ALBERT

Beschreibung: A two-year field study was carried out to determine whether inoculating white spruce, Picea glauca (Moench) Voss, with a native endophytic fungus, Phialocephala scopiformis DAOM 229536 Kowalski & Kehr (Helotiales, Ascomycota), decreased the performance of eastern spruce budworm, Choristoneura fumiferana Clemens, developing on these trees. Second instars were reared at three densities in the mid crown and at one density in the lower, mid, and upper crown. Larval survival (i.e., survival of larvae to pupation) was lower on endophyte-inoculated trees than on control trees in the mid crown and especially the upper crown but was similar in the lower crown, resulting in a significant interaction between endophyte and crown level. A similar but marginally insignificant interaction was observed for overall survival up to adult emergence (i.e., total survival). Larval survival and total survival were approximately 22% and 19% lower, respectively, when developing in the upper crown of endophyte-inoculated trees than in control trees. Larval survival remained relatively constant, with increased density on control trees but decreased with density on endophyte-inoculated trees, resulting in a significant interaction between endophyte and larval density. Sex ratios of emerged adults and wing lengths of emerged females were not influenced by the endophyte. Our results suggest that endophytic fungi could be useful additions to integrated pest management programs.

Beschreibung: Quantitative genetic variation of fiber-dimension traits and their relationship with diameter at breast height (DBH) and solid-wood traits (i.e., density and modulus of elasticity (MOE)) was investigated in lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.). A total of 823 increment cores were sampled from 207 half-sib families at two independent progeny trials, aged 34–35 years, located in northern Sweden. High-resolution pith-to-bark profiles were obtained for radial fiber width (RFW), tangential fiber width (TFW), fiber wall thickness (FWT), and fiber coarseness (FC) using SilviScan. Heritabilities ranged from 0.29 to 0.74, and inheritance increased with cambial maturity. Estimated age–age genetic correlations indicate that early selection between ages 5 and 8 years is highly efficient. Our results indicate that selection for a 1% increase in DBH or MOE incurs a negligible effect on fiber-dimension traits and maximum genetic gains are reached when DBH and MOE are considered jointly. Moreover, simultaneous improvement of growth and stiffness is achievable when a selection index with 7 to 10 economical weights for MOE relative to 1 for DBH is incorporated. However, the unfavorable relationship between solid-wood traits and pulp and paper related traits suggests that breeding strategies must be implemented to improve wood quality of lodgepole pine for multiple uses.

Beschreibung: Lack of generalized equations has prevailed in Brazil, because it is assumed that localized or climate-specific equations are needed. This study aimed to develop generalized stem taper and volume equations applicable to 11 eucalyptus clones and evaluate if climate variation impacts the accuracy of the estimates. A total of 693 trees evenly distributed across 11 clones at 21 sites were used for model fittings and predictive validation. The penalized mixed spline (PMS) approach was developed for predicting stem taper and volume along the stem profile. The Schumacher and Hall (1933) equation was used to predict total tree volume, while volume ratio equations were applied to predict merchantable volume. For every fitted equation, an annual climatic variable was included to assess the improvement in model performance. The overall results highlighted that climatic variation does not need to be accounted for in stem taper and volume modeling. All of the equations displayed desirable accuracy, but the generalized PMS equation may be preferred when the forestry enterprise looks to furnish a range of multiple forest products. The generalized total tree volume equation, combined with the ratio equations, is highly recommended when the forestry enterprise produces a single product.

Beschreibung: Vegetation–soil systems differentially influence the ecosystem processes related to the carbon cycle, particularly when one tree species is dominant over wide geographic regions that are undergoing climate change. The objective of this study was to quantify the stocks of ecosystem carbon in three vegetation–soil systems along a highland elevational gradient in central Mexico. The vegetation–soil systems, from lower to higher elevation, were dominated by Alnus jorullensis Kunth, Abies religiosa (Kunth) Schltdl. & Cham., and Pinus hartwegii Lindl., respectively. Above- and below-ground tree biomass was determined in each system, along with the litter, coarse woody material, roots, and litterfall. The A. religiosa system had the greatest stock of aboveground biomass carbon (216 ± 31 Mg C·ha−1). The A. jorullensis system had the greatest production of litterfall (3.1 ± 0.08 Mg·ha−1·year−1); however, the carbon content of this litter layer (1.2 ± 0.32 Mg C·ha−1) was lower than that of P. hartwegii (10.1 ± 0.28 Mg C·ha−1). Thus, the litter layer in the A. jorullensis system had markedly the shortest residence time (8 years), suggesting high rates of litter decomposition. The soil carbon stock (at soil depth of 1 m) was greater in A. jorullensis (189 Mg C·ha−1) and P. hartwegii (137 Mg C·ha−1) than in A. religiosa (68 Mg C·ha−1). The A. religiosa and A. jorullensis systems had the highest and lowest total ecosystem C content (301 and 228 Mg C·ha−1, respectively). Upward migration of the A. religiosa system in response to global climate change, however, could cause losses by 2030 of 187 Mg C·ha−1 associated with aboveground biomass.

Beschreibung: Wildland fire dynamics are a complex three-dimensional turbulent process. Cellular automata (CA) is an efficient tool to predict fire dynamics, but the main parameters of the method are challenging to estimate. To overcome this challenge, we compute statistical distributions of the key parameters of a CA model using infrared images from controlled burns. Moreover, we apply this analysis to different spatial scales and compare the experimental results with a simple statistical model. By performing this analysis and making this comparison, several capabilities and limitations of CA are revealed.

Beschreibung: It has recently become clear that the regeneration density of serotinous species within a burned area declines with local fire intensity. It is assumed that this occurs because variation in local fire intensity leads to variation in incident heat fluxes and, ultimately, seed necrosis. We argue here that this same relationship between incident heat flux and seed necrosis is important at the scale of individual plant crowns. Using Picea mariana (Mill.) B.S.P. (black spruce), we show that postfire seed viability increases with crown height, depth into the crown, and angle from wind direction (with the windward side enjoying greater viability). All three effects are what one would expect given the physics of buoyant plumes, interactions of moving fire lines with wake flow around cylinders, and heat transfer in porous bodies such as a tree crown. We conclude by discussing the broader consequences of cone cluster size and global change on regeneration in serotinous species.

Beschreibung: Forest attributes such as volume or basal area are concentrated at tree locations and are absent elsewhere. It is, therefore, more meaningful to consider the amount of forest attributes at a prefixed spatial grain, within regular plots of prefixed size centered at the points of the study area. In this way, the diversity of attributes within plots also can be considered and quantified by suitable indexes, giving rise to a diversity surface defined on the continuum of points constituting the area. We analyze the estimation of diversity surfaces when a sample of plots is selected by a probabilistic sampling scheme and diversity within nonsampled plots is estimated using an inverse distance weighting interpolator. We discuss the design-based asymptotic properties of the resulting maps when the survey area remains fixed and the number of sampled points increases. Because diversity surfaces share suitable mathematical properties, if the schemes adopted to select sample points ensure an even coverage of the study areas avoiding large portions of non-sampled zones, it can be proven that the estimated maps approach the true maps.

Beschreibung: Ground-based mechanized forestry requires the traversal of terrain by heavy machines. The routes that they take are often called “machine trails” and are created by removing trees from the trail and placing the logs outside it. Designing an optimal machine trail network is a complex locational problem that requires understanding how forestry machines can operate on the terrain, as well as the trade-offs between various economic and ecological aspects. Machine trail designs are currently created manually based on intuitive decisions about the importance, correlations, and effects of many potentially conflicting aspects. Badly designed machine trail networks could result in costly operations and adverse environmental impacts. Therefore, this study was conducted to develop a holistic optimization framework for machine trail network design. Key economic and ecological objectives involved in designing machine trail networks for mechanized cut-to-length operations are presented, along with strategies for simultaneously addressing multiple objectives while accounting for the physical capabilities of forestry machines, the impact of slope, and the operating costs. Ways of quantitatively formulating and combining these different aspects are demonstrated, together with examples showing how the optimal network design changes in response to various inputs.

Beschreibung: Cable yarding is still a common system for transporting wood in steep terrain. In the Pacific Northwest, United States, and other regions of high-productivity forestry, reduced rotation ages for harvest have resulted in a lack of large stumps to serve as anchors for cable-yarding systems. One of the most common anchoring alternatives to stumps is buried deadman anchors. Conventional design of this system has been limited to simplified charts that account for soil resistance, as well as both shear and bending resistance, of the deadman, which is typically a buried log. However, these charts are limited to larger deadman anchors of only Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), which are likely not readily available in modern operations. Thus, revised, simplified design charts are proposed that consider a variety of different soil failure mechanisms, as well as several different wood types and bending conditions. An updated approach provides a quantitative perspective towards safe anchoring in modern forest operations.

