Thesis (M.S.)--Oregon State University, 1981. / Typescript (photocopy). Includes bibliographical references (leaves 37-38). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1978. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1983. / Typescript (photocopy). Includes bibliographical references (leaves 32-33). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 1983. / Typescript (photocopy). Includes bibliographical references (leaves 32-37). Also available on the World Wide Web.

This full report describes both forested and non-forested ecosystems of the Mountain Hemlock (MH) zone of British Columbia (also referred to as the subalpine MH zone, coastal subalpine forest, or coastal mountain hemlock forest). It is one of 14 technical reports intended to provide a comprehensive account of the biogeoclimatic ecosystem classification (BEC) system as well as some management implications for each zone in the province. These zonal reports should fill the gap between the general description given in “Ecosystems of British Columbia” (Meidinger and Pojar 1991) and the information on site identification and interpretation given in regional field guides (e.g., Banner et al. 1993, Green and Klinka 1994).

This pamphlet provides a summary of a fuller report also issued under the title: The mountain hemlock zone of British Columbia. It describes both forested and non-forested ecosystems of the Mountain Hemlock (MH) zone of British Columbia (also referred to as the subalpine MH zone, coastal subalpine forest, or coastal mountain hemlock forest). It covers classification, reviews of vegetation regions and environmental relationships, as well as silvicultural and resource management implications.

This research was initiated to develop an understanding of the differential radial-growth response of mature mountain hemlock (Tsuga mertensiana) trees located along a line of latitude in northwestern British Columbia. Increment core samples were collected from mountain hemlock stands located at five high-elevation sites between the Queen Charlotte Islands and Smithers. Tree ring-width index chronologies were compared to historical precipitation and air temperature data from four climate stations, as well as the El Nino Southern Oscillation and the Pacific Decadal Oscillation. No two mountain hemlock stands had the same growth response to monthly air temperature and precipitation, indicating that the trees are responding to site-specific limiting factors. The response to El Nino Southern Oscillation events was consistent along the transect, while the response to Pacific Decadal Oscillation phase changes was greatest at coastal sites and decreased towards the interior.

When making decisions on which areas to harvest in a sustained yield, even-flow manner in mountainous areas such those in coastal British Columbia, it is important to know how timber productivity changes with elevation. This information allows foresters to decide at what elevation to start increasing the rotation age and to decide at what elevation sustainable harvesting becomes infeasible due to low productivity. Since Pacific silver fir (Abies amabilis Dougl. ex Forbes) has an elevation range that extends from sea level nearly to the tree line (0 m to approximately 1,650 m; from the Coastal Western Hemlock zone, through the Mountain Hemlock zone; to the lower limits of the Alpine Tundra zone), productivity-elevation relationships are especially important. To acquire quantitative measures of productivity decrease with increasing elevation a regression equation relating site index (the height of the dominant trees at a base age of breast height age of 50 years) to elevation in southern coastal BC was developed. In turn, we used this regression as an input into the height driven yield model named the Variable Density Yield Prediction model (VDYP). The use of the VDYP model allows the site index values to be translated into actual productivity measures (e.g., volume per hectare, mean annual increment at culmination age).

Site classification in the biogeoclimatic ecosystem classification system is based on three differentiating properties: climatic regimes (expressed by biogeoclimatic subzones or variants), soil moisture regimes (SMRs), and soil nutrient regimes (SNRs). A SNR represents a segment of a regional soil nutrient gradient, i.e., soils which provide similar levels of plant-available nutrients over a long period. SNRs are identified in the field using a number of easily observable soil morphological properties and indicator plant species. However, we need to know to what extent soil nutrient properties support these indirect field-estimates. There have been several studies that quantitatively characterize regional soil nutrient gradients in different climatic regions, but no study has yet been done in the subalpine coastal forest (Mountain Hemlock zone). Influenced by a maritime subalpine boreal climate, high-elevation coastal soils differ from low-elevation soils by having a thicker forest floor and a higher organic matter content. In the study summarized here, relationships between soil chemical properties and field-estimated SNRs are examined and soil chemical properties and field-identified SNRs are related to the site index of Pacific silver fir (Abies amabilis (Dougl. ex Loud.) Forbes) - one of the major timber crop species in the Coastal Western Hemlock and Mountain Hemlock zones.

The Mountain Hemlock (MH) zone includes all subalpine forests along British Columbia’s coast. It occurs at elevations where most precipitation falls as snow and the growing season is less than 4 months long. The zone includes the continuous forest of the forested subzones and the tree islands of the parkland subzones (Figure 1). Old-growth stands are populated by mountain hemlock, Pacific silver fir, and Alaska yellow-cedar, and are among the least-disturbed ecosystems in the world. Canopy trees grow slowly and are commonly older than 600 years, while some Alaska yellow-cedars may be up to 2000 years old. Early regeneration failures followed slashburning and the planting of unsuitable species. Currently, the most successful and feasible option for reforesting cutovers is natural regeneration with a mix of the three main tree species, but uncertainties remain about the temporal and spatial pattern of regeneration, changes in species composition, and the time required for stand establishment after cutting. Our study addressed these concerns by examining regeneration patterns on 6 sites that were clearcut 11-12 years prior to sampling and left to regenerate naturally. The sites were located at the lower limits of the zone in the Tetrahedron Range, near Sechelt, at elevations from 1060-1100m.