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.

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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

The inoculum potential for arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) fungi were investigated in thinned and uncut control stands in a northern Arizona ponderosa pine forest. A corn bioassay was used to determine the relative amount of infective propagules of AM fungi, and a ponderosa pine (Pinus ponderosa) bioassay was used to determine the relative amount of infective propagules of EM fungi. Three stands of each treatment were sampled by collecting soil cores along 10 randomly chosen transects within each stand. The relative amount of infective propagules of AM fungi was significantly higher in samples collected from the thinned stands than controls. Conversely, there was a slight decrease in the relative amount of infective propagules of EM fungi in samples collected from thinned stands in comparison to the controls; however, this difference was not significant. These preliminary results indicate that population densities of AM fungi can rapidly increase following restoration thinning in northern Arizona ponderosa pine forests. This may have important implications for restoring the herbaceous understory of these forests because most understory plants depend upon AM associations for normal growth.

https://www.fs.fed.us/rm/pubs/rmrs_p022/rmrs_p022_074_079.pdf

Effect of restoration thinning on mycorrhizal fungal propagules in a northern Arizona ponderosa pine forest: Preliminary results

Fire regimes over a 1070-m elevational gradient, San Francisco Peaks/Dook’o’oosłííd, Arizona, USA

In this study, we used a variety of methods to quantify and describe historical patterns of fire and forest structure in two pinyon-juniper ecosystems of the Southwest. Sites were located on the Kaibab National Forest in Arizona, south of Grand Canyon National Park (Tusayan), and on the Carson National Forest in New Mexico, north of Espanola (Canjilon). Methodological approaches included analysis of fire scars, contemporary forest structure, fire evidence, modern fire records, and forest reconstruction. GIS surface maps, constructed using inverse distance weighted interpolation, were used to assess spatial patterns of fire and forest structure. Results indicated distinct fire histories and recent forest changes at the two sites. At Tusayan, surface fires burned historically at frequencies of 7.2-7.4 years (Weibull median probability) in canyons and draws dominated by ponderosa pine. On uplands dominated by pinyon-juniper communities, longer point fire intervals suggested fires occurred at a mean frequency of 41.6 years. Point intervals stratified by species indicated longer return periods for Utah juniper than pinyon or ponderosa pine. Fire evidence in the form of charred tree structures was ubiquitous at the site and there was no clear relationship between stand age and fire evidence. Live, old trees (300 yr) were prevalent and averaged 26 trees per hectare (TPH). Stands were all ages up to 400 yr and patch sizes were generally small (30 ha). Reconstructions showed a moderate overall increase (39(percent)) in stand density since the late 19th century. Ponderosa pine increases were responsible for the majority of recent structural changes although pinyon density also had apparently increased. We found no evidence of extensive stand replacing fire over the last 400 years at Tusayan and concluded that the historical pattern has been one of frequent surface fires in ponderosa pine communities and small severe fires on pinyon-juniper uplands. At Canjilon, fire scar analysis showed longer mean fire intervals (81.1 yr), suggesting that infrequent crown fires or severe surface fires were an important component of the historical regime. Like Tusayan, charred structures were found across the Canjilon site, although they appeared to be more abundant at lower elevations where stands ages were younger. Few live old trees (300 yr) were found at the site (4.2 TPH). The site dominated by stands in the 200-250-yr and 250-300-yr age classes. Mean patch sizes for stands of these age classes were 24 and 79 ha, respectively. Reconstructions showed relatively greater increases in tree density (61(percent)) with Rocky Mountain juniper and pinyon pine both showing positive changes since the late 19th century. Evidence of stand replacing fire was seen along the eastern edge of the study site and young trees appeared to be encroaching into previously open areas, particularly around big sagebrush meadows. Woodland treatments that may parallel historical patterns of fire and forest structure at these sites include targeted tree thinning and/or use of prescribed fire to create canopy openings of various sizes.