Beschreibung: Stem taper functions are valuable tools for the study of stem profile and predict volume estimates. Such functions have long been analyzed for different birch species in the world. However, Asian white birch (Betula platyphylla Suk.) has not yet been investigated as an individual species in China or abroad. This study presents stem taper and volume equations for B. platyphylla in Northeast China. Eight commonly used taper functions were fit to the data of 615 destructively sampled trees from two regions of Northeast China. A second-order continuous autoregressive error structure was incorporated to address the autocorrelation in the data and to achieve the valid parameter estimation. The condition number was used to detect the multicollinearity in the models. The taper functions were compared in terms of overall evaluation statistics and by examining the box plots of diameter and volume residuals against relative heights and diameter classes. The equations of A. Kozak (2004, For. Chron. 80(4): 507–515; model 2), Z. Fang et al. (2000, For. Sci. 46(1): 1–12), and H. Bi (2000, For. Sci. 46(3): 397–409) were the leading models for diameter and volume estimates. Overall, the equation of Z. Fang et al. (2000, For. Sci. 46(1): 1–12) exhibited the best results for estimating diameter and total and merchantable volumes in terms of statistical performance and lower multicollinearity.

Beschreibung: Protecting wildlife within areas of resource extraction often involves reducing habitat fragmentation. In Canada, protecting threatened woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)) populations requires preserving large areas of intact forest habitat, with some restrictions on industrial forestry activities. We present a linear programming model that assesses the trade-off between achieving an objective of habitat protection for caribou populations while maintaining desired levels of harvest in forest landscapes. The habitat-protection objective maximizes the amount of connected habitat that is accessible by caribou, and the forestry objective maximizes net revenues from timber harvest subject to even harvest flow, a harvest target, and environmental sustainability constraints. We applied the model to explore the habitat protection and harvesting scenarios in the Cold Lake caribou range, a 6726 km2 area of prime caribou habitat in Alberta, Canada. We evaluated harvest scenarios ranging from 0.1 Mm3·year–1 to maximum sustainable harvest levels over 0.7 Mm3·year–1 and assessed the impact of habitat protection measures on timber supply costs. Protecting caribou habitat by deferring or reallocating harvest increases the timber unit cost by Can$1.1–2.0 m–3. However, this impact can be partially mediated by extending the harvest to areas of oil and gas extraction to offset forgone harvest in areas of prime caribou habitat.

Beschreibung: Climate-sensitive height–age models were developed for top height trees of trembling aspen (Populus tremuloides Michx.), jack pine (Pinus banksiana Lamb.), and white spruce (Picea glauca (Moench) Voss) in natural and reclaimed oil sands stands. We used stem analysis data collected from the Athabasca oil sands region in northern Alberta, Canada, and climate data generated by the ClimateWNA model. Height–age trajectories differed between top height trees in natural and reclaimed stands for jack pine and white spruce, but not for trembling aspen. At a given age, white spruce top height trees were taller and jack pine top height trees were shorter in reclaimed stands than those in natural stands, suggesting that it is easier to achieve similar forest productivity for oil sands sites reclaimed with white spruce stands than for sites reclaimed with jack pine stands. The principal climate variables were growing season (May to September) precipitation averaged over the previous 10 years for trembling aspen and jack pine and summer (June to August) precipitation averaged over the previous 10 years for white spruce. These variables had positive effects on the height–age trajectories.

Beschreibung: White spruce (Picea glauca (Moench) Voss) plantations have historically been an important source of high-quality forest products in the Great Lakes Region of North America. Thinning in spruce plantations is a common silvicultural practice for reducing competition and promoting resiliency to forest health threats such as eastern spruce budworm (Choristoneura fumiferana Clemens), a native forest pest of eastern North America. Spruce budworm larvae feed on the foliage of trees, which reduces growth and potentially causes mortality during an outbreak. There has been continual spruce budworm defoliation in northern Minnesota, U.S.A., since the mid-1950s, with higher levels of defoliation in the late 1990s. This research modeled the diameter growth response of white spruce 18 years after initial thinning in stands that presently range between 44 and 64 years old. Some stands received a second thinning in recent years. We used generalized nonlinear least squares and nonlinear mixed-effects models to estimate annual diameter growth using common tree and stand metrics. Growth model performance was improved by including thinning and frequency of spruce budworm defoliation as modifiers of diameter growth. Results of this study highlight how thinning in combination with insect disturbance affect diameter growth in white spruce plantations of northern Minnesota.

Beschreibung: Selection cutting is defined as a tool for uneven-aged silviculture. Dependence on diameter distribution by forestry practitioners for identifying stand conditions has led to misuse of selection-like cuttings in even-aged northern hardwood stands. Our study used several long-term data sets to investigate the temporal stability in numbers of trees per diameter class in uneven-aged northern hardwood stands treated with single-tree selection and in 45-year-old second-growth stands treated with selection-like cuttings. We analyzed data from New York, Michigan, and Wisconsin to determine changes through time in number of trees across 2.5 cm diameter classes, shifts in the shape and scale of the three-parameter Weibull function used to describe the diameter distributions, and dynamics of associated stand attributes. Findings showed that single-tree selection cutting created and sustained stable diameter distributions and uniformity of conditions through consecutive entries in uneven-aged stands. By contrast, these characteristics varied through time in the second-growth stands that had been treated with selection-like cuttings. Analysis also showed that the Weibull shape and scale parameters for stands under selection system migrated towards those of the recommended target diameter distribution in the uneven-aged stands. These parameters diverged from the target with repeated use of selection-like cuttings in the second-growth even-aged stands.

Beschreibung: The positive effects of biodiversity on aboveground biomass in natural terrestrial ecosystems have been well documented, whereas the relationships between tree biodiversity and belowground biomass remain largely unexplored. Traditionally, two sets of hypotheses based on the functional trait approach, niche complementarity (NC) and mass ratio (MR), have been proposed to explain the positive effects of biodiversity. Whereas NC emphasizes that functional discrepancy enhances the collective functioning of a given ecosystem, MR states that ecosystem functioning is mainly regulated by the functional traits of dominant species. This study explored the relative importance of these two hypotheses and the effects of forest stand and environmental characteristics on belowground biomass in an old-growth broad-leaved evergreen forest. The mean coarse-root biomass, fine-root biomass, and fine-root necromass were 117.78 ± 54.000, 4.09 ± 0.85, and 0.60 ± 0.31 Mg·ha−1, respectively. We found positive effects of functional diversity on belowground biomass; however, the community-weighted mean trait values were more relevant, indicating that MR exhibited more explanatory power than NC. The combination of informative environmental factors explained 62.0%, 53.2%, and 37.8% of the variation of coarse-root biomass, fine-root biomass, and fine-root necromass, respectively. Our results suggest that the functional identity of dominant tree species exerts more influence than functional diversity on the belowground biomass in old-growth forest ecosystems and that forest stand characteristics and topographic and edaphic factors also play important roles in shaping belowground biomass patterns in old-growth forest ecosystems.

Beschreibung: Forestry-drained peatlands occupy approximately 15 million ha in boreal and temperate zones. In Finland, they represent almost one-fourth of the total forest area. They are subjected to the same harvesting operations as upland forests. Although the soil deformation caused by timber harvesting is well documented in upland forests, the knowledge on the soil disturbance induced by the harvesting machinery on peat soils is still lacking. To address this, we collected soil samples from six peatland sites that were thinned using a harvester–forwarder combination. Peat samples were taken from the trails formed by the machinery and outside the trails to a depth of 10 cm. To assess the recovery of soil properties after the disturbance, we sampled sites along a chronosequence with respect to time since harvesting. Soil deformation under the machinery appeared to increase the bulk density and field capacity of peat and decrease its total porosity; however, disturbed plots and control plots started to resemble each other in their soil properties within 15 years. The results imply that peat soil is sensitive to disturbance but has a high recovery potential.

Beschreibung: Dry mixed-conifer forests are widespread in the interior Pacific Northwest, but their historical fire regimes are poorly characterized, in particular the relative mix of low- and high-severity fire. We reconstructed a multi-century history of fire from tree rings in dry mixed-conifer forests in central Oregon. These forests are dominated by ponderosa pine (Pinus ponderosa Lawson & C. Lawson), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and grand fir (Abies grandis (Douglas ex D. Don) Lindl.). Across four, 30-plot grids of ∼800 ha covering a mosaic of dry mixed-conifer forest types, we sampled 4065 trees for evidence of both high- and low-severity fire. From 1650 to ∼1900, all four sites sustained frequent, often extensive, low-severity fires that sometimes included small patches of severe fire (50–150 ha during 18%–28% of fire years). Fire intervals were similar among sites and also among forest types within sites (mean intervals of 14–32 years). To characterize the continuous nature of the variation in fire severity, we computed a plot-based index that captures the relative occurrence of low- and high-severity fire. Our work contributes to the growing understanding of variation in past fire regimes in the complex and dynamic forests of North America’s Interior West.

