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Time since death and time since fall were estimated for hybrid spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) logs to quantify temporal changes in log decay and habitat quality in east-central British Columbia. We sampled 136 logs (72 spruce and 64 fir) for species, size, and morphological attributes and used dendroecological techniques to estimate year of death (n = 97) and fall (n = 122). Time since death and time since fall of spruce and fir were similar in decay classes 1 and 2; fir was older than spruce in more advanced stages of decay. Discriminant analysis based on time since fall correctly classified logs into four decay classes for 67% and 80% of spruce and fir, respectively. Function as wildlife habitat changed significantly as logs decayed. Logs served as elevated runways for approximately 15 years and then increased in value as habitat for invertebrates and insectivores as wood softened and vegetation established. Concealed spaces increased as the wood decomposed but decreased when logs collapsed. We conclude that decay classes represent biologically and statistically significant stages of log decomposition that are relevant to wildlife habitat and therefore provide a useful construct for model development and field interpretation.Résumé : Le temps qui s'est écoulé depuis la mort et la chute des arbres a été estimé pour des billes d'épinette hybride (Picea glauca (Moench) Voss × engelmannii Parry ex. Engelm.) et de sapin subalpin (Abies lasiocarpa (Hook.) Nutt.) afin de quantifier les changements temporels dans la décomposition des billes et la qualité des habitats dans le centre est de la Colombie-Britannique. Les auteurs ont échantillonné 136 billes (72 épinettes et 64 sapins) pour en dé-terminer l'espèce, la dimension et les attributs morphologiques, et ils ont utilisé les techniques dendrochronologiques pour estimer l'année de la mort (n = 97) et de la chute (n = 122) des arbres. La période de temps écoulée depuis la mort et la chute des arbres était similaire pour l'épinette et le sapin dans les classes de décomposition 1 et 2; le sapin était plus vieux que l'épinette dans les stades de décomposition plus avancée. L'analyse discriminante basée sur le temps s'est écoulé depuis la chute des arbres a correctement classé les billes dans les quatre classes de décomposition pour respectivement 67 et 80 % des épinettes et des sapins. Le rôle d'habitat pour la faune a changé de façon significative à mesure que les billes se sont décomposées. Les billes ont servi de voies surélevées pendant environ 15 ans. Par la suite, elles sont devenues plus intéressantes comme habitat pour les invertébrés et les insectivores à mesure que le bois s'est ramolli et que la végétation s'est installée. Les espaces abritées ont augmenté à mesure que le bois s'est décomposé mais elles ont diminué lorsque les billes se sont désintégrées. Ils arrivent à la conclusion que les classes de décomposition correspondent à des stades biologiquement et statisti...

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Light interception by vegetation canopies surrounding white spruce (Piceaglauca (Moench) Voss) was studied for four different vegetation complexes on two sites near Prince George, British Columbia. Measurements of canopy percent cover and height, and canopy proximity to the tree, were combined to provide an index that could predict light interception by the canopy. Rates of foliage development of the different vegetation canopies studied had a significant effect on their degree of light interception over the growing season. Canopies dominated by fireweed (Epilobiumangustifolium L.) developed foliage at a faster rate than canopies dominated by other species, especially those dominated by thimbleberry (Rubusparviflorus Nutt.). Understanding the light interception characteristics of different vegetation canopies along with crop tree light requirements should allow the use of the light interception index for assessing the severity of competition for light in young plantations.

Various patterns of harvest in forests influence the length of road and number of stream crossings required. Snags are removed directly by harvesting, but they are also removed along road and opening edges to ensure worker safety. To assess the potential impacts of rate of harvest and pattern of harvest in an old-forest-dominated montane landscape, we developed a spatially explicit landscape dynamics model, which includes submodels for snag removal, harvesting activities, and access management. The model assesses the amount of new road construction and number of streams crossed by new roads, as well as changes in snag density and configuration across the landscape over a time horizon of several decades, in response to various harvesting patterns. We estimated that a dispersed 40-ha cutblock harvest pattern required about one-third more kilometres of new road over a 50-year period and removal of up to 70% more snags per hectare of harvest for safety purposes, compared with a harvest pattern based on natural-patch size distribution. Each 20% increase in stand-level retention resulted in a roughly equivalent increase in new road required. Up to eight times as many snags were removed per hectare of harvest for safety purposes at a stand-level retention of 70% than at a stand-level retention of 10%. The model appears to be an effective tool for determining the future impact of various harvest-pattern options on a number of important indicators of ecological impact.