Historical fire regimes in ponderosa pine forests of the Colorado Front Range, and recommendations for ecological restoration and fuels management

At the request of The Nature Conservancy and the Front Range Fuels Treatment Partnership, the authors of this article are developing brief summaries of the current state of our scientific understanding of historical fire regimes in the forested landscapes of Colorado's Front Range. The area of interest extends from EI Paso and Teller Counties, near Pikes Peak, to Larimer County and the Colorado-Wyoming border. This article focuses on forests in which ponderosa pine is a dominant or co-dominant species. A subsequent article will deal with forests of lodgepole pine, spruce, and fir. M. Kaufmann and T. Veblen have conducted extensive studies of ponderosa pine forest ecology in the southern Front Range (mainly the Cheesman Reservoir area) and the northern Front Range (mainly in and around Boulder County), respectively. This research has led to substantial agreement about the historical role of fire in shaping these forests, and we emphasize these points of agreement in this article, in the section entitled "Things We Know with Relatively High Confidence." Some disagreements and uncertainties also have arisen, and we identify these..

Fire as a fundamental ecological process: Research advances and frontiers

Fire is a powerful ecological and evolutionary force that regulates organismal traits, population sizes, species interactions, community composition, carbon and nutrient cycling and ecosystem function. It also presents a rapidly growing societal challenge, due to both increasingly destructive wildfires and fire exclusion in fire‐dependent ecosystems. As an ecological process, fire integrates complex feedbacks among biological, social and geophysical processes, requiring coordination across several fields and scales of study. Here, we describe the diversity of ways in which fire operates as a fundamental ecological and evolutionary process on Earth. We explore research priorities in six categories of fire ecology: (a) characteristics of fire regimes, (b) changing fire regimes, (c) fire effects on above‐ground ecology, (d) fire effects on below‐ground ecology, (e) fire behaviour and (f) fire ecology modelling. We identify three emergent themes: the need to study fire across temporal scales, to assess the mechanisms underlying a variety of ecological feedbacks involving fire and to improve representation of fire in a range of modelling contexts. Synthesis : As fire regimes and our relationships with fire continue to change, prioritizing these research areas will facilitate understanding of the ecological causes and consequences of future fires and rethinking fire management alternatives

Spruce beetles and fires in the nineteenth-century subalpine forests of western Colorado, USA

We analyzed 17 photographs, taken between 1873 and 1915, that illustrate widespread mortality in subalpine forests of western Colorado. Eight of these photographs, reproduced here, contain three general patterns of mortality, interpreted to result from spruce beetle (Dendroctonus rufipennis) attacks, fires, and wind. Tree-ring chronologies at four of the sites corroborated the role of spruce beetle in killing the trees visible in the photographs. The photographs and tree-ring dates suggest that the spruce beetle outbreak occurred between the 1850s and the 1880s, and affected forests from central New Mexico to north-central Colorado. Spruce beetle outbreaks are a significant type of natural disturbance in these forests. The relative contribution of beetles and fires to subalpine forest structure is in need of further research. The sequence and spatial configuration of disturbances by spruce beetles, fire, and wind varies, and can be spatially heterogeneous, even on small land areas. In such areas, forest responses to uniformly applied disturbance controls (e.g., fire suppression) will be spatially heterogeneous, not affecting all parts of the landscape uniformly

Disturbance patterns in southern Rocky Mountain forests

The pattern of landscape diversity in the Southern Rocky Mountains has been described as resulting from two superimposed vegetation pat- terns: the distribution of species along gradients of limiting factors, and patterns of disturbance and recovery within the communities at each point along the environmental gradients (Romme and Knight 1982). The previous chapter (D. H. Knight and W. A. Reiners, this volume) has emphasized the first pattern whereas this chapter emphasizes the role of natural disturbance in creating landscape patterns. Although human impacts on fundamentally natural disturbances such as fires and insect outbreaks are included, other chapters treat disturbances of exclusively human origin such as logging and road construction

Effect of vegetation on the impact of a severe blowdown in the southern Rocky Mountains, USA

In October 1997, a storm with winds estimated at 200-250 km/h blew down a large percentage of trees in over 10,000 ha of subalpine forest in northern Colorado, USA. In a case study, we analyzed the effect of pre-blowdown tree density, cover-type, and stand structural stage on the percentage of trees blown down. Low tree density led to somewhat lower levels of blowdown than did higher density. Effects of cover-type and habitat structural stage on the pattern of damage from the blowdown varied spatially. At lower elevations, farther from the source of the winds coming over the Continental Divide, aspen forests were less susceptible to blowdown than expected, whereas spruce-fir forests were more susceptible than expected. At higher elevations, closer to the source of the winds, habitat structural stages representing earlier stages of stand development were much less susceptible to blowdown than expected, whereas more advanced structural stages were generally more susceptible to blowdown than expected. Overall, the effects of density, composition, and structural stage on the pattern of damage were modest, but evident. That there is a detectable effect of vegetation composition and structure across this large blowdown implies that, even during extreme wind events, vegetation can influence the extent and pattern of damage, more strongly so in some places than in others. © 2002 Elsevier Science B.V. All rights reserved

Fire history in western Patagonia from paired tree-ring fire-scar and charcoal records

Fire history reconstructions are typically based on tree ages and tree-ring fire scars or on charcoal in sedimentary records from lakes or bogs, but rarely on both. In this study of fire history in western Patagonia (47-48° S) in southern South America