Treesearch

Prior to fire suppression and exclusion, wildfi­res and other disturbances (e.g.,insects, disease, and weather) sustained ecosystem processes in many landscapes of the Western United States. However, wild­fires have been increasing in size, frequency, and intensity in recent years (Kellogg and others 2008). Recognizing the value of wildfi­re, scientists and land managers now promote allowing non-human-caused fi­res to burn in these landscapes, hoping ­fire can recreate the historical distribution and mosaic of presettlement, burned forests.

Forest loss and fragmentation of the remainder threaten the sustainability of many ecological attributes and processes that depend on extensive forest cover. The direct loss of intact forest is an obvious threat; less obvious are the indirect threats posed by isolation and edge effects, which encompass a wide range of biotic and abiotic in­uences on remnant forest (Forman and Alexander 1998, Harper and others 2005, Laurance 2008, Murcia 1995, Ries and others 2004). Because fragmentation is a spatial process, monitoring the threats posed by forest fragmentation necessarily involves analysis...

Beech bark disease (BBD) has long been negatively impacting the American beech (Fagus grandifolia), an important component of hardwood and mixed hardwood forests throughout eastern North America that provides food and habitat for over 40 species of birds and mammals (McCullough and others 2001). BBD is initiated by feeding activities of the beech scale insect (Cryptococcus fagisuga), which create wounds that act as entry points for the Neonectria spp. fungi. It is the fungal component of the disease complex that weakens and kills the tree. Mortality levels in the ­rst wave of the disease...

In preparing the 5-year Forest Inventory and Analysis (FIA) report for Vermont in 2007–08, analyses showed an increase in tree mortality since the previous inventory of 1996–97. Adjacent States had a similar spike in mortality. Further evaluation of FIA plot data helped focus the investigation. Some general characteristics of the mortality included: (1) distribution in both northern and southern Vermont, (2) high-elevation forests and timberland forests were affected, and (3) mortality was not related to stocking levels. Several species seemed to be affected, including red spruce (Picea...

Diseases and insects cause changes in forest structure and function, species succession, and biodiversity, which may be considered negative or positive depending on management objectives (Edmonds and others 2011). An important task for forest managers, pathologists, and entomologists is recognizing and distinguishing between natural and excessive mortality, a task which relates to ecologically-based or commodity-based management objectives (Teale and Castello 2011). The impacts of insects and diseases on forests vary from natural thinning to extraordinary levels of tree mortality, but...

Free-burning wildland ­re has been a frequent ecological phenomenon on the American landscape, and its expression has changed as new peoples and land uses have become predominant (Pyne 2010). As a pervasive disturbance agent operating at many spatial and temporal scales, wildland ­re is a key abiotic factor affecting forest health both positively and negatively. In some ecosystems, wildland ­res have been essential for regulating processes that maintain forest health (Lundquist and others 2011). Wildland ­re, for example, is an important ecological mechanism that shapes the distributions...

Doughts occur regularly in most U.S. forests, but their frequency and intensity vary widely between, as well as within, forest ecosystems (Hanson and Weltzin 2000). In the Western United States, forests commonly experience annual seasonal droughts. In the Eastern United States, forests tend to exhibit one of two prevailing drought patterns: random (i.e., occurring at any time of year), occasional droughts, as typically seen in the Appalachian Mountains and the Northeast; or frequent late-summer droughts, as typically seen in the southeastern Coastal Plain and the eastern edge of the Great...

Tree mortality is a natural process in all forest ecosystems. However, extremely high mortality can 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.

The 2013–2027 National Insect and Disease Forest Risk Assessment represents a nationwide strategic assessment of the hazard of tree mortality due to insects and diseases displayed as a series of maps, the National Insect and Disease Risk Maps (NIDRM) (Krist and others 2014) (­gs. 6.1, 6.2, and 6.3). Risk, or more appropriately termed, hazard, is de­ned in the assessment as the expectation that, without remediation, at least 25 percent of standing live basal area >1 inch in diameter will die over a 15-year time frame (2013–27) due to insects and diseases.