STUDY DESIGN Four conditions (three orthoses, one no orthosis), full cross-over, randomized order, 12 subjects tested 3 months after a lumbar surgical arthrodesis. OBJECTIVES To assess whole torso and lumbar motions and comfort for each orthoses condition during performance of activities of daily living. SUMMARY OF BACKGROUND DATA Previous noninvasive studies measured whole torso (not just ...
In northern Yellowstone National Park, quaking aspen (Populus tremuloides) stands were dying out in the late 20th century following decades of intensive browsing by Rocky Mountain elk (Cervus elaphus). In 1995–1996 gray wolves (Canis lupus) were reintroduced, joining bears (Ursus spp.) and cougars (Puma concolor) to complete the guild of large carnivores that prey on elk. This was followed by a...
We report long-term patterns of quaking aspen (Populus tremuloidesMichx.) 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 constructiondue toherbivorybyRockyMountain elk (Cervus elaphus Linnaeus, 1758) but increasedmore than60-fold within 25 years afte...
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