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The taper equations used by the Ministry of Forests, Lands and Natural Resource Operations in British Columbia (BC), Canada, date back to the mid-1950s. Very little work has been done on examining the effect of climate on taper, particularly for BC but elsewhere as well. The objective of our research was to determine whether climate has an effect on tree taper for lodgepole pine (Pinus contorta Dougl. ex Loud.) in BC. The data for this project consisted of multiple diameter inside bark measurements along the stems of 270 trees across eight biogeoclimatic zones. In addition, 20 climate variables for the sample sites were predicted from the ClimateWNA model. Kozak's variable-exponent taper model was refitted with the climate variables in the exponent of the model. The single temperature- and precipitation-related variables that provided the best fit were incorporated into the final taper model. The model was analysed as a mixed-effects model, with spatial correlation and heteroscedastic errors being explicitly modelled. Mean annual precipitation and the Julian date of the first frost after the summer growing period were the best predictors of taper. Further work is required to understand why these variables are important predictors of taper, but a possible linkage is through the tree's crown. [ABSTRACT FROM PUBLISHER]

Changes to forest growth models used widely in global change research and sustainable forest management are needed to account for expected climate change impacts. We provide a new approach that dynamically merges height-age functions prevalent in forest growth models with transfer functions prevalent in population adaptation research to better represent changes to forest productivity as climates gradually change. Our simulations with data from an extensive provenance test of lodgepole pine ( Pinus contorta) in British Columbia, Canada, suggest that climate change will reduce production in lodgepole pine forests established today by at least 7-13% at the end of this century - considerably less than most predictions based solely on transfer or response functions, which do not integrate impacts as climate gradually changes. This work illustrates the need for forest productivity models to consider the changing climate in which a population is growing relative to the static climate of its origin. It also demonstrates the value of long-term provenance trials in assessing the dynamic impact of climate change on forest productivity, and serves as an example of how provenance trials may be exploited in other forest productivity models or other research fields to assess plant responses to climate. [ABSTRACT FROM AUTHOR]

Stand age is often hard to measure accurately. Measurement error in age affects height estimates when height is projected from one age to another age. In this study, our objective was to derive an estimator for the variance of the component of projection error associated with the error in age. To evaluate the estimator, a simulation approach was employed and the results showed that the estimator worked well in most cases. When the variance of the error in age increases and the projection is forward, however, the estimator might not work as well as in other cases. Another objective was to examine how the error in age behaved under different height-age models and to what extent it affected height and site index estimates. The effect of the error in age depended on its magnitude, the height-age model, initial value of dominant height and age, and projection length. It was also shown that the effect was sometimes negligible, but it could be considerable in other cases. Data from 80 ponderosa pine ( Dougl. ex Laws.) trees in British Columbia, Canada, were used in an illustrative example. [ABSTRACT FROM AUTHOR]

Crown length is a key aspect of vertical structure in multi-aged, multistrata, mixed-species forests. Crown length, defined as the distance from the tree top to the lowest live branch whorl, was determined for 3169 mapped trees ≥4.0 cm in diameter, in four 0.25 ha plots in each of two old-growth Abies lasiocarpa (Hook.) Nutt. – Picea engelmannii Parry ex Engelm. stands. We randomly selected half the trees to build models and half for validation. Crown length was modelled as a function of tree height, incorporating modifiers to account for neighbouring trees. The inclusion radius and height threshold for competition were 3 m and 70%, respectively. The addition of two modifiers significantly improved the model for A. lasiocarpa; crown length decreased as the number of neighbours increased and as the height of surrounding trees increased. In contrast, none of the modifiers significantly improved the model for P. engelmannii. Except at high levels of competition, Abies crowns were longer than those of Picea. However, both species in these forests have long crowns, typically three-quarters of the tree height and rarely less than half. The tightly programmed conical crown architecture of these species likely contributes to long crowns and to the limited effects of neighbours on crown length. La longueur de la cime est un aspect clé de la structure verticale des forêts composées de plusieurs espèces, dont les arbres d’âge variable occupent des strates multiples. La longueur de la cime, définie comme la distance entre le faîte de l’arbre et le plus bas verticille de branches vivantes, a été mesurée sur 3169 arbres cartographiés, dont le diamètre était supérieur ou égal à 4,0 cm, dans quatre parcelles de 0,25 ha dans chacune de deux vieilles forêts composées d’Abies lasiocarpa (Hook.) Nutt. et de Picea engelmannii Parry ex Engelm. Nous avons choisi aléatoirement la moitié des arbres pour étalonner des modèles alors que l’autre moitié a servi à leur évaluation. La longueur de la cime a été modélisée en fonction de la hauteur de l’arbre tout en incorporant des modificateurs pour tenir compte des arbres voisins. Le rayon d’inclusion et le seuil de hauteur de la compétition étaient respectivement de 3 m et de 70 %. L’introduction de deux modificateurs a significativement amélioré le modèle d’A. lasiocarpa. Dans ce cas, la longueur de la cime diminuait avec l’augmentation du nombre et de la hauteur des arbres voisins. À l’opposé, aucun modificateur n’a significativement amélioré le modèle de P. engelmannii. Les cimes d’Abies étaient plus longues que celles de Picea, sauf lorsque la compétition était forte. Toutefois, les deux espèces présentes dans ces forêts ont de longues cimes qui atteignent typiquement les trois quarts et rarement moins de la moitié de la hauteur des arbres. L’architecture conique génétiquement programmée de la cime de ces espèces contribue probablement à leur longue cime et à l’effet limité des voisins sur la longueur de leur cime. [ABSTRACT FROM AUTHOR]

