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Understanding tree vulnerability to freezing temperatures will help resource managers to mitigate the effects of climatic variability. To test the effectiveness of tissue dehardening curves to represent whole seedling responses, we tested the cold tolerance of 4 conifer species to a range of freezing temperatures, − 15, − 25, and − 35 °C in late March, and − 5, − 10, and − 15 °C in early May. Results show that, after a 30-min exposure to freezing temperatures, needle mortality started at − 25 °C in late March (early spring dehardening) before budbreak activation and at − 10 °C in early May (late spring dehardening) when pine buds had flushed and white spruce (Picea glauca) buds had started swelling. Freezing temperatures delayed the timing of budbreak; increased needle, terminal bud, and seedling mortality; and reduced shoot growth and number of top laterals. White spruce and lodgepole pine (Pinus contorta) were more sensitive to freezing in terms of needle, terminal bud, and seedling mortality and growth reduction. The effects of March freezing were generally detected in the first year, whereas those of the May freezing were still evident in the second year on the shoot growth of black spruce (Picea mariana) and jack pine (Pinus banksiana). Although they seem relatively hardier based on first year post-freezing assessments (i.e., less immediate physical damage from freezing), black spruce and jack pine may have sustained more internal or physiological shock/damage. Our study results support the use of tissue cold hardiness–forcing temperature relationships to assess the risk of freezing damage for conifer seedlings. [ABSTRACT FROM AUTHOR]

A two-stage modelling approach was used for developing ingrowth models for four major tree species in Alberta: aspen, lodgepole pine, black spruce and white spruce. The probability of ingrowth presence was modelled first, followed by the modelling of annual amount of ingrowth conditional on ingrowth being present. To handle variable measurement intervals and plot sizes typical of repeatedly measured forestry data, two generalized logistic models were evaluated at the first stage: a traditional model with measurement interval length and plot size factor incorporated as an exponent of a standard logistic function and an alternative model with measurement interval length and plot size factor incorporated as a denominator. Two criteria were evaluated for defining optimal threshold values for plot classification: criterion 1 to maximize the summation of sensitivity and specificity and criterion 2 to maximize the overall rate of correct plot classification. It was found that criterion 1 was superior to criterion 2 for providing better plot classifications. The two ingrowth probability models behaved similarly based on model fitting and model validation results. Annual amount of ingrowth was modelled at the second stage by exponential functions. [ABSTRACT FROM AUTHOR]

Efficacy of commercial formulations of Bacillus thuringiensis ssp. kurstaki ( Btk) against spruce budworm Choristoneura fumiferana in black spruce ( Picea mariana (Mill.) BSP), white spruce ( P. glauca (Moench) Voss) and balsam fir ( Abies balsamea (L.) Mill.) was investigated in Québec's Côte-Nord region. As expected, larval mortality was higher in Btk-treated plots (80.26 ± 2.34 %) than in control plots (66.32 ± 2.80 %). There were no differences in larval mortality among the three host tree species tested. Btk was most efficient in reducing spruce budworm defoliation when applied to black spruce and white spruce trees. Black spruce and white spruce exhibited lower final defoliation in Btk-treated plots than balsam fir. Btk applications produced a reduction in defoliation of 36 % in balsam fir, 44 % in white spruce and 41 % in black spruce. Control plots exhibited about 35 % higher amount of current-year foliage destroyed (AFD) and 56 % lower amount of current-year foliage remaining (ARF) than Btk-treated plots, whereas no differences in the amount of current-year foliage produced (AFP) were observed among host tree species. Black spruce trees showed the lowest AFD. Although not statistically significant, black spruce also showed the highest ARF. Our results suggest that Btk application is more efficient in protecting against spruce budworm damage when it is applied to spruce species than it is to balsam fir. It appears that the observed inter-specific differences in host tree foliage protection might be related to interactions between Btk, host tree foliage, and larval feeding behaviour. [ABSTRACT FROM AUTHOR]

In many situations, information on stem diameters inside bark (dib) are more desirable than on diameters outside bark (dob). However, obtaining dib measurements is usually expensive, time-consuming, and prone to significant measurement errors when done on standing trees. Many bark thickness equations have been proposed to estimate the dibs of standing trees. In this study, we compared several commonly used bark thickness equations for seven conifer species in the Acadian Region of North America. Mixed-effects modeling techniques were employed to fit linear and non-linear bark thickness equations. We found the equation proposed by Cao and Pepper (South J Appl Forestry 10:220-224, 1986; Eq. 5) performed significantly better than other equations for most of our study species. The Cao and Pepper (South J Appl Forestry 10:220-224, ) equation is a function of dob, relative height in the stem, tree height, and the ratio of dib to dob at breast height. The mean absolute bias was found to be reduced up to 74% compared with using a fixed ratio approach employed in the widely used Northeastern variant of the Forest Vegetation Simulator (FVS-NE) growth and yield model. Leave-one-out cross validation was further performed to determine the location of suitable prior measurements in the prediction process for three of the most well-behaved equations. Results show that no unified prior measurement can provide best predictive abilities across all species as the choice of prior dib measurements depends on both species and bark thickness equations. [ABSTRACT FROM AUTHOR]

