Treesearch

Concave curvilinear decreases in diameter growth occurred with increasing stand densities. A convex curvilinear increase in gross growth of basal area and total cubic volume took place with increasing stand density. Maximum cumulative net cubic (total and merchantable) and board-foot yields varied curvilinearly with stand density. These yields peaked at intermediate stand densities or varied little between the four highest stand density levels.

Direct measures of soil-surface respiration are needed to evaluate belowground biological processes, forest productivity, and ecosystem responses to global change. Although infra-red gas analyzer {IRGA) methods track reference CO2 flows in lab studies, questions remain for extrapolating IRGA methods to field conditions. We constructed 10 box lysimeters with homogenized mixtures of sandy loam and cattle manure and kept them free of plants to create a range of CO2 fluxes. Infra-red gas analyzer measurements, applied biweekly, were then compared to mass baiance—based measures of changes...

Phytomass tables are presented for southwest Alaska. The methods used to estimate plant weight and occurrence in the river basin are described and discussed. Average weight is shown for each sampled species of tree, shrub, grass, forb, lichen, and moss in 19 forest and 48 nonforest vegetation types. Species frequency of occurrence and species constancy within the type are presented. Comparisons are made with the results of similar inventories of the Tanana River basin and the southeast Alaska archipelago.

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...