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Wood discoloration was investigated in 721 paper birch (Betula papyrifera Marsh.) trees from 146 sites across the managed forest of Quebec, Canada. Discoloration was present at breast height in 85% of trees, but its impact was limited in terms of tree basal area and volume, with proportions of 6.4% and 3.6%, respectively. These two measures were strongly correlated. Discoloration changed wood appearance but had no effect on microfibril angle and modulus of elasticity. Discolored wood was nevertheless denser, probably due to the accumulation of colored extractives. Predictive models were also developed and applied to 415 711 paper birch trees from 51 689 inventory plots across the province to study regional variation. Higher proportions of discolored basal area were obtained in the southwestern areas of the province where the climate is warmer and drier. In these areas, paper birch trees are larger and, likely, support bigger branches which can cause larger columns of discoloration when broken. Lower proportions were found in eastern regions where snowfall is more abundant. Smaller, more flexible branches in trees growing in these areas could explain this result. This study confirms the feasibility of large-scale mapping of wood discoloration in standing trees based on forest inventory and climate data. [ABSTRACT FROM AUTHOR]

Understanding tree susceptibility to wind damage is central to natural disturbance and succession studies. Susceptibility depends on the wind loads experienced by trees and their ability to resist these loads. In this study, we investigated the wind force or "drag" acting on the crowns of juvenile specimens of three hardwood species common to northwestern North America, black cottonwood (Populus trichocarpa Torr. & A. Gray), red alder (Alnus rubra Bong.), and paper birch (Betula papyrifera Marsh.). Ten freshly cut crowns of each species were exposed to wind speeds from 4 to 20 m/s in a wind tunnel. At 20 m/s, streamlining reduced the frontal area to 28% of its initial value for black cottonwood, 37% for red alder, and 20% for paper birch. Crown drag coefficients calculated using frontal area in still air varied with wind speed. At 20 m/s they ranged from 0.15 to 0.22 for these species. Drag was proportional to the product of mass and wind speed, and to the product of wind speed squared and wind-speed-specific frontal area. Removing branches by whole-branch pruning had little effect on drag per unit branch mass. To further investigate the effect of leaf size, we also used smaller samples of bigleaf maple (Acer macrophyllum Pursh) and trembling aspen (Populus tremuloides Michx.). Whole-crown drag coefficients did not vary systematically with leaf size, but drag per unit of crown mass increased with leaf size. Bigleaf maple had a higher drag per unit of crown mass than other species. [ABSTRACT FROM AUTHOR]

The SB distributional model of Johnson's 1949 paper was introduced by a transformation to normality, that is, z ~ N(0, 1), consisting of a linear scaling to the range (0, 1), a logit transformation, and an affine transformation, z = γ + δu. The model, in its original parameterization, has often been used in forest diameter distribution modelling. In this paper, we define the SB distribution in terms of the inverse transformation from normality, including an initial linear scaling transformation, u = γ′ + δ′z (δ′ = 1/δ and γ′ = –γ/δ). The SB model in terms of the new parameterization is derived, and maximum likelihood estimation schema are presented for both model parameterizations. The statistical properties of the two alternative parameterizations are compared empirically on 20 data sets of diameter distributions of Changbai larch (Larix olgensis Henry). The new parameterization is shown to be statistically better than Johnson's original parameterization for the data sets considered here. [ABSTRACT FROM AUTHOR]

Growth and form are the two main traits used for genetic improvement of maritime pine (Pinus pinaster Ait.) in the southwest of France. In this paper, wood density is studied to answer two main questions: Is there a general trend for density variability throughout tree development and has selection indirectly reduced wood density variability over breeding populations, owing to genetic unfavourable correlation with growth? Wood density and its components were studied in three polycross tests, each representative of one of the successive breeding populations. Wood density was measured with an X-ray densitometer in approximately 50 families per test with >1900 trees. A preliminary study showed that bark-to-pith ring indexing allows for a better estimation of genetic effects than does pith-to-bark indexing. Genetic variability of wood density appears to be highly dependent on the year considered and no general pattern can be detected over time. Whereas the variability of selected traits is known to have decreased over breeding populations, no significant change was found for variability of wood density. [ABSTRACT FROM AUTHOR]