Pinyon-juniper fire regime: Natural range of variability

Isolated forested mountains in deserts have numerous ecological and societal values, but land management practices (e.g., fire-regime alteration) and climate change can affect forest composition. We analyzed tree overstory-understory relationships on 123 sites in the Spring Mountains within the Mojave Desert near Las Vegas, Nevada, USA to assess three hypotheses. We hypothesized that: the tree species comprising understories are less tolerant of fire than species in overstories, reflecting land management practices of fire exclusion; mid-elevation forests have the lowest overstory:understory similarity since this zone could have maximum species mixing; and overstory:understory similarity is correlated with environmental gradients (consisting of 14 topographic and soil variables). We found that Pinus monophylla comprised greater relative canopy cover in understories of juniper Mojave Applied Ecology Notes Summer 2011 Volume 4, Issue 2 Page 2 Applied Ecology Research Group University of Nevada Las Vegas 4505 S. Maryland Parkway Las Vegas, Nevada 89154-4030 RESEARCH STAFF Lindsay Chiquoine, Research Assistant Kenneth Chittick, Student Assistant Donovan Craig, Research Assistant Joslyn Curtis, Botanist Karin Edwards, Botanist Teague Embrey, Botanist Cayenne Engel, Research Associate Sara McPherson, Graduate Assistant Kate Prengaman, Botanist Sarah Schmid, Botanist Sylvia Tran, Student Assistant Peter Van Linn, Graduate Student Dr. Cheryl Vanier, Statistical Analyst PROGRAM MANAGER Scott Abella, Ph.D. scott.abella@unlv.edu Mojave Applied Ecology Notes www.unlv.edu/staff/cengel/AERGHome.htm Summer 2011 Volume 4, Issue 2 Editor: Sharon Altman sharon.altman@unlv.edu Mojave Applied Ecology Notes is a newsletter published quarterly by the UNLV Applied Ecology Research Group. We specialize in working with resource managers to address key information needs for management through applied research. Catastrophic fire possible on Mount Charleston A feature on Mt. Charleston (southern Nevada) fire ecology and management aired on KLAS channel 8 Las Vegas on Monday, June 13, 2011. Scott Abella and UNLV students Sylvia Tran and Ken Chittick were interviewed on site. A link to this feature is available from: http://www.8newsnow.com/story/14900025/fire Excerpt from the newscast: The scars from last summer's Cathedral fire can still be seen at Mount Charleston. UNLV scientists believe each year brings higher chances for a catastrophic fire in that community. UNLV students measure the diameter of trees at a research plot. Overseeing them is ecologist Scott Abella. Stumps show where two large trees grew 100 years ago. The woods are now filled with trees which may be too much of a good thing. "[We are seeing a] Major increase in the density of the forest, so a lot more trees today than a hundred years ago, so a lot more fuel. When we do have a fire today, it can pretty much take everything out," said Dr. Scott Abella, UNLV ecologist. Abella's team hikes to the starting point of last year's Cathedral fire. Only the underbrush should have burned, instead, tall, dead trees remain. "Because we've been so good at actually stopping these fires, we've had this tremendous fuel buildup," he said. UNLV's scientific data show wildfire once burned frequently in the understory. Without that, Abella says it's time to cut down some of these smaller trees to establish a clumped tree pattern mimicking natural forest patterns that also is resistant to catastrophic fire. Mojave Applied Ecology Notes Summer 2011 Volume 4, Issue 2 Page 3 A U.S. Forest Service, Rocky Mountain Research Station research note was recently published which may be of interest to some of you. This note reports a novel use of the Forest Service's region 3 ecosystem survey for estimating tree densities across the landscape. The effort was a collaboration among UNLV, the Forest Service, and the Northern Arizona University Ecological Restoration Institute. Abstract: Maps of historical tree densities for project areas and landscapes may be useful for a variety of management purposes such as determining site capabilities and planning forest thinning treatments. We used the U.S. Forest Service Region 3 terrestrial ecosystem survey in a novel way to determine if the ecosystem classification is a useful