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

We measured soil seed banks in 102 plots within a 110 000 ha Arizona Pinus ponderosa landscape, determined seed-bank responses to fire cues and tree canopy types (open or densely treed patches), co...

Seed banks of an Arizona Pinus ponderosa landscape: Responses to environmental gradients and fire cues

An area burned by prescription in 1977 and a nearby unburned area were measured in 1974 and 1980 to determine effects of the burn on herbage and forage production. Herbage production on the burned area increased significantly in 1980 over its 1974 level, in addition to being greater than the 1980 control production. However, the proportion of forage production to total herbage production in 1980 on the burned area decreased after the burn, and was significantly less than the control area forage production. This reduction in forage production can be attributed to the increase of nonforage species, notably bracken fern. Increases in total herbage production on both burned and unburned areas between 1974 and 1980 are attributed to a number of factors, including increased soil moisture availability during the 1980 growing season which had 50 percent more precipitation than the historical average. FOREST ScI. 30:22--25. ADDITIONAL KEy WORDS. Pinus ponderosa, forage production. FIRE SUPPRESSION in southwestern ponderosa pine has been blamed for a host of negative environmental impacts including decreased forage production, increased fuel loads, and increased severity and destructive potential of wildfires (Weaver 1974). In an attempt to alleviate the wildfire severity problem, land managers are using prescribed burning to reduce these heavy fuel loads. Little is known about the impact of prescribed fire on understory production in southwestern ponderosa pine. Ffolliott and others (1977) found a 13 fold increase (from 3.4 to Authors are former graduate student and Associate Professor, School of Forestry, Northern Arizona University, Flagstaff, Arizona 86011. Oswald is now Instructor of Forest and Range Sciences, College of Ganado, Ganado, Arizona 86505. Support for this study was provided by funds from the Mclntire~ Stennis Cooperative Forestry Research Act. E. L. Fitzhugh provided access to the original data from his study of the same area and assistance during the preliminary stages of this study. Manuscript received 7 August 1981.

/pdf/effect-of-a-prescribed-fire-on-herbage-production-in-25wapocjt0.pdf

Effect of a prescribed fire on herbage production in southwestern ponderosa pine on sedimentary soils

MARCH 2003 7 We are at a fork in the road in the American West. Down one fork lies burned-out, depauperate forest landscapes—landscapes that will be a liability for current and future generations. Down the other fork lies healthy, diverse, sustaining forest landscapes—landscapes that will bring multiple benefits for generations to come. Our present inaction is taking us down the path to unhealthy forest landscapes that are costly to manage. Scientifically based forest restoration treatments, including thinning and prescribed burning, will set us on the path to healthy forested landscapes—landscapes like the early settlers and explorers saw in the late 1800s. Knowing what we now know, it would be grossly negligent for us not to move forward with large-scale, restoration-based fuel treatments in the dry forests of the western United States. Inaction is now the greatest threat to the long-term sustainability of these ecosystems. It is time for ecologists, natural resource professionals, and others with relevant expertise to bring coherent, objective facts, and informed recommendations to the public and to national, regional, and local decision-makers. This paper presents my thinking on how to reverse the trend of increasing catastrophic wildfires in the dry forests of the West. I contend that we can help these forests recover their self-regulatory mechanisms, conserve biological diversity, and improve human habitat values by implementing science-based ecological restoration treatments.