This paper examines the problem of harvest capacity planning at a tactical level. Annual capacity planning allows planners to determine the number of contractors to hire per period throughout the year and to define the duration of their contracts. In practice, this process usually involves the analysis of historical data regarding the operational use of capacity and aggregated demand forecast, the output of which then serves to plan harvest operations. Although this form of hierarchical planning reduces the complexity of the task, the decomposition into subproblems that must be successively resolved can lead to infeasibility or poor use of harvesting capacity. The specific problem addressed here resides in how one can consider the operational impact of harvesting decisions taken at the tactical level to ensure a plan’s feasibility at the operational level. We present a tactical planning process based on Schneeweiss’ generic hierarchical modeling approach. A computational experiment demonstrates how a tactical planning process is influenced by the input of the operational level anticipation model. The anticipation approach we propose appears to be a valid method to better integrate key operational-level decisions into tactical plans. [ABSTRACT FROM AUTHOR]

This paper examined the impact of commercial thinning on selected wood properties of jack pine (Pinus banksiana Lamb.). Wood properties evaluated include wood density (ring density, earlywood ring density, and latewood ring density), percentage of latewood in the ring, and wood bending properties. Nonlinear, mixed-effect models have been developed using data from three commercially thinned sites in eastern Canada. Ring density followed the same pattern as percentage of latewood, in which cambial age, relative height, and ring width were found to have important effects. Earlywood and latewood ring densities changed within the juvenile wood zone until a plateau was reached. Ring width affected earlywood and latewood ring densities mainly in narrow rings. Wood bending stiffness (measured by modulus of elasticity) and strength (measured by modulus of rupture) increased with cambial age and wood density; whereas, wood strength was also affected by ring width. Commercial thinning did not influence the developed models, but it had an indirect effect through increased ring width. Cette étude a examiné l’impact de l’éclaircie commerciale sur certaines propriétés du bois de pin gris (Pinus banksiana Lamb.). Ces propriétés incluaient la densité du bois (densité des cernes, densité du bois initial et densité du bois final), la proportion de bois final dans chaque cerne et les propriétés mécaniques en flexion. Des modèles non linéaires mixtes ont été développés à partir de données provenant de trois stations qui avaient subi une éclaircie commerciale dans l’est du Canada. La densité des cernes s’est révélée être fortement influencée par l’âge cambial, la hauteur relative et la largeur des cernes, suivant ainsi un patron de variation similaire à celui de la proportion de bois final. La densité du bois initial et celle du bois final ont changé à l’intérieur de la zone de bois juvénile pour atteindre un plateau par la suite. La largeur des cernes a aussi affecté ces densités, en particulier dans le cas des cernes étroits. Les modules d’élasticité (MOE) et de rupture (MOR) en flexion ont augmenté avec l’âge cambial et la densité du bois. De plus, le module de rupture a été affecté par la largeur des cernes. L’éclaircie commerciale n’a pas changé les paramètres des modèles, mais elle a eu une influence indirecte à cause de son effet sur la largeur des cernes. [ABSTRACT FROM AUTHOR]

Spatial tree data are required for the development of spatially explicit models and for the estimation of summary statistics such as Ripley’s K function. Such data are rare and expensive to gather. This paper presents an efficient method of synthesizing spatial tree point patterns from nearest neighbour summary statistics (NNSS) sampled in small circular subwindows, which uses a stochastic optimization technique based on simulated annealing and conditional simulation. This nonparametric method was tested by comparing tree point patterns, reconstructed from sample data, with the original woodland patterns of three structurally different tree populations. Analysis and validation show that complex spatial woodland structures, including long-range tree interactions, can be successfully reconstructed from NNSS despite the limited range of the subwindows and statistics. The influence of the NNSS varies depending on the woodland under study. In some cases, the sampling results can be improved by reconstruction. Furthermore, it is clearly shown that it is possible to estimate second-order characteristics such as Ripley’s K function from small circular subwindows through the reconstruction technique. The results offer new opportunities for adding value to woodland surveys by making raw data available for further work such as growth projections, visualization, and modelling. [ABSTRACT FROM AUTHOR]