The effect of seed water content (WC) (2-3, 5-6 and 22-25%, on a fresh weight basis), storage temperature (+4, -20, -80 and -196°C) and storage duration (6, 12, 24, 48 and 60 months) on the germination of white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill.) B.S.P.) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) seed was investigated. Germination of white spruce control (untreated) seeds and seeds adjusted to 2-3% and 5-6% WC declined after 48 months of storage at -80 and -196°C, with a further decline at 60 months at -20, -80, -196°C. Germination remained high when control white spruce seeds and seeds with 2-3, 5-6% WC were stored at +4°C, over all storage durations. Generally, black spruce and lodgepole pine exhibited high germination at all storage temperatures at 2-3% and 5- 6% WC as well as the control (untreated) seed, for up to 60 months in storage. Germination declined for all three species when seed was conditioned to 22-25% WC. This loss in germination was partially recovered in white spruce seed stored at +4, -20 and -80°C after storage durations of 24, 12 and 48 months, respectively, and in black spruce seeds stored at -20 and -196°C after storage durations of 24 months. Mean germination time (MGT) was relatively constant for all species, under all conditions, except for seed conditioned to 22-25% WC, where MGT increased for white spruce seed stored 48 months at -80 and -196°C, and for black spruce seed stored 24 months at +4 and -80°C and 60 months at -196°C. These results show that the optimal storage temperatures are 4°C for white spruce, and 4, -20, -80, and -196°C for black spruce and lodgepole pine, and 2-6% water content is optimal for all 3 species at these temperatures. [ABSTRACT FROM AUTHOR]

Concern about forestry practices creating tree-level monoculture plantations exists. Our study investigates tree diversity responses for six early seral boreal forest plantations in Ontario, Canada, representing three conifer species; black spruce (Picea mariana), white spruce (P. glauca), and jack pine (Pinus banksiana), 14 release treatments, and 94 experimental units. Dominance-diversity curves and Simpson's indices of diversity and evenness indicate tree alpha diversity. We propose a new method for assessing diversity, using percentage of theoretical species maximum (% TSM) which is determined by comparing post-disturbance richness (S) with a theoretical species maximum (TSM). Our results support the hypothesis that alternative vegetation release treatments generally do not reduce tree species diversity levels (% TSM) relative to untreated plots. The only % TSM (P ≤ 0.05) comparison that produced less diversity than in control plots was repeated annual treatments of Vision herbicide at one of the black spruce study sites. Our results generally support the hypothesis that tree monocultures do not develop after vegetation release. Only one out of 94 experimental units developed into a tree layer monoculture (Simpson's reciprocal diversity index = 1). Again this was one of the repeated annual treatments of Vision herbicide at one of the black spruce study sites--a treatment which is atypical of Canadian forest management. [ABSTRACT FROM AUTHOR]

Research was carried out to assess the potential of imaging radar systems formonitoring forest fire danger. In Canada, daily forest fire danger ratings are generated by the Canadian ForestFire Danger Rating System (CFFDRS), based on estimates of fire weather indices (FWI) and measured foliar moisturecontent (FMC). To evaluate the potential of imaging radar, an experiment was conducted using test sitesconsisting of jack pine, black spruce and white spruce stands located in the MacKenzie river basin, NorthwestTerritories, Canada. Radar image intensity values from ERS-1 SAR imagery collected over these stands in 1994 werecompared to FWI indices and FMC data. FWI indices were calculated using data from local weather stations.Seasonal trends in radar backscatter (σ0) were shown to correlate with temperature and precipitation. Significant relationships were found between σ0 and FWI codes and indices, particularly in thecase of the black spruce stands, with slow-drying fuels, like duff moisture code (DMC), drought code (DC), and build-upindex (BUI). Rates of changes in σ0were related to rates of changes in FMC, particularly in the case ofthe jack pine stands for old FMC and in the case of white spruce stands for composite FMC. [ABSTRACT FROM AUTHOR]

As a prelude to modeling regeneration in Ontario, the model 'STOCK' was developed to assist forest nurserymen in evaluating their planting-stock production options. STOCK simulates the growth and survival of seedlings from seed-source selection to fully grown planting stock. The effects of various management options and cultural treatments (such as seed source, stock type, fertilization, thinning and pruning) on growth and survival may be simulated in accordance with empirical models or the user's expectations in the form of simple coefficients or improvement factors. The model simulates various stock-production options in accordance with the user's choices then optimizes the results on the basis of a calculated cost-efficiency index (CEI). In effect, CEI combines the total cost and stock production with growth, survival and the quality of the resulting planting stock. The model is written in both the FORTRAN 77 standard and in Apple BASIC. [ABSTRACT FROM AUTHOR]

Two trials ('Wonowon' and 'Iron Creek') in the Prince George Forest Region of interior British Columbia were begun in the mid 1980s to evaluate site preparation treatments for establishing white spruce (Picea glauca [Moench] Voss) in the Boreal White and Black Spruce biogeoclimatic zone. The 14 treatments (9 or 10 per trial) were: [B.C.] Ministry, Sinkkila, and Bracke mounds; Bracke mounds manually supplemented with 20-, 14-, or 6-cm cappings of mineral soil; fertilized Sinkkila mounds; Bracke patches; fertilized Bracke patches; bladed strips; plowed ground; herbicide; and untreated controls, separately with bothstandard and nominally superior 'alternate' planting stock. With minor aberrations, each trial consists of 5 randomized complete blocks each with one 80-tree plot per treatment; planting was in spring, 1984at Wonowon, 1987 at Iron Creek. All trees in mounding treatments andthe inner 48 trees in other plots were monitored for performance through 1998 at Wonowon, 1996 at Iron Creek. The herbicide and plowing treatments, and mounds capped thickly enough with mineral soil to inhibit weed regrowth, were clearly superior to others. In the mounding treatments at Wonowon, survival rate increased with capping thickness,but, while the 14 and 20 cm cappings were best, significant differences among them were few after 15 growing seasons. In both trials, patch scarification gave poorer results than did planting without site preparation. [ABSTRACT FROM AUTHOR]