Beschreibung: A two-generation pedigree involving 519 Norway spruce (Picea abies (L.) Karst.) plus trees (at clonal archives) and their open-pollinated (OP) progenies was studied with the aim to evaluate the potential of plus-tree selection based on phenotype data scored on the plus trees. Two wood properties (wood density and modulus of elasticity, MOE) and one fiber property (microfibril angle, MFA) were measured with a SilviScan instrument on samples from one ramet per plus tree and 12 OP progenies per plus tree (total of 6288 trees). Three ramets per plus tree and their OP progenies were also assessed for Pilodyn penetration depth and Hitman acoustic velocity, which were used to estimate MOE. The narrow-sense heritability (h2) estimates based on parent–offspring regression were marginally higher than those based on half-sib correlation when three ramets per plus tree were included. For SilviScan data, estimates of the correlation between half-sib, progeny-based breeding values (BVs) and plus-tree phenotypes, as well as repeatability estimates, were highest for wood density, followed by MOE and MFA. Considering that the repeatability estimates from the clonal archive trees were higher than any h2 estimate, selection of the best clones from clonal archives would be an effective alternative.

Beschreibung: Emerald ash borer (EAB; Agrilus planipennis Fairmaire, 1888) has been a persistent disturbance for ash forests in the United States since 2002. Of particular concern is the impact that EAB will have on the ecosystem functioning of wetlands dominated by black ash (Fraxinus nigra Marsh.). In preparation, forest managers need reliable and complete maps of black ash dominated stands. Traditionally, forest survey data from the United States Forest Inventory and Analysis (FIA) Program have provided rigorous measures of tree species at large spatial extents but are limited when providing estimates for smaller management units (e.g., stands). Fortunately, geospatial data can extend forest survey information by generating predictions of forest attributes at scales finer than those of the FIA sampling grid. In this study, geospatial data were integrated with FIA data in a randomForest model to estimate and map black ash dominated stands in northern Minnesota in the United States. The model produced low error rates (overall error = 14.5%; area under the curve (AUC) = 0.92) and was strongly informed by predictors from soil saturation and phenology. These results improve upon FIA-based spatial estimates at national extents by providing forest managers with accurate, fine-scale maps (30 m spatial resolution) of black ash stand dominance that could ultimately support landscape-level EAB risk and vulnerability assessments.

Beschreibung: The grasslands conversion to forests is occurring globally and modifying the population dynamics of species. Here, we characterized the population dynamics of Podocarpus lambertii Klotzsch ex Endl. over four years in southern Brazilian forest–grassland mosaics. We asked (i) if the studied P. lambertii population would decrease or increase over time and (ii) what the role of forest patches is in the growth and recruitment of a P. lambertii population. Thus, we studied forest–grassland mosaics, stratified the population into four demographic classes, evaluated the population dynamics, and estimated the correlation between canopy cover and average number of individuals. All individuals of P. Lambertii occurred in forest patches. Density was high but decreased from seedlings to the reproductive stage. The population growth rate was λ = 1.025, and the recruitment of individuals was high and variable among years. The transition and mortality rates showed a pattern of reduction from seedlings to the reproductive stage. Mortality rate for seedlings and juveniles was low and concentrated at the smaller heights. The correlations between canopy cover and the average number of individuals were positive and significant. The ecological characteristics of this species and specific conditions provided by forest patches allow population growth and species conservation in the southern Brazilian forest–grassland mosaics.

Beschreibung: Increasing gender diversity is no longer just the right thing to do, but also the smart thing to do. Although there is general literature about gender diversity and the perspectives of females in top management and leadership, there are, however, very few forest sector specific studies. This exploratory study utilizes interviews to better understand how female executives in North America and the Nordic countries of Finland and Sweden perceive the impact of the situation of gender diversity in the forest industry. Respondents also provide career advice for young females entering or considering entry into the industry. Female executives in both regions agree that although the forest sector is still seen as a male-oriented industry, there are signs of increasingly positive attitudes regarding industry and company culture towards the benefits of greater gender diversity; however, the described changes represent an evolution, not revolution. Interestingly, despite the status of Nordic countries as leaders in bridging the gender gap, respondents from this region believe that there is significant progress yet to be made in the forest industry, especially at the entry level. With respect to career development, North American respondents suggested that young females should consider sacrificing their social life and leisure time activities, whereas Nordic respondents instead emphasized personal supports or using exit strategy from an unsupportive company or boss.

Beschreibung: In forest management planning, errors in predicted stand attributes might lead to suboptimal decisions that result in decreased net present value (NPV). Forest inventory data will have higher value if the amount of suboptimal decisions can be decreased. Therefore, the value of information can be measured through the decrease in inoptimality losses, which are the NPV differences between the optimal and suboptimal decisions. In this study, four alternative sample plot selection strategies with different numbers of sample plots were compared in terms of expected mean inoptimality losses. Stand-level mean inoptimality losses varied between €41.1·ha–1 and €80.7·ha−1, depending on the sample plot selection strategy and the number of sample plots used as training data in the k-nearest neighbors imputation method. Mean inoptimality losses decreased substantially when the number of sample plots increased from 25 to 100, and the decreasing trend continued until 500 sample plots. Total inoptimality losses can decrease by approximately €1 million in an inventory area of 100 000 ha when the number of sample plots is increased from 100 to 500. The measurement of more sample plots can be justified as long as the field measurement costs do not exceed the decrease in inoptimality losses.

Beschreibung: Both aggregative and disaggregative strategies were used to develop additive nonlinear biomass equations for slash pine (Pinus elliottii Engelm. var. elliottii) trees in the southeastern United States. In the aggregative approach, the total tree biomass equation was specified by aggregating the expectations of component biomass models, and their parameters were estimated by jointly fitting all component and total biomass equations using weighted nonlinear seemingly unrelated regression (NSUR) (SUR1) or by jointly fitting component biomass equations using weighted NSUR (SUR2). In an alternative disaggregative approach (DRM), the biomass component proportions were modeled using Dirichlet regression, and the estimated total tree biomass was disaggregated into biomass components based on their estimated proportions. There was no single system to predict biomass that was best for all components and total tree biomass. The ranking of the three systems based on an array of fit statistics followed the order of SUR2 〉 SUR1 〉 DRM. All three systems provided more accurate biomass predictions than previously published equations.

Beschreibung: Bark beetles in the family Curculionidae present a growing hazard to forests worldwide. Like native bark beetles, introduced exotic species can pose a serious threat to North American forests. Ips typographus (Boerner) and Ips sexdentatus (Linnaeus), both native to Europe, are two such pests that have caused widespread forest loss in their native ranges. International trade has led to increased interceptions of Scolytine beetles at ports of entry to the United States. Most intercepted individuals are not identified to species due to lack of expert identifiers, poor specimen quality, or incomplete taxonomy. These same problems affect identification for domestic surveys. Therefore, development of molecular methods for identification of potentially invasive Ips species is essential. Because of the need to scrutinize large numbers of beetles in an efficient manner, we describe a duplex droplet digital PCR (ddPCR) assay to identify I. typographus and I. sexdentatus simultaneously in bulk trap samples containing 500 Scolytinae specimens using a scalable, two-step DNA extraction. This ddPCR method is highly effective for processing the entire contents of beetle traps and identifying these potentially invasive species in a timely and definitive manner. We also describe a nondestructive DNA extraction technique that preserves specimens for morphological identification.

Beschreibung: Dioecious woody species often exhibit male-biased sex ratios under drought habitat, which may result in vulnerability in drying soils. However, whether biased sex ratios are associated with sex-specific responses in growth and defence against insect herbivory under drought stress conditions is unknown. We investigated the sexual responses in terms of growth and defence in Populus yunnanensis Dode in response to two water treatments (40% and 100% field capacity). Drought stress reduced the plant growth (e.g., height increment, gas exchange, photosynthetic nitrogen use efficiency, and water potential) of both sexes and reduced the leaf water content and defensive performance (increased damaged area by leaf-chewing generalists and decreased leaf contents of total phenolics, condensed tannins, and flavonoids) of the females but not the males. Moreover, female defensive performance was lower than that of the males under drought conditions. Additionally, the plant mortality rate increased for both sexes, and it was higher for females than for males during drought stress in response to all leaf defoliation treatments. Our results suggest that sexual responses in terms of growth and defence to drought are significantly different and that P. yunnanensis females have a lower defence capability than males, which may explain the male-biased sex ratio that exists in the natural population. Hence, this study provides new insight into forecasting population dynamics for dioecious plant species in drying habitats.

Beschreibung: Additions of fire residues in the form of charcoal and wood ash may better emulate natural disturbance processes in managed boreal forests. We examined the effects of a poplar (Populus) wood biochar and a high-carbon wood ash on soil and vegetation in a 3-year experiment in northwestern Ontario, Canada. Both soil amendments increased soil pH and soil Ca levels; high-carbon wood ash also increased soil Cu, Zn, B, S, and Pb. Amendments had large effects on plant community composition, favoring a subset of ruderal species including raspberry (Rubus idaeus L.) and goldenrod (Solidago canadensis L.). The addition of high-carbon wood ash resulted in declines in growth of planted white spruce (Picea glauca (Moench) Voss); a path analysis suggests that this was due to the effects of toxic elements rather than the indirect effects of competition. We conclude that high-carbon wood ash, while qualifying as a type of biochar and having some beneficial effects on soil properties, can enhance toxic metals in boreal forest soils, with negative consequences to early tree growth. Differences in plant species responses to biochars and the potential for toxicity effects and indirect effects mediated by plant competition will require screening and field trials of potential biochars prior to their use in operational forestry and forest restoration.