This paper uses survey information to examine several common assertions about the institutional prerequisites for successful profitability when a First Nation enters an economic enterprise either independently or in joint effort with an outside firm. In the winter of 2004–2005, we interviewed managers on both the First Nations and private sides of joint ventures and other business alliances in Canada, to determine what affected their recent profitability experience. We gathered information on the ages, sizes, and activities of the firms. We also gathered information about the firms’ management structures and relationship with the First Nation, and the characteristics of the government of the First Nation. With a sample size of 40 firms that responded, we found that several institutional characteristics affected profit positively: strong separation of management from band governance, participation in management planning, and the use of staggered terms in band council elections. We found that the likelihood of profitability decreased if the band had been in third party management as well as if there was formal participation of elders or hereditary chiefs in decision making. We offer interpretations of these results. Cet article utilise les données d’un sondage réalisé au cours de l’hiver 2004–2005 afin d’examiner plusieurs assertions courantes au sujet des préalables institutionnels requis pour atteindre la profitabilité des entreprises initiées par des Premières nations agissant seules ou en partenariat avec des acteurs privés. Nous avons interviewé des gestionnaires impliqués dans de tels partenariats d’affaires au Canada et provenant tant des Premières nations que du secteur privé. Nous voulions déterminer ce qui affectait la profitabilité qu’ils avaient connue récemment. Nous avons rassemblé de l’information sur l’âge, la taille et les activités des entreprises. Nous avons aussi recueilli des données sur la structure de gestion des entreprises, les relations avec les Premières nations et les caractéristiques de la gouvernance en vigueur dans les communautés d’accueil. Un échantillon, regroupant les quarante entreprises qui ont répondu, nous permet d’observer que plusieurs caractéristiques institutionnelles, comme la séparation claire entre la gestion des projets et la gouvernance des communautés, la participation dans la planification managériale et le recours à des mandats échelonnés lors des élections au conseil de bande, affectent positivement les profits. Nous avons aussi remarqué que les chances de profitabilité diminuent si les conseils de bandes jouent un rôle en tant que de tierce partie dans la gestion des entreprises et si les aînés ou les chefs héréditaires participent formellement au processus décisionnel. Nous tentons d’interpréter ces résultats. [ABSTRACT FROM AUTHOR]

The term “aboriginal forestry” is used increasingly to describe the evolving role of First Nations peoples in Canadian forestry over the last 30 years. This paper reviews a diversity of experiences and identifies issues that have important implications for governments, forest planners, and First Nations: a forestry regime that reflects the interests of governments and industry rather than those of First Nations; variable implementation of aboriginal rights in forestry practice; benefits and problems of economic partnerships; limitations on consultation, traditional knowledge, and comanagement in forestry; and finally, different forestry paradigms. Among these experiences and issues, we recognise different visions for the participation of First Nations peoples in Canadian forestry. At one end of the spectrum, “forestry excluding First Nations” is no longer accepted. The most common form may be “forestry by First Nations,” representing a role for First Nations within existing forestry regimes. Other options include “forestry for First Nations,” in which forest managers seek to incorporate aboriginal values and knowledge in management activities and “forestry with First Nations,” in which aboriginal peoples are equal partners in forest management. However, aboriginal forestry is better understood as a potential new form of forestry that uses knowledge and techniques drawn from both traditions and conventional forestry and is based on aboriginal rights, values, and institutions. Au Canada, le terme « foresterie autochtone »gagne en popularité pour décrire le rôle grandissant des Premières nations en foresterie au cours des trente dernières années. Cet article passe en revue de nombreuses expériences et identifie des enjeux aux conséquences importantes pour les gouvernements, les gestionnaires forestiers et les Premières nations. Un régime forestier qui reflète les intérêts des gouvernements et des industriels plutôt que ceux des Premières nations, la reconnaissance inégale des droits autochtones dans les pratiques forestières, les bénéfices et les problèmes associés aux partenariats d’affaires, les limites propres à la consultation, la place des savoirs traditionnels et de la cogestion en foresterie et enfin, la variété des paradigmes forestiers composent ces enjeux. Parmi ces expériences et enjeux, nous reconnaissons l’expression de différentes façons de concevoir la participation autochtone à la foresterie canadienne. À un bout du spectre, « une foresterie qui exclut les Premières nations »n’est plus une option acceptable. La vision la plus répandue est probablement celle d’« une foresterie par les Premières nations »signifiant que celles-ci ont un rôle à jouer dans les régimes forestiers existants. Une autre conception est celle de « la foresterie pour les Premières nations »lorsque les gestionnaires forestiers tentent d’intégrer des valeurs et des savoirs autochtones à leurs activités d’aménagement. Enfin, les situations où les autochtones sont partenaires à part entière dans l’aménagement de la forêt s’inscrivent sous la rubrique « la foresterie avec les Premières nations ». Cependant, la foresterie autochtone est mieux comprise lorsqu’elle implique la possibilité d’une nouvelle foresterie qui a recours à des savoirs et des techniques inspirés à la fois des traditions et de la foresterie conventionnelle et qui est fondée sur des droits, des valeurs et des institutions autochtones. [ABSTRACT FROM AUTHOR]

