Treesearch

Many factors increase susceptibility of forests to wildfire. Among them are increases in human population, changes in land use, fire suppression, and frequent droughts. These factors have been exacerbating forest susceptibility to wildfires over the last century in southern California. Here we report on the significant role that air pollution has on increasing forest susceptibility to wildfires, as unfolded in the San Bernardino Mountains from 1999 to 2003. Air pollution, specifically ozone (O3), and wet and dry deposition of nitrogenous compounds from fossil fuel combustion, has significan...

We describe methodologies currently in use or those under development containing features for estimating fire occurrence risk assessment. We describe two major categories of fire risk assessment tools: those that predict fire under current conditions, assuming that vegetation, climate, and the interactions between them and fire remain relatively similar to their condition during recent history, and those that anticipate changes in fire risk as climate and vegetation communities change through time. Three types of models have proven useful for predicting fire under current conditions: (1)...

The Random Forests multiple regression tree was used to develop an empirically based bioclimatic model of the presence-absence of species occupying small geographic distributions in western North America. The species assessed were subalpine larch (Larix lyallii), smooth Arizona cypress (Cupressus arizonica ssp. glabra), Paiute cypress (syn. Piute cypress) (Cupressus arizonica ssp. nevadensis), and Macfarlane’s four-o’clock (Mirabilis macfarlanei). Independent variables included 33 simple expressions of temperature and precipitation and their interactions. These climate variables were...

This study was designed to test the feasibility of combining a method designed to populate pixels with inventory plot data at the 30-m scale with a new national predictor data set. The new national predictor data set was developed by the USDA Forest Service Remote Sensing Applications Center (hereafter RSAC) at the 250-m scale. Gradient Nearest Neighbor (GNN) imputation was designed by the USDA Forest Service Pacific Northwest Research Station (hereafter PNW) to assign a plot identifier, and, therefore, a link to associated plot data, to each pixel within a target raster. Gradient Nearest...

Risk is a combined statement of the probability that something of value will be damaged and some measure of the damage’s adverse effect. Wildfires burning in the uncharacteristic fuel conditions now typical throughout the Western United States can damage ecosystems and adversely affect environmental conditions. Wildfire behavior can be modified by prefire fuel treatments, thereby reducing risks to firefighters, structures, and ecosystems, but such projects pose their own environmental risks. To support fuels treatment decisions, environmental analysis of alternatives is generally required,...

To assess threats or predict responses to disturbances, or both, it is essential to recognize and characterize the population structures of forest species in relation to changing environments. Appropriate management of these genetic resources in the future will require (1) understanding the existing genetic diversity/variation and population structure of forest trees, (2) understanding climatic change and its potential impacts on forest species and populations, and (3) development and use of new tools to identify populations at risk and geographic areas that will provide suitable habitat...

The Forests on the Edge project, sponsored by the USDA Forest Service, uses geographic information systems to construct and analyze maps depicting threats to the contributions of America’s private forest lands. For this study, watersheds across the conterminous United States are evaluated with respect to the amount of their private forest land. Watersheds with at least 10 percent forest land, of which 50 percent is privately owned, are then ranked relative to the contributions of their private forest lands to water quality, timber supply, at-risk species habitat, and interior forest. In...

Swiss needle cast disease of Douglas-fir (Pseudotsuga menziesii) is caused by the ascomycete fungus Phaeocryptopus gaeumannii. Symptoms of the disease are foliage chlorosis and premature needle abscission due to occlusion of stomata by the ascocarps of the pathogen, resulting in impaired needle gas exchange. Severe defoliation and growth losses of 20 to 50 percent because of Swiss needle cast have been reported for about 150 000 ha of Douglas-fir plantations in western Oregon since 1996. Because the physiological effects of the disease (impaired CO2 uptake and photosynthesis) are quantitati...

A framework that organizes natural and protected areas is often used to help understand the potential risks to natural areas and aspects of their ecological and human dimensions. The spatial (or landscape) context of these dynamics is also a critical, but, rarely considered, factor. Common classification systems include the U.S. Geological (USGS) Gap Analysis Program GAP) stewardship coding scheme, the International Union for the Conservation of Nature (IUCN) Protected Area Management Categories, and the American Planning Association (APA) Land-Based Classification Standards. The GAP and...

Wildland arson makes up the majority of fire starts in some parts of the United States and is the second leading cause of fires on Eastern United States Federal forests. Individual arson fires can cause damages to resources and communities totaling over a hundred million dollars. Recent research has uncovered the temporal and spatial patterns of arson fires and their long- and short-term drivers. In statistical analyses, explanatory variables include those associated with general economic conditions and law enforcement. Research findings indicate that wildland arson ignitions are consistent...