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The recruitment of saplings in forest stands into merchantable stems is a very complex process, thus making it challenging to understand and predict. The dynamics of recruitment in the Acadian Forest Region of New Brunswick are not well known or well documented. Our objective was to garner information from existing large-scale routine forest inventories regarding the different dynamics behind the recruitment from the sapling layer into the commercial tree size layer. We focused on the density and occurrence of sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britt.) following harvesting, by looking at many factors on a wide range of spatial and temporal scales using models. The results suggest that the variation in density and probability of occurrence is best explained by the intensity of silvicultural treatment, by the merchantable stem density in each plot, and by the proportion of merchantable basal area of each group of species. The number of recruits of sugar maple and yellow birch stems tend be higher when time since last treatment increases, when mid to low levels of silvicultural treatment intensity were implemented, and within plots having intermediate levels of merchantable stem density. Lastly, our modeling efforts suggest that the probability of occurrence and density of recruitment of both species tend to increase while its share of merchantable basal area increases. Key words: tolerant hardwoods, generalized linear mixed model (GLMM), Acadian forest, recruitment modeling, zero-inflated. Le passage de gaules a tiges marchandes dans les peuplements forestiers est un processus tres complexe qui le rend difficile a comprendre et a prevoir. La dynamique du recrutement dans la region forestiere acadienne du Nouveau-Brunswick n'est pas bien connue ni documentee. Notre objectif etait de tirer des renseignements a partir des inventaires forestiers a grande echelle realises de facon routiniere en ce qui concerne la dynamique de passage des gaules a arbres de dimension commerciale. Nous nous interessons particulierement a la densite et l'occurrence du recrutement d'erables a sucre (Acer saccharum Marsh.) et de bouleaux jaunes (Betula alleghaniensis Britt.) apres la coupe en examinant de nombreux facteurs sur une large gamme d'echelles spatiales et temporelles a l'aide de modeles. Les resultats des meilleurs modeles indiquent que la densite et la probabilite d'occurrence sont reliees a l'intensite du traitement sylvicole, a la densite des tiges marchandes dans chaque parcelle et a la proportion de la surface terriere marchande occupee par chaque groupe d'especes. Le nombre de recrues d'erable a sucre et de bouleau jaune a tendance a etre plus eleve lorsque le temps ecoule depuis le dernier traitement augmente, lorsque les traitements sylvicoles sont d'intensite faible a moyenne, et dans les parcelles ayant un niveau intermediaire de densite de tiges marchandes. Finalement, nos efforts de modelisation indiquent que la probabilite d'occurrence et la densite de recrutement des deux especes ont tendance a augmenter lorsque leur proportion de la surface terriere marchande augmente. [Traduit par la Redaction] Mots-cles : feuillus tolerants a l'ombre, modele lineaire mixte generalise (GLMM), foret acadienne, modelisation du recrutement, exces de zeros., 1. Introduction Forests are continuously evolving dynamic biological systems that are influenced by a multitude of environmental, ecological, and silvicultural factors (Messier et al. 2019). A key concept at the [...]

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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. [...]

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 [...]

