Treesearch

The potential for biodiversity to mitigate risk of infectious diseases in ecological communities – known as the diversity-disease risk hypothesis – is fundamental to understanding links between landscape change and environmental health of forests affected by sudden oak death (SOD). Previous research of the Phytophthora ramorum pathosystem found evidence for a dilution effect, where areas of high woody plant diversity were found to have significantly lower disease prevalence. However, little is known regarding the resilience of biodiversity effects subject to ecological disturbances. We...

Our knowledge of sudden oak death (SOD) disease dynamics indicate that without bay laurel (Umbellularia californica) there is seldom oak (Quercus) infection. This requirement of an alternate host species for disease transmission to oak species is an example of pathogen spillover. We developed a path analysis to test specific hypothesized relationships between physical and ecological factors affecting pathogen spillover. Path analysis enables simultaneous examination of direct and indirect effects from multiple factors, which can enhance our understanding of the multiple influences on...

Failure to build consensus amongst stakeholders has been a primary obstacle barring progress in developing and implementing strategies to manage sudden oak death (SOD). Consensus as to the goals of in situ management of SOD has rarely been reached, because stakeholders’ visions of success vary widely and often compete with each other across the complex landscape of forest resources, ownership types, and overlapping jurisdiction in which this epidemic unfolds. Investments in research on the pathology of P. ramorum have yielded dynamic spread models identifying and ranking communities at...

Since Phytophthora ramorum established in the wildlands of California during the 1990s, the disease has spread rapidly throughout the state’s coastal and adjacent counties, likely by a combination of human-aided events (e.g., nursery plant introductions) and natural dispersal. While human-aided events are almost impossible to predict, dedicated efforts have been made to model the natural spread of the disease throughout California. These models have been built upon aerial survey mortality data and/or extensive plot-level data gathered for infested and non-infested locations throughout the...

Understanding the impacts of climate change on frost-free seasons is key to designing effective adaptation strategies for ecosystem management and agricultural production. This study examines the potential changes in the frost-free season length between historical (1971−2000) and future (2041−2070) periods over the contiguous USA with a focus on spatial variability and the uncertainties surrounding the projections, using daily minimum temperature outputs from a 6-member ensemble composed of 3 regional-climate models nested within 3 general-circulation models provided by the North American...

The Sudden Oak Death Sixth Science Symposium provided a forum for current research on sudden oak death, caused by the exotic quarantine pathogen Phytophthora ramorum. More than 50 submissions describing papers or posters on the following sudden oak death/P. ramorum topics are included: biology, genetics, nursery and wildland management, monitoring, and ecology. Abstracts are also provided from a special session on Phytophthoras in California native plant nurseries and restoration sites.

In many parts of North America, ash (Fraxinus) stands have been reduced by the emerald ash borer (Agrilus planipennis) invasion to a few surviving mature trees, saplings, basal sprouts, and seedlings. Without a soil seed bank for Fraxinus spp., tree recovery will require survival and maturation of these younger cohorts to reproductive age. Here we report and analyze the population dynamics of emerald ash borer and its associated natural enemies in ash saplings (2.5–5.8 cm DBH) in six deciduous forest stands in southern Michigan. At these sites, the outbreak population of the pest collapsed...

The degraded stand pictured in this 1955 USDA Forest Service photograph from Maine was dominated by balsam fir (Abies balsamea), red maple (Acer rubrum), paper birch (Betula papyrifera), and American beech (Fagus grandifolia). Stands such as these were typical of second-growth, lowland spruce–fir (Picea–Abies) forests in the Northeast following repeated high grading in the 1800s and early 1900s (Judd 1997). In light of concerns about the sustainability of the eastern spruce–fir cover type, the Forest Service began researching these forests in 1926 at the 1,863-acre Gale River Experimental...

This resource update provides an overview of forest resources in Michigan based on inventories conducted by the U.S. Forest Service, Forest Inventory and Analysis (FIA) program of the Northern Research Station. Estimates are based on field data collected using the FIA annualized sample design and are updated yearly. The annual inventory started in 1999. For the 2016 inventory, estimates for current variables such as area, volume, and biomass are based on 6,662 plot samples collected from 2011 to 2016. Change variables, such as net growth, removals, and mortality, are based on 6,076 samples...

In the eastern United States, American chestnut (Castanea dentata) was historically a major component of forest communities, but was functionally extirpated in the early 20th century by an introduced pathogen, chestnut blight (Cryphonectria parasitica). Because chestnut is fast-growing, long-lived, and resistant to decay, restoration of American chestnut using blight-resistant stock could have the potential to increase carbon sequestration or storage in forested landscapes. However, carbon dynamics are also affected by interspecific competition, succession, natural disturbance, and forest...