Treesearch

Forests cover a vast area of the United States, 304 million ha or approximately one-third of the Nation’s land area (Smith and others 2009). These forests possess substantial ecological and socioeconomic importance. Both their ecological integrity and their continued capacity to provide goods and services are of concern in the face of a long list of threats, including insect and disease infestation, fragmentation, catastrophic fire, invasive species, and the effects of climate change.

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 fire has been a frequent ecological presence 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 fire is a key abiotic factor affecting forest health both positively and negatively. In some ecosystems, wildland fires have been essential for regulating processes that maintain forest health despite causing extensive tree mortality (Lundquist and others 2011). Wildland fire, for example, is an important ecological...

Fire is a natural disturbance that occurs in most terrestrial ecosystems. It is also a tool that has been used by humans to manage a wide range of natural ecosystems worldwide. Wildland fire covers a spectrum from low severity, localized prescribed fires, to landscape-level high severity wildfires. The Earth is a fire planet whose terrestrial ecosystems have been modified and impacted by fire since the Carboniferous Period, some 300 to 350 million years before the present time. In the Holocene Epoch of the past 10,000 years, humans have played a major role in fire spread across the planet....

Sediment deposition changes the physical characteristics of river beds, and may alter the production and/or processing of allochthonous and autochthonous organic matter, with potential consequences for stream food webs. We conducted a comparative study of biofilm standing crop and metabolism in the Salmon Trout River, a tributary of Lake Superior where watershed disturbances have led to 3-fold increases in streambed fine sediments, predominately sand, in the past decade. We compared biofilm standing crop and metabolism rates using light–dark chambers in reaches where substrate consisted of...

Recent studies suggest that stream restoration at the reach scale may not increase stream biodiversity, raising concerns about the utility of this conservation practice. We examined whether reach-scale restoration in disturbed agricultural streams was associated with changes in macroinvertebrate community structure (total macroinvertebrate taxon richness, total macroinvertebrate density, Ephemeroptera, Plecoptera, Trichoptera [EPT] taxon richness, % abundance of EPT taxa) or secondary production (macroinvertebrate biomass over time). We collected macroinvertebrate samples over the course...

Crown dieback and declines in tree health of sugar maple (Acer saccharum) have been reported on various land ownerships in the western Upper Great Lakes region in recent years (MDNR 2009, 2010, 2012). In some areas, the crown dieback has affected high-value crop trees. Historically, sugar maple dieback (­g. 10.1) has been reported more frequently in the eastern part of its range and has not been described on the same scale in the Great Lakes region since the 1950s and 1960s (Bal and others 2015, Millers and others 1989). As a result, fewer studies of canopy health of sugar maple exist in...

Beech bark disease (BBD) has spread across roughly half of the range of American beech (Fagus grandifolia) in North America since it was introduced into Nova Scotia around 1890 (Erlich 1932, 1934; Gwiazdowski and others 2006; Houston 1994). The nonindigenous beech scale insect, Cryptococcus fagisuga Lind., mediates BBD by piercing the outer bark of beech trees, facilitating entry of the nonindigenous fungi Neonectria faginata, which colonizes only Fagusspp., or Neonectria ditissima (synonymous with N. galligena), which occurs on a variety of hardwood species in North America and Europe...

The Pinaleño Mountains in southeastern Arizona represent a Madrean sky island ecosystem that contains the southernmost expanse of spruce-­r forest type in North America. This ecosystem is also the last remaining habitat for the Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamenis), a federally listed endangered species. Due to a general shift in species composition and forest structure of spruce-­r type forests across the Southwest, the ecosystem is being threatened by large high-severity ­res, insect infestation, and a general loss of biodiversity. These risk factors have led the...