Beschreibung: Despite recent developments in molecular markers, most forest tree breeding programmes do not use them routinely. One way to integrate markers would be to use them for pedigree reconstruction after a simplified mating design through polymix or open-pollinated breeding. Thanks to the latest developments in the POPSIM simulator, various breeding strategies, including some based on paternity recovery, were evaluated with specified constraints on the level of diversity over breeding cycles. These simulations were carried out in two case studies: the French Pinus pinaster (Ait.) and the New Zealand Eucalyptus nitens (H. Dean & Maiden) Maiden breeding programmes. The Pinus pinaster case study produced lower genetic gain for the polymix breeding strategy with paternity recovery compared with double-pair mating or optimal-contribution strategies. However, the polymix breeding strategy could be of interest if the mating design is faster to complete. In the Eucalyptus nitens case study, pedigree recovery was shown to be a mandatory step to controlling the erosion of diversity over breeding cycles. In both cases, the strategies based on pedigree reconstruction were applicable with a limited level of genotyping. Finally, these simulations allow some general recommendations to be drawn to help breeders when designing a strategy for forest tree breeding.

Beschreibung: Camptotheca acuminata Decne (Nyssaceae) is major natural source of camptothecin, an anticancer drug widely used for clinic therapy. Previous works have shown that many plant hormones or elicitors could regulate camptothecin biosynthesis, but few reports have examined sustainable effects of these plant hormones on plants for producing camptothecin. In this work, seedlings obtained from in vitro rapid propagation were used for investigating the sustainable effect of salicylic acid (SA) on transplanted C. acuminata tissues, especially leaves, for camptothecin biosynthesis. Our results indicate that exogenous SA could continuously induce the expression of iridoids pathway genes in C. acuminata leaves for promoting camptothecin production. High expression of iridoids pathway genes still could be observed in bioactive young leaves 180 days after seedlings had been transplanted to soil. In C. acuminata, iridoids pathway genes are expressed at very low levels or are not detectable in old leaves, resulting in decreasing production of camptothecin with leaf development. Interestingly, the expression of these genes could be detected clearly in old leaves of transplanted C. acuminata pretreated with 10 μmol·L–1 of SA during the in vitro rapid propagation phase, which indicates the particular function of SA for a sustainable effect on maintaining relatively high expression levels of iridoids pathway genes for camptothecin biosynthesis.

Beschreibung: The Faustmann–Hartman setup is widely established for specifying the economics of forest values besides timber, but it is criticized as restrictive for capturing diversity values. We show that extending the model to cover diversity attributes, i.e., mixed species and internal heterogeneity within species, is not enough to overcome these restrictions. Additionally, it is necessary to extend forest harvesting regimes to cover thinning, continuous cover forestry, and the management of commercially useless trees. Restrictions in the Faustmann–Hartman setup are first shown analytically with optimized thinning but without tree size structures. The empirical significance of these findings is shown by a model that includes four tree species, tree size structures, an extended set of forest management activities, a detailed description of harvesting costs, and a measure for stand diversity as a key factor behind ecosystem services. We show how an optimal harvesting regime, net revenues, wood output, and stand diversity depend on model flexibility, economic parameters, and the valuation of ecosystem services. In a setup allowing flexible management regimes, the costs of reaching a specified level of ecosystem services are negligible compared with those of the Faustmann–Hartman specification.

Beschreibung: Like other outcrossing species, Scots pine (Pinus sylvestris L.) is thought to carry a “genetic load” of deleterious recessive alleles. When these alleles occur as homozygotes in inbred progeny, their expression can give rise to “inbreeding depression”. Although this phenomenon has been studied in several conifer species through selfing, few studies have quantified inbreeding depression in crosses with lower levels of relatedness between parents. We report here on the generation of a set of F3 study materials in Scots pine in which 142 families arose from a mating design among 49 F2 parents, representing nine levels of expected inbreeding coefficients between 0.0 and 0.5, and repeated over two consecutive seasons. Whereas the numbers of extractable seeds were unaffected by inbreeding, the proportion with fully developed embryos was strongly affected. This was expressed as inbreeding depression in the yield of full seeds per cone but not in their mean mass. Levels of germination of these full seeds were affected by inbreeding, but the depression was rather small and only weakly significant. The roles of pollen competition and polyembryony in mitigating the impact of inbreeding depression are discussed. The materials have been outplanted for future assessment of inbreeding depression on growth and survival.

Beschreibung: Forest insects are showing increasing intensity of outbreaks and expanded ranges, and this has become a major challenge for forest managers. An understanding of these systems often depends upon detailed examination of complex interactions involving multiple organisms. In 2013, a team of researchers formed TRIA-Net, an NSERC support Strategic Network, with the explicit goal of exploring such interactions in the mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins, 1902) – pine (Pinus sp.) – blue stain fungi (Ophiostomatales) system. Contributions of this network include novel genetic and genomic resources and insights, as well as exploration of how landscape structure affects MPB movements. This review highlights the unique contributions of TRIA-Net to our understanding of the MPB outbreak system. We also highlight how the insights we generated can be used to inform management strategies — including assessing stand susceptibility, predicting spread, and developing better monitoring approaches — and how the approach taken by the TRIA project can be used as a model for tackling other challenging forest insect outbreaks.

Beschreibung: This study analyzes the effects of adopting an adaptive harvest strategy in even-aged forest management under timber price uncertainty on the production of nontimber goods. We use the reservation price strategy (“harvest when the observed timber prices are higher than the reservation prices”) on a longleaf pine (Pinus palustris Mill.) stand and employ the Faustmann–Hartman model as a benchmark. We assume that a longleaf pine stand can be managed for timber production, water production, carbon sequestration, and pine straw raking, depending on the planting density. Our results indicate that the reservation price strategy leads to longer expected harvest age when planting density is high. The reservation price strategy does not lead to increases in water production and carbon sequestration with low planting density. With high planting density, the reservation price strategy leads to increases in the amount of in situ carbon sequestered by 14.4–24.7 Mg·ha–1. Our findings suggest that managing longleaf pine forests in good- or poor-quality sites is a profitable alternative and enables water production and carbon sequestration.

Beschreibung: We investigated how herpetofauna respond to burning and burn season in longleaf pine (Pinus palustris Mill.) sandhills by contrasting preburn species richness, diversity, and evenness and captures of six reptile and six amphibian species to the first (Y+1) or second (Y+2) year after burn or between dormant-season burns (DSB) and growing-season burns (GSB). Responses to burning overall or burn season were inconsistent among species; several showed no response, whereas others responded positively or negatively. Most responses were evident only in Y+1. Reptile species richness, diversity, and evenness responses were not detected. Amphibian richness increased after burning overall; diversity and evenness decreased more in GSB than in DSB in Y+1. Southern toad (Anaxyrus terrestris (Bonnaterre, 1789)) captures increased and Florida crowned snake (Tantilla relicta Telford, 1966) captures decreased following burns overall in Y+1. Ground skink (Scincella lateralis (Say in James, 1823)) captures increased more in DSB than GSB in Y+1. Florida gopher frog (Lithobates capito (LeConte, 1855)) and southeastern five-lined skink (Plestiodon inexpectatus; Taylor, 1932) captures increased, and oak toad (Anaxyrus quercicus (Holbrook, 1840)) decreased more in GSB than DSB in Y+2. Responses were likely due to changes in aboveground activity affecting captures or (for amphibians especially) annual variability in captures unrelated to burns. Our results indicated that reptiles and amphibians of sandhills are resilient to short-term effects of burning overall and burn season.

Beschreibung: Protocols were investigated in the short-term conservation of Castanea dentata (Marsh.) Borkh. to maximize axillary shoot multiplication rates at the genotype level and to reduce the incidence of shoot tip necrosis (STN). Factors investigated included explant growth stage (embryo, seedling, and mature stages) of the source material and two culture incubation temperatures (21 ± 1 °C and 31 ± 1 °C). Multiplication rate was measured across 22 genotypes. The role of 6-benzylaminopurine (0.5, 1.0, 2.0, and 4.0 μmol·L–1), calcium (3.0 and 6.0 mmol·L–1), boron (0.025 mmol·L–1), magnesium (3.0 mmol·L–1), and gelling agent (agar, 6.0, 7.0, and 8.0 g·L–1; gellan gum, 3.0, 3.5, and 4.0 g·L–1) on STN was investigated. Genotypes derived from 4-month-old seedlings had the greatest overall multiplication rate (7.87 ± 0.38 at 6 weeks). Temperature affected multiplication rate in three of eight genotypes tested, with multiplication rate greater at 21 ± 1 °C for one genotype and greater at 31 ± 1 °C for two genotypes. Multiplication rates differed significantly between genotypes and ranged from 1.45× at 12 weeks to 13.25× at 6 weeks. Incidence of STN was decreased to 1.40% ± 0.02% at 4.0 μmol·L–1 6-benzylaminopurine. The development of an efficient axillary shoot culture system for C. dentata greatly benefits current conservation efforts.

