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Using three recently fitted taper functions, this note evaluates the accuracy and precision of log volume assortment estimates for five major Saskatchewan timber species. All three functions showed similarly good performance for the five species examined. The results indicated that the magnitude of both absolute bias and standard error of estimate depended on the average volume of the particular log assortments; larger average volumes had greater bias and standard errors of estimate. The coefficients of variation were inversely related to average log assortment volume, with the smallest assortment volumes having the largest coefficients. This results from the high variation relative to those small averages. This also means that estimates of log volume assortments would always be less accurate than those of the entire merchantable stem. Key words: forest mensuaration, Saskatchewan, log volume estimation, stem taper functions

In this case study of the Saskatchewan provincial timber inventory, the major sources of errors were identified and suitable procedures presented for their estimation. Applying those procedures on a pilot area, the results showed that sampling error was by far the most important component affecting the accuracy of volume estimates. Variances arising from the use of taper functions to estimate tree volumes were under 0.05%, and variances from 3P subsampling were about 3% of the total variance. A computer simulation experiment showed that a 2% measurement bias in both diameter and height measurements may result in 8% bias in the volume estimate. Key words: 3P sampling, taper functions, error budget

This paper presents a new density-dependent height-growth model for lodgepole pine (Pinuscontorta var. latifolia Engelm.) in Alberta. It predicts stand top height growth as a function of present top height, breast height age, and density. The model is an extension of Czarnowski's stand dynamics theory, using an iterative height increment model with variable site and density components. Using 946 annual growth periods from permanent sample plots, the calibration shows a good fit and simulates reasonable values, even beyond the database.

Anchor chains, Rome disks, or shark finned barrels were dragged by a D8H tractor in one or two directions in dense, 9-year-old, fire-origin lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) stands in west-central Alberta. All three implements were equally effective in killing trees, although they also damaged a fairly high proportion. The two-directional treatments, with the second perpendicular to the first to approximate greater intensity of thinning, killed more than twice as many, or nearly 40% of mainly the larger trees. Large trees were also more damage-prone. In the 11 years after treatment the thinned stand recovered, and now the trees show virtually no signs of earlier damage. Their growth surpasses that of trees in the unthinned area. Treatments like these may be useful in dense lodgepole pine stands when thinning budgets are low and some reduction in usable yield, as compared to selective thinning, is acceptable.

Red belt damage (reddening and death of foliage) occurs frequently in lodgepole pine Pinuscontorta var. latifolia Engelm. stands between certain elevations and may affect tree growth and even cause mortality. We examined growth impact in four pine stands (10, 55, 90, and 115 years old) where nearly all trees showed symptoms of damage. On young trees, visible damage ranged from 0 to 80% of foliage, and averaged about 35%. A highly significant reduction in height growth and terminal bud length (p

Stem growth data from breast height were collected from about 2000 trees on 192 sample transects (plots) located adjacent to seismic lines. Sampled stands represented the most important forest cover types between 10 and 100 years of age over a range of site conditions in the foothills of western Albetra from Rocky Mountain House to Grande Prairie. Line clearing stimulated breast height radial increment fairly consistently in the 20% range of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.), white spruce (Picea glauca (Moench) Voss), and black spruce (Picea mariana (Mill.) B.S.P.) trees. This improvement expressed in terms of stand growth, however, fell far short of that required to make up for the loss of wood production over these lines if the cut trees are not utilized. The lack of significant stimulation from line clearing in aspen (Populus tremuloides Michx.) stands indicates a complete loss of production due to the lines.

Young lodgepole pine (Pinus contorta Doug. var. latifolia Engelm.) stands that originate after fires are frequently very dense. It is not uncommon to find stands with 40,000 or more trees per acre (100,00O/ha) at 10 years of age. Tree growth is reduced at such high densities and if natural thinning is slow there is a danger of stagmation and considerable or even complete loss of merchantable yield. Thus, thinning such stands may be economically justified. Selective thinning with hand tools is an expensive operation. Recently, various non-selective multi-stem mechanical thinning techniques have been tried which are much cheaper. A drumchopper dragged by a crawler-type tractor was found to be most effective for mechanical strip thinnling of pine stands in Alberta and in Manitoba (Bella and De Franceschi 1971, Bella 1972). But this technique is unsuitable for thinning if numerous large, dead trees are standing in the young stands as after fire or if large size slash and/or boulders are present on the ground. Under these conditions, light portable machines are more suitable. Newly developed portable circular power saws, 'brush saws' or 'clearing saws', seemed to be potentially useful. In a pilot scale thinning operation in Ontario Riley (1973) reported that one man with a brush saw could thin an acre of 9-year-old jack pine (Pinus banksiana Lamb.) from 5,300 stems/acre down to 1,600 in about 4 hours (Riley 1973). The! equivalent time to thin 1 hectare from 13,100 stems/ha down to 3,950 stems/ha would be 10 h. My objectives were to evaluate labour input required to thin young lodgepole pine stands of various densities with one of the better, currently available brush saws in I/ undisturbed conditions and 2/ stands that had previously received mechanical strip thinning.

To reduce the cost and increase the efficiency of obtaining individual tree height information required for sample plot volume estimation, two general height–diameter (H/D) regression models were developed using two-stage regression analysis and data from 96 lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) sample plots. The derived models were examined using an independent data set of 28 plots. In addition to diameter at breast height (D), these models also included two easily measurable stand parameters as independent variables: quadratic mean diameter (Dq) and the height of a tree with diameter Dq (Hq). With a practical method to estimate Hq (from up to three heights measured) and using these two new H/D models in conjunction with available regional standard volume equations (V = f (D,H)), the stand volume estimates, on the average, were 0.003% higher (SD 4.1%) for the first model and 1.081% lower (SD 4.6%) for the second model than those obtained using traditional H/D curves for each plot based on 30 or more height measurements. The new models are therefore recommended for use in height estimation of lodgepole pine trees within the range of conditions of the data. This approach may be applied to other species and regions.

