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Wildland fire is expected to increase with global change, but responses may be spatially heterogeneous and temporally variable, complicating detection. In this study, I analyzed twenty-five years of spatial data on wildfires in woody sagebrush (Artemisia spp.) shrublands across 48 million ha of the Western United States, to test eleven hypotheses about trend and heterogeneity in wildfires. No upward trend in annual area burned was found across the whole study area, consistent with previous simulations that suggest fire may not increase in semiarid shrublands. At a finer scale, a significant trend occurred only in montane sagebrush, of five sagebrush types, and in two of seven floristic provinces. Area burned was concentrated in years with large fires. These years generally lacked or had only a weak trend, comparing two halves of the twenty-five-year period. Sagebrush types did not differ significantly in recent fire rotation, which did differ among floristic provinces and appears shorter now than historic...

Feverfew has been studied for the treatment of migrane in several studies and the pharmacologic mechanisms are preliminarily understood. We performed a systematic review of randomized controlled trials and present the clinical findings and potential implications. The modality of data collection and reporting in the individual studies does not support a pooling of results, but does suggest benefit of feverfew in migraine prophylaxis for at least subsets of the population with the disorder. Pharmacologically, there is some potential for concern with long-term dosing given its cyclooxygenase-2 inhibiting effects and longer-term studies will be needed to ameliorate these concerns in coronary disease patients.

Three major disturbances affect subalpine forests in the Rocky Mountains: blowdown, insect outbreaks, and fire. These disturbances may influence one another temporally and spatially, creating a mosaic of disturbance patches. In 1997, a severe windstorm blew down trees on over 10,000 ha of subalpine forest in northern Colorado. Did previous disturbances influence the spatial pattern of blowdown in a representative part of the blowdown in the Middle Fork Elk River watershed? Dendrochronological evidence and a geographic information system were used to reconstruct the disturbance history, and the relationship between disturbance history (i.e., patch age) and the 1997 blowdown was examined. The fire regime varies temporally and spatially, with an area-weighted mean fire interval/fire rotation of 108 to 195 years. Stand-replacing fires appear to have had the most impact on the fire regime, but evidence of non-stand-replacing fires was also found. South-facing, lower-elevation slopes were the settings ...

Many studies have helped us understand where blowdowns occur, how forests regenerate and respond to large disturbances. However, few studies have analysed how physical and biological factors affect blowdowns or interact with one another to determine susceptibility to blowdown. These factors range from the natural physical setting to past disturbances, and human-related features, such as roads and timber harvest units. These factors were examined in this study. Patches of the blown-down forest were mapped for the 1997 Routt-Divide blowdown, which affected over 10 000 ha of subalpine forest in north-central Colorado. A systematic sampling scheme was used to extract information on predictors for sampling points inside and outside the blowdown. Data on predictors were used in Classification and Regression Trees (CART) and logistic regression to model blowdown occurrence and severity. Two models were applied, and both were able to predict with an overall success rate of 75% or more. These two models produced s...

Natural disturbances such as fires have been widely studied, but less is known about their spatial ecology than about other aspects of them. We reconstructed and mapped pre–Euro-American fire history in a subalpine forest landscape in southeastern Wyoming, and analyzed the fires using GIS. Mean fire interval varies little with topography (elevation, aspect, slope) and is spatially autocorrelated at distances of at least 2 km. Fires often spread downslope, and spread more than expected from the north and south and less than expected from the west, under the influence of particular synoptic climatic conditions. The landscape of 1868 a.d., at the time of Euro-American settlement, was strongly influenced by fires. However, it contained large patches of connected forest and few high-contrast edges, unlike the modern landscape, which is fragmented by industrial forestry and roads. The spatial ecology of the natural fire regime may be a useful guide for management.

Landscapes in the ecotone between forest and tundra contain a mosaic of patches of trees, meadows, lakes, disturbed areas, and other features. The structure of this mosaic affects species habitat and potential ecotone response to global change. However, the alpine forest-tundra ecotone may be insensitive to climatic change if it is a climatic relict or is frequently disturbed. We used GIS and multivariate statistics to (1) analyze landscape structure in transects across the ecotone in Rocky Mountain National Park, (2) identify the major variants of forest-tundra ecotone, and (3) identify the influence of the environment and natural disturbances on variation in the landscape structure of the ecotone. There are six major types of ecotone varying in the amount of natural disturbances, permanent features (e.g., lakes), closed forest, patch forest, and krummholz. Variation is primarily related to slope, elevation, aspect, and geology associated with the morphology of the mountains and the disturbances they pro...