Beschreibung: This study addresses a situation in which a forest manager has been using a whole-stand model that seems to predict well for their stands and now wants to derive an individual-tree model from it to form an integrated system that can perform well at both stand and tree levels. A simple method was developed to derive tree survival models from three existing stand-level survival models. The derived tree survival models were based on the difference between the diameter of a given tree and the diameter at which tree and stand survival probabilities are equal. For stand survival prediction, each stand model performed less adequately than its derived tree model, and one of the derived tree survival models was the best overall. For tree survival prediction, the same derived tree model also performed best overall. Even though only three stand-level survival models were considered in this study, the method presented here should be applicable to any stand survival model. When no tree survival data were available, tree survival models derived from stand survival models ranked lowest in terms of performance but produced acceptable evaluation statistics for predicting tree-level survival.

Beschreibung: Volume growth is a key indicator in forest management and planning and, accordingly, an integral part of the estimation procedure of forest resources from sample based inventories. Growth estimation from successive double sampling for stratification (2SS) is somewhat challenging and has not been sufficiently addressed in the pertinent literature. Applying 2SS on successive occasions, with updated stratification on each occasion, may lead to fluctuation of sampling units among the strata and to a certain number of sample plots that have to be discarded or that have to be newly established on the second occasion, to obtain the required per-strata sampling proportions, which are stipulated in advance. After presenting a notation to implement growth estimation into 2SS standard formulas, the question of strata shifts and the occurrence of discarded and of new sample plots in the context of growth estimation is addressed. Although growth, unlike net change, can only be estimated from direct observations on remeasured sample plots, it was shown that ignoring discarded or new plots might lead to severely biased estimators. Modified estimators for mean growth and variances are provided and their application is illustrated using data from a repeated survey in a central German forest district.

Beschreibung: Climate-induced increases in tree mortality are reported for many forests worldwide. Understanding the potential effects on carbon pools requires long-term monitoring of changes in forest biomass. We measured aboveground biomass (AGB) of living trees over a 34-year period (1982–2016) in permanent plots with varying stand ages, species compositions, and topographic settings in a subalpine forest in the Colorado Front Range. Stand-level and species-level AGB varied spatially and temporally in relation to stand age, successional processes, and site moisture classification. Young (ca. 122 years) postfire stands composed of lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson) had lower mean AGB than older (〉250 years) mixed-species stands. Mesic stands had higher AGB than xeric or hydric stands of similar age. At the level of individual species, significant shifts in AGB among species were primarily explained by successional replacement of shade-intolerant pines by shade-tolerant Engelmann spruce (Picea engelmannii Parry ex Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.). The permanent plot network recorded significant shifts in species dominance and tree densities between 1982 and 2016, reflecting successional patterns developing over several centuries and the effects of recent localized windthrow, insects, and pathogens. Despite increases in tree mortality, there was a general pattern of increasing AGB across the forest.

Beschreibung: In this paper, we examine the transferability of airborne laser scanning (ALS) based models for individual-tree detection (ITD) from one ALS inventory area (A1) to two other areas (A2 and A3). All areas were located in eastern Finland less than 100 km from each other and were scanned using different ALS devices and parameters. The tree attributes of interest were diameter at breast height (Dbh), height (H), crown base height (Cbh), stem volume (V), and theoretical sawlog volume (Vlog) of Scots pine (Pinus sylvestris L.) with Dbh ≥ 16 cm. All trees were first segmented from the canopy height models, and various ALS metrics were derived for each segment. Then only the segments covering correctly detected pines were chosen for further inspection. The tree attributes were predicted using the k-nearest neighbor (k-NN) imputation. The results showed that the relative root mean square error (RMSE%) values increased for each attribute after the transfers. The RMSE% values were, for A1, A2, and A3, respectively: Dbh, 13.5%, 14.8%, and 18.1%; H, 3.2%, 5.9%, and 6.2%; Cbh, 13.3%, 15.3%, and 18.3%; V, 29.3%, 35.4%, and 39.1%; and Vlog, 38.2%, 54.4% and 51.8%. The observed values indicate that it may be possible to employ ALS-based tree-level k-NN models over different inventory areas without excessive reduction in accuracy, assuming that the tree species are known to be similar.

Beschreibung: Competition indices play a significant role in modeling individual-tree growth and survival. In this study, six distance-independent competition indices were evaluated using 200 permanent plots of loblolly pine (Pinus taeda L.). The competition indices were classified into three families: (1) size ratios, which include diameter ratio and basal area ratio; (2) relative position indices, which include basal area of larger trees (BAL) and tree relative position based on the cumulative distribution function (CDF); and (3) partitioned stand density index and relative density. Results indicated that different families of competition indices were suitable for different tree survival or diameter growth prediction tasks. The diameter ratio was superior for predicting tree survival, whereas the relative position indices (BAL and CDF) performed best for predicting tree diameter growth, with CDF receiving the highest rank.

Beschreibung: In the northeastern United States, eastern white pine (Pinus strobus L.) is a leading species in the forest products industry. The native pathogen Caliciopsis pinea Peck is associated with Caliciopsis canker of white pine, with symptoms including excessive resin production and cankers. This study processed 28.0 m3 of white pine lumber to (i) quantify losses resulting from Caliciopsis canker, (ii) assess how damage varies between Caliciopsis canker symptom severity and thinning, and (iii) quantify economic loss resulting from damage. Caliciopsis canker damage was present in 37% of lumber, yet only 10% was downgraded due to canker damage. Of the downgraded lumber, the vast majority (77%) lost one grade. Additionally, severely symptomatic trees consistently had more damage, and their lumber was more likely to be downgraded than trees with low symptom severity. Caliciopsis canker damage resulted in average revenue losses of 2.3%, yet much of the sampled lumber had other, more significant damage that resulted in downgrade: highly symptomatic trees averaged 63% of the revenue of low or asymptomatic trees. Caliciopsis canker, therefore, can be used as an indicator of poor quality trees. We recommend thinning Caliciopsis canker symptomatic trees to meet low-density stocking guidelines, which may minimize revenue loss while simultaneously minimizing stress to residual stock.

Beschreibung: The geographic variation of the mitochondrial DNA in Siberian fir (Abies sibirica Ledeb.) was studied using the newly developed markers and compared with the phylogeographic pattern of another previously studied Siberian conifer, Siberian larch (Larix sibirica Ledeb.). Similar to Siberian larch, the distribution of mtDNA haplotypes in Siberian fir revealed clear differentiation among distinct geographic regions of southern Siberia and the Urals, likely indicating postglacial recolonization from several sources. The northern part of the range of both species was genetically homogeneous, which is probably due to its recent colonization from one of the glacial refugia. This conclusion is in agreement with published pollen and macrofossil data in Siberian fir and with the reconstruction of environmental niches indicating a dramatic reduction of the range and a likely survival of fir in certain southern areas during the Last Glacial Maximum (LGM), 21 thousand years ago. Although the modeling of the Siberian larch ecological niche reconstructed a shift of the range to the south at that period, the paleontological data indicated the presence of this species in most areas of the current range during LGM, which corresponds to the results of a previous historical demographic study suggesting that the population expansion preceding the LGM.

Beschreibung: Diameter distributions and tree-lists provide information about forest stocks disaggregated by size and species and are key for informing forest management. Diameter distributions and tree-lists are multivariate responses, which makes the evaluation of methods for their prediction reliant on the use of dissimilarity metrics to summarize differences between observations and predictions. We compared four strategies for selection of k nearest neighbors (k-NN) methods to predict diameter distributions and tree-lists using LiDAR and stand-level auxiliary data and analyzed the effect of the k-NN distance and number of neighbors in the performance of the predictions. Strategies differed by the dissimilarity metric used to search for optimal k-NN configurations and the presence or absence of post-stratification. We also analyzed how alternative k-NN configurations ranked when tree-lists were aggregated using different DBH classes and species groupings. For all dissimilarity metrics, k-NN configurations using random-forest distance and three or more neighbors provided the best results. Rankings of k-NN configurations based on different dissimilarity metrics were relatively insensitive to changes on the width of the DBH classes and the definition of the species groups. The selection of the k-NN methods was clearly dependent on the choice of the dissimilarity metric. Further research is needed to find suitable ways to define dissimilarity metrics that reflect how forest managers evaluate differences between predicted and observed tree-lists and diameter distributions.

Beschreibung: Coastal watersheds of the North Pacific benefit immensely from bear-mediated uploading of salmon nutrients, which increases aquatic and terrestrial productivity. To quantify the influence of spawning salmon on tree-ring signatures, we analyzed 543 rings from the heartwood of 13 old-growth Sitka spruce (Picea sitchensis (Bong.) Carrière) trees from five geographically separated watersheds in coastal British Columbia. In comparison with adjacent control trees, those receiving salmon nutrients (salmon trees) have rings that are, on average, 1.5 mm wider, 4.5‰ more enriched in isotopic nitrogen, and 0.021% more elevated in total nitrogen (P 〈 0.001, Mann–Whitney–Wilcoxon test). In this study, salmon nutrients enhance average stem growth by 19%. Furthermore, salmon trees show that increases in tree-ring width and nitrogen values lag sporadic, high salmon runs by 0 to 5 years. Using differences between control and salmon trees from the same site, our results collectively indicate that tree-ring width, isotopic nitrogen, and total nitrogen are valid, complementary tools for investigating historic, annual fluctuations in salmon abundance in coastal watersheds. We recommend their use in future, tree ring based reconstructions of past nutrient cycling over decadal to centennial time scales.

