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Growth and yield systems are essential tools for enhancing forest management decision-making. This study systematically evaluated three stand-level models and two data types for predicting stand survival and basal area of Chinese fir (Cunning lanceolate (Lamb.) Hook.) plantations in southern China. The first model links survival and diameter through the self-thinning concept. The second model incorporates stand diameter, the previous year's diameter, and stand survival, while the third model treats stand survival and diameter as mutually independent functions of only stand age. Model 2 was the best performer for short-term prediction (2–4 years), whereas Model 3 excelled in longer projection periods (6–10 years). Despite the independent predictions of stand survival and diameter in Model 3, it closely tracked observed self-thinning trajectories in long-term predictions. Tree-level model growth derived from Models 2 and 3 performed optimally for short-term and long-term tree-level predictions, respectively. While limited to four experimental sites, this research contributes theoretical groundwork to growth and yield modeling for Chinese fir plantations. [ABSTRACT FROM AUTHOR]

Leaf area is an important ecophysiological variable for quantifying the potential production of trees, since it is closely related to tree growth. However, it is difficult to measure the leaf area completely because of the large number of leaves, so it is particularly important to develop accurate species-specific leaf area models. In this study, using 144 parse trees from 48 plots of different climate zones and ages of Chinese fir, tree leaf area models were developed based on sapwood area at breast height (SABH), diameter at breast height (DBH), and diameter at crown base (DCB), respectively. The results showed that the population-averaged levels of nonlinear mixed-effects (NLME) models were better than the plot-levels and base models, and the leaf area models based on DCB performed the best. Finally, the NLME model (16) based on DCB was used as the final model for tree leaf area of Chinese fir plantations, which was consistent with the pipe model theory. All the variables had certain biological and statistical significance and were easy to obtain in the field work (nondestructive). In addition, this study can also provide a reference for other tree species in predicting tree leaf area. [ABSTRACT FROM AUTHOR]

As forest managers increasingly seek to implement partial-harvest silviculture systems in complex forests, more data are required on the potential development of the residual stand following treatment. In this study, we present 25-year data from a long-term silvicultural study of tree- and stand-level responses to differing levels of basal area following partial harvest in a complex spruce–fir forest in central British Columbia, Canada. Reducing stand basal area elicited stronger basal area increment response in fir than spruce; however, spruce productivity was overall higher than fir across all treatments. Smaller trees increased their size proportionally more than larger trees, and thinning resulted in increased recruitment of smaller trees into larger diameter classes. At the stand-level, basal area reductions to well below 20 m2/ha resulted in higher volume and basal area growth over the length of this study, and suggest that optimum stand-level growth may be achieved at lower basal areas than suggested in prior literature. We also found a positive relationship between stand-level residual basal area and mortality. In central British Columbia, stand structure, species composition, and growth rates in complex spruce–fir forests can be maintained through partial-harvest silviculture treatments. [ABSTRACT FROM AUTHOR]

Subalpine fir, Abies lasiocarpa, occurs throughout western North America, often in forest–tundra parkland. To resolve the presence of varieties in this species, we surveyed microsatellite genetic markers in 11 populations containing three putative varieties of Abies lasiocarpa: (1) var. lasiocarpa, (2) var. bifolia, and (3) var. arizonica. We tested primers from related taxa, and 13 of the best primer pairs were used for assays. Within populations, both heterozygosity and allelic richness were approximately 10% lower in var. lasiocarpa. The STRUCTURE procedure struggled to assign populations to groups correctly; at K = 3, individuals were assigned to their putative varieties with approximately 70% accuracy. Regardless, both lasiocarpa and bifolia were correctly assigned more than expected by chance, indicating that these taxa are distinct. A dendrogram of genetic distances showed var. arizonica to exhibit higher evolutionary distance from the other two varieties and serves as an outgroup. The dendrogram also showed a nesting of var. bifolia clades within var. lasiocarpa, indicating a complex relationship between var. lasiocarpa and var. bifolia. Comparisons among the STRUCTURE population assignments for K = 2, K = 3, and K = 4 identified populations with cryptic admixture and indicate a "lasiocarpa–bifolia" subspecies complex that warrants further study. [ABSTRACT FROM AUTHOR]

Owing to its rapidity and accuracy, near-infrared (NIR) spectroscopy is a powerful tool to establish appropriate prediction models with an innovative method to evaluate wood properties. To reveal the mechanical qualities of clonal Chinese fir woods and to determine sound prediction models of mechanical properties, four main mechanical properties of six Chinese fir clones (Yang 020, Yang 061, Kaihua 3, Kaihua 13, Daba 8, Kailin 24) were evaluated by NIR spectroscopy. The clones Kaihua 13, Kailin 24, and Yang 020 showed good mechanical properties. To estimate mechanical properties with NIR spectroscopy, different methods should be adopted for different properties. The average spectra of radial and tangential sections combined with multiple scattering correction (MSC) and Savitzky–Golay (S–G) smoothing methods were used to predict the modulus of rupture and modulus of elasticity. By adopting cross section spectra and taking MSC and S–G smoothing methods for pretreatment, the models of compressive strength parallel to grain could deliver the best results. For wood hardness, the models established with average spectra of three sections and first-derivative method were preferred. The correlation coefficients of the prediction models were between 0.84 and 0.90, and those of the calibration models were between 0.75 and 0.96. [ABSTRACT FROM AUTHOR]

The functional traits of roots play an important role in nutrient acquisition in plants, which affects the outcome of plant–plant interactions. However, few studies have comprehensively investigated the plastic responses of plant root traits to plant–plant interactions. A pot experiment was conducted to quantify the effects of intraspecific and interspecific interactions on seedling growth and on multiple root traits of two coniferous species, Picea asperata Mast. and Abies faxoniana Rehd. et Wils. The results showed that plant–plant interactions changed the root physiology of these two species but had no effect on the morphological, architectural, and biotic traits of their root system. Intraspecific interaction resulted in lower root nitrogen content and stronger resource competition than interspecific interaction. Under intraspecific interaction, P. asperata had lower root vigor and nitrate reductase activity, which impeded the acquisition and utilization of the limited resources, and thus resulted in marginally decreased total biomass, where the total biomass for A. faxoniana was not significantly affected. Under interspecific interaction, the high total biomass of A. faxoniana could be explained by rhizosphere interactive effects and reduced metabolic (carbon and nitrogen) costs due to lower root exudative outputs. Our results demonstrate that root physiological responses can explain the effects of short-term plant–plant interactions on plant growth. [ABSTRACT FROM AUTHOR]

Forest disturbance is usually described by effects on trees, and small disturbances to forest understory are seldom studied. Nevertheless, effective analyses of succession need to consider both stand-replacing and subsequent "secondary" disturbances in both the canopy and understory. We estimated the characteristics of 13 types of secondary disturbances in old-growth forest understory, as well as change in the canopy cover, after the deposition of tephra (aerially transported volcanic ejecta) in 1980 from Mount St. Helens, Washington. We sampled 100 plots (1 m2) at each of four sites for vegetation change and types of disturbance at 10 different times from 1980 to 2010; we sampled the tree canopy above each plot in 1980 and 2016. The number of canopy gaps increased by 23% and mean gap dimension increased by 68% over 36 years, mostly from the loss of Abies amabilis (Douglas ex Loudon) Douglas ex Forbes. Secondary disturbance in understory affected 1.4% of stand area per year. The areas affected by soil disturbance and effects of woody litter were similar. Erosion, greater in deep than in shallow tephra, peaked in 1981, whereas most litter-caused disturbances increased after 2000. Less frequent litter-based disturbances covered greater area. Our results differ from conclusions about nonvolcanic understory disturbances. Secondary disturbances are variable, need more study, and are likely to affect many other systems. [ABSTRACT FROM AUTHOR]

