Treesearch

During early stand development, coniferous forests of the coastal Pacific Northwest commonly pass through a period of dense shade and intense competition during which the abundance and diversity of understory plants decline dramatically. In young, managed forests, silvicultural thinning has been proposed to enhance the structural and floristic diversity of the understory. Although germination of buried seeds is likely to be stimulated by thinning, we know little about the composition of the soil seed bank in these forests. We used the greenhouse emergence method to assess the potential...

Ponderosa pines (Pinus ponderosa Dougl. ex. Laws) 21 to 60 yr old were used to assess the relative importance of environmental stressors (O3, drought) versus an enhancer (N deposition) on foliar retention, components of aboveground growth, and whole tree biomass allocation. Sites were chosen across a well-described gradient in ozone exposure (40 to 80 ppb per h, 24 h basis, 6 month growing season) and nitrogen deposition (5 to 40 kg ha−1 yr−1) in the San Bernardino Mountains east of Los Angeles, California. A high level of chlorotic mottle indicated high 0, injury at sites closest to the...

Many species of Dendroctonus, particularly the so-called aggressive species, are notorious outbreak organisms with more or less predictable or characteristic, cyclic patterns of outbreak locally if not regionally. D. frontalis, for example, exhibits an approximately 7-10 year cycle with 2-3 year duration of outbreak. The last south-wide outbreak of D. frontalis began in 1992 and peaked in 1995, with an estimated timber resource loss of $350 million in that year alone (Price and others 1998). The previous peak occurred in 1986. The presumption is that at epidemic levels, beetle populations...

Private timberlands in the United States have the biological potential to provide larger quantities of timber on a sustainable basis than they do today. Most opportunities for increasing growth and harvest lie on nonindustrial private lands in the South. Past studies, based on fixed scenarios of future prices, also suggest that many of these opportunities for intensified management can be undertaken with positive economic returns. Translation of these physical and apparent economic potentials into projections of future management and harvest requires a model of private timber management...

In western Oregon and Washington, recent changes in federal forest management policy contained in the Northwest Forest Plan have led to new harvest prescriptions on millions of acres of public lands. For example. on upland sites, standards and guidelines now require that live (green) trees are retained in at least 15% of the area within each harvest unit and recommend that at least 70% of this retention is in patches of moderate to larger size (0.2- 1.0 ha or more). These prescriptions [-'or green-tree retention were based on the professional judgment and collective knowledge of many of...

About 90 percent of the land in Maine is in forests. We analyzed past land use trends in Maine and developed projections of future land use. Since the 1950s, the area of forest in Maine has increased by almost 400,000 acres; however, the trends differ among ownerships, as the area of nonindustrial private timberland declined by 800,000 acres since 1950, while private industrial area rose by 681,000 acres. We used econometric analyses to identify variables affecting land allocation, such as population density. Estimated equations were used to generate decadal land use projections to 2050....

Controlled-exposure studies have shown that several plant species native to the Pacific Northwest are potentially sensitive to elevated ambient concentrations of tropospheric ozone. This guide reports visual and descriptive documentation of ozone injury symptoms for common tree, shrub, and herbaceous species in the region. Symptoms observed in leaves of these species include chlorotic mottle, pigmented stipple, necrosis, and premature senescence, with considerable variation among and within species. Resource managers and scientists can use the photo documentation in this guide to identify...

This report describes the logic and design of an effectiveness monitoring program for the Northwest Forest Plan. The program is prospective, providing an early warning of environmental change before irreversible loss has occurred. Monitoring is focused at two resource levels: individual species and specific ecosystem types. Selection of prospective indicators for the status of species or ecosystems is based on the development of conceptual models relating resource change to reliable, early warning signals of change. Ecosystems, such as late seral stage forest communities, are monitored on...

Mortality and growth of self and outcross families of three wind-pollinated, mixed-mating, long-lived conifers, Douglas-fir (Pseudotsuga menziesii), ponderosa pine (Pinus ponderosa), and noble fir (Abies procera) were followed from outplanting to age 26 (25 for noble fir) in spaced plantings at a common test site. Response to inbreeding differed greatly among species over time and in all regards. Only Douglas-fir and noble-fir will be contrasted here, because ponderosa pine usually was intermediate to the other two in its response to inbreeding. In earlier reports, compared to noble fir...

The USDA Forest Service Pacific Northwest Research Station in Corvallis, Oregon, has developed the ecosystem management decision support (EMDS) system. The system integrates the logical formalism of knowledge-based reasoning into a geographic information system (GIS) environment to provide decision support for ecological landscape assessment and evaluation. The knowledge-based reasoning schema of EMDS uses an advanced object- and fuzzy logic-based propositional network architecture for knowledge representation. The basic approach has several advantages over more traditional forms of...