In tolerant hardwood forests of eastern North America, multiple-aged silvicultural systems rely on advanced regeneration to restock the forests. Evaluation of the long-term influence of advanced regeneration on the mature stand is critical for improving management practices. We used a retrospective approach to evaluate the influence of advanced regeneration present at the time of harvest on the current (2012) stand structure and the quality of the growing stock. The study was carried out in partially harvested stands in northwestern New Brunswick, Canada. Trees were sampled from stands with varying degrees of harvest intensities, times since harvest, and site characteristics. Pre-existing advanced regeneration contributed the bulk of trees in the 10-19 cm diameter class across the stands. In stands with low-intensity harvest, the overstory was dominated by sugar maple (Acer saccharum Marsh.) that originated as advanced regeneration. In stands with high-intensity harvest, however, yellow birch (Betula alleghaniensis Britt.) pre-existing advanced regeneration dominated the overstory. The probability of sugar maple and yellow birch being acceptable growing stock peaked at a diameter at breast height (DBH) of about 30-40 cm, while other species combined peaked at a DBH of around 20-25 cm. Our results suggest that harvest intensities based on the dominant advanced regeneration composition and harvesting systems that minimize the risk of physical damage to advanced regeneration are required to achieve partial harvesting objectives. Key words: northern hardwoods, partial harvest, mortality rate, advanced regeneration, stand structure. Dans les forets de feuillus tolerants a l'ombre de l'est de l'Amerique du Nord, l'efficacite des systemes sylvicoles inequiennes repose sur la regeneration preetablie pour repeupler les forets. L'evaluation a long terme de l'influence de la regeneration preetablie sur le peuplement mature est importante pour ameliorer les pratiques d'amenagement. Nous avons utilise une approche retrospective pour evaluer l'influence de la regeneration preetablie presente au moment de la coupe sur la structure actuelle (2012) du peuplement et sur la qualite des arbres sur pied. Cette etude a ete realisee dans des peuplements partiellement coupes du nord-ouest du Nouveau-Brunswick, au Canada. Des arbres ont ete echantillonnes dans des peuplements presentant divers degres d'intensite de coupe, de temps depuis la coupe et de caracteristiques de la station. La majorite des arbres de la classe de diametre de 10 a 19 cm des peuplements provenaient de la regeneration preetablie. Dans les peuplements ayant subi une faible intensite de coupe, le couvert dominant etait surtout compose d'erables a sucre (Acer saccharum Marsh.) provenant de la regeneration preetablie. Toutefois, dans les peuplements ayant subi une forte intensite de coupe, des bouleaux jaunes (Betula alleghaniensis Britt.) provenant de la regeneration preetablie composaient surtout le couvert dominant. La probabilite que les erables a sucre et les bouleaux jaunes forment un effectif de qualite acceptable etait maximale lorsqu'ils avaient atteint un DHP de 30 a 40 cm comparativement a un DHP d'environ 20 a 25 cm pour l'ensemble des autres especes. Nos resultats indiquent qu'il faut ajuster l'intensite de la coupe selon la composition dominante de la regeneration preetablie et adopter des systemes de coupe qui minimisent les risques d'endommager la regeneration preetablie pour atteindre les objectifs d'une coupe partielle. [Traduit par la Redaction] Mots-cles: feuillus nordiques, coupe partielle, taux de mortalite, regeneration preetablie, structure du peuplement., 1. Introduction Northern hardwood forests cover an extensive landscape in eastern North America (Seymour et al. 2002) and represent an important resource in the region (USDA Forest Service 2001). Partial [...]

The emergence of mobile laser scanning (MLS) systems that use simultaneous localization and mapping (SLAM) technology to map their environment opens up new opportunities for characterizing forest structure. The speed and accuracy of data acquisition makes them particularly adapted to operational inventories. MLS also shows great potential for estimating inventory attributes that are difficult to measure in the field, such as wood volume or crown dimensions. Hardwood species represent a significant challenge for wood volume estimation compared to softwoods because a substantial portion of the volume is included in the crown, making them more prone to allometric bias and more complex to model. This study assessed the potential of MLS data to estimate tree structural attributes in a temperate hardwood stand: height, crown dimensions, diameter at breast height (DBH), and merchantable wood volume. Merchantable wood volume estimates were evaluated to the third branching order using the quantitative structural modeling (QSM) approach. Destructive field measurements and terrestrial laser scanning (TLS) data of 26 hardwood trees were used as reference to quantify errors on wood volume and inventory attribute estimations from MLS data. Results reveal that SLAM-based MLS systems provided accurate estimates of tree height (RMSE = 0.42 m (1.78%), R2 = 0.93), crown projected area (RMSE = 3.23 m2 (5.75%), R2 = 0.99), crown volume (RMSE = 71.4 m3 (23.38%), R2 = 0.99), DBH (RMSE = 1.21 cm (3.07%), R2 = 0.99), and merchantable wood volume (RMSE = 0.39 m3 (18.57%), R2 = 0.95), when compared to TLS. They also estimated operational merchantable volume with good accuracy (RMSE = 0.42 m3 (21.82%), R2 = 0.94) compared to destructive measurements. Finally, the merchantable stem volume derived from MLS data was estimated with high accuracy compared to TLS (RMSE = 0.11 m3 (8.32%), R2 = 0.96) and regional stem taper models (RMSE = 0.16 m3 (14.7%), R2 = 0.93). We expect our results would provide a better understanding of the potential of SLAM-based MLS systems to support in-situ forest inventory. [ABSTRACT FROM AUTHOR]