Climate has a considerable influence on tree growth. Forest managers benefit from the empirical study of the historic relationship between climatic variables and tree growth to support forest management frameworks that are to be applied under scenarios of climate change. Through this research, we have utilized long-term permanent sample plot records, historic climate data sets, and linear mixed modelling techniques to evaluate the historic influence of climatic variables on the growth rates of major boreal tree species in Newfoundland and Labrador, Canada. For the commercially significant spruce and fir forests of the province, we found growing degree-days (GDD) to negatively correlate with tree productivity in warmer regions, such as much of Newfoundland (±1350 GDD), but positively correlate with growth in cooler regions, such as those in Labrador (±750 GDD). With respect to precipitation, environmental moisture was not on average a limiting factor to species productivity in the province. These dynamics have implications for the productivity of the spruce–fir forests of the study area when considered alongside contemporary climate projections for the region, which generally entail both a warmer and wetter growing environment. [ABSTRACT FROM AUTHOR]

The population dynamics of shade-tolerant tree species often includes a seedling bank — small trees persisting in the understory until canopy opening allows increased height growth. We studied the growth and morphology of 0.1–1.3 m tall Abies amabilis Douglas ex J. Forbes trees in the seedling bank of an ancient (>1300 years old) subalpine conifer forest on Vancouver Island, western Canada. We determined rates of height growth by counting growth rings at 10 cm intervals along the main stem and assessed crown morphology by measuring the length and location of each branch along the main stem. These small trees were very old (mean basal ring count, 112 years) and grew very slowly, taking on average 170 years to reach a height of 1 m. Instead of the typical conical form of open-grown Abies Mill., seedling bank individuals had flat crowns. Most branches were near the top of the main stem. The maximum distance along the main stem plus a branch was 1.6 times the main stem length, indicating that resource allocation is focused on lateral growth. The ability to grow slowly and adjust crown morphology allows seedling bank trees to persist for decades to centuries and to retain the possibility of release and growth into the canopy. [ABSTRACT FROM AUTHOR]

In Europe, mixed mountain forests, primarily comprised of Norway spruce (Picea abies (L.) Karst.), silver fir (Abies alba Mill.), and European beech (Fagus sylvatica L.), cover about 10 × 106 ha at elevations between ∼600 and 1600 m a.s.l. These forests provide invaluable ecosystem services. However, the growth of these forests and the competition among their main species are expected to be strongly affected by climate warming. In this study, we analyzed the growth development of spruce, fir, and beech in moist mixed mountain forests in Europe over the last 300 years. Based on tree-ring analyses on long-term observational plots, we found for all three species (i) a nondecelerating, linear diameter growth trend spanning more than 300 years; (ii) increased growth levels and trends, the latter being particularly pronounced for fir and beech; and (iii) an elevation-dependent change of fir and beech growth. Whereas in the past, the growth was highest at lower elevations, today's growth is superior at higher elevations. This spatiotemporal pattern indicates significant changes in the growth and interspecific competition at the expense of spruce in mixed mountain forests. We discuss possible causes, consequences, and silvicultural implications of these distinct growth changes in mixed mountain forests. [ABSTRACT FROM AUTHOR]

Fir (Abies Mill.) forests of Mexico are relicts of the boreal forests that advanced southwards during glaciation periods. Mexico is a center of diversification of the Abies genus, as there are eight species in its territory, six of which are endemic. The forests of Abies religiosa (Kunth) Schltdl. & Cham. near Mexico City are subject to a process of deterioration. We analyzed the fragmentation dynamics of the A. religiosa forest in the northern region of the Sierra Nevada, Mexico. Land cover change detection was done by means of high-resolution images acquired by the SPOT satellite in 2005, 2010, 2015, and 2018. Habitat fragmentation was observed, with a decrease in the size of dense Abies masses. The area covered by Abies decreased by 22.9%. The area occupied by forest openings increased 3% from 2005 to 2010 and then decreased by 1.8% and 1.6% in the following periods. The land patch type Other Forest Cover increased in both frequency and size, with the area increasing by 23.3%, which warns of a change process towards this patch type. The formation of increasingly smaller and isolated remnants of A. religiosa forest in the Sierra Nevada can lead to the loss of this vegetation relict and its replacement by other types of cover in the short term. [ABSTRACT FROM AUTHOR]

The seed coat of fir (Abies), hemlock (Tsuga), and cedar (Thuja) species contain terpenoid resin vesicles. Although information is limited about the morphology and allelopathy of these vesicles, their damage during seed processing can negatively impact germination success. We examined resin vesicle morphology of western redcedar (Thuja plicata Donn ex D. Don), eastern white cedar (Thuja occidentalis L.), amabilis fir (Abies amabilis Douglas ex J. Forbes), balsam fir (Abies balsamea (L.) Mill.), grand fir (Abies grandis (Douglas ex D. Don) Lindl), and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) seeds by 1H magnetic resonance imaging to characterize resin vesicle volume, shape, and number. Western redcedar genotypes with known differences in the quantity of foliar monoterpenes also had parallel differences in the resin vesicle volume of corresponding seeds. Germination assays with the cedar and fir species, eastern hemlock (Tsuga canadensis (L.) Carrière), mountain hemlock (Tsuga mertensiana (Bong.) Carrière), and western hemlock (Tsuga heterophylla (Raf.) Sarg.) confirmed that resin vesicle damage prior to stratification (moist chilling) significantly reduced germination success for most species. Extracts of these resin vesicles from the Abies and Thuja species strongly inhibited the germination of Arabidopsis Col-0 seeds but inhibited the germination of only a small percentage of Arabidopsis abscisic acid insensitive mutant abi3-6 seeds. Resin extracts from Thuja species were 10 times more effective than those from Abies species in inhibiting Arabidopsis Col-0 germination. [ABSTRACT FROM AUTHOR]

Tree mortality models are important tools for simulating forest dynamic processes, and logistic regression is widely used for modeling tree mortality. However, most of the mortality models that have been developed generally ignore the hierarchical structure. In this study, Bayesian logistic multilevel mortality models were developed with the independent variables of initial planting density, competition, site index, and climate factors in Chinese fir ( Cunninghamia lanceolata (Lamb.) Hook.) plantations in southern China. The results showed that a Bayesian three-level model was best for describing tree mortality data with multiple sources of unobserved heterogeneity compared to fixed-effects and two-level models. The variance partition coefficient of tree mortality due to the tree level was much larger than that due to the plot level. The initial planting density and site index were positively correlated with mortality and symmetric competition was negatively correlated. For climate variables, the mortality probability decreased with the increasing mean annual temperature and previous summer mean temperature. By contrast, the mortality probability increased with the increasing previous winter mean minimum temperature and annual heat-moisture index. Identifying different sources of variation in tree mortality will help further our understanding of the factors that drive tree mortality during climate change. [ABSTRACT FROM AUTHOR]