Tree-ring chronologies have been widely used in studies of tree mortality where variables of recent growth act as an indicator of tree physiological vigour. Comparing recent radial growth of live and dead trees thus allows estimating probabilities of tree mortality. Sampling of mature dead trees usually provides death-year distributions that may span over years or decades. Recent growth of dead trees (prior to death) is then computed during a number of periods, whereas recent growth (prior to sampling) for live trees is computed for identical periods. Because recent growth of live and dead trees is then computed for different periods, external factors such as disturbance or climate may influence growth rates and, thus, mortality probability estimations. To counteract this problem, we propose the truncating of live-growth series to obtain similar frequency distributions of the “last year of growth” for the populations of live and dead trees. In this paper, we use different growth scenarios from several tree species, from several geographic sources, and from trees with different growth patterns to evaluate the impact of truncating on predictor variables and their selection in logistic regression analysis. Also, we assess the ability of the resulting models to accurately predict the status of trees through internal and external validation. Our results suggest that the truncating of live-growth series helps decrease the influence of external factors on growth comparisons. By doing so, it reinforces the growth–vigour link of the mortality model and enhances the model’s accuracy as well as its general applicability. Hence, if model parameters are to be integrated in simulation models of greater geographical extent, truncating may be used to increase model robustness. [ABSTRACT FROM AUTHOR]

This paper has three main objectives: (i) to investigate whether the four-quadrant approach introduced by J.S. Maini reveals a useful typology for grouping countries by gross domestic product (GDP) and forest cover per capita, (ii) to determine if the framework can enhance our understanding of the relationship between forest cover and GDP per capita, and (iii) to investigate why countries in the four-quadrant world occupy different quadrants and to determine the principal factors affecting country movement across and within the individual quadrants. The examination reveals that countries can be classified into four broad categories and that GDP and forest cover per capita have a low but consistent level of negative association. After regressing economic, institutional, social capital, and other variables on a country’s occupancy and movement in the four-quadrant world, the results suggest that countries in each quadrant share different characteristics and that factors underlying country movement vary according to the quadrant being observed. Overall, countries with less corruption and higher education are likely to experience increases in both forest cover and GDP per capita, while countries exporting a significant proportion of forest products have a reduced probability of increasing both variables. [ABSTRACT FROM AUTHOR]

The aim of this paper is to find a parametric model for the diameter distribution when a sample of trees in a stand is measured by a harvester. It has important applications prior to and during harvesting for the assessment of the production potential of the stand marked for cutting. We apply the finite mixture models for tree species separately. Our data consist of six real forest stands measured in Finland. Our results showed that, for practical implementation, a three-component Lognormal mixture distribution seemed to be a reasonable choice. The subsample analysis indicated that, for certain stands, a sample size as low as 100 provides a quite good average fit for the chosen three-component mixture distribution, but for other stands, the sample size should be much larger. [ABSTRACT FROM AUTHOR]