Abstract: A midrotation commercial thinning experiment conducted in two independent spruce plantations compared several tree selection strategies as both early (age 19 or 24 years) single and double (again at [...]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• High harvest intensity reduced American beech sapling density at well-drained sites. • Overstory tree mortality and depth-to-water had a positive effect on sugar maple sapling density. • Depth-to-water changed the magnitude to which tree species diversity respond to harvest intensity. • Implications for timber production and species diversity management objectives. The northern hardwoods forest ecosystem of eastern North America provides a wealth of products and services to human society. These forests have been managed under partial harvesting treatments to meet wood production objectives of desired species while maintaining or increasing structural and compositional heterogeneity. Few studies have examined how disturbance and site factors interactions may influence sapling dynamics and species diversity in northern hardwood forests. We used a retrospective approach to examine the impacts of disturbance and site factors on sapling (trees > 130 cm in height and <10.0 cm dbh) dynamics and species diversity across 37 stands with time since harvest ranging from 6 to 20 years. We assessed American beech (Fagus grandifolia Ehrh), sugar maple (Acer saccharum Marsh.), red maple (Acer rubrum L.) and yellow birch (Betula alleghaniensis Britt.) saplings density as functions of disturbance intensity (% basal area cut and overstory tree mortality rate (%)) and site factors. We also examined the effects of disturbance, site factors and relative density of American beech, red maple, sugar maple and yellow birch saplings on species diversity at the sapling layer. The density of American beech saplings decreased significantly with harvest intensity. High harvest intensity significantly reduced American beech sapling density at high depth-to-water sites. However, the densities of red maple and yellow birch saplings increased significantly with increasing harvest intensity. We found that high harvest intensities had less negative effect on sugar maple sapling density compared with American beech. Our results also showed that tree species diversity (Shannon diversity index (H ′)) increased with harvest intensity up to about 75% and then declined. However, depth-to-water (DTW) significantly changed the magnitude of tree species diversity response to harvest intensity. Red maple appeared to have contributed more to species diversity than the other hardwood tree species. Given that sugar maple sapling density was generally higher than American beech at high harvest intensities in this study, management regimes that promote mid-tolerant species in American beech-presence stands may eventually benefit sugar maple more than American beech in these forest types. These strategies may also increase species diversity and improve forest ecosystems functions and services. [ABSTRACT FROM AUTHOR]

In northern hardwood forests, light availability is considered to be the main factor limiting seedling and sapling growth. However, field measurement of this variable is time-consuming. To address this issue, we developed random forest regression models to estimate canopy cover from a Landsat 8 OLI image of a northern hardwood forest in northwestern New Brunswick, Canada. We then assessed the accuracy of model predictions with a canopy height model (CHM) derived from LiDAR data. We selected 2 threshold heights (1.3 and 5 m) to distinguish the understory from the overstory and to determine the impact of the understory on top-of-canopy reflectance. Our results show that the understory influenced top-of-canopy reflectance and that a 1.3 m height threshold provided the most accurate estimation of canopy cover. In contrast with studies conducted in softwood stands, we found no evidence that the shortwave infrared (SWIR1) band decreased the influence of the understory on top-of-canopy reflectance. In northern hardwood forests, the estimation of canopy characteristics, such as canopy cover and leaf area index, should be focused on the green band, as it was least influenced by understory vegetation. [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]

