Treesearch

Numerous 'exotic' tree pathogens are arriving in Europe, North America, and elsewhere due to flaws in current international plant health sanitary and phytosanitary (SPS) protocols. These include lack of protection against the many organisms unknown to science, an emphasis on promoting trade rather than promoting environmental biosecurity, a steadily increasing globalization of the trade in rooted plants, and the failure of regulatory authorities to take meaningful and effective action (Brasier 2005, 2008; Liebhold et al. 2012,Webber 2010). The United Kingdom, for example, has experienced...

Balsam woolly adelgid (BWA) (Adelges piceae) is an exotic, aphid-like sucking insect originally from Europe that feeds only on Abies species. North American species are particularly susceptible, with the apparently most susceptible being subalpine (A. lasiocarpa), Frasier (A. fraseri), and balsam fir (A. balsamea) (Newton and Hain 2005). The BWA feeds directly through the bark on stems, branches, and buds, causing swelling at the buds and branch nodes (“gouting”), dieback, and tree death. During feeding, the insect injects a salivary substance into the host tree, causing branch calluses...

Whitebark pine (Pinus albicaulis Engelm.) is in serious decline across its range, largely due to the combined effects of Cronartium ribicola J. C. Fisch (an introduced fungal pathogen that causes white pine blister rust), replacement by late successional species, and widespread infestation of mountain pine beetle (Dendroctonus ponderosae Hopkins) (Gibson and others 2008, Hoff and others 1980).

Larch sawfly (LSF) (Pristiphora erichsonii) is an invasive defoliator in Alaska. Based on aerial survey data, this insect has impacted an estimated 600,000 to 700,000 acres of eastern larch (Larix laricina) stands in Alaska during a 6-year period between 1999 and 2004. Mortality of larch within the sawfly-defoliated area was 80 percent or more (aerial survey data) in the majority of affected larch stands. Consecutive years of larch defoliation on the poorest sites resulted in 100 percent mortality.

As humans introduce competing land uses into natural landscapes, the public concerns regarding landcover patterns are expressed through headline issues such as urban sprawl, forest fragmentation, water quality, and wilderness preservation. The spatial arrangement of an environment affects all human perceptions and ecological processes within that environment, but this usually happens in competing ways, so the task for resource managers is to maintain appropriate amounts and patterns of different landcover types to provide the desired balance of social and ecological benefits. A prerequisite...

Virtually all U.S. forests experience droughts, although the intensity and frequency of the droughts vary widely between, as well as, within forest ecosystems (Hanson and Weltzin 2000). Generally, forests throughout the Western United States are subject to annual seasonal droughts, while forests in the Eastern United States can be characterized by one of two predominant patterns: random, occasional droughts (in the Appalachian Mountain region and the Northeast) and common late-summer droughts (in the Southeastern Coastal Plain and near the eastern edge of the Great Plains) (Hanson and...

Given the importance of standing dead trees to numerous forest ecosystem attributes/ processes such as fuel loadings and wildlife habitat, the Forest Inventory and Analysis (FIA) Program of the Forest Service, U.S. Department of Agriculture, initiated a consistent nationwide inventory of standing dead trees in 1999. As the first cycle of annual standing dead tree inventories nears full national implementation, the goal of this study was to conduct one of the first empirical assessments of the Nation’s standing dead tree resources. Results indicate that there are a substantial number of...

Federal agencies are currently developing guidelines for forest soil critical acid loads across the United States. A critical acid load is defined as the amount of acid deposition (usually expressed on an annual basis) that an ecosystem can absorb. Traditionally, an ecosystem is considered to be at risk for health impairment when the critical acid load exceeds a level known to impair forest health. The excess over the critical acid load is termed the exceedance, and the larger the exceedance, the greater the risk of ecosystem damage. This definition of critical acid load applies to a...

Land conversion and forest fragmentation is an important issue across the country. Forest fragmentation is one of the international Montréal criteria and indicators that the Forest Service, U.S. Department of Agriculture, must assess periodically (Riitters and others 2004). Characteristics of increased fragmentation include increases in the amount of forest-nonforest edge, and decreases in the size of forest patches. Edges are associated with greater drying of forest fuels and the spread of weedy species (both plants and animals). As forest patches become smaller and distances between them...

Yellow-cedar is a culturally, economically, and ecologically important tree in coastal Alaska that has been experiencing a widespread mortality known as yellow-cedar decline for about 100 years. Mapping during annual aerial detection surveys has identified nearly the entire geographical distribution of the problem, which totals over 500,000 acres in Alaska (Lamb and Wurtz 2009) and additional acreage in adjacent British Columbia (Hennon and others 2005). This broad-scale approach to detection has been useful in determining the general occurrence of this forest decline, but mapping from...