The Van Wagner crown scorch model is widely used to estimate crown component necroses in surface fires. The model is based on buoyant plume theory but accounts for crown heat transfer processes using an empirical proportionality factor k. Crown scorch estimates have used k values for foliage, but k varies with heat transfer characteristics, and branch and bud necroses are more relevant to tree mortality. This paper derives and validates a more physically complete model of crown scorch in surface fires (I ≤ 2500 kW·m–1). The model links a buoyant plume model with a lumped capacitance heat transfer analysis applicable to branches, buds, and foliage (~1 cm maximum diameter). The lumped capacitance analysis is validated with vegetative-bud heating experiments, and the entire heat transfer model of crown scorch is validated with fireline intensity and foliage necrosis data. The model is more general than the Van Wagner model and is independent of experimental fire data. Predictions require measurements of fireline intensity, residence time, ambient temperature, and five thermophysical properties of crown components. The model predicts differences between bud and foliage necrosis heights, and illustrates why heat transfer processes should be considered in crown scorch models. [ABSTRACT FROM AUTHOR]

Indices quantifying spatial forest structure are frequently used to monitor spatial aspects of tree attributes including biodiversity in research plots of limited size. The treatment of edge trees, which are close to the plot boundaries, can affect the estimation of such indices that include neighbour effects, since some of their neighbours are likely to fall outside the plot. This paper investigates whether and under what circumstances edge-correction methods are necessary and evaluates the performance of six different approaches: no edge correction, translation, reflection, buffer zone, and two new nearest-neighbour methods. The performance of edge-correction methods depends strongly on the algorithmic structure of the indices and the spatial pattern of tree positions involved. Some edge-correction methods introduce more error than ignoring edge bias altogether. For indices accounting for the diversity of tree positions and especially for those computing angles, translation or buffer zone methods reduce the estimation error regardless of the sample size. The use of the reflection method is associated with large bias values. One of the new nearest-neighbour edge-correction methods proves to be capable of reducing the bias considerably. The results confirm the need for sufficiently large monitoring plots to avoid bias from edge effects. Where this is impossible, neighbours beyond the plot boundary need to be included in the survey, thus providing unbiased estimates but at the cost of extra measurements. Sensitivity analysis is required for newly introduced indices prior to their first application. [ABSTRACT FROM AUTHOR]

Point-to-tree distance sampling designs, sometimes also referred to as k-tree sampling or fixed-count sampling, are practical response design options for field sampling in forest inventories and ecological surveys. While practitioners accept and use several approaches to estimate stem density and other stand attributes, a major concern from a statistical point of view is the lack of a general unbiased estimator for this class of sampling strategies. In this paper we analyse point-to-tree distance sampling in the framework of design-based probabilistic sampling and present an unbiased estimator valid for estimation of any stand attribute. This estimator draws upon the idea of defining an inclusion zone around each tree. A tree is taken as a sample tree if a selected sample point falls into its inclusion zone. The size of the inclusion zone is therefore a measure of the individual tree's inclusion probability when sampling is done with random sample points. Once the inclusion probabilities are known for all sampled trees, the Horwitz-Thompson estimator can be used as an unbiased estimator for any stand variable. In point-to-tree distance sampling, the inclusion zone of a particular tree depends exclusively on the spatial arrangement of the neighbouring trees. Such inclusion zones are determined by k-order Voronoi polygons, where k is the number of trees being sampled per sample point. The approach, however, requires the positions of the k sample trees and a number of surrounding trees to be mapped. Field application is therefore difficult, but a comparison of plot designs by simulation studies in fully mapped stands can now also be done with an unbiased estimator for k-tree sampling. [ABSTRACT FROM AUTHOR]