Beschreibung: There are only a few studies focusing on the financial aspects of management regimes on peatland forests and even fewer studies investigating intensive management. Such studies, however, are urgently needed, particularly in Finland, where a considerable proportion of drained peatlands is reaching a phase requiring active management. An empirical data set derived from the 10th National Forest Inventory (NFI10) is applied for stand-level simulations (MOTTI stand simulator) until final cut. The data are a representative sample of the most common drained peatland site types and their current stand structures in Finland. Based on several different initial stand conditions, tree growth was projected according to four management regimes: (1) passive management (only one clearcut executed), (2) management according to prevailing silvicultural recommendations, (3) stand-level optimum without ditch network maintenance (DNM) and fertilization (FERT), and (4) stand-level optimum with DNM and FERT (intensive management). The intensive management regime financially outperformed the other management options distinctively, regardless of the climatic region, peatland site type, and initial stand structure. However, towards more harsh climatic conditions and a more barren site type, the financial difference between management options flattened out, and silvicultural recommendations even resulted in a higher mean annual increment (MAI) compared with intensive management.

Beschreibung: The challenges faced recently by the North American forest products industry have forced it to review many of its key operations. Implementing logistics centers for such a context may therefore help in allocating the wood fibre more efficiently and in reducing sorting and transportation costs. This paper aims to better understand the interaction between a forest logistics center and a complex forest network while exploring the business environment favoring the use of such a structure. A profit maximization model is proposed and applied to a real case in the Mauricie region in Quebec, Canada. A total of 18 groups of scenarios are tested, based on the use of a sort yard and of backhauling. Results show that a logistics center already in operation adds $0.52 in profits for each cubic metre of wood available for harvest (over 2 580 411 m3 per year) for the network under study ($1.4 million annually). A sensitivity analysis also highlights that higher prices and sorting error rates have the greatest impact on the logistics center’s profitability.

Beschreibung: Landscape-scale prescribed burning may be appealing for natural community restoration due to operational efficiency and possible heterogeneity in fire effects across broad spatial scales. We monitored plant community responses for 〉15 years with variable prescribed fire frequencies applied across a Missouri Ozarks landscape stratified into distinct ecological site types. Through the study period, burning had no effect on the overstory tree density or basal area. Midstory stem densities decreased rapidly in periodically burned units and more gradually with annual fire. Burning increased total ground flora cover and the cover of forbs, grasses, and legumes. The effect of burning on species richness differed among site types, with increased species richness through time on exposed slopes. There was no effect of prescribed burning on species richness on two of three protected slope site types, and annual burning decreased species richness in upland waterways. Among the site types, the upland waterways had the most species associated with pre-burn communities. We conclude that (i) burning consistently increased cover of ground layer vegetation across the landscape, while decreasing the midstory stem densities, and (ii) site type moderated ground flora richness response, with more pronounced effects of prescribed burning on exposed sites than on protected sites.

Beschreibung: Forest soils often exhibit low bearing capacities and as a result are often incapable of withstanding high axle loads. In New Brunswick, Canada, five different brush amounts (0, 5, 10, 15, and 20 kg·m–2) were applied as brush mats on machine operating trails during a cut-to-length harvesting operation in a softwood stand to analyze soil disturbance as a result of off-road forest harvesting machine traffic. Soil absolute and relative bulk density and soil penetration resistance measurements were completed below the varying brush mats both before and after forwarding. The mean differences between pre- and post-impact absolute soil dry bulk density values recorded on track areas were 0.24 g·cm–3 for 5–20 kg·m–2 of brush and 0.33 g·cm–3 for 0 kg·m–2 of brush. On average, 40.5%, 17.9%, 14.3%, 15.5%, and 3.6% of all post-forwarding measurements exceeded the threshold for growth-impeding soil bulk density (80% standard Proctor density) for 0, 5, 10, 15 and 20 kg·m–2 of brush, respectively. Soil penetration values 〉3.0 MPa represented 23.7%, 15.0%, 9.4%, 4.6%, and 0.7% of all post-forwarding test plots with 0, 5, 10, 15, and 20 kg·m–2 of brush, respectively. The results suggest that softwood brush mats of 10 to 20 kg·m–2 placed on machine operating trails play a considerable role in reducing forwarder-induced soil compaction and penetration resistance.

Beschreibung: Progeny testing of resistance to needle loss caused by Cyclaneusma minus (cyclaneusma needle cast) has been included in the needle disease resistance strategy of Pinus radiata D. Don in New Zealand since the late 1970s. Data on progeny trials, two in the North Island of New Zealand and one in Tasmania, Australia, were available to estimate heritability between trait genetic correlations and genotype × environment interaction. Resistance to cyclaneusma needle cast had moderate estimates of heritability (0.25 to 0.46) at all sites. Genetic correlations between the assessed traits indicated that selection for faster early growth, i.e., tree height at age 4 years and diameter at breast height at age 6 years, favours trees that are prone to Cyclaneusma infection, while a favourable genetic association between resistance to cyclaneusma needle cast and productivity was evident at a later assessment at age 9 years. No significant genotype × environment interaction was found for resistance to cyclaneusma needle cast; however, stability of genotypes across a wider range of environments and with a high genetic connectedness requires more research. Considerable genetic improvement can be achieved for resistance to cyclaneusma needle cast and indirect selection for the trait should be pursued by selecting for productivity and culling susceptible genotypes from breeding.

Beschreibung: Contemporary fire regimes of Canadian forests have been well documented based on forest fire records between the late 1950s to 1990s. Due to known limitations of fire datasets, an analysis of changes in fire-regime characteristics could not be easily undertaken. This paper presents fire-regime trends nationally and within two zonation systems, the homogeneous fire-regime zones and ecozones, for two time periods, 1959–2015 and 1980–2015. Nationally, trends in both area burned and number of large fires (≥200 ha) have increased significantly since 1959, which might be due to increases in lightning-caused fires. Human-caused fires, in contrast, have shown a decline. Results suggest that large fires have been getting larger over the last 57 years and that the fire season has been starting approximately one week earlier and ending one week later. At the regional level, trends in fire regimes are variable across the country, with fewer significant trends. Area burned, number of large fires, and lightning-caused fires are increasing in most of western Canada, whereas human-caused fires are either stable or declining throughout the country. Overall, Canadian forests appear to have been engaged in a trajectory towards more active fire regimes over the last half century.

Beschreibung: There have been limited efforts to investigate the association between wood decay and electrical resistance; consequently, we have examined the change in the electrical resistance of wood progressively decayed by brown-rot fungi to elucidate the effect of the degree of decay. The rate of mass loss of wood was used as an indicator of the degree of fungal decay. The changes in the moisture content and ion concentrations were measured at various decay stages. The results showed a significant difference in the electrical resistances of sound wood and fungal-treated wood after 24 weeks. The electrical resistance significantly decreased with the exposure time. The degree of decay increased as the mass loss increased, resulting in the severe breakdown of cell walls and the accumulation of fungal mycelia. Empirical models related to the rate of mass loss and the percent decrease in the electrical resistance were established. The moisture content and cation concentrations increased to various degrees in decayed wood. This increase in the cation concentration was considered to play a dominant role in the decrease in the electrical resistance. The study results provide valuable information for developing an electrical resistance based method coupled with ion content measurements for incipient wood decay detection.

Beschreibung: This is the first study to generate and analyze the climate signal in blue intensity (BI) tree-ring chronologies from Alaska yellow-cedar (Callitropsis nootkatensis (D. Don) Oerst. ex D.P. Little). The latewood BI chronology shows a much stronger temperature sensitivity than ring width and can thus provide information on past climate. The well-replicated BI chronology exhibits a positive January–August mean maximum temperature signal for 1900–1975, after which it loses temperature sensitivity following the 1976–1977 shift in northeastern Pacific climate. The positive temperature response appears to recover and remains strong for the most recent decades, but the coming years will continue to test this observation. This temporary loss of temperature sensitivity from about 1976 to 1999 is not evident in ring width or in a change in forest health but is consistent with prior work linking cedar decline to warming. A confounding factor is the uncertain influence of a shift in color variation from the heartwood–sapwood boundary. Future expansion of the yellow-cedar BI network and further investigation of the influence of the heartwood–sapwood transitions in the BI signal will lead to a better understanding of the utility of this species as a climate proxy.

Beschreibung: Insect epidemics such as the mountain pine beetle (MPB) outbreak have a major impact on forest dynamics. In Cypress Hills, Canada, the Forest Service Branch of the Saskatchewan Ministry of Environment aims to control as many new infested trees as possible by conducting ground-based surveys around trees infested in previous years. Given the risk posed by MPB, there is a need to evaluate how well such a control strategy performs. Therefore, the goal of this study is to assess the current detection strategy compared with competing strategies (random search and search based on model predictions via machine learning), while taking management costs into account. Our model predictions via machine learning used a generalized boosted classification tree to predict locations of new infestations from ecological and environmental variables. We then ran virtual experiments to determine control efficiency under the three detection strategies. The classification tree predicts new infested locations with great accuracy (AUC = 0.93). Using model predictions for survey locations gives the highest control efficiency for larger survey areas. Overall, the current detection strategy performs well but control could be more efficient and cost-effective by increasing the survey area, as well as adding locations given by model predictions.

