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Abstract: Three lodgepole pine and aspen mixedwood sites located in the central interior of British Columbia within the Sub Boreal Spruce (SBS) biogeoclimatic zone were chosen to study the neighbourhood aspen competition and canopy light environment of 14–19-year-old lodgepole pine. All three sites had previously been established as separate research trials designed to explore various silviculture options for controlling aspen competition (aspen brushing, herbicide, thinning and untreated areas). For each site, 33–36 pine trees were selected to represent the observed range of light regimes under the influence of various aspen competition levels. At each sample pine, competition and stand measurements were made and a series of vertical canopy light measurements from the top to the base of the live crown. After an evaluation of a variety of competition indices, the index DRD; sum of the ratio of each of the three nearest neighbour''s DBH to the subject pine divided by their distance and, amount of available light at the top of the crown (DIFNt) were found as the best overall predictors of pine stem volume growth. A site specific exponential relationship of relative pine stem volume growth to DRD was found and minimum growth response competition thresholds were determined, which could provide useful targets where maximizing pine volume is intended. Evaluation of both linear and non-linear models of DIFNt versus height growth indicated the response to be linear across the observed range of available light. Implications for management are discussed. [Copyright &y& Elsevier]

Abstract: Establishing white spruce (Picea glauca (Moench) Voss) by planting it under established aspen (Populus tremuloides Michx.), stands has substantial potential as a technique for regenerating boreal mixedwood stands. The presence of an aspen overstory serves to ameliorate frost and winter injury problems and suppresses understory vegetation that may compete with white spruce. In this study we examine the growth of white spruce during the first 10 years after being planted underneath a 39-year-old stand of trembling aspen following thinning and fertilization. Results indicate successful establishment and reasonable growth rates of white spruce planted under thinned and unthinned aspen stands, even with aspen basal area of 51m2 ha−1. Thinning of overstory aspen to 1000 or 2000stemsha−1 did not increase light reaching seedlings, but did result in improvements in light above the shrub layer and in diameter and height growth of the underplanted seedlings. However, these increases in growth of underplanted spruce may not justify the expense of thinnings. Fertilization of these stands prior to planting had no effect on spruce growth. Growth of spruce underplanted at this site near Fort Nelson was similar to that at two other stands near Dawson Creek, B.C. Information on treatment effects on light, beam fraction, air temperature, and soil temperature are presented. Measurements of light obtained using LAI-2000 and hemispherical photography were compared with those obtained from hourly PPFD measurements. Results indicate that while both methods provide estimates of transmittance that are highly correlated with those provided by actual light measurements, they provide substantial underestimates of actual light levels. [Copyright &y& Elsevier]

Abstract: Establishing white spruce (Picea glauca (Moench) Voss) by planting it under established aspen (Populus tremuloides Michx.), stands has substantial potential as a technique for regenerating boreal mixedwood stands. The presence of an aspen overstory serves to ameliorate frost and winter injury problems and suppresses understory vegetation that may compete with white spruce. In this study we examine the growth of white spruce during the first 10 years after being planted underneath a 39 year-old stand of trembling aspen following thinning and fertilization. Results indicate successful establishment and reasonable growth rates of white spruce planted under thinned and unthinned aspen stands, even with aspen basal area of 51m2 ha−1. Thinning of overstory aspen to 1000 or 2000stemsha−1 did not increase light reaching seedlings, but did result in improvements in light above the shrub layer and in diameter and height growth of the underplanted seedlings. However, these increases in growth of underplanted spruce may not justify the expense of thinnings. Fertilization of these stands prior to planting had no effect on spruce growth. Growth of spruce underplanted at this site near Fort Nelson was similar to that at two other stands near Dawson Creek, B.C. Information on treatment effects on light, beam fraction, air temperature, and soil temperature are presented. Measurements of light obtained using LAI-2000 and hemispherical photography were compared with those obtained from hourly PPFD measurements. Results indicate that while both methods provide estimates of transmittance that are highly correlated with those provided by actual light measurements, they provide substantial underestimates of actual light levels. [Copyright &y& Elsevier]

High-elevation, late-successional forests over much of British Columbia are dominated by Engelmann spruce (Picea engelmannii Parry ex. Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.). Throughout the range of these forests, however, there is a wide variation in natural disturbance and successional dynamics as influenced by diverse climate and topography. We divided these high elevation forests into four groups arranged along a regional climatic gradient that affects forest composition, structure and disturbance regime. For each, we describe the climate, topography, major vegetation, and natural disturbance dynamics. We suggest that management practices reflect the ecological variability demonstrated for these high elevation forests. [ABSTRACT FROM AUTHOR]

Abstract: Coarse woody debris (CWD) forms an important and specific habitat for many species of lichens, liverworts and mosses. We studied the relationships of 88 macrolichen and bryophyte species to CWD characteristics in mature mesic sub-boreal spruce forests in north central British Columbia. CWD characteristics and macrolichen and bryophyte species richness and abundance data were collected. Ordination, regression tree analysis and indicator species analysis were used to establish relationships between selected CWD variables and macrolichen and bryophyte species assemblages, overall species richness and individual species presence and abundance. Decay class and height from ground were the two CWD characteristics that most influenced macrolichen and bryophyte communities. Species composition varied along a continuum of assemblages from a dominance of arboreal lichens on decay class 1 (less decayed) CWD, to Cladonia, Dicranum and Brachythecium species and a diversity of liverworts on decay class 3, to feathermosses and Plagiomnium and Peltigera species on decay class 4 (more decayed) CWD. The height from ground of a log influenced the growth of liverwort and moss species with restricted growth on logs over about 10cm above the ground. Log species, bark cover and diameter showed more limited influence on community composition in this study. Species were not greatly influenced by aspect (northern versus southern log aspect); however, macrolichen and moss species were more common on the upper sides of logs and several liverwort species were restricted to the lower sides of CWD (upper versus lower sides of logs). These results provide insight into the relationships between CWD characteristics and macrolichen and bryophyte communities, provide a basis for examining forest management impacts on lichen and bryophyte composition and highlight the importance of maintaining a diversity of CWD on the landscape. [Copyright &y& Elsevier]