Commercial thinning (CT) is an important silvicultural practice in the northeastern United States. Relatively little is known, however, about the interaction of harvest system and treatment (removal intensity or timing of entry) on the overall profitability of CT. To address this question, 10-year measurements from a controlled CT experiment across six sites in Maine were used to project the long-term effect of removal intensity (33% and 50% relative density reduction) and timing of entry (no delay, 5-year delay, 10-year delay) on ( i) maximum net present value (NPV), ( ii) timing of maximum NPV, and ( iii) the effect of three harvesting systems (cut-to-length, whole-tree, hybrid systems) on maximum NPV. A regional growth and yield model was used to project individual-tree growth and mortality into the future. Harvest costs for the harvesting systems were estimated using regional cycle-time equations. No difference was found in maximum NPV between the CT and non-CT areas or the timing of CT entry. Stand age at time of maximum NPV differed between delays but not between the two removal intensities. Our results indicate that there is no economic benefit in delaying a CT or removing more volume at the time of thinning for the range of stand conditions evaluated. [ABSTRACT FROM AUTHOR]

The endemic Fraser fir ( Abies fraseri (Pursh) Poir.) is found in only seven montane regions in the southern Appalachians above ca. 1500 m elevation. Due to widespread insect-caused mortality from the invasive balsam woolly adelgid ( Adelges piceae Ratzeburg), as well as possible impacts from climate change and atmospheric pollution, the future of Fraser fir populations remains uncertain. Long-term monitoring programs have been in place since the 1980s, and here we present the first predictive population models for endemic Fraser fir populations using the inventory data from Great Smoky Mountains National Park, which contains 74% of extant Fraser fir forests. Using two kinds of population data (understory density counts and overstory census data), we model Fraser fir population dynamics on five different mountaintops as a stage-structured matrix model with transition parameters estimated using hierarchical Bayesian inference. We predict robust recovery over the next several decades for some Fraser fir populations, particularly where mature overstory fir has persisted throughout the last two decades, and continued decline for populations at the lowest elevations. Fraser fir densities are already low at these lower elevations, suggesting that this population is vulnerable to local extirpation. [ABSTRACT FROM AUTHOR]

Young and mature trees are usually characterized by asynchronous growth resumption of xylem. Here, we test the hypothesis that the later onset of xylem growth in older trees is related to the longer distance of the stem from the developing buds, which represents the main source of hormones triggering vascular tissue differentiation. We compared the onset of xylogenesis at different heights along the stems of young and mature Smith fir ( Abies georgei var. smithii (Viguie & Gaussen) W. C. Cheng & L. K. Fu)) trees in the Sygera Mountains, southeastern Tibetan Plateau. Xylem formation was monitored weekly in 2012 on anatomical sections of wood microcores. The onset of xylogenesis differed between young and mature trees, with most phases occurring 2 weeks later in mature trees. No effect of the sampling height was observed on the growth resumption. Our results suggest that the later resumption of xylogenesis in older conifer trees is not related to their longer distance from the crown. [ABSTRACT FROM AUTHOR]

Volatile piperidine alkaloids are widespread compounds found in low amounts in coniferous species. Here, we investigated the variation of piperidine alkaloid chemistry of Norway spruce ( Picea abies (L.) Karst.) in a provenance-type experiment. Volatile piperidine alkaloids were analysed from current-year mature needles of 12 geographical origins grown for 35 years at the same site. Results indicate that, despite long-lasting similar growth conditions, origins were still showing different alkaloid composition and concentrations, indicating solid genotype variation. The highest total piperidine alkaloid concentrations were detected in the northernmost origins, and a marked positive correlation between piperidine alkaloid concentrations and latitude was found. Positive correlation with latitude seems to be closely linked to negative correlation with annual temperature sum of origins. Interestingly, the changes in concentrations detected were not related to needle size and dilution effect. Regarding the possible herbivore-defense role of P. abies piperidine alkaloids, the high variation between origins could play a role for preventing the invasion of genotypes from different geographical areas. [ABSTRACT FROM AUTHOR]

Norway spruce ( Picea abies (L.) Karst.) seed is collected from both forest stands after final felling and from seed orchards. To produce high-germinability seed lots that are easy to use in nursery sowing machines, empty, insect-damaged, and other poor-quality seeds are culled. Sorting is done typically by weight or size. Previous studies of conifer seed have indicated wide variation in seed weight between individual trees or clones. However, the intratree or intraclone variations have rarely been taken into account, and intracone variation in seed weight has not been examined. We collected cones from a forest stand and from a clonal seed orchard in central Finland. Each seed from each cone was extracted, weighed, and x-rayed to assess their quality. Trees and clones differed in terms of the proportions of different quality seed. Variance component analysis showed that the intracone variation explained a larger proportion of the total variation in seed weight than did the intercone/intertree or interclone variations. Thus weight-based seed sorting has less effect on the genetic diversity of a seed lot than previously believed. We also conclude that the large differences in proportion of full seed among trees and clones impact the contribution of genotypes in seed and, eventually, in seedling lots. [ABSTRACT FROM AUTHOR]

Knowledge on the range of variability of montane European forests is hampered by limited data on the natural disturbance regime and by the small size of old-growth remnants. We studied the mixed -- Lom forest reserve (55.8 ha) in Bosnia and Herzegovina at three different scales: a grid of 40 sampling points to describe the structural characteristics and their range of variability, three transects to analyse gap size and gap fraction, and a 1.1 ha permanent plot to reconstruct age structure and disturbance history. The forest is characterized by a high volume of living trees (763 m3·ha-1 in the 55.8 ha core area and 1160 m3·ha-1 in the permanent plot) and of coarse woody debris (327 and 383 m3·ha-1, respectively). The percentages of forest area in canopy and expanded gaps are 19% and 41%, respectively. The median canopy gap size is 76.9 m2 and ranges from 11.1 to 708.0 m2. There are large (up to 120 cm diameter at breast height) and very old trees (441, 432, and 416 years for silver fir ( Mill.), Norway spruce ( (L.) Karst.), and European beech ( L.), respectively). During the last three centuries, the disturbance patterns have been characterized by single-tree or small group mortality. In central Europe, this forest is at the end of a gradient from forests characterized by intermediate disturbances to those where very small-scale processes predominate. [ABSTRACT FROM AUTHOR]

It has recently been hypothesized that genetic markers experiencing high rates of gene flow would be better suited to differentiate closely related species. We tested this hypothesis by examining genetic variation in the chloroplast (cp) DNA ( trnS- trnG and trnL- trnF) and mitochondrial (mt) DNA ( nad5 intron 4 and nad7 intron 1) of two fir species, Abies nephrolepis (Trautv.) Maxim. and Abies holophylla Maxim., with overlapping distributions in northeastern China. Two mitotypes were identified; one was common to both species, whereas the other occurred only in A. holophylla. However, four chlorotypes were identified, clustered into two species-specific groups exhibiting distinct mutations; species delimitation using these generated genetic variants was congruent with those obtained by morphological delimitation. Our findings supported the hypotheses that cpDNA, with its high rates of gene flow, is more useful than mtDNA for species delimitation in fir trees. In addition, the low intraspecific diversity observed for both species may result from their repeated range retractions and expansions in response to climatic oscillations in the history. [ABSTRACT FROM AUTHOR]

