Treesearch

The U.S. Clean Air Act establishes the goal of preventing future and remedying existing visibility impairment in 156 Class I areas (national parks, wilderness areas, and wildlife refuges). A key element in implementing this goal is the Regional Haze Regulation (RHR). RHR is based on relating impaired visibility, using metrics of extinction (inverse megameters and/or ‘‘deciviews’’), to concentration of ambient particulate matter (PM), especially the chemical components of particulates smaller than 2.5 μm in diameter, collectively known as PM2.5. PM2.5itself is also subject to national...

An analysis on the number of forest fires and burned area distribution as retrieved by the European Forest Fire Information System (EFFIS) database is presented. On average, from 2000 to 2005 about 95,000 fires occurred annually in 23 European countries, burning almost 600,000 ha of forest land every year. Of these about two-thirds or 65,000 fires occurred in 5 European Union (EU) Mediterranean countries (France, Greece, Italy, Portugal, and Spain) where on average half a million hectares of forest land were burned every year. In addition, out of the 23 European countries, the total burned...

Each summer forest fires in southern Europe emit large quantities of pollutants to the atmosphere. These fires can generate a number of air pollution episodes as measured by air quality monitoring networks. We analyzed the impact of forest fires on air quality of specific regions of southern Europe. Data from several summer seasons were studied with the aim of identifying air pollution episodes related to the occurrence of forest fires. Emissions from forest fires were estimated on the basis of vegetation burned and fire characteristics. Emissions from aircrafts used to fight forest fires...

Air pollution generated by vegetation fire smoke (VFS) is a phenomenon that has influenced the global environment in prehistoric and historic time scales. Although historic evidence of the impacts of VFS on societies is scarce, there are indications that VFS has been a factor that influenced society significantly since the Middle Ages. In recent decades, increasing application of fire as a tool for land-use change has resulted in more frequent occurrence of extended fire and smoke episodes with consequences on human health and security. Some of these events have been associated with...

Weather and climate have a profound influence on wildland fire ignition potential, fire behavior, and fire severity. Local weather and climate are affected by large-scale patterns of winds over the hemispheres that predispose wildland fuels to fire. The characteristics of wildland fuels, especially the moisture content, ultimately determine fire behavior and the impact of fire on the landscape. The physical processes related to combustion, fire, and plume behavior are largely affected by both daily weather and long-term climate.

Smoke emissions from wildland fire can be harmful to human health and welfare, impair visibility, and contribute to greenhouse gas emissions. The generation of emissions and heat release need to be characterized to estimate the potential impacts of wildland fire smoke. This requires explicit knowledge of the source, including size of the area burned, burn period, characteristics and condition of the fuels, amount of fuel consumed, and emission factors for specific pollutants. Although errors and uncertainties arise in the process of estimating emissions, the largest errors are related to...

Wildland fires are major sources of trace gases and aerosol, and these emissions are believed to significantly influence the chemical composition of the atmosphere and the earth’s climate system. The wide variety of pollutants released by wildland fire include greenhouse gases, photochemically reactive compounds, and fine and coarse particulate matter. Through direct emissions and secondary chemical and physical processes, wildland fire can have a significant impact on tropospheric chemistry and serve as a major source of air pollution. We provide a synthesis of emission factor data from...

Past records on fire-resilient, biodiverse stands could offer models for the future. This year marks the centennial of the Forest Service’s nationwide network of 80 experimental forests and ranges, which serve as field laboratories for long-term studies on the science and management of national forests. At the Stanislaus-Tuolumne Experimental Forest in the central Sierra Nevada, a research resurgence is underway thanks to the fortuitous discovery of a trove of useful historical data.

The interaction between smoke and air pollution creates a public health challenge. Fuels treatments proposed for National Forests are intended to reduce fuel accumulations and wildfire frequency and severity, as well as to protect property located in the wild land-urban interface. However, prescribed fires produce gases and aerosols that have instantaneous and long-term effects on air quality. If fuels treatment are not conducted, however, then wild land fires become more severe and frequent causing worse public health and wellfare effects. A better understanding of air pollution and smoke...

The stem cells of the vascular cambium divide to produce daughter cells, which in turn divide before undergoing differentiation during the radial growth of woody stems. The genetic regulation of these developmental events is poorly understood, however. We report here the cloning and functional characterization of a Populus class-I KNOX homeobox gene, ARBORKNOX2 (ARK2), which we show influences terminal cell differentiation and cell wall properties during secondary growth. In the early stages of secondary growth, ARK2 is expressed broadly in the cambial zone and in terminally differentiating...