Single-tree selection has been employed widely in northern Japanese mixed forests, but management-induced changes in forests are not well understood. This study examined demographic parameters of major tree species during a 20-year study of a 68 ha stand in which single-tree selection has been conducted since 1971. Results showed that growth and survival of conifers (mostly Abies sachalinensis (Fr. Schm.) Masters) was the most strongly positively affected by the treatment. Nevertheless, recruitment of conifers was not sufficiently improved, suggesting their decreased dominance over the longer term. Instead, shade-intolerant broad-leaved species (mainly Betula ermanii Cham.) will gradually increase because of their higher recruitment rates after the treatment. Shade-tolerant broad-leaved species (mainly Acer mono Maxim. and Tilia japonica (Miq.) Simonkai) appeared to experience the most distinct negative effects, especially on survival. These trends differed markedly from those reported in previous papers concerning partial harvesting systems, which predicted an increase in dominance of shade-tolerant species. The results shown here should be generalized carefully because we have investigated only one stand without repetition of the control area. Nevertheless, trends described in this large-scale, long-term study could provide a basis for simulating stand dynamics. We discussed possible reasons for the observed patterns and provided implications for sustainable management in the region. [ABSTRACT FROM AUTHOR]

Invasions by nonindigenous forest insects can have spectacular effects on the biodiversity, ecology, and economy of affected areas. This introduction explores several critical issues that are generally relevant to invasions by forest insects to provide an extended background for this special issue of the Canadian Journal of Forest Research and highlights the key findings of the papers included in the issue. The topics covered address new information about (1) the role of cargo shipments as invasion pathways for the arrival of insects such as wood borers and bark beetles, (2) biogeographical effects that can influence the ecological and economic impact of insects feeding on exotic tree species, (3) the influence of biodiversity on impacts of forest insects and on the invasibility of ecosystem, and (4) recent advances in the detection, monitoring, and management of invasive species and native pests, including DNA barcoding for identification, the use of pheromones for monitoring and mating disruption, and biological control. These findings are likely to become even more important with elevated prevalence of invasions as a result of increasing global trade and international travel. Avenues of international communication and cooperation among scientists should be encouraged to enhance the sharing of information about biological invasions and to find solutions to this alarming problem. [ABSTRACT FROM AUTHOR]

In the Pacific Northwest, the process of conifer development after stand-replacing disturbance has important implications for many forest processes (e.g., carbon storage, nutrient cycling, and biodiversity). This paper examines conifer development in the Coast Range Province and Western Cascades Province of Oregon using repeat interpretation of historic aerial photographs from 1959 to 1997 to examine the canopy cover change of different life forms: shrubs, hardwood trees, and conifer trees. Ninety-four stands from the Western Cascades Province and 59 stands from the Coast Range Province were photointerpreted in roughly 5-year intervals. A Chapman–Richards growth function was used to model conifer cover development for all sample stands. Based on the photo data and the Chapman–Richards function, these stands were classified into one of seven early forest successional trajectories defined by the vegetation physiognomy. Succession in the Coast Range Province and Western Cascades Province were compared using parameters derived from the Chapman–Richards growth function. Our results echo previous studies in that rates and densities of conifer regeneration varied markedly among sites; however, our results also indicate that early forest succession differs in the two study regions in terms of both trajectories and rates. Conifer regeneration in the Western Cascades Province tends to have longer delays in establishing and slower rates compared with the Coast Range Province. [ABSTRACT FROM AUTHOR]

The detection of release events in the annual growth increments of trees has become a central and widely applied method for reconstructing the disturbance history of forests. While numerous approaches have been developed for identifying release events, the preponderance of these methods relies on running means that compare the percent change in growth rates. These methods do not explicitly account for the autocorrelation present within tree-ring width measurements and may introduce spurious events. This paper utilizes autoregressive integrated moving-average (ARIMA) processes to model tree-ring time series and incorporates intervention detection to identify pulse and step outliers as well as changes in trends indicative of a deterministic exogenous influence on past growth. This approach is evaluated by applying it to three chronologies from the Forest Responses to Anthropogenic Stress (FORAST) project that were impacted by prior disturbance events. The examples include a hemlock (Tsuga canadensis (L.) Carrière) chronology from New Hampshire, a white pine (Pinus strobus L.) chronology from Pennsylvania, and an American beech (Fagus grandifolia Ehrh.) chronology from Virginia. All three chronologies exhibit a clustering of step, pulse, and trend interventions subsequent to a known or likely disturbance event. Time-series analysis offers an alternative approach for identifying prior forest disturbances via tree rings based on statistical methods applicable across species and disturbance regimes. [ABSTRACT FROM AUTHOR]

