Treesearch

Bacterial leaf scorch (BLS) of shade trees is the common name for a disease caused by Xylella fastidiosa, a xylem-inhabiting bacterium that has fastidious nutritional requirements and is difficult to culture or verify by culturing. Forest trees including oak, sycamore, elm, planetree, sweetgum, mulberry and maple are species susceptible to Xylella infection (McElrone and others 1999) throughout the Eastern and Southeastern United States. It is not yet known how common and widespread BLS is in trees in the North Central States (Iowa, Illinois, Indiana, Michigan, Minnesota, Missouri, and...

Both the National Fire Plan (http://199.134.225.50/nwcc/t2_wa4/ pdf/RuralAssistance.pdf) and the Healthy Forest Initiative (http://www.fs.fed.us/projects/ hfi/2003/august/documents/hfi-fact-sheet. pdf) call for reduction of hazardous fuels. Consequently, estimations of forest fuel loading at various scales become necessary. The Forest Inventory and Analysis (FIA) Program of the Forest Service, U.S. Department of Agriculture, is currently sampling down woody materials (DWM) at its phase 3 plots at the intensity of one plot every 96,000 acres. In this study, DWM is defined as a collection of...

The forests of North America cover approximately 677.5
106 ha, one-third of the total land area of North America (UNFAO, 2005) and 17% of the global forest area, with Canada and the United States ranking the third and fourth, respectively, among countries with the largest forest areas.

Droughts are common in virtually all U.S. forests, but their frequency and intensity vary widely both between and within forest ecosystems (Hanson and Weltzin 2000). Forests in the Western United States generally exhibit a pattern of annual seasonal droughts. Forests in the Eastern United States tend to exhibit one of two prevailing patterns: random occasional droughts, typical of the Appalachian Mountains and of the Northeast, or frequent late-summer droughts, typical of the Southeastern Coastal Plain and the eastern edge of the Great Plains (Hanson and Weltzin 2000). For plants, a...

Tree mortality is a natural process in all forest ecosystems. However, extremely high mortality can also be an indicator of forest health issues. On a regional scale, high mortality levels may indicate widespread insect or disease problems. High mortality may also occur if a large proportion of the forest in a particular region is made up of older, senescent stands.

Fragmentation is a continuing threat to the sustainability of forests in the Eastern United States, where land use changes supporting a growing human population are the primary driver of forest fragmentation (Stein and others 2009). While once mostly forested, approximately 40 percent of the original forest area has been converted to other land uses, and most of the remainder is not original forest (Smith and others 2009). The direct loss of forest land is an obvious threat; less obvious are the threats posed by isolation and edge which encompass a wide range of negative biotic and abiotic...

Many plant species have been introduced to the United States by humans since European settlement, sometimes deliberately and sometimes inadvertently, such as in contaminated crop seed or soil. Some species have successfully escaped cultivation and become invasive, spreading and establishing new populations distant from original population centers. Indeed, introduced plant species have forever changed the vegetative landscape of North America.

The ozone indicator, an important research component of the Forest Health Monitoring (FHM) Program of the Forest Service, U.S. Department of Agriculture, was developed and implemented to address specific concerns about the negative effects of ground-level ozone pollution on forest health and productivity. Ozone is a highly toxic air contaminant that has been shown repeatedly to damage tree growth and cause significant disturbance to forest ecosystems. Ozone also causes distinct foliar injury symptoms to certain species (bioindicator plants) that can be used to detect and monitor ozone...

Savanna ecosystems were once a dominant feature of the Midwestern Corn Belt Plains ecoregion, occurring within the dynamic boundary between prairies to the west and forests to the east, and maintained in the landscape by complex interactions between fire, climate, topography, and human activities (Anderson 1998). Characterized by their continuous understory layer and widely scattered overstory trees, primarily oak species, Midwestern savannas are today extremely rare, largely converted to agricultural or transitioned to woodlands following changes to disturbance regime. Today, less than 1...

Analyzing patterns of forest pest infestations, diseases occurrences, forest declines and related biotic stress factors is necessary to monitor the health of forested ecosystems and their potential impacts on forest structure, composition, biodiversity, and species distributions (Castello and others 1995). Introduced nonnative insects and diseases, in particular, can extensively damage the diversity, ecology and economy of affected areas (Brockerhoff and others 2006, Mack and others 2000). Examining pest occurrences and related stress factors from a landscape-scale perspective is useful,...