Detailed information on plants' responses to varying temperature conditions will be useful when assessing the potential effects of climate change. We conducted reciprocal transplantations in Abies faxoniana Rehd. et Wils. to detect responses of seedlings to different winter (non-growing-season) temperatures in the Wanglang National Nature Reserve, China. Winter temperature variation might alter nitrogen allocation between 1-year-old leaves and branchlets. In leaves, coupling acclimation between photosynthesis potential (evident in pigment content and composition and carbon isotope composition (δ13C)) and adversity tolerance (detectable in peroxidase activity, malondialdehyde content, and nonstructural carbohydrate composition) to winter temperature variation was documented, whereas in branchlets, warming winter did not result in a δ13C-discriminative respiration process at tissue level. Although the experiment included only a short winter period, warming winter was found to pose a negative influence (decreased storage and increased leaf thickness) on A. faxoniana seedlings of subalpine forest understory. As both genetic adaptation and phenotypic plasticity could be responsible for such physiological variation, a detailed altitudinal investigation and a long-term experiment on A. faxoniana seedlings are needed to properly assess their responses to climate change. De l'information détaillée sur la réponse des plantes à différentes conditions de température sera utile pour évaluer les effets potentiels du changement climatique. Nous avons réalisé des transplantations réciproques d'Abies faxoniana Rehd. et Wils. pour détecter les réponses des semis à différentes températures hivernales (saison dormante) dans la Réserve naturelle nationale de Wanglang, en Chine. La variation de la température hivernale pourrait modifier l'allocation de l'azote entre les aiguilles d'un an et les rameaux. Dans les aiguilles, nous avons établi le lien entre la capacité photosynthétique (déterminée par le contenu en pigments et leur composition ainsi que la composition isotopique du carbone (δ13C)) et la tolérance au stress (déterminée par l'activité de la peroxidase, la teneur en malonaldéhyde et la composition en hydrates de carbone non structuraux) causé par la variation de la température hivernale. Par contre, dans les rameaux le réchauffement hivernal n'a pas entraîné de processus de respiration discriminatif à l'endroit de δ13C dans les tissus. Même si l'expérience incluait seulement une petite partie de la saison dormante, nous avons observé que le réchauffement hivernal avait une influence négative (diminution des réserves et augmentation de l'épaisseur des aiguilles) sur les semis d'A. faxoniana en sous-étage de la forêt subalpine. tant donné que l'adaptation génétique tout comme la plasticité phénotypique pourraient être responsables de telles variations physiologiques, une étude altitudinale détaillée et une expérience à long terme avec des semis d'A. faxoniana est nécessaire pour évaluer correctement leurs réactions au changement climatique. [ABSTRACT FROM AUTHOR]

Neonectria fuckeliana (C. Booth) Castl. & Rossman is known to be associated with a stem canker disease of Pinus radiata D. Don in New Zealand plantation forests. Although N. fuckeliana has been previously recorded as a wound invader or weak pathogen of Picea and Abies species in the Northern Hemisphere, little is currently known about the basic biology of the fungus. This paper outlines early investigations into the spore production and dispersal of N. fuckeliana in New Zealand. Perithecia of N. fuckeliana occur frequently on pruned stubs and on the surface of cankers, and ascospores appear to be the primary means of dispersal for this fungus in New Zealand. Both field collections and spore trapping show that mature perithecia contain viable ascospores in all seasons, and spores are ejected and dispersed using moisture. The conidial phases are rarely found in the field. Optimum temperature for both growth of mycelium and ascospore germination was between 15 and 25 °C. Some spore germination occurred at temperatures as low as 5 °C, but above 25 °C spore germination was abnormal. Ascospores and perithecia favoured storage in lower temperatures: overall, ascospores from perithecia stored at room temperature gradually lost their viability, whereas those stored at 4 and –8 °C maintained their viability over an 18 month period. [ABSTRACT FROM AUTHOR]

Fraser fir (Abies fraseri (Pursh) Poir.) is an endemic tree species found only in refugial mountain-top forests in the southern Appalachian Mountains, USA. Very few studies have investigated the ecophysiology of this species in its natural environment. We measured and compared photosynthetic gas exchange and water relations of understory germinant seedlings (<3 cm height), older seedlings (>3 years old and ~0.15–1 m tall), and saplings (>10 years old and ~1–2 m tall) on a leaf-level basis. No significant differences in gas exchange were found among the age classes, although midday xylem water potentials were significantly different among the age classes. Differences in maximum photosynthesis (Amax) were <13%, ranging between 2.4 and 2.7 μmol·m–2·s–1 (P = 0.26). Maximum leaf conductances (gmax) were between 0.16 and 0.18 mol·m–2·s–1, varying less than 13% (P = 0.15). Midday xylem water potentials were similar between SE and SA (–1.2 to –1.4 MPa), but GS values were significantly less negative (–0.2 to –0.5 MPa). Thus, gas exchange and water relations in these understory age classes appeared similar, indicating no particular limitation to advanced regeneration between age classes. [ABSTRACT FROM AUTHOR]

The island-like populations of Fraser fir (Abies fraseri (Pursh) Poir.) have been isolated since the end of the late-Wisconsinian glaciation on the highest peaks of the Southern Appalachian Mountains and therefore offer an opportunity to investigate the genetic dynamics of a long-fragmented forest tree species. An analysis of eight microsatellite markers isolated from Fraser fir found that the species was out of Hardy–Weinberg equilibrium, with a significant deficiency of heterozygosity and a high degree of inbreeding (FIS = 0.223) relative to other conifers, perhaps associated in part with the young life stage of the trees included in the analysis. The analysis detected a significant but small amount of genetic differentiation among Fraser fir populations (FST = 0.004) and revealed that the geographical and latitudinal distances between populations, but not population area, were significantly correlated with their pairwise genetic differences. Both gene flow and postglacial migration history may have influenced the genetic architecture of the species. The results will be useful in the genetic conservation of Fraser fir, a species experiencing severe mortality following infestation by an exotic insect. [ABSTRACT FROM AUTHOR]

Red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea (L.) Mill.) are sympatric in much of the Acadian Forest, but their relative regeneration success during the changing climates of the Holocene and after harvest in the modern forest has been distinctly different. Early life stage behavior may contribute to these differences. We report that seed germination by red spruce was equally fast and complete in warm and cool temperature regimes, while balsam fir germination was slower and less complete in both, especially the cool regime. Also, seedling shoot growth of red spruce exhibited a highly plastic response to increased light and water by maintaining continuous neoformed growth throughout the growing season, while balsam fir seedlings set bud after very little epicotyl development. Therefore, the root/shoot ratio of balsam fir was about twice that of red spruce, regardless of available light or water. Neoformed shoot growth under conditions of ample moisture and light would give red spruce a competitive advantage, but the relatively high root/shoot ratio of balsam fir seedlings would lower the likelihood that water and (or) mineral nutrients would limit shoot growth. The effects of these and other differences in life stage behavior on species abundance over time are discussed. [ABSTRACT FROM AUTHOR]

We evaluated geographic variations in mean fire return intervals and postfire forest succession within a 66 497 km2 land area located in the eastern Quebec boreal forest. Fire return intervals were calculated using a time since last fire map for 1800–2000, and forest dynamics were studied by superimposing 3204 forest inventory plots onto the fire map. Mean fire return interval proved significantly shorter in the western part of the study area, at 270 years, compared with the eastern part, where it was probably more than 500 years. The two main tree species in the study area were balsam fir (Abies balsamea (L.) P. Mill.) and black spruce (Picea mariana (Mill.) BSP). Balsam fir abundance increased progressively as a function of time since fire, whereas black spruce abundance increased during the first 90 years after fire and then declined. Balsam fir was significantly more abundant in the southeastern portion of the study area, which we attribute to the combined limitations imposed by temperature along the north–south axis and by fire along the east–west axis. Large forest patches (i.e., ≥200 km2) dominated by early successional tree species, within a matrix of irregular black spruce – balsam fir mixtures, are an important feature of preindustrial forest landscapes in this region. [ABSTRACT FROM AUTHOR]