We studied community development and mortality among tree species at multiple spatial scales in a 236-year mixedwood chronosequence at Lake Duparquet, Quebec. Spatial relationships, species associations, and understory–overstory replacement patterns were studied using spatial statistics, patch indices, G tests, and transition matrices. Results of these analyses showed that shade-intolerant and shade-tolerant tree communities formed increasingly fine-grained patches in midsuccession. These fine-grained associations appear to be partly due to suppressed stems being released into a slowly thinning canopy and partly due to new recruitment of shade-tolerant conifers. In 1-ha plots, tree species richness and evenness peaked in 25-, 100-, and 400-m2 subplots during midsuccession. Forest cover type diversity also peaked in midsuccessional landscapes assessed using aerial photographs. The oldest 1-ha plot was dominated by monospecific patches of eastern white cedar (Thuja occidentalis L.), which was the most likely replacement for live and dead trees and the most abundant species in the numerous subplots that were occupied by trees smaller than 8 cm DBH. In spite of this dominance, long-lived paper birch (Betula papyrifera Marsh.) and residual fir (Abies balsamea (L.) Mill.) seedlings may maintain the mixedwood character of this stand into the future. The implications of our findings for stand management and conservation are discussed. [ABSTRACT FROM AUTHOR]

In this study a finite element model of a back spar system was developed with three guylines opposing the skyline strap tension. In this paper the allowable skyline strap tension is the tension in the skyline strap that results in the maximum normal stress on a transverse cross section of the tree being equal to an assumed allowable stress. An iterative routine was developed to find the allowable skyline strap tension, and this routine was found to converge rapidly from initial values that were below and above the allowable skyline strap tension. Two algorithms were developed for finding the maximum normal stress on a transverse cross section of a tree, method 1 and method 2. If the plane that the tree displaced in was known a priori, then method 2 could be used, and it was found to be less sensitive to mesh coarseness. If the plane that the tree displaced in was not known a priori, then method 1 had to be used with a less coarse mesh. It was found that the stress concentrations due to simplified cable connections were not significant for rigging configurations that allowed a larger rigging point displacement. The rigging configurations that allowed larger rigging point displacements have stress fields that are dominated by bending, while for rigging configurations that allow only small rigging point displacements, the stress fields are dominated by axial compression. [ABSTRACT FROM AUTHOR]

This paper presents data on early postfire tree regeneration. The data were obtained from repeated observations of recently burned forest stands along the Yukon – British Columbia border and in interior Alaska. Postfire measurements of tree density were made periodically for 20–30 years, providing direct observations of early establishment patterns in boreal forest. Recruitment rates of the dominant tree species in both study areas were highest in the first 5 years after fire, and additional net establishment was not observed after 10 years. The postfire population of spruce (Picea mariana (Mill.) BSP and Picea glauca (Moench) Voss s.l.) remained constant after the first decade in the two study areas. Populations of aspen (Populus tremuloides Michx.) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) both declined after 10 years in mixed-species stands along the Yukon – British Columbia border. Mortality rates of aspen and pine were positively correlated with their initial densities, indicating that thinning occurred as a density-dependent process. At all sites, measurements of stand density and composition made early were highly correlated with those made late in the monitoring period, indicating that patterns of stand structure initiated within a few years after fire are maintained through subsequent decades of stand development. [ABSTRACT FROM AUTHOR]

