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Northern hardwood species display a variety of forms and defects that can reduce stem quality and complicate their timber management. However, for the most part, growth and yield models do not account for the influence of stem form and damage. This study determined the influence of stem form and damage on growth, survival, and projected future sawlog value among several northern commercial hardwood species. To accomplish this, hardwood trees on 112 permanent plots across three long-term research sites in Maine were assigned stem form and risk classes using a tree classification system developed in New Brunswick. A highly significant influence of stem form and risk on annualized individual-tree diameter increment and survival was found. Inclusion of these equations into a regional growth and yield model highlighted the importance of stem form and defects on long-term simulations as projected stand-level future value was significantly reduced by over 17%, on average (range of 13% to 28%), when compared with projections that did not include that tree-level information. The results highlight the importance of stem form and defects, as well as the need to account for them, in growth and yield applications that assess the forecasted value of commercially important hardwood stands. Key words: paper birch, quaking aspen, red maple, red oak, yellow birch. Le tronc des especes de feuillus nordiques presente une variete de formes et de defauts qui peuvent diminuer la qualite des arbres et compliquer l'amenagement de ces essences pour la production de bois d'oeuvre. Cependant, la plupart des modeles de croissance et de rendement tiennent encore tres peu compte de l'impact de la forme du tronc et des defauts. Cette etude avait pour but de determiner l'influence de la forme du tronc et des defauts sur la croissance, la survie et la valeur future estimee des billes de sciage de plusieurs especes commerciales de feuillus nordiques. A cette fin, nous avons utilise un systeme de classification des arbres elabore au Nouveau-Brunswick et attribue une forme du tronc et une classe de risque de perte de vigueur a chaque tige de feuillus nordiques presente dans 112 placettes permanentes reparties dans trois stations de recherche a long terme situees dans le Maine. La forme du tronc et le risque avaient une influence tres significative sur le taux de survie et l'accroissement en diametre annualise des tiges prises individuellement. L'inclusion de ces equations dans un modele regional de croissance et de rendement a mis en evidence l'importance de la forme du tronc et des defauts pour les simulations a long terme etant donne que la valeur future estimee a l'echelle du peuplement etait significativement reduite, de plus de 17 % en moyenne (etendue de 13 a 28 %), comparativement aux projections qui n'incluaient pas cette information au sujet de chaque tige. Les resultats font aussi ressortir l'importance de la forme du tronc et des defauts, ainsi que la necessite d'en tenir compte, dans les applications de croissance et de rendement qui evaluent la valeur anticipee des peuplements feuillus qui ont une importance commerciale. [Traduit par la Redaction] Mots-cles : bouleau blanc, peuplier faux-tremble, erable rouge, chene rouge, bouleau jaune., Introduction Northern hardwood and mixed-wood forest types account for approximately 8.1 million ha across the northeastern United States (US) and portions of Canada adjacent to this region (Leak et al. [...]

Measuring and modelling the shape of tree stems is a fundamental component of forest inventory systems for both commercial and biological purposes. The change in diameter of the stem along its length (a.k.a. 'taper') is one of the most important and widely used means of predicting tree stem volume. Until recently, the options for obtaining accurate estimates of stem taper and developing stem taper models have been limited to measurements of felled trees or the use of optical dendrometers on standing live trees. Here, we tested both a tripod-mounted terrestrial laser scanner (TLS; a Focus 3D 120 of FARO Technologies, Inc. Lake Mary, FL, USA), and a mobile laser scanner (MLS; the ZEB1 of the GeoSLAM Ltd, Nottingham, UK) to measure tree diameters at various heights along the stem of 20 destructively harvested broadleaf and needleleaf species using the outer hull modelling method, for the purpose of developing individual-tree and species-specific taper models. Laser scanner specifications were a major factor determining stem taper measurement accuracy. The longer-range, low beam divergence TLS could estimate stem diameter to an average of 15.7 m above ground (about 79 per cent of the canopy height), while the shorter-range high beam divergence MLS could estimate an average of 11.5 m above ground (about 45 per cent of the canopy height). Stem taper error increased with respect to height above ground, with the TLS providing more consistent and reliable diameter measurements (root mean square error (RMSE) = 1.93 cm; 9.57 per cent) compared with the MLS (RMSE = 2.59 cm; 12.84 per cent), but both methods were nearly unbiased. We attribute ~60 per cent of the uncertainty in stem measurements to laser beam diameter and point density, showing positive and negative correlations, respectively. MLS was unable to converge on the two tested taper models but was found to be an efficient means of easily sampling diameters at breast height (DBH) and reconstructing stem maps in simple forest stands with trees greater than ~10 cm DBH. TLS provided precision stem diameter measurements that allowed for the creation of similar taper models for three out of the four study species. Future work should focus on evaluating MLS systems with improved specifications (e.g. beam divergence and range), since these instruments will likely lead to dramatic improvements in reliable estimates of forest inventory parameters, in line with the current TLS technology. [ABSTRACT FROM AUTHOR]