a guide for estimating historical (1880) ponderosa pine (Pinus ponderosa) tree densities on a northern Arizona landscape. Based on sampling 53 sites spanning 9 ecosystem types, we grouped the types into low and high density categories. Tree density was less than 24/ acre on 91 percent (21 of 23) of sites in cinder, dry limestone, and clay basalt ecosystems. In contrast, 70 percent (21 of 30) of sites that contained densities exceeding 24 trees/acre were in basalt, mixed igneous, and moist limestone ecosystems. Maps of historical tree densities for project areas and landscapes may be useful for a variety of management purposes such as determining site capabilities and planning forest thinning treatments. We used the U.S. Forest Service Region 3 terrestrial ecosystem survey in a novel way to determine if the ecosystem classification is a useful a guide for estimating historical (1880) ponderosa pine (Pinus ponderosa) tree densities on a northern Arizona landscape. Based on sampling 53 sites spanning 9 ecosystem types, we grouped the types into low and high density categories. Tree density was less than 24/ acre on 91 percent (21 of 23) of sites in cinder, dry limestone, and clay basalt ecosystems. In contrast, 70 percent (21 of 30) of sites that contained densities exceeding 24 trees/acre were in basalt, mixed igneous, and moist limestone ecosystems. A link to this publication is online: http://www.treesearch.fs.fed.us/pubs/37962 Using a terrestrial ecosystem survey to estimate the historical density of ponderosa pine trees By Scott Abella, Charles Denton, David Brewer, Wayne Robbie, Rory Steinke, and W. Wallace Covington Creosotebush Examples of stumps (foreground, and to the left of the large tree), indicative of historical tree locations, and a live tree of pre-settlement origin (left-center). Photo by S.R. Abella in 2009, Forest Road 3E, Coconino National Forest, northern Arizona (UTM:440,918 m E, 3,885,850 m N, North American Datum 1983). RMRS cont. on next page Mojave Applied Ecology Notes Summer 2011 Volume 4, Issue 2 Page 4 Location of 53 sample sites on a northern Arizona landscape. Sizes of Points for sites are scaled to reflect ponderosa pine tree density reconstructed for 1880 forests. Shading depicts gradients in annual precipitation estimated from sample site values using the PRISM model (Daly and others 2008). Coordinates are UTM, North American Datum 1983. Mojave Applied Ecology Notes Summer 2011 Volume 4, Issue 2 Page 5 Student research with the AERG Lab Our lab actively has engaging research opportunities for undergraduate and graduate students who are motivated to build project experience and resumes and make positive contributions to advancing environmental management in Las Vegas and the Southwest. This summer, to advance those goals as well as to provide course credit (to help students graduate) given the budget-related uncertainty of the Environmental Science program, we have been offering a variety of undergraduate and graduate research course credits. Two of the students, undergraduates Sylvia Tran and Ken Chittick, were introduced in our last issue, and are continuing their work on a mesquite habitat restoration project and other projects. Several other students and volunteers are working on an array of other projects. Nayeli Carvajal, a graduate student, supplied a bio for this issue. Nayeli is working on a project in the Spring Mountains of southern Nevada seeking to understand the effects of chips and slash on Nayeli Carvajal completed a Bachelor’s degree in International Business from CESUES University in Sonora, Mexico and she will be obtaining her M.S in Environmental Policy and Management from UNLV this Fall semester. After completion of her Master’s degree, she plans to pursue a Ph.D. in Ecology. Nayeli is currently working on a butterfly habitat assessment project in the Spring Mountains. She enjoys spending her free time outdoors and traveling.

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W. Wallace Covington

Papers

Effect of restoration thinning on mycorrhizal fungal propagules in a northern Arizona ponderosa pine forest: Preliminary results

Fire regimes over a 1070-m elevational gradient, San Francisco Peaks/Dook’o’oosłííd, Arizona, USA

Pinyon-juniper fire regime: Natural range of variability

Mojave Applied Ecology Notes Summer 2011