Tree diameter, height, form, and number of stem defects were recorded in 26-year-old plantations of Sitka spruce, Piceasitchensis (Bong.) Carr., established at three initial spacings (2.74 × 2.74, 3.66 × 3.66, and 4.57 × 4.57 m). These plantations were heavily attacked by the Sitka spruce weevil, Pissodesstrobi Peck, from an early age. Denser plantations sustained a lower intensity of attack than the more open plantations. Although the three spacings had similar average number of stem defects per tree, trees in the close spacing had a significantly higher frequency of trees of good form relative to the more open plantations. It was concluded that trees planted at close spacing had lower levels of weevil damage. As a management regime, it is recommended that Sitka spruce plantations be started at close spacing (2.74 × 2.74 m) and precommercially thinned at age 25. By this age trees will average about 19 cm in dbh and 12 m in height, thus ensuring a first log of good quality.

The assumption that measurement errors are negligible during a forest inventory was tested using forestry students. The magnitude of personal bias in measuring tree diameter at breast height (dbh), total height, and basal area Rer hectare was obtained. Bias was negligible in dbh measurements and the among-crew coefficient of variation (CV) was 8.16%. Heights were significantly underestimated and the among-crew CV was 21.86%. The percentage error in basal area Der hectare determination was 4.09% at the measurement biases are summarized by Loetsch et al. (1973); and for dbh, the most notable is the work of Myers (1961).It has been suggested that if the measurement errors occur randomly, their effect approaches zero. In this paper, the assumption that measurement errors are negligible during a forest inventory was tested. Specifically, the magnitude of personal bias and variation in measuring tree dbh, tree total height, and stand basal area was determined. 95% probability level, using a prism of basal area factor 6. Measurement errors are., in general, not negligible. Their rnagn~tude Method of Data Collectionshould be estimated per inventory and included in the total error of the inventory estimate.Data for the study were collected at the University of British Columbia Research Forest, Maple Ridge, B.C., during the third year forestry students' field school in mensuration. ROsum6Sixty sampling points were systematically set at about 80-m intervals in a 70-year-old second growth stand containinaLe fait que les erreurs de mesurage s'avbrent n6gligeables.lors d'inventaire forestier a BtB verifie avec des Btudiants en foresterie. On calcula I'importance de I'influence du personnel mesurant le diametre de I'arbre a hauteur de poitrine (1,30 m), la hauteur totale et la surface terriere a I'hectare. Celle-ci fut donc negligeable pour les mesures du diametre et le coefficient de la variation (CW entre les membres d'une mbme Bquipe se chiffra 8.16%. Par contre les prises de la hauteur furent fortement sous-estim6es et le coefficient de la variation (CV) entre les membres d'une mbme equipe se fixa a 21.86%. Le pourcentage d'erreur enregistre pour le calcul de la suface terriere a I'hectare fut de 4.09% suivant le taux de probabilite de 95% et utilisant un prisme facteur 6 pour cet item. En general, les erreurs de mesurage ne sont pas negligeables. Leur importance devrait btre estimee pour chaque inventaire en plus d'6tre incluse dans l'erreur totale de I'inventaire.

A means of estimating tree diameter at breast height from stump measurements has many applications. In this paper, metric equations are derived for estimating diameters at breast height from measured stump heights for all commercial tree species in British Columbia by age class and biogeoclimatic zones. The model found best was the same one as used by Alemdag and Honer (1977) for eleven tree species from eastern and central Canada. This prediction system can be incorporated into any local volume equation to derive a tree volume prediction model based on stump diameter and stump height.

A simultaneous curve-fitting procedure for obtaining a set of tree height–diameter curves that do not cross, for a plot measured on several occasions, is described. It involves restricting one parameter of a three-parameter equation to be the same for all measurement occasions, keeping another parameter fixed for each measurement occasion, and allowing the remaining parameter to vary for each measurement occasion. An example shows that the simultaneously fitted height–diameter curves do not cross over the observed range of diameters for the plot and give reasonably accurate height estimates for the measurement occasions with inadequate height samples.

Equations were derived for estimating stump volume, stump inside bark diameter at any given height from ground and diameter at breast height from measured stump height and stump inside bark diameter. The equations were tested on 33 British Columbia commercial tree species groups and the results of four species groups are presented in this paper. This prediction system will play an important role in "waste" or "residue" surveys in British Columbia and in reconstructing the initial stand conditions by estimating diameter at breast height.Des Cquations ont Ct C ClaborCes afin de permettre l'estimation du volume de la souche, du diambtre avec Ccorce de la souche B toute hauteur au dessus du sol ainsi que le diambtre B hauteur de poitrine B partir de la hauteur mesurCe de la souche et du diambtre avec Ccorce de la souche. Ces Cquations ont Ct C testCes sur 33 groupes d'espbces d'arbres de valeur commerciale en Colombie-Britannique et les rCsultats de quatre des groupes d'espbces sont prCsentCs dans cet exposC. Ce systbme de prCdiction jouera un rBle important lors des inventaires de "dCchets" ou de "rCsidus" effectuCs en Colombie-Britannique et dans la reconstitution des conditions initiales du peuplement au moyen de l'estimation du diambtre B hauteur de poitrine.