Beschreibung: Recently, the World Scientists’ Warning to Humanity: a Second Notice was issued in response to ongoing and largely unabated environmental degradation due to anthropogenic activities. In the warning, humanity is urged to practice more environmentally sustainable alternatives to business as usual to avoid potentially catastrophic outcomes. Following the success of their warning, the Alliance of World Scientists called for discipline-specific follow-up papers. This paper is an answer to that call for the topic of wildland fire. Across much of Canada and the world, wildfires are anticipated to increase in severity and frequency in response to anthropogenic activities. The world scientists’ second warning provides the opportunity for wildland fire researchers to raise the profile of the potential impacts that anthropogenic activities are likely to have on future fire regimes and, in return, what impacts future fire regimes may have on humanity. We discuss how wildfire is related to several issues of concern raised in the world scientists’ second warning, including climate change, human population growth, biodiversity and forests, and freshwater availability. Furthermore, we touch on the potential future health impacts and challenges to wildfire suppression and management in Canada. In essence, our wildfire scientists’ warning to humanity is that we, as a society, will have to learn to live with more fire on the landscape. We provide some recommendations on how we might move forward to prepare for and adapt to future wildfire regimes in Canada. Although this paper is primarily Canadian in focus, the concepts and information herein also draw from international examples and are of relevance globally.

Beschreibung: The majority of plant diversity in North American boreal forests is comprised of understory plant communities undergoing continuous interspecific competition. Anthropogenic activities, particularly surface mining, have introduced higher severity disturbances that not only remove vegetation, but also modify soil. During reclamation, soils used to cap overburden materials have inhibited native plant growth and increased weed invasion. This study aimed to examine the effectiveness of seeding and weeding treatments for promoting the establishment of native understory plant communities, as well as a common deciduous tree species, on three different reclamation cover soils (forest floor – mineral mix, peat–mineral mix, and transitional). The broadcasting of a native forb seed mix was not successful on any of the cover soils, whereas weeding affected each cover soil differently. With weeding, the forest floor – mineral mix and transitional cover soils experienced a decrease in the relative abundance of introduced forbs and an increase in the relative abundance of graminoids. The increase in graminoid cover on the forest floor – mineral mix was mostly attributed to the expansion of Calamagrostis canadensis (Michx.) P. Beauv. Overall, weeding effectively eliminated introduced plant species, allowing competitive native grasses to establish. However, weeding may have unintentionally hindered the development of a native understory plant community via the over-establishment of grass on reclamation sites.

Beschreibung: Studies with conifer-infesting bark beetles commonly use bolts cut from trees to evaluate the effects of host tree quality on various aspects of insect biology. Yet, whether host quality changes between live trees and bolts cut from these trees has not been assessed. Particularly, changes in concentrations of defense chemicals (such as monoterpenes) and nutrients (such as nitrogen and carbon) have not been compared between live trees and their cut bolts. To determine whether monoterpene and nutrient concentrations differ after cutting, jack pine (Pinus banksiana Lamb.) trees in Lac La Biche (Alberta) were selected and sampled for phloem tissue. Then, these trees were harvested into two bolts per tree and stored at 4 °C for 3 and 6 months. Phloem was sampled from both live trees and bolts 3 and 6 months after storage. We found that major monoterpenes of jack pine were higher in phloem from bolts than from live trees. Storage time did not affect the results. Furthermore, some nutrients including nitrogen were also higher in bolts and varied between storage times. We conclude that researchers should be aware of the observed changes in the host quality that may have positive or negative effects on the development and behavior of bark beetles under observation.

Beschreibung: This study investigated the origins and spread patterns of Heterobasidion root disease in three Pinus contorta Dougl. ex Loudon plantations established on forest and agricultural land and subjected to three different management scenarios. Trees with decline symptoms and stumps remaining from the previous rotation were sampled for fungal isolations. Ten isolates of Heterobasidion parviporum Niemelä & Korhonen and 425 of Heterobasidion annosum (Fr.) Bref. were tested for clonality through somatic compatibility tests. The following conclusions were reached: (i) P. contorta is highly susceptible to H. annosum and H. parviporum and both pathogens cause dieback of P. contorta; (ii) H. annosum from previous-rotation P. sylvestris stumps can effectively transfer to P. contorta; (iii) the pathogens may form constantly expanding territorial clones; (iv) basidiospores of both pathogens colonise stumps of P. contorta (primary infections); (v) H. parviporum clones expanded more slowly than clones of H. annosum; (vi) clonal spread proceeded more quickly from stumps with established secondary infections than from stumps with primary infections; (vii) H. annosum can persist in pine stumps for at least 26 years; and (viii) stump treatment should be considered to control Heterobasidion primary infections.

Beschreibung: Despite catastrophic ash (Fraxinus spp.) mortality observed by the mid-2000s in the epicenter of the emerald ash borer (EAB) (Agrilus planipennis Fairmaire) invasion in southeast Michigan, we noticed numerous live white ash (Fraxinus americana L.) in some forests in this region. In 2015, we inventoried overstory trees and regeneration in 28 white ash sites spanning 11 counties. White ash survival ranged from 0% to 100% of stems. Overall, 75% of 821 white ash trees, ranging from 10.0 to 44.0 cm diameter at breast height, and 66% of the white ash basal area, ranging from 0.3 to 3.5 m2·ha–1, were alive. Nearly all live white ash had signs of previous EAB colonization, but 83% had healthy canopies (≤10% canopy dieback). Green ash trees were recorded in 27 sites, but 92% were killed by EAB. Model selection indicated that variation in white ash survival was related to white ash abundance and distance of sites from the original EAB epicenter but not to green ash related variables or to the distance of sites from the Asian parasitoid release or recovery locations. Regeneration strata were dominated by white ash, suggesting that some white ash populations may persist in post-invasion areas.

Beschreibung: Forest edges are an important legacy of natural and anthropogenic disturbances. Edges of intact forest fragments are influenced by adjacent non-forested ecosystems, resulting in compositional and structural differences at the edge and into the intact forest. Edge influence (EI) is the altered biotic and abiotic interactions that occur along the edge-to-interior gradient in disturbed forests. Few studies have analyzed natural disturbance created edges, particularly in woodland structures, which contain fewer trees per hectare and are typically less light-limited than forests. The goal of our study was to examine the EI of a tornado-created edge in a Pinus palustris Mill. (longleaf pine) woodland in Alabama. In 2011, an EF-3 tornado impacted a restored P. palustris woodland, resulting in a distinct edge. We installed transects perpendicular to the edge to quantify biotic and abiotic response variables and calculate the distance of EI. Reduced structural forest complexity and basal area (negative EI) were evident 70 m into the interior woodland. Ground flora richness and diversity experienced a positive EI, with higher richness and diversity at the edge. Results of this study add to our understanding of EI on woodland composition and structure and naturally created edges and may help guide natural disturbance based silvicultural systems.

Beschreibung: In the managed forest of Canada, forest fires are actively suppressed through efficient initial attack capability; however, the impact of different factors on the suppression success remains to be understood. The aim of this paper was to analyze the influence of operational suppression objectives (fire detection, initial attack, and fire control) along with fire intensity, fuel type, fire ignition cause, year, workload, and homogeneous fire regime zones on the achievement of the fire suppression objective (fire 〈 3 ha) using the Forest Fire Protection Agency of Quebec (SOPFEU) as a case study. The overall success of the suppression objective was very high (88%) over the study period (1994–2015). Both detection and control had significant effects on the suppression success through their interaction with fuel type, ignition cause, fire intensity, and zone variables. When the suppression objective was not achieved, final fire size was influenced by control, fuel type, fire intensity, and zone. The paper highlights the importance of the operational objectives and of regional differences for both fire suppression success and final fire size. Our results can help forest fire protection agencies to better understand their wildland fire suppression systems for a better adaptation to the upcoming fire regime changes.

Beschreibung: Rapid loss of ash (Fraxinus spp.) trees in riparian forests from an invasive insect, the emerald ash borer (EAB; Agrilus planipennis Fairmaire, 1888), could pose risk of altering organic matter inputs to water bodies that underpin many aquatic ecosystem processes. We measured the composition of riparian forests and their leaf-litter contributions to headwater streams and determined the relative palatability of ash leaves and leaves of three other common riparian trees to aquatic invertebrate leaf-litter consumers (the stonefly (Pteronarcys sp.) and the cranefly (Tipula sp.)) in laboratory microcosms and whole invertebrate communities in forest streams. Ash trees contributed, on average, 24% to riparian tree density and 20% to total litterfall. Among the four common streamside trees accounting for 65% of total litterfall, ash was the first or second most preferred food source for consumers. Leaf packs without ash decomposed at slower rates than packs containing 25%–100% ash leaves. Preferential feeding on ash leaves infers a high-quality food source selected by consumers, and this concurred with comparatively high N content and low C–N ratio of ash leaves. Aquatic invertebrate communities on leaf packs in streams differed among leaf mixtures with or without ash, although community dissimilarity was low. The loss of ash in riparian forests represents an EAB-induced reduction in a high-quality resource subsidy to organic matter consumers in streams. We discuss how this has implications for risk predictions and management response strategies.