Thinned stands of young lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) in west-central Alberta had a higher incidence of attack by common pest organisms than unthinned stands. Based on a sample of nearly 3000 potential crop trees (on 240 temporary plots) growing on 120 naturally regenerated cut blocks, the rate of attack in thinned vs. unthinned stands was 30% and 18% for western gall rust (Endo-cronartium harknessii (J.P. Moore) Y. Hiratsuka) and 25%. and 16% for leader damage due to terminal weevil (Pissodes terminalis Hopp.) and pitch twig moth (Petrova spp.) Damage from other agents, including that from small mammals, was low and little affected by thinning. Forest management implication of these results are discussed. Key words: western gall rust terminal weevil, pitch twig moth, snowshoe hares, red squirrels.

A general stand model is fitted to a set of permanent sample plot data for lodgepole pine in Alberta. The model represents a site-specific, variable-density stand model for volume growth and mortality of lodgepole pine. The structure of the model provides a general framework for examining volume growth and mortality in lodgepole pine. The model's performance is compared with the Alberta Forest Service yield tables and with the results of an experimental thinning study.

A sample of 29 405 lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) trees was assessed from 1982 to 1985, and stem analysis data of 75 trees from five heavily infested second-growth stands in the foothills of the Rockies were analyzed to determine the incidence, development, and impact of western gall rust Endocronartiumharknessii (J.P. Moore) Y. Hiratsuka, in relation to age of trees and stand and site factors. The incidence of western gall rust increased with stand age and time. In stands up to 12 years old, the incidence averaged about 5% and increased rapidly to about 20% at age 20. A rapid increase in incidence over time occurred in younger age-classes. In stands 20 years or older, the incidence of new infection was low. Mortality associated with western gall rust among crop trees was low. There was, however, 30% mortality in an unthinned 22-year-old stand over its life. Impact on growth was highly significant (p

An operational thinning in a 25-year-old lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) stand in Alberta resulted in nearly a 5O0/0 increase in diameter at breast height (dbh) and height increment in the last 5 years. Initial stand density had no effect on dbh increment beyond that of initial tree size. The release effect extended throughout the narrow (around 1.5 m) leave strips. Mortality continued to occur at about the same rate in both treated and untreated plots, thus reducing the need for follow-up selective thinning. Although the treated area had much lower stand volumes, it has a faster growth rate and may catch up or even surpass the untreated area in merchantable yield at harvest. Resume Une eclaircie operationnelle dans un peuplement de pin tordu latifolie (Pinus contorta Dougl. var. latifolia Engelm.) de 25 ans en Alberta s'est soldee par un accroissement de pres de 50% en diametre a hauteur de poitrine (dhp) et en hauteur au cours des 5 dernieres annees. La densite initiale du peuplement n'a exerce aucun effet sur I'accroissement en dhp au dela de la taille initiale des arbres. L'effet de degagement s'est fait sentir a travers les etroites bandes de reserve (1,5 m). La mortalite continuait de sevir a peu pres au mgme niveau dans les parcelles traitees et celles non traitees, ce qui reduisait la necessite d'une eclaircie selective complementaire. Malgre ses volumes de peuplement beaucoup plus faibles, I'aire traitee peut, par sa vitesse de croissance superieure, ratrapper et meme surpasser I'aire non traitee en rendement techniquement realisable a la recolte.

The unscreened kraft pulp yields at permanganate No. 14 for 7-, 13-, and 22-year-old trembling aspen (Populustremuloides Michx.) trees from Manitoba for effective alkali applications of 14% were 56.2, 55.7, and 54.8% (o.d. wood), respectively. Specific gravity data for green and ovendry wood are presented, but no relationship with tree height could be established. Pulp strength values from the 7-, 13-, and 22-year-old aspen were, respectively, 60, 67, and 65 for tear factor; 67, 71, and 72 for burst factor; and 10.1, 10.4, and 10.7 (km) for breaking length, respectively. These data indicate that trees of any of the three ages will make a kraft pulp comparable in yield and strength to commercial hardwood–softwood pulp.

In a sample of 121 young lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) stands in naturally regenerated cut blocks near Hinton, Alta., strong positive correlations were observed in the incidence of gall rust (Endocronartiumharknessii (J. P. Moore) Y. Hiratsuka) and leader damage from terminal weevil (Pissodesterminalis Hopp.) and from pitch twig moth (Petrova spp.) with tree size in both thinned and unthinned stands. Although tests on a selected number of the largest trees from each plot showed no significant differences in incidence of the two pest categories between thinned and unthinned stands, thinning that retains the large trees may result in an increase in relative incidence of these pests unless special effort is made to cut damaged trees and retain undamaged ones.

A study was started in 1965 to quantify the effect of logging variables on initial sucker stand density and subsequent development of aspen (Populus tremuloides Michx.). The study found excellent stocking and density of sucker regeneration after both summer and winter logging of 70- to 80-year-old stands in east-central Saskatchewan. Logging slash on the ground reduced suckering but the density of regeneration even with heavy slash cover was similar to that found in fire-origin stands. Winter logging resulted in more uniform and less dense sucker regeneration. Large initial differences in stand density diminished to a 30% range or less by 5 years of age. This suggests that flexibility may be exercised in harvest scheduling and method of logging.

A fast, accurate and handy diameter-measuring device for small trees (diameters of 4 inches or less) is described. It can be constructed quickly from a piece of plywood 7 x 12 x ¼. inches.