To induce somatic embryogenesis of Greek fir, Abies cephalonica Loud., the influence of different cultivation media, sampling dates, and cold treatment storage were examined. The initiation frequencies ranged from 1% to 25%. The sampling date had a significant effect on the initiation of embryogenic cultures and a high frequency was observed within a 5 week window. The effect of cone storage, composition of initiation media, and the medium by storage interaction also remained nonsignificant after 3 and 10 months of proliferation growth. At the maturation phase, the highest tested concentrations of abscisic acid (ABA), 16 and 32 µmol/L, increased both the capability of embryogenic cell masses (ECMs) to produce embryos and the mean number of embryos. Of the two tested carbohydrates, maltose-containing media produced more embryos altogether (1943, on the average of 22.3 embryos per gram fresh mass) and 76% of the ECMs were able to produce embryos when compared with the corresponding values (152, on the average 3.0 embryos per gram fresh mass) and 15.3%, respectively, on sucrose-containing medium. However, 93.5% of embryos on maltose-containing medium died during the germination phase, whereas the corresponding percentage on sucrose-containing medium was 78.2%. [ABSTRACT FROM AUTHOR]

This study investigated aboveground pools and fluxes of biomass, carbon (C), and nitrogen (N) in the overstory and understory of a southern Appalachian red spruce (Picea rubens Sarg.) – Fraser fir (Abies fraseri (Pursh) Poir.) forest, following adelgid-induced fir mortality and spruce windthrow. Using fifty 20 m × 20 m plots, stratified by elevation (1700–1900 m), we estimated standing biomass and fluxes of all growth forms from periodic stand inventories (1998–2003), vegetation surveys, and existing or derived allometric equations. Total C and N pools and fluxes were calculated from plant- and tissue-specific C and N concentrations. Total aboveground biomass attained predisturbance values, ranging from 313 Mg·ha–1 at the lower elevations to 204 Mg·ha–1 at the upper elevations. Overstory biomass production (5650 kg·ha–1·year–1) and N uptake (11–15 kg·ha–1·year–1) exceeded earlier reported values, indicating forest recovery. Woody understory accounted for 3% of aboveground biomass, 10% of annual productivity, and 19% of total N uptake (~7 kg·ha–1·year–1). Herbaceous vegetation, which comprised only 1% of total biomass, took up 18–21 kg N·ha–1 annually, >50% of total ecosystem N uptake (37 kg·ha–1·year–1). This suggests that N-rich understory vegetation plays an important role in N cycling. [ABSTRACT FROM AUTHOR]

To clarify the mechanisms underlying the coexistence of Abies mariesii Masters and Abies veitchii Lindl. in a fir-wave forest, we surveyed the population dynamics of the two Abies species throughout stand development on Mount Shimagare, central Japan. We established three belt transects and found that, overall, A. veitchii dominated this fir-wave forest. However, A. mariesii dominated the canopy initially, whereas A. veitchii increased as stand development progressed; thus, dominant A. mariesii was eventually replaced by A. veitchii. This replacement was explained by the presence of an A. mariesii sapling bank that formed under the canopy of a mature stand and by the large A. veitchii seedling bank resulting from greater seed production. For ordinary canopy individuals, which are taller than midcanopy individuals, the increase in height suggested that taller individuals grow faster vertically regardless of species; moreover, height growth did not differ significantly between the two Abies species, which facilitated the growth of A. mariesii into the canopy and the production of seeds for the next generation. We concluded that the persistence of A. mariesii in this fir-wave forest is supported by its shade tolerance. [ABSTRACT FROM AUTHOR]

Johnson’s SB and the logit–logistic are four-parameter distribution models that may be obtained from the standard normal and logistic distributions by a four-parameter transformation. For relatively small data sets, such as diameter at breast height measurements obtained from typical sample plots, distribution models with four or less parameters have been found to be empirically adequate. However, in situations in which the distributions are complex, for example in mixed stands or when the stand has been thinned or when working with aggregated data, then distribution models with more shape parameters may prove to be necessary. By replacing the symmetric standard logistic distribution of the logit–logistic with a one-parameter “standard Richards” distribution and transforming by a five-parameter Richards function, we obtain a new six-parameter distribution model, the “Richit–Richards”. The Richit–Richards includes the “logit–Richards”, the “Richit–logistic”, and the logit–logistic as submodels. Maximum likelihood estimation is used to fit the model, and some problems in the maximum likelihood estimation of bounding parameters are discussed. An empirical case study of the Richit–Richards and its submodels is conducted on pooled diameter at breast height data from 107 sample plots of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.). It is found that the new models provide significantly better fits than the four-parameter logit–logistic for large data sets. [ABSTRACT FROM AUTHOR]

Currently used logging methods have a tendency to decrease the proportion of old-growth forests and fragment the landscape with adverse effects on some animal groups using these habitats. When the landscape comprises few old-growth forests, conservation strategies could consider some stands with good ecological restoration potential to address this conservation issue. We analysed the structure and biodiversity of second-growth mixed fir stands affected by a spruce budworm (Choristoneura fumiferana (Clem.)) outbreak from 1974 to 1986 for their similarities to those of old-growth mixed fir forests. Three structural criteria were analysed and two groups known to contain species typical of old-growth forests were considered: nonvascular plants and saprophytic fungi and forest birds. Second-growth fir stands show structural characteristics similar to those of old-growth mixed fir stands and include species belonging to indicator groups of old-growth forests. Consequently, the second-growth mixed fir stands that we studied are resilient and have the restoration potential of old-growth forests. [Journal translation] [ABSTRACT FROM AUTHOR]

Abies koreana Wilson is an endemic tree species that is facing critical population declines in Korea. To identify factors affecting the natural regeneration of A. koreana, we examined the role of seed pathogens in the overwintering survival of seeds in natural seedbeds on Mount Halla, Korea. In September 2003, seeds of A. koreana were placed on seedbeds in the following three types of sites: Sasa dominated, shaded by rocks, or forest floor; seeds were then recovered from beneath the snow cover in April 2004 and were analyzed for the occurrence of harmful microfungi. Racodium therryanum Thuem. was the fungus most often isolated from retrieved seeds and was also the most detrimental of the eight fungal species tested in a pathogenicity trial. In vitro, R. therryanum caused a total loss of germination ability in A. koreana seeds at 0 °C after 100 days. The infection rate of R. therryanum was negatively correlated with the seed germination rate. The infection rate of R. therryanum was highest on the forest floor and increased with the duration of snow cover. The occurrence of R. therryanum was temporally restricted to the period of snow cover and spatially to the thick A0 soil layer on the forest floor. This study suggests that R. therryanum may be a significant factor inhibiting the natural regeneration of A. koreana at the seed stage. [ABSTRACT FROM AUTHOR]

