Treesearch

The impact of increasing the number of crosses per parent on the efficiency of backwards selection was examined using Monte Carlo simulation. Both the efficiency of reselection and its associated variance leveled off after two to three crosses per parent. Because so few crosses appear to be needed to estimate parental GCA values, a quasi-complementary mating design option was investigated where only a subset of the full-sib families were planted into replicated field trials, while the remainder were established in less expensive pure-family full-sib blocks. Breeding values for families...

A series of 18 precommercial thinning trials was established in true fir-hemlock stands in the Olympic Mountains and along the west side of the Cascade Range in Washington and Oregon from 1987 through 1994. This paper documents establishment of these installations and presents some preliminary observations and results. Substantial differences in growth rates in height and diameter were observed among Pacific silver fir, western hemlock, and noble fir. Diameter growth of all species increased as spacing increased, but height growth of silver fir and noble fir decreased at wider spacings in...

In a recent volume of this journal, Nelson (Land Use Policy 16 (1999) 121) defines and computes several statewide indicators designed to evaluate the effectiveness of growth management efforts in Oregon and Florida. Two indicators are intended to measure how well states have contained urban sprawl and preserved farmland. They are computed using US Census of Population and US Census of Agriculture data. In this comment, I highlight potential problems associated with using these data to evaluate urban sprawl and farmland preservation, and recompute Nelson's indicators using alternative land...

The objectives of this paper were to (1) analyze recent rates of transitions among forest cover types on private timberland, (2) identify differences by ownership class, and (3) project future changes under different scenarios related to current policy issues in the Pacific Northwest. Timber harvests are the dominant class of disturbance on private timberland in western Oregon and Washington. Net changes in forest type areas depend on the relative mix of natural and human-related forces. Transitions among forest types after harvest may be planned, as in conversion of red alder (Alnus rubra...

We defined habitat requirements (source habitats) and assessed trends in these habitats for 91 species of terrestrial vertebrates on 58 million ha (145 million acres) of public and private lands within the interior Columbia basin (hereafter referred to as the basin). We also summarized knowledge about species-road relations for each species and mapped source habitats in relation to road densities for four species of terrestrial carnivores. Our assessment was conducted as part of the Interior Columbia Basin Ecosystem Management Project (ICBEMP), a multiresource, multidisciplinary effort by...

The lack of growth and yield information for young even-aged western hemlock (Tsuga heterophylla(Raf.) Sarg.)-Sitka spruce (Picea sitchensis (Bong.) Carr.) stands in southeastern Alaska served as the impetus for a long-term stand-density study begun in 1974. The study has followed permanent growth plots in managed stands under various thinning regimes. Between 1974 and 1987, 272 plots were established at 59 locations throughout southeastern Alaska. Remeasurement of the plots occurs every two to four years and will continue until harvest. Additional thinnings will occur on a portion of the...

A qualitative social assessment targeted salient issues connected to the Colville National Forest creating opportunities (CROP) research program that examines forest management alternatives for small-diameter stands in northeastern Washington. Research spanned various communities in three counties and investigated the diversity of fundamental values people attach to small-diameter stands, beliefs about appropriate forest management directions, and perceived impacts from the CROP program. To focus on people’s knowledge of and interest in small-diameter stand management, semistructured...

Predictions of future forestland area are an important component of forest policy analyses. In this article, we test the ability of econometric land use models to accurately forecast forest area. We construct a panel data set for Alabama consisting of county and time-series observation for the period 1964 to 1992. We estimate models using restricted data sets-namely, data from early periods-and use out-of-sample values of dependent and independent variables to construct precise tests of the model's forecasting accuracy. Three model specifications are examined: ordinary least squares, dummy...

Yellow mycelia and cords of Piloderma fallax (Lib.) Stalp. were more frequently observed in old-growth stands than in younger managed stands of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Piloderma fallax frequency and percent cover data were collected from 900 plots in three replicate stands in each of three forest age classes over 2 years in both spring and fall. Piloderma fallax is strongly associated with stand age; it occurred in 57% of plots in old-growth, 6% of rotation-age, and 1% of young stands. Presence of Piloderma fallax was related to the percent cover of coarse woody...

Management strategies for promoting late-seral attributes in second-growth forest need evaluation for their efficacy in maintaining biodiversity, including complete forest-floor, small-mammal communities. Two common strategies in the Pacific Northwest are (1) management with thinnings to promote large trees with developed understories and (2) retention of legacies, defined as live trees, logs, and snags from the preceding forest, at harvest, followed by protection but not thinnings of the new stand. We compared small-mammal communities resulting from >65 yr of application of these strategie...