Computer simulation is the only realistic method of evaluating alternative methods of breeding hybrid forest trees. Empirical tests would be very long term and expensive. This paper describes the development of a simulation program, called XSIM, which generates two different but closely related outcrossing tree species. The genetic correlation between performance in each parental species and performance in the resulting hybrid can be set, in addition to the amounts and types of variances in each parental species. The breeding strategies available for testing include conventional reciprocal recurrent selection, reciprocal recurrent selection with forward selection, recurrent selection within each pure species, and the creation of a synthetic species. XSIM allows the strategies to be compared using the same base populations, equivalent selection intensities, and comparable mating patterns. Innovative best linear unbiased prediction procedures allow all ancestral and current progeny generation data, from both parental species and the hybrid, to be analysed together. The theoretical basis for the simulation is given, and genetic and statistical models are described. In summary, XSIM allows rigorous comparisons of the strategies in terms of genetic gain per time and provides useful insight into hybrid forest tree breeding. [ABSTRACT FROM AUTHOR]

Many aspects of temporal variation in tree seed production (e.g., the proability distribution, periodicity, uni modality) are poorly understood. In this paper, we used 32 annual seed production records from 22 species to show that there are no discernible endogenous cycles, and there is a modest (but seldom significant) tendency for a high seed production year to be followed by an unusually low production year. Finally, we found that all of the records conformed to a single lognormal probability distribution, although our ability to discriminate among species, given short and extremely variable records, is admittedly very limited. We used the lognormal to develop the distribution of the sums of local seed production events (summed across 4 years) as an aid in predicting postharvest or postfire tree regeneration success. Our conclusion is that reliable (defined as 90% of the time) adequate stocking at the edge of an area source requires that the species of interest must comprise a very large fraction of the total basal area per area. Indeed, if the species constitutes less than about 50% of the source, neither burns nor even very narrow strip cuts will be reliably stocked. [ABSTRACT FROM AUTHOR]

In this paper, we describe the new genus and species Lollipopaia minuta from a tropical rain forest in Thailand. The ascomata were long beaked and seated on a pseudoparenchymatous stroma that was erumpent through the bark of a decaying branch. Mature ascomata were readily formed under laboratory conditions. Lollipopaia minuta had ascomatal walls forming a textura intricata in surface view and deliquescent paraphyses. The asci floated freely at maturity and had a nonstaining apical ring. These characters are found in the Diaporthales. However, the habit of the stroma combined with the filiform ascospores distinguished L. minuta from all known genera of the Diaporthales. Thus, a close relationship to taxa outside the Diaporthales was considered. Lollipopaia minuta was similar to Ophioceras or Pseudohalonectria in shape of the ascomata, asci, and ascospores. However, phylogenetic analyses based on small subunit ribosomal DNA sequences confirmed the placement of L. minuta within the Diaporthales with 100% bootstrap support. A closest relative within the Diaporthales was not determined.Key words: Magnaporthaceae, microfungi, taxonomy, tropical mycology.Les auteurs décrivent le nouveau genre et nouvelle espèce Lollipopaia minuta récoltée en forêt tropical humide, en Thaïlande. Les ascomata ont un long bec et reposent sur un stroma pseudoparenchymateux qui émerge à travers l'écorce de branches en décomposition. Les ascomata matures se forment facilement en laboratoire. Le L. minuta possède des parois ascomatales formant une textura intricata, en vue superficielle, et des paraphyses déliquescentes. A maturité, les asques flottent librement et montrent un anneau apical ne se colorant pas. Ces caractéristiques se retrouvent chez les Diaporthales. Cependant, le port du stroma, combiné avec les ascospores filiformes, différencie le L. minuta de tous les autres genres connus de Diaporthales. Ainsi, les auteurs ont été amenés à considérer des relations étroites avec des taxons à l'extérieur des Diaporthales. Le L. minuta ressemble aux Ophioceras ou aux Pseudonectria quant à la forme des ascomata, des asques et des ascospores. Cependant, l'analyse génétique, basée sur les séquences de la petite sous-unité de l'ADN mitochondrial, confirme l'appartenance du L. minuta aux Diaporthales avec un support en lacet (bootstrap) de 100%. Aucun proche parent chez les Diaporthales n'a pu être déterminé.Mots clés : Magnaporthaceae, microgungi, taxonomie, mycologie tropicale.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]