Restoring Ecosystem Health in Frequent-Fire Forests of the American West

Ecological Restoration, Vol. 21, No. 3, 2003 ISSN 1522-4740 E-ISSN 1543-4079 ©2003 by the Board of Regents of the University of Wisconsin System. Roads are a prevalent component of forested landscapes throughout the United States, and their effects on forested ecosystems are numerous. Roads are known to cause habitat loss and fragmentation, which can directly alter plant and animal species composition (Andrews 1990, Auerbach and others 1997). They also affect natural disturbance regimes and hydrology with wideranging impacts on ecosystem functioning (Hobbs and Huenneke 1992, Swift and Burns 1999). About 435,000 miles (700,350 km) of road dissect U.S. Forest Service lands (USDA Forest Service 1999). New Forest Service road management policy attempts to reverse the adverse ecological impacts associated with roads on national forest lands by decommissioning unneeded forest roads and restoring their ecological processes (USDA Forest Service 2001). Natural recovery of roads is often impaired by highly compacted soils (Knapp 1992, Kamaruzaman 1996), so some form of rehabilitation is necessary to restore ecological processes. Although general information exists on the benefits of various road rehabilitation options (Cotts and others 1991, Luce 1997, Bagley 1998, Walker and Powell 1999), regionally specific information may be needed for effective results. No studies have been conducted in the ponderosa pine (Pinus ponderosa) forests of northern Arizona that address the effectiveness of road rehabilitation practices. Efforts to rehabilitate roads in the region range from simply blocking road entrances to ripping and seeding. This latter activity requires the use of bulldozers that drag rock rippers or subsoilers through the soil in order to reduce soil compaction, increase soil moisture, and improve seedbed conditions by breaking up soil clods and increasing the amount of pore space between them (Miles and Froehlich 1988, Cotts and others 1991). Seeding after ripping takes advantage of the decompacted soil and may facilitate natural regeneration by reducing surface erosion and improving soil structure (Swift and Burns 1999). Rapidly establishing and maintaining native plant communities on decommissioned forest roads is vital because until adequate plant cover is established, ripping alone provides only temporary and marginal improvements in soil structure (Luce 1997). Vegetative cover on roads can improve soil structure by increasing soil organic matter (Greacen and Sands 1980), reducing erosion (Swift 1984, 1986), and restoring the habitat lost from road construction. Successful revegetation may also help to keep roads closed by reducing their visibility. This is particularly important in the ponderosa pine forests of northern Arizona where the relatively open forest structure and moderate terrain makes it difficult to keep roads closed to vehicle use. Studies in other regions have found that the addition of soil amendments, specifically topsoil (Cotts and others 1991, Claassen and Zasoski 1993, Holmes 2001) Forest Road Revegetation: Effects of Seeding and Soil Amendments

Forest Road Revegetation: Effects of Seeding and Soil Amendments

Ecological restoration treatments using thinning and prescribed burning have been proposed to reverse the decline of old-growth ponderosa pines in the Southwest. However, long-term data on the effectiveness of such treatments are lacking. In 19931994, two ecological restoration treatments and a control were established at the G. A. Pearson Natural Area (GPNA) near Flagstaff, AZ. The thinned treatment removed many postsettlement-aged trees to create tree density and stand structure similar to pre-Euro-American forests. The thinned + burned treatment included prescribed burning of the forest floor in combination with this thinning. The control was a dense stand of pre- and postsettlement trees with no thinning or burning. Crown dieback of presettlement trees decreased by about 3 percent in both thinned treatments over 6 years since initiation of treatments, whereas dieback increased by about 4 percent in the control. Crown dieback was not related to tree age. Change in height of presettlement trees between 1994 and 2000 did not differ among treatments. Of 146 presettlement trees monitored for survival between 1994 and 2000, four died between 1997 and 2000, and all were in thinned treatments. Two of the four trees that died toppled or the stem broke in a severe windstorm in 1997. The other two dead trees died between 1997 and 2000 following the severe regionwide drought of 1996. These two dead trees had large amounts of canopy dieback prior to treatment initiation, suggesting that thinning did not contribute to their mortality. Our results indicate that heavy thinning of postsettlement trees improved the crown condition of presettlement trees at the GPNA over 6 years since treatment, but also may have increased windthrow and wind breakage.

https://www.fs.fed.us/rm/pubs/rmrs_p022/rmrs_p022_061_066.pdf

W. Wallace Covington

Papers

Seed banks of an Arizona Pinus ponderosa landscape: Responses to environmental gradients and fire cues

Effect of a prescribed fire on herbage production in southwestern ponderosa pine on sedimentary soils

Restoring Ecosystem Health in Frequent-Fire Forests of the American West

Forest Road Revegetation: Effects of Seeding and Soil Amendments

Six-year changes in mortality and crown condition of old-growth ponderosa pines in ecological restoration treatments at the G. A. Pearson Natural Area