Historic range of variability for upland vegetation in the Medicine Bow National Forest, Wyoming

Abstract

An approach for synthesizing the results of ecological research pertinent to land management is the analysis of the historic range of variability (HRV) for key ecosystem variables that are affected by management activities. This report provides an HRV analysis for the upland vegetation of the Medicine Bow National Forest in southeastern Wyoming. The variables include live tree density, dead tree (snag) density, canopy cover, abundance of coarse woody debris, species diversity, fire return intervals, the abundance of various diseases, the proportion of the landscape in different land cover types, and the degree of patchiness in the landscape. The variables were examined at the stand and landscape scales, using information available in the literature and USFS databases. High-elevation landscapes were considered separately from low-elevation landscapes. Much of the report pertains to forests dominated by lodgepole pine, subalpine fir, and Engelmann spruce at high elevations, and by ponderosa pine and aspen at lower elevations. We defined the HRV reference period for the MBNF as approximately 1600 to 1860.Keywords: aspen, bark beetles, canopy gaps, coarse woody debris, comandra blister rust, dwarf mistletoe, Engelmann spruce, fire effects, disease in Rocky Mountain forests, forest fragmentation, insects in forests, interior forest, landscape ecology, lodgepole pine, mistletoe, mountain pine beetle, ponderosa pine, roads, Rocky Mountain forests, snags, spruce beetle, subalpine fir, subalpine forests, timber harvesting effects, white pine blister rust, wind in forests Executive SummaryThe challenges of sustainable land management have led to an increased emphasis on incorporating the results of science in the decision making process. One approach for accomplishing this objective is through the analysis of the historic range of variability (HRV) for key ecosystem variables that are affected by management activities. The rationale for HRV analyses is that the chances of sustainable forest management are greater if the variation in managed ecosystems includes the range of conditions that are expected at various scales in ecosystems relatively uninfluenced by humans. This report provides an HRV analysis for the upland vegetation of the Medicine Bow National Forest (MBNF).By definition, HRV analyses require the identification of specific variables and an estimation of how those variables fluctuated, at more than one scale, prior to the advent of resource extraction and management by EuropeanAmericans. A complete list of the variables that we examined is found in table 7. Examples include live tree density, dead tree (snag) density, canopy cover, abundance of coarse woody debris, species diversity, fire return intervals, the abundance of various diseases, the proportion of the landscape in different land cover types, and the degree of patchiness in the landscape. We examined variables at two scales-the stand and the landscape-and we separated high-elevation landscapes from low-elevation landscapes. Much of the repo...

Disturbance legacies of historic tie-drives persistently alter geomorphology and large wood characteristics in headwater streams, southeast Wyoming

“…Published estimates of stand age suggest that within the Sierra Madre and Snowy ranges, only 15% to 30% of trees are more than 150 years old and therefore stands qualifying as oldgrowth (generally thought to be between 200 and 300 years old in spruce-fir dominated regimes) are very limited (Dillon et al, 2005). Stream channel morphology in the area is consistent with channel morphology in other mountainous regions (Montgomery and Buffington, 1997) and…”

“…Engelmann spruce (Picea engelmannii), subalpine fir (Abies lasiocarpa), and aspen (Populus tremuloides) that vary in relative abundance depending on elevation and aspect (Dillon et al, 2005). Published estimates of stand age suggest that within the Sierra Madre and Snowy ranges, only 15% to 30% of trees are more than 150 years old and therefore stands qualifying as oldgrowth (generally thought to be between 200 and 300 years old in spruce-fir dominated regimes) are very limited (Dillon et al, 2005).…”

“…The underlying geology of the area ranges in origin from granitic, metasedimentary, and metavolcanic rocks to glacial deposits in the higher elevations (Love and Christiansen, 1985). Elevations within the Medicine Bow National Forest boundary range from 2170 to 3640 m. Both the Snowy Range and Sierra Madre were glaciated during the Pleistocene resulting in numerous till fields, moraines, and lakes throughout the area (Dillon et al, 2005).…”

The use of historical range and variability (HRV) in landscape management

“…Wong et al (2003) compiled an extensive reference of historical disturbance regimes for the entire province of British Columbia, Canada. Dillon et al (2005) and Meyer et al (2005) detail the historical variations in upland vegetation for two national forests in Wyoming. These efforts are excellent qualitative references for understanding and interpreting historical conditions, however, they do not provide the quantitative detail needed to implement the described reference conditions directly into management applications (see Fig.…”

Effects of past logging and grazing on understory plant communities in a montane Colorado forest

“…In Pinus ponderosa C. Lawson-dominated forests of the Rocky Mountains, USA, intense land use including logging, domestic grazing, and fire suppression began at the time of European-American settlement in the mid to late 1800s (Cooper 1960;Dillon et al 2005;Veblen and Donnegan 2005). Researchers have recently begun to investigate how this past land use has altered forest overstories from the pre-settlement condition by examining early photographs, written descriptions, and scientific studies, and also by reconstructing historical stand conditions from living and remnant woody material (e.g., Brown and Cook 2006;Fulé et al 1997;Kaufmann et al 2001).…”