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Abstract (from http://link.springer.com/article/10.1007%2Fs10980-015-0160-1): Content Changing aspen distribution in response to climate change and fire is a major focus of biodiversity conservation, yet little is known about the potential response of aspen to these two driving forces along topoclimatic gradients. Objective This study is set to evaluate how aspen distribution might shift in response to different climate-fire scenarios in a semi-arid montane landscape, and quantify the influence of fire regime along topoclimatic gradients. Methods We used a novel integration of a forest landscape succession and disturbance model (LANDIS-II) with a fine-scale climatic water deficit approach to simulate dynamics of...
The forest vegetation of the northern Colorado Front Range was studied using a combination of gradient analysis and classification methods. A graphical model of forest composition based on elevation and topographic-moisture gradients was constructed using 305 0.1 ha samples. To derive the topographic-moisture gradient, stands were stratified into eight 200 m elevation belts, and then ordinated by correspondence analysis using understory (<1 m) data. Each of the resultant gradients was scaled against a standard site moisture scalar derived from incident solar radiation and topographic position. Except for krummholz sites, the vegetation defined gradients fit the moisture scalar closely. Once scaled, these gradients...
Because ecotones often represent the physiological or competitive limit-of-distribution of species, they serve to define a species? local distribution. We take a relatively new approach to gradient analysis to quantify the changes in forest dominance (basal area of dominant tree species) and environmental factors (elevation, slope, aspect, intercepted photosynthetically active radiation [PAR], summer soil moisture, and soil depth and texture) across current lodgepole pine (Pinus contorta) ecotones in Rocky Mountain National Park, Colorado, USA. Based on canonical correspondence analysis on data from eight 20 m wide, 140?480 m long vegetation transects, we found that lodgepole pine distribution, is described generally...
This study explores how the relationship between flow and riparian vegetation varies along a montane river. We mapped occurrence of woody riparian plant communities along 58 km of the San Miguel River in southwest- ern Colorado. We determined the recurrence interval of inundation for each plant community by combining step-back- water hydraulic modeling at 4 representative reaches with Log-Pearson analysis of 4 stream gaging stations. Finally, we mapped bottomland surficial geology and used a Geographic Information System to overlay the coverages of geology and vegetation. Plant communities were distinctly arrayed along the hydrologic gradient. The Salix exigua Nuttall (sand- bar willow) community occurred mostly...
We integrated experimental and natural gradient field methods to investigate effects of climate change and variability on flowering phenology of 11 subalpine meadow shrub, forb, and graminoid species in Gunnison County, Colorado (USA). At a subalpine meadow site, overhead electric radiant heaters advanced snowmelt date by 16 d and warmed and dried soil during the growing season. At three additional sites, a snow removal manipulation advanced snowmelt date by 7 d without altering growing season soil microclimate. We compared phenological responses to experimental climate change with responses to natural microclimate variability across spatial gradients at small and landscape scales, as well as across a temporal gradient...
The relative importance of macro-and micro-scale processes in the biosphere is controversial, with some researchers emphasizing micro-scale population dynamics and others macro-scale landscape dynamics. I hypothesize that there is spatial variation in the linkage between and importance of macro-and micro-environmental influences on vegetation, and explore this hypothesis in a case study of riparian vegetation in the mountains of western Colorado. I estimate percent cover, by species, in 115-0.1 ha samples of riparian vegetation at relatively undisturbed sites. Environmental variables measured at each site include several channel characteristics, valley characteristics, geographical coordinates, and drainage basin...
This study explores how the relationship between flow and riparian vegetation varies along a montane river. We mapped occurrence of woody riparian plant communities along 58 km of the San Miguel River in southwest- ern Colorado. We determined the recurrence interval of inundation for each plant community by combining step-back- water hydraulic modeling at 4 representative reaches with Log-Pearson analysis of 4 stream gaging stations. Finally, we mapped bottomland surficial geology and used a Geographic Information System to overlay the coverages of geology and vegetation. Plant communities were distinctly arrayed along the hydrologic gradient. The Salix exigua Nuttall (sand- bar willow) community occurred mostly...