Treesearch

A molecular diagnostic assay for Phytophthora spp. that is specific, sensitive, has both genus- and species-specific detection capabilities multiplexed, and can be used to systematically develop markers for detection of a wide range of species would facilitate research and regulatory efforts. To address this need, a marker system was developed based on the high copy sequences of the mitochondrial DNA utilizing gene orders that were highly conserved in the genus Phytophthora but different in the related genus Pythium and plants to reduce the importance of highly controlled annealing...

Low-density polyethylene (LDPE) plastic is used to keep piled debris from silvicultural activities—activities associated with development and care of forests—dry to enable efficient disposal by burning. The effects of inclusion of LDPE in this manner on smoke emissions are not well known. In a combustion laboratory experiment, 2-kg mixtures of LDPE and manzanita (Arctostaphylos sp.) wood containing 0, 0.25, and 2.5% LDPE by mass were burned. Gaseous and particulate emissions were sampled in real time during the entire flaming, mixed combustion phase—when the flaming and smoldering phases...

Soils sustain our terrestrial ecosystems, help fuel plant growth, and govern key ecosystem services such as the storage and provision of clean water, degradation of toxic compounds, and regulation of atmospheric gases. Preserving the integrity of soil thus is an earnest responsibility of land stewardship in the United States. This report provides a synthesis of soil chemical, biological, and physical responses to various prescribed fire and mechanical thinning practices and offers practical considerations for use in fuel reduction planning. A wide range of current topics, identified in a...

This paper reviews the status and management of sudden oak death and “sudden larch death” in the urban and wildland forests of California, Oregon, and the UK. The causal pathogen, Phytophthora ramorum, was discovered in all three locations over a decade ago; however, efforts to contain and eliminate infestations have been unsuccessful. These less than satisfactory management intervention outcomes underscore the importance of prevention, for once forest pathogens become established, response is costly and difficult, and eradication is unlikely.

Many western USA fire regimes are typified by mixed-severity fire, which compounds the variability inherent to natural regeneration densities in associated forests. Tree regeneration data are often discrete and nonnegative; accordingly, we fit a series of Poisson and negative binomial variation models to conifer seedling counts across four distinct burn severities and three forest types 10 years after the 23,000-ha Storrie Fire, a large mixed-severity fire in northern California. Despite the accessibility and power of the zero-inflated negative binomial mixture model, a flexible heterogeneo...

The transition of surface fire to live shrub crown fuels was studied through a simplified laboratory experiment using an open-topped wind tunnel. Respective surface and crown fuels used were excelsior (shredded Populus tremuloides wood) and live chamise (Adenostoma fasciculatum, including branches and foliage). A high crown fuel bulk density of 6.8 kgm-3 with a low crown fuel base height of 0.20m was selected to ensure successful crown fire initiation. Diagnostics included flame height and surface fire evolution. Experimental results were compared with similar experiments performed in an...

Scientists from PSW considered the effects of severe wildfire in the Sierra Nevada and southern Cascade Range in a recent synthesis that focused on promoting resiliency of forests and the societies connected to them. Fire is indispensable to maintaining the health and productivity of most forests in the Sierra Nevada, and fires can also rejuvenate aquatic systems by reforming in-stream habitats and increasing the supply of light, water, and nutrients. However, the size and unpredictability of mega-fires impacts people’s well-being, and their tendency to burn extraordinarily large and...

The conservation of species at risk of extinction requires data to support decisions at landscape to regional scales. There is a need for information that can assist with locating suitable habitats in fragmented and degraded landscapes to aid the reintroduction of at-risk plant species. In addition, desiccation and water stress can be significant barriers to the success of at-risk plant reintroduction programs. We examine how airborne light detection and ranging (LiDAR) data can be used to model microtopographic features that reduce water stress and increase resource availability, providing...

The Cascades frog (Rana cascadae) is a montane, lentic-breeding amphibian that has become rare in the southern Cascade Range and remains relatively widespread in the Klamath Mountains of northern California. In the southern Cascades, remaining populations occur primarily in meadow habitats where the fungal disease, chytridiomycosis, and habitat desiccation pose threats to persistance. Major risk factors in the Klamath Mountains include introduced fish and chytridiomycosis. Conservation actions are needed for the Cascades frog in California and especially in the southern Cascades. Conservati...

The pathogen, Phytophthora ramorum, causal agent of sudden oak death (SOD) of oaks and tanoaks, continues to expand its range within Oregon despite an effort to eradicate it from native forests. With its early detection and prompt removal of infected hosts, the Oregon SOD eradication program has produced a landscape distribution of disease resulting predominantly from the long distance (100 m to 4 km) dispersal of inoculum between sites. Using a regionally restricted randomization test reflecting the south to north intensification of the SOD epidemic in Oregon, we assessed if the movement...