Changes in landscape patterns and associated forest succession on the western slope of the Rocky Mountains, Colorado
Using repeat photography, we conducted a qualitative and quantitative analysis of changes in forest cover on the western slope of the Rocky Mountains in Colorado. For the quantitative analysis, both images in a pair were classified using remote sensing and geographic information system (GIS) technologies. Comparisons were made using three landscape metrics: total relative cover, mean relative patch size, and number of patches per major vegetation type. We noted several important changes in the pattern of the landscape and the structure of the forests. The relative area covered by interspersed, nonforested rangelands has decreased significantly, and the total forest cover across these landscapes has increased. Statistical analyses (ANOVA) of other landscape characteristics (patch number and patch size distribution) did not detect changes. However, nonstatistical observation of the trends in these data revealed that in many cases, there has been important, observable change in the configuration of the landscape at many of these locations. Furthermore, our field data show that 96% of the sampled forests have a conifer component in the overstory, understory, or both.
Landscape Composition in Aspen Woodlands Under Various Modeled Fire Regimes
Quaking aspen (Populus tremuloides) is declining across the western United States. Aspen habitats are diverse plant communities in this region and loss of these habitats can cause shifts in biodiversity, productivity, and hydrology across spatial scales. Western aspen occurs on the majority of sites seral to conifer species, and long-term maintenance of these aspen woodlands requires periodic fire. We use field data, remotely sensed data, and fire atlas information to develop a spatially explicit landscape simulation model to assess the effects of current and historic wildfire regimes and prescribed burning programs on landscape vegetation composition in the Owyhee Mountains, Idaho. The model is run in the Tool for Exploratory Landscape Scenario Analyses (TELSA) environment. Model outputs depict the future structural makeup and species composition of the landscape at selected time steps under simulated management scenarios. Under current fire regimes and in the absence of management activities, loss of seral aspen stands will continue to occur. However, a return to historic fire regimes, burning 12–14 percent of the modeled landscape per decade, maintains the majority of aspen stands in early and mid seral woodland stages and minimizes the loss of aspen. A fire rotation of 70–80 years was estimated for the historic fire regime while the current fire regime resulted in a fire rotation of 340–450 years. Implementation of prescribed burning programs, treating aspen and young conifer
Possibilities of Managing Aspen
The management of aspen or popple (Populus tremuloides) has received little attention in the past, largely because of the former abundant supply of other and more valuable tree species in the Lake States. Because of a rapidly expanding market for all forest products during the past decade, particularly during the war, the attention and ingenuity of industry have turned toward the use of aspen. As a consequence, aspen has now become one of the important pulpwood species in the Lake States, and is used for many other products. That it will retain its place for some time to come seems quite certain in view of its large acreage, its aggressiveness, and new uses which are constantly being found. For this reason, there is need for information on the possibilities of managing aspen as a forest crop.