Data from 585 balsam fir (Abies balsamea (L.) Mill.) and spruce (Picea spp.) permanent sample plots (PSPs) >50 years old in New Brunswick, Canada, measured between 1987 and 1998, were used to quantify the timing, magnitude, and causes of decline in stand growth, measured as negative net volume increment. Plots were subdivided into classes based on species group, ecoregion, and volume-development pattern (decreasing, fluctuating, stable, or increasing volume with time). Decline began at an earlier age in balsam fir – spruce (BFSP) PSPs (~70 years old) than in spruce – balsam fir (SPBF) PSPs (~120 years). One-third of plots (29%) fell into the decreasing volume-development category. Variation in the proportion of decreasing plots occurred among ecoregions (range 0%–60%) and, to a lesser extent, among species groups (26%–33%). Decreasing BFSP plots exhibited double the rate of volume loss of their SPBF counterparts (–7.4 and –3.9 m3·ha–1·year–1, respectively). Decline was caused by an increased rate of mortality, which was highest in the decreasing volume-development classes (7.5 m3·ha–1·year–1) and lowest in the increasing volume-development classes (1.4 m3·ha–1·year–1). Growth of surviving trees remained relatively stable (2.5–4.2 m3·ha–1·year–1) among volume-development classes. Blowdown was the biggest cause of tree mortality, accounting for approximately 50% of dead trees in BFSP and SPBF plots. The rate of mortality was influenced by ecoregion, species, and the combined effect of previous insect-outbreak and wind disturbances. [ABSTRACT FROM AUTHOR]

The declining health of high-elevation red spruce (Picea rubens Sarg.) and Fraser fir (Abies fraseri (Pursh) Poir.) in the southern Appalachian region has long been linked to nitrogen (N) deposition. Recently, N deposition has also been proposed as a source of negative health impacts in lower elevation deciduous forests. In 1998 we established 46 plots on six sites in North Carolina and Virginia dominated by American beech (Fagus grandifolia Ehrh.), sugar maple (Acer saccharum Marsh.), and yellow birch (Betula alleghaniensis Britt). We evaluated several response variables across an N deposition gradient, including annual basal area growth; foliage percent N, Al, P, K, Mg, and Ca; and forest floor percent N, Mg, and C, pH, and potential net nitrification and N mineralization rates. We found a significant linear relationship between N deposition and basal area growth in sugar maple, but not in American beech or yellow birch. In addition, we found a significant relationship between N deposition and foliar chemistry (foliar %N in all species, foliar Mg/N and %K in sugar maple, and %P in sugar maple and yellow birch). Foliar %N of the three studied species was high relative to values reported in other studies in the United States and Canada. Several forest floor response variables (%N, C/N, pH, Mg/N, and potential net nitrification and N mineralization rates and nitrification/mineralization fractions) were also correlated with N deposition. The correlations between the above response variables and N deposition are consistent with the influence of chronic N deposition on forested ecosystems measured in other regions and suggest that chronic N deposition may be influencing forest structure and chemistry within the southern region. [ABSTRACT FROM AUTHOR]

To determine the impact of fertilization and thinning on growth and development of red fir (Abies magnifica A. Murr.) stands, we established an experiment in a 60-year-old stand using a 2 × 3 factorial design with nitrogen-fertilized and nonfertilized treatments and three stocking levels. Plots were established in 1976 and were measured every 5 years for 26 years. The periodic annual increment in basal area was 97%, 51%, 38%, and 33% greater in fertilized trees than in nonfertilized trees during the first, second, third, and fourth 5-year periods, respectively. After 20 years, annual basal area increment was greater in nonfertilized trees. The response of annual volume increment to fertilization was not statistically significant until the fourth period. Yet, volume increases of the fertilized plots were 25%–92% greater than those of the nonfertilized plots from 1976 to 1996. Similarly, basal area increment was greater in lightly thinned plots than in unthinned plots from the second period on, until heavy mortality during 1996–2002. Basal area increment was greater in the heavily thinned plots from the fourth period on. Results indicate that red fir can respond to fertilization and thinning quickly and that both treatments speed stand development. In addition, fertilization increases the stand's carrying capacity. Therefore, forest managers can use these silvicultural practices to improve stand growth, to reduce fire fuels, and to accelerate stand development. [ABSTRACT FROM AUTHOR]

Aboveground net primary productivity (ANPP) was measured in three balsam fir (Abies balsamea (L.) Mill.) forests on a climatic transect extending from southern New Brunswick ("warm" study area) to central Quebec ("cool" study area). Annual foliar production was estimated with a relationship between cross-sectional area at breast height of the current-year annual xylem ring and the mass of current-year foliage, using data obtained by harvesting trees at the beginning of the study. This relationship differed among study areas. Annual branch production was determined from annual foliar production and the ratio of annual branch production to annual foliar production. The ratio of branch to foliar production was estimated from intensive measurement of a sample of branches collected at the end of the study period; it varied among years but was similar for all study areas. ANPP was 3.36 Mg C·ha–1·year–1 at the warm study area, 3.73 Mg C·ha–1· year–1 at the mid-transect study area, and 3.04 Mg C·ha–1·year–1 at the cool study area. These estimates of ANPP were greater than those estimated using a conventional method of summing up increment and litterfall. On average, the conventional estimate of ANPP was 83% of the estimate using relationships described above. Because net ecosystem productivity is the difference between NPP and heterotrophic respiration, a 17% underestimate of NPP can have a substantial effect on the estimate of carbon-sink activity of a forest. [ABSTRACT FROM AUTHOR]

Experimental seeding of balsam fir (Abies balsamea (L.) Mill.) and white spruce (Picea glauca (Moench) Voss) was implemented in three mature trembling aspen (Populus tremuloides Michx.) stands in southeastern Manitoba to test (i) the effect of vegetation (light) competition and seedbed type (undisturbed forest floor, exposed mineral soil, and rotten logs) on seedling recruitment over the first 2 years and (ii) the effect of broadleaf litter exclusion on seedling mortality during the first winter. The study indicated that, with adequate seed supply, seedbed type was the most important factor limiting seedling recruitment, especially the recruitment of white spruce, in trembling aspen stands. Seedling recruitment on the best and the worst seedbeds differed by 1.8 times for balsam fir but by 19 times for white spruce. Significant differences in soil moisture and temperature were found between seedbed types. Broadleaf litter exclusion also facilitated the recruitment of balsam fir and white spruce, but only on undisturbed forest floor. Vegetation (light) competition, however, did not limit seedling recruitment. On the contrary, the presence of understory vegetation benefited seedling recruitment on rotten logs. Compared with white spruce, balsam fir is better adapted to regenerate in trembling aspen stands. Balsam fir was about 4, 12, and 36 times better than white spruce when regenerating on exposed mineral soil, rotten log, and undisturbed forest floor, respectively. [ABSTRACT FROM AUTHOR]

Physical, anatomical, chemical, and microbiological properties of wetwood in heartwood were compared with those of sapwood and normal heartwood in balsam fir (Abies balsamea (L.) Mill.). Wetwood found only in heartwood of balsam fir had significantly higher moisture content (MC) than normal heartwood but not significantly higher MC than sapwood. No differences in relative density or shrinkage properties were found among tissue types. Wetwood tissue needed longer times to dry to an equilibrium MC of 15%, not only because of its high initial MC, but also because of its lower moisture permeability (diffusion coefficient) in this particular MC range (from initial MC to 15% equilibrium MC). However, there were no significant differences in drying rates for the different tissues when drying from 15% MC to 8% MC. Anatomically, wetwood is similar to normal heartwood, and it has no distinctive characteristics except a greater frequency of bacteria. Energy dispersive X-ray analysis showed that all of the tissues contained the same inorganic elements. Both high-performance liquid chromatography and ash analysis showed that wetwood is chemically closer to normal heartwood than to sapwood. Wetwood was significantly more acidic than either normal heartwood or sapwood. A large number of bacterial genera were found in all three tissues, but there were no consistent or significant differences in bacterial presence or activity among tissue types. [ABSTRACT FROM AUTHOR]