Northern hardwood trees display a wide variety of stem forms and defects, which can substantially reduce their financial value and also complicate their silviculture. While attributes of stem form and defect have been incorporated into tree classification systems, their ability to assess product value and recovery in standing trees has not been adequately tested. To address this issue, we classified stem form and risk using a system developed by the Northern Hardwoods Research Institute (NHRI) for four species across several locations in Maine, New Hampshire, and New Brunswick: sugar maple (Acer saccharum Marsh.), red maple (Acerrubrum L.), yellow birch (Betula alleghaniensis Britton), and northern red oak (Quercus rubra L.). Using these data, we (i) quantified interspecific and regional variation in stem form and damage, (ii) related potential sawlog recovery to tree size, form, and risk, and (iii) compared the efficacy of the NHRI system with a commonly used classification system and a continuous measure of stem quality. High variation in both stem form and damage among the species was found, with red maple showing the largest range. A simplified NHRI system including three form classes proved to be sufficient in differentiating sawlog potential in individual trees, while a model using a continuous measure of stem quality (estimated merchantable sawlog height) performed best. Key words: stem form, risk, northern hardwoods, classification systems, sawlog potential. Le tronc des feuillus nordiques presente une variete de formes et de defauts qui peuvent reduire substantiellement leur valeur financiere et aussi compliquer leur sylviculture. Bien que les attributs de la forme et des defauts du tronc aient ete incorpores dans des systemes de classement des arbres, leur capacite a estimer le rendement et la valeur des produits chez les arbres sur pied n'a pas ete adequatement testee. Pour aborder ce probleme, nous avons classe la forme du tronc et le risque de perte de vigueur a plusieurs endroits dans le Maine, le New Hampshire et le Nouveau-Brunswick en utilisant un systeme developpe par l'Institut de recherche sur les feuillus nordiques (IRFN) pour quatre especes : l'erable a sucre (Acer saccharum Marsh.), l'erable rouge (Acer rubrum L.), le bouleau jaune (Betula alleghaniensis Britton) et le chene rouge (Quercus rubra L.). A l'aide de ces donnees nous avons (i) quantifie la variation interspecifique et regionale de la forme de la tige et des dommages, (ii) relie le rendement potentiel en billes de sciage a la taille de l'arbre, la forme du tronc et le risque de perte de vigueur et (iii) compare l'efficacite du systeme de l'IRFN a celle d'un systeme de classement generalement utilise ainsi qu'a la mesure continue de la qualite du tronc. Nous avons trouve une grande variation de la forme du tronc et des dommages parmi les especes; l'ampleur de la variation etait la plus importante chez l'erable rouge. Le systeme de l'IRFN simplifie comportant trois classes de de forme s'est avere suffisant pour differencier les billes de sciage potentielles chez les arbres individuels tandis qu'un modele utilisant la mesure continue de la qualite du tronc (hauteur marchande estimee en billes de sciage) etait le plus performant. [Traduit par la Redaction] Mots-cles: forme du tronc, risque de perte de vigueur, feuillus nordiques, systeme de classement, bille de sciage potentielle., Introduction The northern hardwood forest type covers approximately 8.1 million ha in the United States (US), spanning from New York into portions of Canada adjacent to this region (Leak et [...]

