Stand-density study of spruce-hemlock stands in southeastern Alaska.

Abstract

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 plots. Future plans include extending the study through establishment of installations in stand types not currently represented. Once data for an entire rotation are obtained, a comprehensive set of growth and yield tables for various management regimes can be developed. This information will answer questions forest managers have on whether and when to thin a stand, at what level of intensity, and how frequently to enter the stand.

Recent research on the management of hemlock–spruce forests in southeast Alaska for multiple values

“…The forest plan revision highlighted many information needs, and the research program developed after the revision provided many new opportunities for researchers and resource managers to collaborate in framing research questions, implementing studies, and integrating new findings into management activities. In silvicultural research, however, there was already a long-standing tradition of close cooperation between research and management, exemplified by our studies of stand-density management (DeMars, 2000), variable-retention harvesting , and thinning effects on understory plants (Zaborske et al, 2002). This collaboration continues and it is growing, with new large-scale studies of commercial thinning, managing young stands to enhance understory vegetation and wildlife habitat, and effects of silvicultural treatments on wood quality.…”

“…This is significant because the stands used to calibrate this model are generally of moderate to high productivity (DeMars, 2000), and critics of its use in the planning process suggested that this yielded a model bias toward overestimation of growth.…”

“…The secondary objective was to determine if the effects of thinning on these properties could be identified with this technique. Stands sampled in this study were part of a PNW standdensity study (DeMars, 2000) and provided trees grown at several densities and thinned at stand ages of 14-48 years.…”

Red Alder-Conifer Stands in Alaska: An Example of Mixed Species Management to Enhance Structural and Biological Complexity

“…Mixed red alder-conifer stands provided different tree size distributions and more complex forest structures than found in even-aged conifer stands that develop after stand replacing disturbances such as clearcutting. Pure conifer young-growth stands in this coastal region are typically very densely stocked with relatively uniform tree height and diameter distributions and simple species composition of mostly Sitka spruce and western hemlock trees [70]. The inclusion of alder trees within these predominantly conifer stands provide different tree size distributions and create a multi-layered forest canopy with a few large overstory conifers, a mid-canopy level of red alder trees and a lower canopy level of small diameter conifers.…”

“…On average productive sites in southeast Alaska, Sitka spruce trees can be expected to reach about 27 m in height within 50 years after attaining breast height [55,70]. Average site index at elevations near sea level varies inversely with latitude, declining from 48 m at base age 100 years in Lincoln County, OR, to 33 m in southeast Alaska, at the rate of about 1 m per degree of latitude [62].…”