Insect outbreaks, such as the current mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreak in lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forests in British Columbia, are major disturbances in many forests. After an insect outbreak, the advance regeneration typically forms a new canopy, which may be adequate for timber objectives in some stands. Our purpose was to quantify and then model the abundance and spatial distribution of advance regeneration (trees <10.0 m tall). We sampled understory and overstory trees in 28 lodgepole pine stands in south-central British Columbia at two spatial scales: 0.1 ha plots and 25 m2 subplots. We developed models predicting advance regeneration abundance and spatial distribution. Density of advance regeneration averaged 2689 trees/ha (range 120 to 23 000 trees/ha), most of which were <1 m tall. Although advance regeneration was clumped, 75% of the subplots contained at least one individual. Models indicated negative relationships of advance regeneration abundance to overstory basal area and density. Over half the stands had enough advance regeneration to form new stands of adequate density, indicating that use of advance regeneration is a viable option in this mountain pine beetle outbreak and probably other insect disturbances. [ABSTRACT FROM AUTHOR]

Shade-tolerant trees that start in the understory but ultimately reach the canopy persist through different microhabitat conditions during their ontogeny. We evaluate how the height to diameter ratio and the crown ratio (crown length/tree height) change during development and differ among four coniferous species (Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes, Chamaecyparis nootkatensis (D. Don) Spach, Tsuga mertensiana (Bong.) Carrière, and Tsuga heterophylla (Ref.) Sarg.) in ancient forests. At two sites, we measured diameter, height, and height to the base of live crown for trees ≥4.0 cm diameter at breast height in four 0.25 ha plots. For each species, we constructed models of height based on diameter and crown length using part of the data for model development and part as the test data set. Models predicting tree height were effective for all species, and adding crown length considerably improved the prediction over diameter alone. The height to diameter ratio increased until the subcanopy and then decreased for two shade-tolerant species (A. amabilis and T. heterophylla) but decreased linearly throughout ontogeny for C. nootkatensis. Crown ratio increased as trees became larger except for C. nootkatensis, where the reverse occurred. Differences in allometric relationship among species reflect patterns of crown development and also suggest different approaches to a common structural constraint in these forests: heavy snow loads. Les arbres tolérants à l’ombre qui poussent dans le sous-bois avant d’atteindre finalement le couvert, persistent dans différentes conditions de microsite pendant leur ontogénie. Nous évaluons comment le rapport hauteur/diamètre et le rapport de cime (longueur de la cime/hauteur de l’arbre) changent pendant leur développement et diffèrent parmi quatre espèces de conifères (Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes, Chamaecyparis nootkatensis (D. Don) Spach, Tsuga mertensiana (Bong.) Carrière, and Tsuga heterophylla (Ref.) Sarg.) dans les forêts anciennes. Dans deux stations, nous avons mesuré le diamètre, la hauteur et la hauteur à la base de la cime vivante pour les arbres dont le diamètre à la hauteur de poitrine était ≥4,0 cm dans quatre placettes de 0,25 ha. Pour chaque essence, nous avons construit des modèles de hauteur basés sur le diamètre à la hauteur de poitrine et la longueur de la cime, en utilisant une partie des données pour la calibration et l’autre partie pour la validation. Les modèles de prédiction de la hauteur des arbres étaient efficaces pour toutes les essences et l’ajout de la longueur de la cime a considérablement amélioré la prédiction par rapport à l’utilisation seule du diamètre à la hauteur de poitrine. Pour les deux espèces tolérantes à l’ombre (A. amabilis et T. heterophylla), le rapport hauteur/diamètre a augmenté jusqu'à l’étage des codominants pour ensuite diminuer. Mais, pour le C. nootkatensis, ce rapport a diminué linéairement durant toute l’ontogénie. Le rapport de cime a augmenté à mesure que les arbres sont devenus plus gros, sauf dans le cas du C. nootkatensis où le contraire s’est produit. Les différences dans les relations allométriques entre les espèces reflètent les différents patrons de développement de la cime et suggèrent également différentes approches face à une contrainte structurale commune dans ces forêts, soit d’importantes charges de neige. [ABSTRACT FROM AUTHOR]

Studies the height growth of black spruce in British Columbia. Growth patterns; Use of indicator variables to test for differences in height growth patterns between subzones; Largest divergence in growth.

An active program of developing growth intercept models in British Columbia is underway. In lieu of a proper validation procedure, we devised a method of assessing the growth intercept models, which we describe and demonstrate for interior spruce. Four sources of error in the site index predictions of the growth intercept models are examined: measurement, sampling, model, and application error. The impact of the measurement errors tend to be intolerably large at young ages, decreasing to acceptable levels as the trees near the index age. Sampling error was small in our example. The tested models were unbiased and have good precision. An analysis of the application error indicated that the growth intercept models may underestimate site index. [ABSTRACT FROM AUTHOR]