Treesearch

Tanoak (Lithocarpus densiflorus) trees are among Phytophthora ramorum’s most susceptible hosts. Extensive mortality in this species has led researchers to question whether selective breeding for resistance can be used to sustain populations; the answer depends on the extent and heritability of pathogen resistance within the host. Consequently, we have undertaken a multi-year common garden study of resistance to P. ramorum in tanoak seedlings grown from acorns collected by collaborators at sites in California and southern Oregon. We have sown 12,650 acorns from nine unique sites in a common...

Phytophthora ramorum was first discovered in Oregon forests in July 2001 where it was killing tanoak (Lithocarpus densiflorus) and infecting Pacific rhododendron (Rhododendron macrophyllum) and evergreen huckleberry (Vaccinium ovatum). At that time, nine infested forest sites were identified ranging in size from 0.2 to 5 hectares, and totaling 16 hectares on non-industrial private forest lands, industrial private forest lands, and federal forest land administered by the Coos Bay District, Bureau of Land Management (BLM). A 23 square kilometer quarantine area was established around the area...

Monitoring occurrence and distribution of Phytophthora species, including Phytophthora ramorum, in forest ecosystems can be achieved in several ways including sampling symptomatic plants, infested soils, and infested streams. Collecting plant and soil samples can be laborious and time consuming due to the distance surveyors need to travel. Not all forests are available for survey because of limited accessibility and stand density. Species of Phytophthora are well adapted to aquatic habitats and more diverse populations of Phytophthora spp. are found in forest streams than in nearby soils...

In the face of the sudden oak death (SOD) epidemic, decreasing foliar moisture content (FMC) of tanoak (Lithocarpus densiflorus) has land managers, fire managers, and property owners concerned with the increased possibility of crown fire in affected areas. A need exists to link local SOD-affected foliar moisture content (FMC) values and current FMC data to decision support tools, allowing managers to better predict crown fire in areas where SOD-affected tanoaks are prevalent. We tracked FMC of live (uninfected) tanoaks, Phytophthora ramorum-infected tanoaks, dead tanoaks, and surface...

Land managers, fire suppression professionals, and research scientists have speculated about the relationship between increased Phytophthora ramorum-caused hardwood mortality and wildfire incidence, severity, and behavior in coastal California. Little quantitative data has emerged to measure the nature of any such relationship. The Basin Complex and Chalk fires in the summer and fall of 2008 along the Big Sur Coast provided the first opportunity for observers to confirm or disconfirm speculations about fire and P. ramorum. In an effort to focus research, outreach, and technical assistance,...

In late June 2008, a large, dry lightning storm ignited thousands of fires across California. The largest of these fires became the Basin-Indians Complex Fire in Big Sur, along the State’s central coast. The fire burned over 240,000 acres (USDA Forest Service 2008) and required over a month of intense firefighting operations to contain the perimeter. Media reports and anecdotal accounts from firefighters linked the intensity of the fire and difficulty of firefighting operations to increased fuels from tree deaths caused by an emergent forest disease, sudden oak death (SOD). Coastal...

Particle Image Velocimetry (PIV) measurements were performed in laboratory-scale experimental fires spreading across horizontal fuel beds composed of aspen (Populus tremuloides Michx) excelsior. The continuous flame, intermittent flame, and thermal plume regions of a fire were investigated. Utilizing a PIV system, instantaneous velocity fields for the three regions were measured and special attention was given to the coherent fluid dynamic structures that are present in a propagating fire environment. Measurements were performed inside the fire itself and in the surrounding environment....

Combustion emissions and strong Santa Ana winds had pronounced effects on patterns and levels of ambient ozone (O3) in southern California during the extensive wildland fires of October 2007. These changes are described in detail for a rural receptor site, the Santa Margarita Ecological Reserve, located among large fires in San Diego and Orange counties. In addition, O3 changes are also described for several other air quality monitoring sites in the general area of the fires. During the first phase of the fires, strong, dry and hot northeasterly Santa Ana winds brought into the area clean...

Following a wildfire in the Santa Ana Mountains of northeast Orange County, California, a monitoring project was established to test whether aerial hydromulch reduced post-fire hillslope and small watershed erosion, and to document its impact on re-growing vegetation. The study site received below normal rainfall both the first and second winters after the fire. A high-intensity thunderstorm at the end of May 2008 produced very high peak rainfall intensities, providing an extreme test for the hydromulch. It appears that the mulch reduced hillslope erosion during low and moderate rainstorms,...

Co-existence of both mating types A1 and A2 within the EU1 lineage of Phytophthora ramorum has only been observed in Belgium, which begs the question whether sexual reproduction is occurring. A collection of 411 Belgian P. ramorum isolates was established during a 7-year survey. Our main objectives were genetic characterization of this population to test for sexual reproduction, determination of population structure, evolution and spread, and evaluation of the effectiveness and impact of control measures. Novel, polymorphic simple sequence repeat (SSR) markers were developed after screening...