As part of a quantitative survey of Maine's bumble bee fauna (Butler et al. 2021), we compared and contrasted genetic diversity, parasite and pathogen burdens, and pesticide exposure of the relatively common Bombus ternarius Say, 1937 and the spatially rare Bombus terricola Kirby, 1837. We recorded 11 Bombus species at 40 survey sites across three Maine ecoregions, and B. ternarius was the most common species, while B. terricola was spatially rare. Nonmetric multidimensional scaling indicated that B. terricola was associated with higher elevation sites in Maine, while B. ternarius was more broadly distributed in the state. Pollinator networks constructed for each bee indicated B. ternarius foraged on more plant species than B. terricola, but that there was considerable overlap (73%) in plant species visited. Genetic diversity was greater in the spatially restricted B. terricola, whereas the widely distributed B. ternarius was characterized by greater genetic differentiation among regions. Bombus terricola had higher molecular marker levels of the microsporidian fungi Nosema spp. and the trypanosome Crithidia spp., and both species had high levels of Trypanosoma spp. exposure. No Western Honey Bee (Apis mellifera, Linnaeus, 1758) viruses were detected in either species. Pesticides were not detected in pollen samples collected from workers of either species, and B. ternarius worker tissue samples exhibited only trace levels of diflubenzuron. [ABSTRACT FROM AUTHOR]

Global declines of bumble bees place natural and agricultural ecosystems at risk. Given bumble bees importance to Maine's major agricultural crops, we conducted a statewide, quantitative survey of bumble bee species seasonal and ecoregional abundance, richness, diversity, and floral resource use. We recorded 11 Bombus species at 40 survey sites across Maine's three ecoregions, with Bombus ternarius Cresson, 1863 and Bombus impatiens Cresson, 1863 being the most common and Bombus citrinus Smith, 1854 the least commonly encountered. Bumble bee species richness did not differ as a function of ecoregion, but did decline over the season, while species diversity differed by ecoregion and also declined over the season. Multiple response permutation procedure (MRPP) indicated ecoregional differences in species composition of bumble bee assemblages and nonmetric multidimensional scaling produced a stable ordination suggesting assemblage differences were associated with survey site variables including forage plant cover, forage plant richness, elevation, development, and deciduous forest cover. Both MRPP and correspondence analysis also revealed differences in the floral resources utilized by bumble bee species in each ecoregion. Low connectance and nestedness levels indicated low stability pollinator networks in each ecoregion, suggesting Maine bumble bee assemblages may be at risk of decline in response to additional external perturbations. [ABSTRACT FROM AUTHOR]

The occurrence (probability) and extent (proportion) of tree internal stem decay are important attributes influencing potential wood quality and value, but variation in decay by species, tree size and geographic range are rarely evaluated and modelled. In this analysis, we used 1246 destructively sampled trees across 33 species in the northeastern United States and New Brunswick, Canada to determine the factors influencing the combined probability and proportion of decay. In the process, we evaluated three modelling approaches including a two-part conditional model, multinomial model and generalized additive model for location, scale and shape (gamlss) that simultaneously predicted both probability and proportion of decay. Predictive capability for all three methods were nearly identical when classifying decay occurrence. Compared with the other methods, the gamlss model had a lower mean bias and root mean square error (RMSE) when predicting decay extent. Tree diameter to height ratio (ratio of diameter at breast height to total height), height, crown ratio, species tolerance to flooding and drought, leaf longevity, and an assessment of perceived tree risk of mortality (risk class) were selected as predictors in the best overall model for decay occurrence. For predicting decay extent, the best model included risk class, crown ratio and the last freezing date of spring. Further analysis identified significant species differences, which we used to develop functional species groupings based on decay occurrence and extent. Despite these observed relationships, a high degree of unexplained variation remained, highlighting the challenges of modelling decay in trees of different species across a range of growing environments. [ABSTRACT FROM AUTHOR]

