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.

/pdf/warming-and-earlier-spring-increase-western-u-s-forest-33qvd39h8z.pdf

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.

/pdf/fire-in-the-earth-system-481yvwaoo1.pdf

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

Although quaking aspen (Populus tremuloides Michx.) bark appears greener at higher elevations in the Sangre de Cristo mountain range of New Mexico, chlorophyll concentrations are inversely correlated (p = .001) with altitude. The higher concentration of chlorophyll at lower elevations is effectively masked by a white bloom of dead periderm cells which is also characteristic of exposed site trees. At higher elevations the bloom is yellow—brown and more translucent, thus allowing the chlorophyll layers beneath to show through. Therefore, trees at higher elevations appear greener even though they have lower cortical chlorophyll concentrations. The altitudinal gradient in bark reflectance characteristics may be of adaptive value. If cortical photosynthesis is more important at higher elevations, the translucent bloom would be advantageous in making more light available for photosynthesis. Increased light absorption might also be important in raising bark temperatures for physiological activity during the winter months. At lower elevations where air temperatures are higher, the highly reflective bloom may protected the trees from high bark temperatures and sunscald.

/pdf/altitudinal-variation-of-chlorophyll-concentration-and-4rnpwldkus.pdf

Altitudinal variation of chlorophyll concentration and reflectance of the bark of populus tremuloides

Relationships of exotic plant communities with native vegetation, environmental factors, disturbance, and landscape ecosystems of Pinus ponderosa forests, USA.

The decision whether to seed with native species follow- ing restoration treatments should be based on existing vegetation, species present in or absent from the soil seed bank, past manage- ment history, microclimate conditions and soils. We installed three permanent monitoring plots in two areas (total 18.6 ha) at Mt. Trumbull, AZ. Trees were thinned and the sites burned in 1996 and 1997. A 5 ha area was seeded with native shrub, grass and forb species; the remaining 13.6 ha were unseeded. Pretreatment spe- cies richness ranged from none to five species per plot. We recorded 13 graminoid and eight shrub species in the seeded area, and four graminoid and four shrub species in the unseeded area. The greatest increase in species richness in both seeded and unseeded plots occurred approximately 1.8 years posttreatment. Perennial native species dominated plant cover by 2.8 years, although annual native forbs dominate the soil seed bank. Perennial grasses are nearly absent from the seed bank. The seeded area had the highest diversity, but it also had twice as many nonnative species (14 versus 7 in the unseeded plots). By August 1999, maximum species rich- ness reached 51 species on the seeded plot. Of these species, 80 percent were native. Although seeding increases diversity, it may also have the long-term tradeoff of introducing new genotypes and species, both native and nonnative.

https://fs.fed.us/rm/pubs/rmrs_p022/rmrs_p022_067_073.pdf

Seeding versus natural regeneration: A comparison of vegetation change following thinning and burning in ponderosa pine

To test an approach for restoring historical stand densities and increasing plant species diversity of a pinyon-juniper ecosystem, we implemented a demonstration project at two sites (CR and GP) on the Grand Canyon-Parashant National Monument in northern Arizona. Historical records indicated that livestock grazing was intensive on the sites beginning in the late 1800s and continuing through the mid 1900s. Repeat aerial photographs (1940 and 1992) indicated recent increases in stand density and encroachment of trees into formerly open areas. Age distributions indicated that the majority of pinyon trees at both sites were less than 100 years of age and juniper establishment appeared to peak in the late 1800s to early 1900s, although some junipers had establishment dates as early as 1700-1725. Pretreatment understory communities were sparse ( 50% pinyon mortality, which was positively related to tree size and age. The demonstration treatment consisted of thinning small trees (< 25 cm diameter at root collar (DRC)), lopping and scattering thinned trees, and seeding native understory species. Thinning and mortality reduced overstory density from 638 and 832 trees per hectare pretreatment (258 and 337 trees per acre) to 280 and 251 trees per hectare (113 and 102 per acre) posttreatment at CR and GP, respectively. Posttreatment densities were similar to those suggested for the late 1800s by dendrochronological stand reconstructions. Thinning small diameter pinyon increased residual quadratic mean diameter (QMD) at CR and the relative importance of juniper at both sites. Live canopy fuels were reduced by treatment at CR and by thinning plus beetle-related mortality at GP. Although thinning slash was lopped and scattered, woody surface fuels were not significantly different between treated and control units at either site, perhaps due to the small size of thinned trees and the large interspace areas into which slash was scattered. Treatment had no immediate effects on herbaceous cover or species richness, both of which may take more time to develop. Further monitoring will help to clearly evaluate the effectiveness of this treatment for satisfying restoration and conservation goals.

https://www.fs.fed.us/rm/pubs/rmrs_p051/rmrs_p051_121_133.pdf

A demonstration project to test ecological restoration of a pinyon-juniper ecosystem

The Lepidoptera (butterflies and moths) can be useful indicators of ecosystem change as a result of a disturbance event. We monitored changes in butterfly abundance in two restoration treatment units paired with adjacent untreated forest at the Mt. Trumbull Resource Conservation Area in northern Arizona. Restoration treatments included thinning trees to density levels comparable to densities at the time of Euro-American settlement, and reintroducing a low to medium intensity fire to the system. One unit was treated in 1996, the second in 1998. Butterfly communities, nectar availability, and herbaceous species richness were compared between treated and adjacent control forests, and between 3-year posttreatment and 1-year posttreatment forests. Butterfly species richness and abundance were two and three times greater, respectively, in restoration treatment units than in adjacent control forests. Nectar plant species richness ranged from two to 10 times greater in restoration treatment units than in adjacent control forests. Comparison of the 3-year posttreatment unit with the 1-year posttreatment unit showed little difference in butterfly species richness and abundance, although no statistical comparisons can be made due to sample size. These restoration treatments offer a unique opportunity to study responses to and recovery from disturbance and restoration at a landscape level.

https://www.fs.fed.us/rm/pubs/rmrs_p022/rmrs_p022_088_094.pdf

W. Wallace Covington

Papers

Altitudinal variation of chlorophyll concentration and reflectance of the bark of populus tremuloides

Relationships of exotic plant communities with native vegetation, environmental factors, disturbance, and landscape ecosystems of Pinus ponderosa forests, USA.

Seeding versus natural regeneration: A comparison of vegetation change following thinning and burning in ponderosa pine

A demonstration project to test ecological restoration of a pinyon-juniper ecosystem

Butterfly response and successional change following ecosystem restoration