Treesearch

Thinning is one of our most important ways to influence tree and stand development. The objectives may include increasing the volume, size, and quality of wood produced from a forest and developing particular stand structures and characteristics for other values, such as wildlife or aesthetics. The Levels-of-Growing-Stock (LOGS) Cooperative was initiated in the early 1960s, stretching from Southern Oregon through Washington to Vancouver Island, B.C. The study was designed to provide information on the relation between tree and stand growth, and thinning treatments, as a basis for managing...

It is widely accepted that wildfire has been part of the Douglas-fir region for millennia, but the variations across space and time in frequency, severity, pattern, and influence of native people are poorly understood. With wildfire raging every summer across parts of the West, interest is growing in the roles of fire in ecosystems, the possible use of fire and fuels management, and the use of fire history in landscape management. This Science Findings synthesizes the results of several tree-ring-based fire history studies carried out independently over the past two decades in a north...

When large trees die, individually or in clumps, gaps are opened in the forest canopy. A shifting mosaic of patches, from small single-tree gaps to very large gaps caused by wildlife, is a natural part of the development of composition and structure in mature forests. Gaps increase the diversity of forests across the landscape and present local environments that encourage the establishment and growth of new species. The role, however, of small gaps is not yet well understood. A long-term study established in 1990 seeks to uncover the role of gaps in creating forest diversity, their...

Public debate on postfire logging has intensified in recent years, particularly since passage of the "salvage rider" in 1995, directing accelerated harvest of dead trees in the western United States. Supporters of postfires logging argue that it is part of a suite of restoration techniques, and that removal of timber means reduction of fuels for future fires (the "reburn" effect). Opponents argue that it causes damage to burned sites, particularly to soils, that it increases sediment transport, and that it removes large dead trees that have important ecological functions.Considerable...

Garry oak (Quercus garryana) woodlands provide unique habitat for many Pacific Northwest species but these habitats are rapidly disappearing as species composition shifts to conifer or land use changes to urban or agricultural. Many oak trees from former savannas or oak woodlands on Fort Lewis Military Reservation (near Tacoma, WA, USA) are currently overtopped by Douglas-fir (Pseudotsuga menziesii). The shade-intolerant oak has probably survived in these stands due to past thinning activities; however, as the Douglas-fir continues to increase in height, we expect most of the oaks will not...

Acorn production in Oregon white oak is variable and not well understood. To determine tree, stand, and environmental characteristics influencing acorn production, we surveyed 284 trees in September and October 1999. Surveyed trees extended from Whidbey Island, Washington, to Roseburg, Oregon, and ranged in age from 11 to over 300 yr. Acorn production was ranked on a 1-4 scale (nonproducing to heavily producing), and tree size, condition, site, stand, and vegetation characteristics were recorded. All acorns were counted on 18 trees. Acorn production started around 20 yr and plateaued...

Developing sustainable forestry practices requires a perspective that encompasses whole and large landscapes; and a broad view of time and geographic space. However; understanding and visualizing the effects of different forest policies on ecological and socioeconomic conditions at such scales is a major challenge. Until recently; we lacked the conceptual framework and analytical tools to study the potential effects of different approaches to forest management over large areas and long periods. With advances in remote sensing; geographic information systems (GIS); and steadily increasing...

Managing forest stands to produce wood while also producing other values, such as wildlife habitat, recreation, or special forest products, requires information on forest components not always measured in traditional silviculture studies. For example, some managers may want to predict potential growth rates of herbs, shrubs, and trees in the understory—as these components will determine future forest composition and structure—or may be interested in flowering of plants in forest understories, since berry and seed production are important factors in determining species habitat suitability....

Concentrations of air pollutants were monitored during the May–November 1999 period on a network of forested sites in Sequoia National Park, California. Measurements were conducted with: (1) active monitors for nitric oxide (NO), nitrogen dioxide (NO2) and ozone (O3); (2) honeycomb denuder/filter pack systems for nitric acid vapor (HNO3), nitrous acid vapor (HNO2), ammonia (NH3), sulfur dioxide (SO2), particulate nitrate (NO3–
), ammonium (NH4+, and sulfate (SO42–
); and (3) passive samplers for O3, HNO3 and NO2. Elevated concentrations of O3 (seasonal means 41–71 ppb), HNO3 (seasonal...

In highly polluted sites, stomatal behavior is sluggish with respect to light, vapor pressure deficit, and internal CO2 concentration (Ci) and poorly described by existing models. Statistical models were developed to estimate stomatal conductance (gs) of 40-year-old ponderosa pine at three sites differing in pollutant exposure for the purpose of calculating O3 uptake. Gs was estimated using julian day, hour of day, pre-dawn xylem potential and photosynthetic photon flux density (PPFD). The median difference between estimated and observed field gs did not exceed 10 mmol H2O m
–2 s
–1, and...