Treesearch

Particle size distribution from biomass combustion is an important parameter as it affects air quality, climate modelling and health effects. To date, particle size distributions reported from prior studies vary not only due to difference in fuels but also difference in experimental conditions. This study aims to report characteristics of particle size distributions in well controlled repeatable lab scale biomass fires for southwestern United States fuels with focus on chaparral. The combustion laboratory at the United States Department of Agriculture-Forest Service's Fire Science Laborator...

Park management frameworks developed in the US (e.g., VERP, etc.) are being applied in other countries, notably Taiwan. The social forces that drive visitor experiences and how they are reflected in practice are very important in these new contexts. The diversity of meanings, types of experiences desired or expected, and the ways to gauge "success" are highlighted. I review a couple of recent VERP applications, propose an expanded sociological basis for expanding VERP, reflect on the Taiwan situation, then propose a "meta-analysis" to better understand the role of social science in this...

Avian influenza virus (AIV) is an important public health issue because pandemic influenza viruses in people have contained genes from viruses that infect birds. The H5 and H7 AIV subtypes have periodically mutated from low pathogenicity to high pathogenicity form. Analysis of the geographic distribution of AIV can identify areas where reassortment events might occur and how high pathogenicity influenza might travel if it enters wild bird populations in the US. Modelling the number of AIV cases is important because the rate of co-infection with multiple AIV subtypes increases with the...

The Point Arena mountain beaver (Aplodontia rufa nigra) is a federally listed endangered species, but has been the subject of few studies. Mountain beavers use burrows that include a single subterranean den. Foremost among the information needs for this subspecies is a description of the above-ground habitat features associated with dens. Using telemetry we located dens of 23 individuals in Manchester State Park, Mendocino County, California. We measured vegetation and topographic variables directly above the dens and at two available sites within the same burrow system. Alternative...

Accurately differentiating age classes is essential for the long-term monitoring of resident New World tropical bird species. Molt and plumage criteria have long been used to accurately age temperate birds, but application of temperate age-classification models to the Neotropics has been hindered because annual life-cycle events of tropical birds do not always correspond with temperate age-classification nomenclature. However, recent studies have shown that similar molt and plumage criteria can be used to categorize tropical birds into age classes. We propose a categorical age-classificatio...

Little is known about the probability of fire-scar formation. In this study, we examined all mixed conifer trees for fire-scar formation in a 16 ha watershed that burned as part of a 2003 wildfire in Sierra San Pedro Ma´rtir National Park (SSPM), Mexico. In addition, we examine the probability of fire-scar formation in relation to the previous fire interval in forests in the SSPM and Sierra Nevada. Within the 16 ha SSPM watershed, 1647 trees were assessed (100% census) for new fire scars. The SSPM wildfire burned around the base of 78% of the trees, but only 8% developed a new fire scar....

Data from four continuous ozone and weather monitoring sites operated by the National Park Service in Sierra Nevada, California, are used to develop an ozone forecasting model and to estimate the contribution of wildland fires on ambient ozone levels. The analyses of weather and ozone data pointed to the transport of ozone precursors from the Central Valley as an important source of pollution in these National Parks. Comparisons of forecasted and observed values demonstrated that accurate forecasts of next-day hourly ozone levels may be achieved by using a time series model with historic...

Biochemical changes in trees stressed by drought and air pollution may attract bark beetles, which overwhelm the trees’ defense mechanisms.

We investigated the effect of leaf age on the response of net photosynthesis (A), stomatal conductance (gwv), foliar injury, and leaf nitrogen concentration (NL) to tropospheric ozone (O3) on Prunus serotina seedlings grown in open-plots (AA) and open-top chambers, supplied with either carbon-filtered or non-filtered air. We found significant variation in A, gwv, foliar injury, and NL (P < 0.05) among O3 treatments. Seedlings in AA showed the highest A and gwv due to relatively low vapor pressure deficit (VPD). Older leaves showed significantly lower A, gwv, NL, and higher foliar injury (P...

Individual samples of high moisture fuels from the western and southern United States and humidified aspen excelsior were burned over a flat-flame burner at 987° ± 12°C and 10 ± 0.5 mol% O2. Time-dependent mass and temperature profiles of these samples were obtained and analysed. It was observed that significant amounts of moisture remained in the individual samples after ignition occurred. Temperature histories showed a plateau at 200°–300°C at the leaf perimeter rather than at 100°C, with a plateau of 140°C for the leaf interior. Implications are that classical combustion models should...