Accurate estimation of forest biomass and carbon stocks at regional to national scales is a key requirement in determining terrestrial carbon sources and sinks on United States (US) forest lands. To that end, comprehensive assessment and testing of alternative volume and biomass models were conducted for individual tree models employed in the component ratio method (CRM) currently used in the US' National Greenhouse Gas Inventory. The CRM applies species-specific stem volume equations along with specific gravity conversions and component expansion factors to ensure consistency between predicted stem volumes and weights, and additivity of predicted live tree component weights to match aboveground biomass (AGB). Data from over 76 600 stem volumes and 6600 AGB observations were compiled from individual studies conducted in the past 115 years - what we refer to as legacy data - to perform the assessment. Scenarios formulated to incrementally replace constituent equations in the CRM with models fitted to legacy data were tested using cross-validation methods, and estimates of AGB were scaled using forest inventory data to compare across 33 states in the eastern US. Modifications all indicated that the CRM in its present formulation underestimates AGB in eastern forests, with the range of underestimation ranging from 6.2 to 17 per cent. Cross-validation results indicated the greatest reductions in estimation bias and root-mean squared error could be achieved by scenarios that replaced stem volume, sapling AGB, and component ratio equations in the CRM. A change in the definitions used in apportioning biomass to aboveground components was also shown to increase prediction accuracy. Adopting modifications tested here would increase AGB estimates for the eastern US by 15 per cent, accounting for 1.5 Pg of C currently unaccounted for in live tree aboveground forest C stock assessments. Expansion of the legacy data set currently underway should be useful for further testing, such as whether similar gains in accuracy can be achieved in estimates of regional or national-scale C sequestration rates. [ABSTRACT FROM AUTHOR]

This study quantifies area and perimeter measurement errors, traverse times, recording intervals, and overall time and cost effectiveness for using a mapping-grade differential Global Positioning System (GPS) receiver in forested settings. We compared two configurations including one that maximized data collection productivity (position dilution of precision (PDOP) 20, signal to noise ratio (SNR 33), and minimum elevation mask 5°) and a second that involved traditional receiver settings that was designed to improve accuracies (PDOP 6, SNR 39, and minimum elevation mask 15°). We determined that averaging 30 positions and using the settings that maximized productivity was the most time effective combination of recording interval and settings. This combination of recording interval and settings proved slightly more cost effective than other traditional surveying methods such as a laser with digital compass and string box. Average absolute per cent area errors when averaging 30 positions and using maximum settings were 2.6% and average absolute per cent perimeter errors were 2.0%. These results should help forest resource professionals more effectively evaluate GPS techniques and receiver configurations. [ABSTRACT FROM AUTHOR]

We collected measurements using five identical high-quality mapping-grade GPS receivers that were configured the same and collected data simultaneously in two distinctly different settings within a forest. Our primary objective was to determine whether measurement accuracies were different among the mapping-grade GPS receivers. A secondary objective was to determine whether measurement accuracies were different depending on whether receivers established their locations by taking a single 1-second measurement or by averaging 30 or 60 measurements. In the open-sky setting, where receivers had few obstructions overhead, we found that all five receivers recorded measurements with similar positional accuracies. Errors were lower when measurements were differentially corrected(postprocessed). We found an average error of 1.6 m for unprocessed data and an average error of 0.2 m for postprocessed data. Our results indicate that in open-sky conditions, all five receivers performed similarly when measurements were postprocessed. In addition, there was no significant difference in accuracy whether 1, 30, or 60 points were averaged, regardless of whether data were postprocessed. In the young-forest test course, examination of errors between receivers revealed that one receiver had significantly different errors compared with other receivers, which was likely the result of environmental influences on satellite signal strength and availability. We also found that measurement errors for all five receivers were significantly lower when measurements were postprocessed. On average, measurement errors were 5.9 m for unprocessed data and 1.4 m for postprocessed data. In analyzing individual receiver errors, no receiver had significantly different measurement errors whether 1, 30, or 60 measurements were recorded. [ABSTRACT FROM AUTHOR]