Abstract:We investigated the relationship of stem diameter to tree, site and stand characteristics for six major tree species (trembling aspen, white birch, balsam fir, lodgepole pine, black spruce, and white spruce) in Alberta (Canada) with data from Alberta Sustainable Resource Development Permanent Sample Plots. Using non-linear mixed effects modeling techniques, we developed models to estimate diameter at breast height using height, crown and stand attributes. Mixed effects models (with plot as subject) using height, crown area, and basal area of the larger trees explained on average 95% of the variation in diameter at breast height across the six species with a root mean square error of 2.0 cm (13.4% of mean diameter). Fixed effects models (without plot as subject) including the Natural Sub-Region (NSR) information explained on average 90% of the variation in diameter at breast height across the six species with a root mean square error equal to 2.8 cm (17.9% of mean diameter). Selected climate variables provided similar results to OPEN ACCESSForests 2011, 2 815 models with NSR information. The inclusion of nutrient regime and moisture regime did not significantly improve the predictive ability of these models.

. 1998. Soil nutrient and vegetation response to patch clear-cutting of an aspen forest near Meadow Lake, Saskatchewan. Can. J. Soil Sci. 78: 59-68. Alternate silviculture systems, such as small patch clearcuts, may become important in the development of sustainable forest management strategies in aspen forests. A study was initiated in a 64-yr-old trembling aspen (Populus tremuloides Michx.) stand in Meadow Lake Provincial Park, Saskatchewan to determine changes in nutrient dynamics and secondary succession following patch clear-cutting. One hectare replicated patch cuts were logged in the winter of 1993-1994. There was no site preparation following harvest. Annual vegetation, regeneration and soil and plant nutrient data were collected annually, 1 yr prior to, and 3 yr following harvest. Aspen regeneration was 48 375 stems ha -1 2 yr after treatment. Stand (alpha) diversity of the understory was not affected by harvesting, although annual species turnover (beta diversity) increased slightly after harvest. There was an increase in aspen foliar nitrogen (N) for 2 yr following harvest. Soil nutrient concentrations did not differ between patch cut and unharvested plots except total potassium (18% lower in the LFH of the harvested treatments 3 yr after harvesting). Small patch cuts with the litter horizon kept intact may be appropriate for aspendominated stands in the boreal mixed wood to minimize ecological disturbance while maintaining aesthetics within a park setting.Key words: Ammonium, aspen regeneration, diversity, nitrate, plant community structure, soil productivity Maynard, D. G. et MacIsaac, D. A. 1998. Réaction du bilan nutritif du sol et de la végétation à l'exploitation par blocs dans une forêt de peupliers faux-trembles située près de Meadow Lake, en Saskatchewan. Can. J. Soil Sci. 78: 59-68. Des systèmes alternatifs de sylviculture, comme la coupe à blanc par petites trouées, pourraient devenir une composante importante dans l'élaboration des stratégies d'aménagement durable des forêts de trembles. Nous avons étudié un peuplement de peupliers fauxtrembles (Populus tremuloides Michx.) âgé de 64 ans dans le parc provincial Meadow Lake, en Saskatchewan, afin de déterminer les modifications dans la dynamique des éléments nutritifs et la succession secondaire après une coupe à blanc par trouées. Au cours de l'hiver 1993-1994, une coupe à blanc par trouées a été pratiquée sur un hectare, avec répétition. Il n'y a eu aucune pré-paration du terrain après la coupe. Nous avons recueilli des données sur la végétation annuelle, la régénération, le sol et les éléments nutritifs, un an avant la coupe et, chaque année après celle-ci, pendant trois ans. La régénération de la tremblaie soumise au traitement a été de 48 375 tiges par hectare deux ans après la coupe. La diversité (alpha) de l'étage inférieur n'a pas été modifiée par la coupe, mais le renouvellement annuel des espèces (bêta) a augmenté légèrement après la coupe. Il y a eu une augmentation de l'azote (N) foliaire chez le tremble pendant deux ans après la...

Recent advances in remote sensing provide increasingly detailed forest information in a timely and cost-effective manner. Individual tree stem diameter, an important variable for operational forest inventory, cannot be determined directly from remotely sensed data; stem diameter must be estimated from ancillary measures of tree crown, tree height, and/or measures related to stand structure. In this study, we developed predictive models of diameter as a function of height and crown attributes using a nonlinear mixed-effects approach. Long-term silvicultural experiments provided data for several species: black spruce, Douglas-fir, and lodgepole pine. Addition of crown area and crown area of larger trees to diameter-height models significantly improved predictive performance, resulting in low root mean squared error values between 0.9 and 1.8 cm (10–11% of mean diameter). Our models indicated the need to include additional explanatory variables at wider levels of spacing and thinning. This case study highlights several practical implications for developing and refining individual tree diameter models based on variables that can be remotely sensed.

Abstract:The relationships between white spruce radial increment and wood properties were investigated in relation to tree and stand attributes using data from mature white spruce stands in the boreal forest of western Canada that experienced a range of shelterwood treatments. The model with the highest predictive ability was radial increment (adj-R 2 = 67%) and included crown attributes, diameter at breast height (DBH), average height of competitors, and a climate index. Radial growth was positively related to live crown ratio, whereas wood density and modulus of elasticity were negatively correlated to the crown attribute. Tree slenderness had a significant negative effect on wood density and modulus of elasticity, as it reflects the mechanical stability requirement of the tree. The models consistently improved when using annual averages calculated over longer periods of time. However, when the annual averages were calculated using time periods of 5-10 and 10-20 years prior to sampling, the predictive ability of the models decreased, which indicated that the current tree and stand conditions were the best predictors of growth and wood properties up to five years prior to sampling. This study suggests that crown length equal to 2/3 of the tree height might represent an optimal balance between radial growth and wood quality.