The development and function of the pollination mechanism were studied in Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes growing in clonal seed orchards. Two adaxial ovules developed on each scale after dormancy and each ovule formed a funnel-like integument tip with a nucellus at the base of the shallow funnel. At receptivity, the seed cones were erect and the ovules inverted. No pollination drop was observed in fresh specimens but lipid microdrops were secreted on the rim and inner surface of the funnel. Water applied as spray beaded on all cone surfaces except where microdrops were present. Surfaces of the cone were observed using scanning electron microscopy to determine the presence and ultrastructure of the waxy cuticle. All surfaces that were not wettable with water were covered with epicuticular wax. Pollen did not adhere firmly to cone surfaces having epicuticular wax but adhered to the microdrops on the funnel. Drops of water picked up pollen as they moved over the waxy surfaces toward the cone axis. There, the inverted ovules were arranged in a tight helix around the cone axis. Beads of water, often containing pollen, settled on the scale surface just below the funnels and then touched and wetted the inside of the funnels, forming a column of water from the scale surface below to the funnel above. The saccate, buoyant pollen then floated up and into the funnel. Experiments were done to determine the effect of pollen application on pollen uptake into the ovule: without water, with water applied before or after pollen was applied, or as a pollen–water mix. Results support the hypothesis that A. amabilis, and likely other Abies species, lacks a conspicuous pollination drop and water as rain or dew substitutes for a pollination drop. [ABSTRACT FROM AUTHOR]

The red spruce (Picea rubens Sarg.) – Fraser fir (Abies fraseri (Pursh) Poir.) forest of the southern Appalachians contains a significant amount of coarse woody debris (CWD) that may affect the nitrogen (N) export signal in streams originating from this N-saturated system. Interpretation of the N sink versus source status of CWD of red spruce and Fraser fir was dependent on the method used. Over a chronosequence of decay, (1) N concentrations suggested a N sink (i.e., a net gain of N of 923% in red spruce and 563% in Fraser fir relative to N in live trees); (2) N contents that reflected changes in density suggested a smaller N sink (i.e., a net gain of N of 218% in red spruce and 125% in Fraser fir relative to N in live trees), but the stoichiometry of N and C suggested a N source in early stages of decay and a N source in the most advanced stage of decay only; and (3) N contents that reflected changes in volume suggested a N source (i.e., a net N loss of –172% in red spruce and –122% in Fraser fir). The C/N ratios in CWD suggested that the shift from a N source to a N sink represented a shift from the mobilization of dissolved organic N to the immobilization of ammonium N and (or) nitrate N. The magnitude of the net change in N contents in both red spruce and Fraser fir was amongst the highest reported in literature, suggesting that CWD plays a particularly important role in N dynamics in N saturated forests. [ABSTRACT FROM AUTHOR]

Possible mitigation of nitrate losses associated with clearcuts through harvesting smaller gaps was tested in a high-elevation forest of Engelmann spruce (Picea engelmannii Parry ex Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.). We measured concentrations of ammonium and nitrate after 6-week buried bag incubations of forest floor and mineral soil samples in replicated plots of uncut forest and gaps of 10, 1.0, and 0.1 ha and single-tree removal for 7 years after harvest. Nitrate concentrations in forest floor and mineral soil were elevated 3–7 years after harvesting in gaps of 0.1 ha and larger. Removal of the same proportion of trees as single trees did not result in increased nitrate concentrations, suggesting that nitrate losses could be reduced by harvesting single trees rather than creating gaps. Greater N availability was not associated with faster rates of decomposition of litter and forest floor, which were similar in gaps of all sizes (0–10 ha). Reciprocal transplant of forest floor and soil from the 10-ha gaps and the uncut forests indicated that changes in the nature of the forest floor or soil following harvest had a greater influence on nitrate concentrations than the changes in environmental conditions in the gaps. [ABSTRACT FROM AUTHOR]

Five years after spacing a young, 11 m tall paper birch (Betula papyrifera Marsh.) stand, we examine relationships between growth of understory white spruce (Picea glauca (Moench) Voss), subalpine fir (Abies lasiocarpa (Hook.) Nutt.), and level of birch retention. Our objectives were to evaluate the effectiveness of selected measures of competition for estimating the effects of the residual birch and to evaluate the influence of residual birch densities on growth responses of naturally regenerated subalpine fir and white spruce. Basal area of Scouler willow (Salix scouler iana Barratt) and birch were found to effectively predict light transmittance (diffuse noninterceptance). The best models for predicting 4-year volume growth of subalpine fir and white spruce incorporate initial crown volume of the subject trees and transmittance as independent variables. Lorimer's index and Hegyi's index gave similar results to those obtained using basal area and transmittance, suggesting that there is little benefit in including measurements of proximity in a competition index. For both species, the correlation between basal area increment and light was substantially stronger than observed for volume increment. However, height increment of both subalpine fir and spruce was only weakly correlated with measured light levels. The ratio of height increment to volume increment decreased with both increasing initial height and transmittance for subalpine fir and white spruce. [ABSTRACT FROM AUTHOR]