The nature of public space in contemporary society is changing. This paper uses the turmoil over People's Park in Berkeley, California, as a means for exploring changing ideas about and practices in public space. I argue that as public space is increasingly privatized or otherwise brought under greater control, possibilities for democratic action are minimized. To make this claim, I provide a brief outline of the roots of the August 1991 riots at People's Park. I then examine the role that public space plays in modern democracies, and how ideas about public space have developed dialectically with definitions of who counts as “the public.” In American democracy, “the public” is constituted by private individuals. In this paper, I suggest that the presence of homeless people in public spaces raises important contradictions at the heart of this definition of “the public.” Many commentators suggest that these contradictions have led to “the end of public space” in contemporary cities, or at the very ...

Department of Geography and As an ecological boundary zone, the forest-tundra ecotone is a valuable location Regional Development, University of to study the initial response of vegetation to global climate change. The purpose Arizona. Tucson, Arizona 8572 1. of this study is to predict the potential response of the forest-tundra ecotone in U.S.A. Rocky Mountain National Park to future climate change using data on historical episodes of establishment in patch forest openings of the forest-tundra ecotone. William L. Baker We hypothesized that recent seedling establishment in patch forest openings of Department of Geography and the forest-tundra ecotone, not balanced by mortality, was triggered by a warm, Recreation, University of Wyoming, but wet period following the end of the Little Ice Age ca. A.D. 1850. At four Laramie, Wyoming 8207 1, U.S.A. sampling locations distributed throughout the Park, we determined dates of es-tablishment among patch forest trees using increment cores and basal disks. We studied the relationship between establishment dates in relation to historical cli- mate records using t-tests and logistic regression. In Rocky Mountian National Park, tree invasion in patch forest openings is episodic in nature, concentrated between 1951-1964, and is not balanced by mortality, suggesting more than a short-term change in the ecotone. On the basis of the climate record, t-tests, and logistic models, we concluded that both high temperatures and high snow depths must occur simultaneously for several years in order to generate climatic condi- tions suitable for tree establishment. The historic climate record indicates that a warmer and wetter period occurred during the 1950s and 1960s, but climate data are unavailable before 1880. According to proxy climate records, it appears that the regional climate of the southern Rocky Mountain region has been both warmer and wetter since the end of the Little Ice Age (ca. A.D. 1350-1850). We conclude that these climatic conditions may be related to the tree invasion we observed in patch forest openings of Rocky Mountain National Park.

We measured tree seedling and krummholz leader growth in various environments within the alpine forest-tundra ecotone of Rocky Mountain National Park to assess the potential pattern of response to ...

To analyze trends in the structure of forests dominated by Colorado bristlecone pine (Pinus aristata Bailey) the author sampled size class structures, collected environmental data, and determined the approximate year of origin of these forests at 65 sites scattered throughout the range of P. aristata in Colorado. Cluster analysis and detrended correspondence analysis (DCA) were used to identify major trends in the size class data. The size class data suggest that P. aristata is a long-lived species that primarily regenerates following fires. The DCA results suggest that (1) the major trend in variation in structure was related to time since disturbance, and (2) Populus tremuloides Michx. is present as numerous small stems in some of the P. aristata forests regardless of the age of these forests, a role for P. tremuloides that is at odds with the traditional view of this tree as primarily a seral species in the Rocky Mountains. Many P. aristata stands originated near A.D. 1900 and between A.D. 1625 and 1700. These were warm, dry periods that might have promoted fires, and they were also periods when sunspot numbers were low. The Southern Oscillation Index did not correlate with times of abundant stand origins. Although manymore » P. aristata forests are over 500 yr old, these forests do not appear to be stable or unchanging.« less

Trees in 7 diameter-classes, in 57 contiguous 0.1 ha plots, were tallied along a 10 km reach of the Animas River, southwestern Colorado. The age, height above water, and elevation for each plot, as well as the valley width and aspect at each plot location were determined. Detrended correspondence analysis (DCA) and two-way indicator species analysis (TWINSPAN) were then used to analyze these data. Age of the stand and its height above the water were significantly correlated with the first DCA axis, while only height above the water was significantly correlated with the second axis. Populus angustifolia and Pinus ponderosa have seedlings and saplings in stands 60 years old. Picea pungens and Pseudotsuga menziesii have seedlings and saplings in stands of all ages. A strict successional interpretation of the overall time-trends fails, because “succession” changed after 1927-...

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 dyna...