Beschreibung: A problem in the single-scan setup of terrestrial laser scanning is that some trees are shaded by others and therefore not detected in the scan. A basic estimator for forest characteristics such as tree density or basal area is based on the visible area of a scanner. However, simply compensating for nondetection by the visible area may result in considerable bias even in Poisson forests, especially if the detection of a tree depends on its size. We propose a new estimator that is a generalization of the visible area based estimator. Most importantly, the new estimator allows different detection rules; for example, full or partial visibility of a tree can be required for detection. By a simulation study, it is shown to work adequately in different types of simulated and empirical forests with different detection rules.

Beschreibung: As various methods for precision inventories, including light detection and ranging (LiDAR), are becoming increasingly common in forestry, planning at the individual-tree level is becoming more viable. In this study, we present a method for finding the optimal thinning times for individual trees from an economic perspective. The method utilizes a forest growth model based on individual trees that has been fitted to Norway spruce (Picea abies (L.) Karst.) stands in northern Sweden. We find that the optimal management strategy is to thin from above (i.e., harvesting trees that are larger than average). We compare our optimal strategy with a conventional management strategy and find that the optimal strategy results in approximately 20% higher land expectation value. Furthermore, we find that for the optimal strategy, increasing the discount rate will reduce the final harvest age and increase the basal area reduction. Decreasing the cost to initiate a thinning (e.g., machinery-related transportation costs) increases the number of thinnings and delays the first thinning.

Beschreibung: Since the 1960s, canopy photography has been widely used in forestry. Hemispherical photography has been the most widely used technique, but a great drawback of this method is its perceived sensitivity to hemispherical image acquisition and processing. Over the last decade, several alternative photographic approaches using restricted view angle have been proposed. Cover photography acquired via a normal lens was the first of the recently introduced photographic techniques. Use of a restricted view (often fixed) lens has subsequently contributed to the extension of canopy photography to new sensors and platforms, which ultimately have provided answers to some previous challenges regarding within-crown clumping correction, isolated and urban tree measurements, understory assessment, operational leaf inclination angle measurements, and phenological monitoring. This study provides a comprehensive review of the use of canopy photography in forestry and describes the theory and definitions of the variables used to quantify canopy structure. A case study is presented to illustrate and compare the different features and performance of the existing overstory photographic techniques; the results make it possible to suggest sampling strategies for consistent overstory canopy photographic measurements. Emerging operational fields of canopy photography are also described and discussed.

Beschreibung: Fire regime zonation systems are critical tools for research and management activities. In this study, we develop a hierarchical framework that applies both qualitative and quantitative approaches to create a two-level fire regime zonation system for Canada. The finer scale level, Fire Regime Units (FRUs), was created through a stepwise synthesis of fire regime metrics based on 1970–2016 fire records, environmental attributes such as topographic features and vegetation, literature review, and expert advice. Each of these 60 FRUs exhibits an internal homogeneity in fire regime. As non-contiguous units can show similar patterns in fire-related measurements, we performed a clustering analysis on the FRUs to define 15 broad-scale Fire Regime Types (FRTs). Each type is characterized by a unique set of indices related to fire activity, seasonality, and ignition cause. This two-level fire regime zonation system has a large range of applications (e.g., modeling, gradient analysis) and is flexible enough to be updated with new data or when notable shifts in fire dynamics occur.

Beschreibung: This experiment assessed the effects of plant-derived smoke water, potassium nitrate (KNO3), and their combined effect on germination of cold-stratified and non-stratified seed from 18 native boreal forest plant species. Seeds were treated with smoke water diluted to 1:20, 0.1% KNO3, and smoke water + KNO3. Nine species responded positively to smoke water; these responses were dependent on the type of stratification, and three of these species only had a positive response to smoke water + KNO3 solution. Five species responded positively to KNO3 and four of those were associated with smoke water + KNO3 solution. Smoke water induced germination of several species, but only for seeds that had been previously cold-stratified. Vaccinium myrtilloides Michx. had the largest increase in germination using smoke water and the most reduced germination using KNO3. The interactions between smoke water, KNO3, and stratified seeds are not well understood. The effects and applications of smoke water and KNO3 (or other nitrogen sources) should be further researched to determine alternative approaches to restoration of disturbed boreal forest ecosystems.

Beschreibung: Based on a 30-year quarterly data set, this paper examines the dynamics of the softwood sawtimber stumpage market in Louisiana, United States, from 1988 to 2017. Cointegration analysis and the vector error correction model were used to examine the demand and supply of softwood sawtimber stumpage products in Louisiana. Competition among different stumpage products, seasonality patterns in the market, and the impact of some exogenous events were also investigated. The results showed that the demand for softwood sawtimber products is inelastic to its own price, whereas the supply is elastic. Strong seasonality patterns were detected for both stumpage price and harvest quantity. Significant substitution effects were also found among different types of stumpage products. In addition, the estimation results of the dynamic model suggested that, when facing an exogenous impact, the harvest quantity adjusts far quicker than the stumpage price in the Louisiana softwood sawtimber stumpage market.

Beschreibung: Regionally fitted allometric equations for individual trees and root-to-shoot ratio values are normally used to estimate local aboveground and belowground forest biomass, respectively. However, uncertainties arising from such applications are poorly understood. We developed equations for both aboveground and belowground biomass using destructive sampling for three dominant upland boreal tree species in northwestern Alberta, Canada. Compared with our equations, the diameter-based national equations derived for use across Canada underestimated aboveground biomass for Picea glauca (Moench) Voss but gave reasonable estimates for Populus balsamifera L. and Populus tremuloides Michx. The national equations based on both tree diameter and height overestimated aboveground biomass for the Populus species but underestimated it for Picea glauca in our study area. The approach of root-to-shoot ratio proposed by the Intergovernmental Panel on Climate Change (IPCC) overestimated belowground biomass by 16%–41%, depending on forest cover type, in comparison with our values estimated directly on site, with the greatest bias in deciduous-dominated stands. When the general allometric equations for aboveground biomass and the root-to-shoot ratio for belowground biomass were combined to estimate stand biomass, overestimation could be as high as 18% in our study area. The results of our study support the development of improved regional allometric equations for more accurate local-scale estimations. Incorporating intraspecific variation of important traits such as tree taper may be especially helpful.

Beschreibung: Plant inoculation with ectomycorrhizal fungi (EMF) maximizes the productive potential of forest stands. Thus, the inoculation efficiency of calcium alginate gel entrapped EMF vegetative mycelium was evaluated in a commercial nursery using cuttings of Eucalyptus clones GG100 and GG680. The cuttings were inoculated with Pisolithus microcarpus G. Cunn. (Cooke & Massee), Hysterangium gardneri E. Fisch., and Scleroderma areolatum Ehrenb. The cuttings were cultivated under low phosphate fertilization and compared with uninoculated control treatments with reduced phosphate (low P control) and full phosphate (high P control) fertilization. Pisolithus microcarpus inoculation increased shoot height, root collar diameter, shoot dry mass, total dry mass, and frequency of maximum score for root ball formation of the two clones compared with the low P control treatment. Also, in relation to the low P control treatment, H. gardneri inoculation increased shoot dry mass in GG100 rooted cuttings. Scleroderma areolatum inoculation did not enhance any characteristic of Eucalyptus rooted cuttings. Inoculation of vegetative mycelium with EMF impregnated in calcium alginate gel intensified rooted cutting growth in a commercial Eucalyptus nursery and decreased the phosphate dose required. Based on the comparison of two Eucalyptus clones, efficiency of the inoculants in promoting benefits depends on the fungus and the Eucalyptus clone. Pisolithus microcarpus is most promising for inoculation in Eucalyptus cuttings.

Beschreibung: Understanding the effects of fire on advance regeneration of oak (Quercus L.) species and their competitors is an important step in determining the role of prescribed fire in regenerating and restoring upland oak ecosystems. Our study aimed to understand how dormant-season prescribed fire affects advance regeneration of chinkapin oak (Quercus muehlenbergii Engelm.), black oak (Quercus velutina Lam.), and their major competitors at sites targeted for woodland restoration and management. We analyzed relationships between stem size and survival probability; determined the effect of fire temperature on survival probability; and compared how mortality, sprouting, and survival differed among species. For chinkapin oak, black oak, and bitternut hickory (Carya cordiformis (Wangenh.) K. Koch), mortality was low and rate of sprouting was high after shoot dieback. Initial basal diameter was significantly related to survival probability after one fire for all species except chinkapin oak and black oak. Height was a significant predictor of survival probability for all species except chinkapin oak. Although sugar maple (Acer saccharum Marsh.) also responded to fire by sprouting, it did so at a much lower rate than oaks and hickory (20% versus 43%–68%). These data reveal that heavily invaded, fire-suppressed woodlands on the prairie–forest border region may not experience major structural and compositional shifts without repeated burning or mechanical treatments.