Western United States forest wildfire activity is widely thought to have increased in recent decades, yet neither the extent of recent changes nor the degree to which climate may be driving regional changes in wildfire has been systematically documented. Much of the public and scientific discussion of changes in western United States wildfire has focused instead on the effects of 19th- and 20th-century land-use history. We compiled a comprehensive database of large wildfires in western United States forests since 1970 and compared it with hydroclimatic and land-surface data. Here, we show that large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons. The greatest increases occurred in mid-elevation, Northern Rockies forests, where land-use histories have relatively little effect on fire risks and are strongly associated with increased spring and summer temperatures and an earlier spring snowmelt.

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Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity

There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

Fire is a worldwide phenomenon that appears in the geological record soon after the appearance of terrestrial plants. Fire influences global ecosystem patterns and processes, including vegetation distribution and structure, the carbon cycle, and climate. Although humans and fire have always coexisted, our capacity to manage fire remains imperfect and may become more difficult in the future as climate change alters fire regimes. This risk is difficult to assess, however, because fires are still poorly represented in global models. Here, we discuss some of the most important issues involved in developing a better understanding of the role of fire in the Earth system.

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Fire in the Earth System

Many physical, chemical, mineralogical, and biological soil properties can be affected by forest fires. The effects are chiefly a result of burn severity, which consists of peak temperatures and duration of the fire. Climate, vegetation, and topography of the burnt area control the resilience of the soil system; some fire-induced changes can even be permanent. Low to moderate severity fires, such as most of those prescribed in forest management, promote renovation of the dominant vegetation through elimination of undesired species and transient increase of pH and available nutrients. No irreversible ecosystem change occurs, but the enhancement of hydrophobicity can render the soil less able to soak up water and more prone to erosion. Severe fires, such as wildfires, generally have several negative effects on soil. They cause significant removal of organic matter, deterioration of both structure and porosity, considerable loss of nutrients through volatilisation, ash entrapment in smoke columns, leaching and erosion, and marked alteration of both quantity and specific composition of microbial and soil-dwelling invertebrate communities. However, despite common perceptions, if plants succeed in promptly recolonising the burnt area, the pre-fire level of most properties can be recovered and even enhanced. This work is a review of the up-to-date literature dealing with changes imposed by fires on properties of forest soils. Ecological implications of these changes are described.

/pdf/effects-of-fire-on-properties-of-forest-soils-a-review-1ymllzm5e7.pdf

Effects of fire on properties of forest soils: a review

https://bio.uib.no/te/papers/Grimm_2010_The_ODD_protocol_.pdf

The ODD protocol: A review and first update

This conference brought together scientiests and managers from federal, state, and local agencies, along with private-sector interests, to examine key concepts involving sustainable ecological systems, and ways in which to apply these concepts to ecosystem management. Session topics were: ecological consequenses of land and water use changes, biology of rare and declining species and habitats, conservation biology and restoration ecology, developing and applying ecological theory to management of ecological systems, sustainable ecosystems and forest health, and sustainable ecosystems to respond to human needs. A plenary session established the philosophical and historial contexts for ecosystem management.

Sustainable ecological systems: Implementing an ecological approach to land management

Frequent, low-intensity fire is a key disturbance agent in the long-needled pine forests of western North America, but little is known about the fire ecology of the Mexican forests which have been least affected by fire exclusion. We compared fire disturbance history and forest structure at four unharvested or lightly-harvested study sites differing in recent fire history. Frequent, low-intensity fires, recurring between 4 to 5 years for all fires and 6 to 9 years for widespread fires, characterized all the sites until the initiation of fire exclusion in the mid-twentieth century at three of the four sites. Although most fires in the study area are ascribed to human ignitions, evidence of both lightning and human-caused burning was observed on the study sites. A possible connection between fire occurrence and climate was indicated by a correspondence between regional fire years and positive extremes of the Southern Oscillation index, which is associated with cold/dry weather conditions. Forest ecosystem structures differed in ways consistent with the thinning and fuel consuming effects of fire. Two sites with extended fire exclusion were characterized by relatively dense stands of smaller and younger trees, high dead woody biomass loading, and deeper forest floors. In contrast, a site which had burned following a 29-year fire exclusion period, and the final site where frequent fires had continued up to the present, were both relatively open forests dominated by larger trees. The recently burned sites had lower dead woody biomass loading, especially of rotten woody fuels, and more shallow duff layers. The high regeneration density but low overstory density at the recently burned sites is also consistent with the thinning effect of low-intensity fire. Long-term management and conservation strategies for these forests should recognize the historic role of fire disturbance as well as the potential for changes in fire intensity and ecological effects following extended fire exclusion.

/pdf/fire-regimes-and-forest-structure-in-the-sierra-madre-33p3qvo115.pdf

Fire regimes and forest structure in the sierra madre occidental, durango, mexico

Developing the Conceptual Basis for Restoration Ecology

This volume is divided into three sections: (1) Ecological, Biological, and Physical Science; (2) Social and Cultural; and (3) Economics and Utilization. Effective ecological restoration requires a combination of science and management. The authors of the first section exemplified this integration in the course of addressing a broad range of topics, from detailed microsite and small-scale changes in fungal, plant, and animal communities, up through landscape, regional, and subcontinental scales. Although the themes were diverse, papers were linked by underscoring the relationship between restorative management actions and ecological effects. Social sciences play a key role in ecosystem restoration because collaboration, development of common goals, and political and economic feasibility are essential for success. The authors of the second section focused on public attitudes, partnerships, and the relationship between social and ecological factors. In the third section, the economics and utilization of products from forest restoration were compared in several Western locations. Both the markets for these products and the range of utilization opportunitiesfrom small-diameter logs to energy creationwill surely evolve rapidly as society moves to address the fire hazards and other problems caused by stressed and weakened ecosystems. The turn of the century is an appropriate point to capture dramatic changes in perspective: consider how attitudes toward Western forests have evolved between 1900 and 2000. The papers in this volume chronicle adaptive research that continues to deepen our understanding of restoration in ecosystems and social systems.

https://www.fs.fed.us/rm/pubs/rmrs_p022.pdf

Ponderosa pine ecosystems restoration and conservation: steps toward stewardship; 2000 April 25-27; Flagstaff, AZ

Patterns of spatial arrangement, tree density, and species composition were compared in three unharvested pine-oak forests under different recent fire regimes: (1) an uninterrupted frequent fire regime, (2) fire exclusion, and (3) fire exclusion followed by the return of fire. Regeneration was dense and highly aggregated at all sites but the frequent-fire overstory was random to uniform in spatial distribution and relatively open while the fire-excluded sites had clumped overstory trees with a high density of smaller trees. Dominance by sprouting species was greatest at the fire-excluded sites. Mortality was spatially aggregated at all sites, consistent both with thinning by fire and density-dependent mortality, but competitive self-thinning appeared insufficient to counteract the increased tree density without fire. The return of fire after 29 years of exclusion reduced tree density but left overstory trees aggregated and led to vigorous oak and alder sprouting. Frequent fire disturbance is considered essential to maintain open pine forests; fire exclusion with or without subsequent fire appears to lead to denser forests dominated by smaller trees of sprouting species.

W. Wallace Covington

Papers

Sustainable ecological systems: Implementing an ecological approach to land management

Fire regimes and forest structure in the sierra madre occidental, durango, mexico

Developing the Conceptual Basis for Restoration Ecology

Ponderosa pine ecosystems restoration and conservation: steps toward stewardship; 2000 April 25-27; Flagstaff, AZ

Spatial patterns of Mexican pine-oak forests under different recent fire regimes