A white birch (Betula papyrifera Marsh.) overstory of a 30+ year old stand was thinned or completely removed, releasing an advance regeneration of subalpine fir (Abies lasiocarpa (Hook.) Nutt.). The overstory was clear-cut (T0), thinned to 600 (T600) or to 1200 (T1200) stems/ha, or left uncut (control). Three years after release, understory responses were best demonstrated by decreasing specific leaf area with increasing release level and by changes to height and radial growth increments. Clear-cutting the overstory stalled the height growth in fir for two seasons and radial growth at the tree base for one season. Compared with the control, the 3-year height increment was proportionally greatest in intermediate trees of T600, and this treatment produced the overall best response in height growth. Complete birch removal produced the best radial growth response despite the initial growth check. However, no release treatment significantly affected the whole tree variables (aboveground biomass, height, diameter at breast height (DBH), live crown ratio) within the studied time frame. Shoot silhouette ratios were lowest in the completely released understory trees, while they were similar to those of the controls in all partial-release treatments. Tree sturdiness (height/DBH ratio) was 80–90 in most treatments except T0, where it declined to below 80. Despite this improvement, large trees in T0 have been damaged by wind and snow.L'étage dominant composé de bouleau blanc (Betula papyrifera Marsh.) dans un peuplement de plus de 30 ans a été éclairci ou complètement enlevé pour dégager la régénération préexistante de sapin subalpin (Abies lasiocarpa (Hook.) Nutt.). L'étage dominant a été coupé à blanc (T0), éclairci à 600 (T600) ou à 1200 (T1200) tiges à l'hectare, ou laissé intact (témoin). Trois ans après le dégagement, la réaction du sous-étage était le mieux illustrée par la surface foliaire spécifique qui diminuait avec l'augmentation de l'intensité du dégagement et par les changements dans l'accroissement en hauteur et la croissance radiale. La coupe totale de l'étage dominant a arrêté la croissance en hauteur du sapin pendant deux saisons et la croissance radiale à la base de l'arbre pendant une saison. Comparativement au témoin, l'accroissement en hauteur après 3 ans a été le plus fort chez les arbres intermédiaires dans le traitement T600 et ce traitement a dans l'ensemble produit la meilleure réponse pour la croissance en hauteur. L'élimination complète du bouleau a produit la meilleure réponse pour la croissance radiale malgré la stagnation initiale de la croissance. Cependant, aucun traitement de dégagement n'a affecté les variables de l'arbre entier (biomasse épigée, hauteur, diamètre á hauteur de poitrine (DHP), rapport de cime verte) pendant la durée de l'étude. Le rapport de silhouette des pousses des arbres de sous-étage était le plus faible chez les arbres complètement dégagés alors qu'il était semblable à celui observé dans les parcelles témoin dans tous les traitements de dégagement partiel. La robustesse des arbres (rapport de la hauteur sur le DHP) a atteint 80–90 dans la plupart des traitements à l'exception du traitement T0 où la valeur a descendu au-dessous de 80. Malgré cette amélioration, les gros arbres ont été endommagés par le vent et la neige dans le traitement T0.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Concern exists that soil respiration (R[sub s] ) will increase with global warming, thereby reducing the sink strength of forest ecosystems for carbon (C) or making them sources. We measured R[sub s] at three balsam fir (Abies balsamea (L.) Mill.) sites on a climatic gradient from 1997 to 2000 to assess potential responses to global warming. Mean annual R[sub s] varied from 0.67 kg C·m[sup -2] ·year[sup -1] at the cool site, to 1.19 kg C·m[sup -2] ·year[sup -1] at the midtransect site, to 1.52 kg C·m[sup -2] ·year[sup -1] at the warm site. Trenched plots were installed in 1999 to partition R[sub s] into root respiration (R[sub r] ) and heterotrophic respiration (R[sub h] ). Differences in trenched-plot respiration (R[sub t] ) among sites were much less than differences in R[sub s] , because trenching reduced R[sub s] at the warm site more than at the cool site. Annual R[sub t] was 22% less than annual R[sub s] at the cool site, 36% less at the midtransect site, and 50% less at the warm site. After making adjustments for extraordinary decomposition of killed roots in trenched plots, it was estimated that annual R[sub h] varied little among sites (0.40 kg C·m[sup -2] ·year[sup -1] at the cool site to 0.54 kg C·m[sup -2] ·year[sup -1] at the warm site), but annual R[sub r] varied substantially among sites (0.24 kg C·m[sup -2] ·year[sup -1] at the cool site to 0.98 kg C·m[sup -2] ·year[sup -1] at the warm site). We conclude that R[sub s] varied among sites, because climatically driven differences in primary productivity caused greater R[sub r] and greater detrital production for R[sub h] . On craint que la respiration des sols (R[sub s] ) augmente avec le réchauffement planétaire, ce qui réduirait l'efficacité des écosystèmes forestiers comme puits pour le carbone (C) ou les transformerait en sources. Nous avons mesuré la valeur de R[sub s] dans trois sapinières (Abies balsamea (L.) Mill.) le long d'un gradient climatique, de 1997 à 2000, pour évaluer leurs réactions potentielles au réchauffement planétaire. La valeur moyenne annuelle de R[sub s] variait de 0,67 kg C·m[sup -2] ·an[sup -1] dans le site frais à 1,19 kg C·m[sup -2] ·an[sup -1] dans le site intermédiaire et à 1,52 kg C·m[sup -2] ·an[sup -1] dans le site chaud. Des parcelles en tranchées ont été aménagées en 1999 pour partager R[sub s] en respiration radiculaire (R[sub r] ) et en respiration hétérotrophe (R[sub h] ). Les différences dans la respiration des parcelles en tranchées (R[sub t] ) d'un site à l'autre étaient nettement inférieures aux différences entre les valeurs de R[sub s] , parce que l'aménagement de tranchées réduisait la valeur de Rs dans le site chaud plus que dans le site frais. La valeur annuelle de R[sub t] était inférieure de 22 % à la valeur annuelle de R[sub s] dans le site frais, de 36 % dans le site intermédiaire et de 50 % dans le site chaud. Après avoir apporté les ajustements pour la décomposition des racines arrachées dans les parcelles en tranchées, on a constaté que la valeur annuelle de R[sub h] variait assez peu d'un site à l'autre (0,40 kg C·m[sup -2] ·an[sup -1] dans le site frais à 0,54 kg C·m[sup -2] ·an[sup -1] dans le site chaud), mais il y avait une variation assez importante de la valeur de R[sub r] entre les sites (0,24 kg C·m[sup -2] ·an[sup -1] dans le site frais à 0,98 kg C·m[sup -2] ·an[sup -1] dans le site chaud). Nous avons conclu que la valeur de R[sub s] variait d'un site à l'autre à cause des différences d'origine climatique dans la productivité primaire qui ont entraîné une augmentation de R[sub r] et une production détritique plus grande pour R[sub h] .[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Presents a study that examined the effects of harvesting on fine root biomass and decomposition in an Engelmann spruce--subalpine fir forest. Method of the study; Results and discussion; Conclusion.

Presents a study that investigated short-term impacts of partial cutting on lichen retention and canopy microclimate in an Engelmann spruce--subalpine fir forest in north-central British Columbia. Method of the study; Results and discussion; Conclusion.

Remeasures two sets of permanent plots in old-growth, spruce?fir forests on Whiteface Mountain to quantify ongoing vegetation dynamics at sites impacted by spruce decline. Set of plots that was a stratified random sample of the vegetation in a subalpine watershed (Baldwin site); Other that was selected to represent forest conditions in a high-elevation subset of the spruce?fir forest (Esther site); Increase in aboveground tree biomass at Baldwin with the majority of the increment due to the growth of canopy-sized trees that was significant; Growth that occurred with little change in either species composition or size structure; Annual mortality rate for canopy-sized red spruce (Picea rubens Sarg.) in Baldwin that almost matched the recruitment rate; Relative growth rate of spruce that was significantly faster than associated species; Spruce trees in Esther that died; Obvious community-level trend at Esther that was an increase in overall tree density with most of this increase due to ingrowth of small trees; Demography of the spruce population at Baldwin that suggests that the decline is over for at least this population.

Reports on the use of a micrometeorological dispersal model to simulate seed and seedling distributions derived from subcanopy balsam fir (Abies balsamea (L.) Mill.) source trees in a trembling aspen (Populus tremuloides Michx.) dominated forest. Objective that was to determine the effect of substituting basal area for cone production as a proxy for seed output; Objective that was to determine the effects of changing the median horizontal wind speed; Median speed in this forest environment that varies according to the proportion of leaves abscised; Demonstration that the simple one-dimensional model that can have added precision if the dispersal parameters are chosen so as to allow more fine-scale variation.

Presents the results of a study of regional variation in growth-limiting factors and responses to climatic variability in subalpine forests by analyzing growth patterns for 28 tree-ring growth chronologies from subalpine fir (Abies lasiocarpa (Hook.) Nutt.) stands in the Cascade and Olympic Mountains in Washington and Oregon. Introduction; Study areas; Methods; Chronology growth patterns; Climate-growth relationships; Conclusions.

Reports on an experiment where two juvenile hormone related compounds (JRCs), juvabione and dehydrojuvabione, were isolated from Fraser fir, Abies fraseri (Pursh) Poirit. How both juvabione and dehydrojuvabione concentrations had large variations across the tested trees and within trees; How there was no significant difference in either chemical in relation to high, low, or middle branch position; Efforts to determine if juvabione concentration was influenced by an infestation of balsam woolly adelgid, Adelges piceae Ratz., branches from infested and uninfested 11-year-old Abies fraseri with were sampled at the bottom, middle, and top branches of each tree.