UAV laser scanning (ULS) has the potential to support forest operations since it provides high-density data with flexible operational conditions. This study examined the use of ULS systems to estimate several tree attributes from an uneven-aged northern hardwood stand. We investigated: (1) the transferability of raster-based and bottom-up point cloud-based individual tree detection (ITD) algorithms to ULS data; and (2) automated approaches to the retrieval of tree-level (i.e., height, crown diameter (CD), DBH) and stand-level (i.e., tree count, basal area (BA), DBH-distribution) forest inventory attributes. These objectives were studied under leaf-on and leaf-off canopy conditions. Results achieved from ULS data were cross-compared with ALS and TLS to better understand the potential and challenges faced by different laser scanning systems and methodological approaches in hardwood forest environments. The best results that characterized individual trees from ULS data were achieved under leaf-off conditions using a point cloud-based bottom-up ITD. The latter outperformed the raster-based ITD, improving the accuracy of tree detection (from 50% to 71%), crown delineation (from R2 = 0.29 to R2 = 0.61), and prediction of tree DBH (from R2 = 0.36 to R2 = 0.67), when compared with values that were estimated from reference TLS data. Major improvements were observed for the detection of trees in the lower canopy layer (from 9% with raster-based ITD to 51% with point cloud-based ITD) and in the intermediate canopy layer (from 24% with raster-based ITD to 59% with point cloud-based ITD). Under leaf-on conditions, LiDAR data from aerial systems include substantial signal occlusion incurred by the upper canopy. Under these conditions, the raster-based ITD was unable to detect low-level canopy trees (from 5% to 15% of trees detected from lower and intermediate canopy layers, respectively), resulting in a tree detection rate of about 40% for both ULS and ALS data. The cylinder-fitting method used to estimate tree DBH under leaf-off conditions did not meet inventory standards when compared to TLS DBH, resulting in RMSE = 7.4 cm, Bias = 3.1 cm, and R2 = 0.75. Yet, it yielded more accurate estimates of the BA (+3.5%) and DBH-distribution of the stand than did allometric models −12.9%), when compared with in situ field measurements. Results suggest that the use of bottom-up ITD on high-density ULS data from leaf-off hardwood forest leads to promising results when estimating trees and stand attributes, which opens up new possibilities for supporting forest inventories and operations. [ABSTRACT FROM AUTHOR]

Sustainable forest management relies on practices ensuring vigorous post-harvest regeneration. Data on regeneration structure and composition are often collected through intensive field surveys. Remote sensing technologies (e.g., Light Detection and Ranging (LiDAR), satellite imagery) can cover a much larger spatial extent, but their ability to estimate regeneration characteristics is often challenged by the obstruction associated with canopy foliage. Here, we determined whether the integration of LiDAR and Sentinel-2 images can increase the accuracy of sapling density estimates and whether this accuracy decreased with canopy cover in the Acadian forest of New Brunswick, Canada. Using random forest regression, we compared the accuracy of three models (LiDAR and Sentinel-2 images alone or combined) to estimate sapling density for two species groups: saplings of all species or commercial species only. The integration of both sensors did not increase the accuracy of sapling density estimates, nor did it reduce the negative influence of canopy cover for either species group compared to LiDAR, but it increased the accuracy by approximately 15% relative to Sentinel-2 images. Under very high canopy cover, the accuracy of density estimates for all species combined was significantly lower with Sentinel-2 images only. We recommend using LiDAR and high-resolution satellite images acquired in the fall to obtain more accurate estimates of sapling density. [ABSTRACT FROM AUTHOR]

Digital aerial photogrammetric (DAP) techniques applied to unmanned aerial system (UAS) acquired imagery have the potential to offer timely and affordable data for monitoring and updating forest inventories. Development of methods for individual tree crown detection (ITCD) and delineation enables the development of individual tree-based, rather than stand based inventories, which are important for harvesting operations, biomass and carbon stock estimations, forest damage assessment, and forest monitoring in mixed species stands. To achieve these inventory goals, consistent and robust DAP estimates are required over time. Currently, the influence of seasonal changes in deciduous tree structure on the consistency of DAP point clouds, from which tree-based inventories can be derived, is unknown. In this study, we investigate the influence of the timing of DAP acquisition on ITCD accuracies and estimation of tree attributes for a deciduous-dominated forest stand in New Brunswick, Canada. UAS imagery was acquired five times between June and September 2017 over the same stand and consistently processed into DAP point clouds. Airborne laser scanning (ALS) data, acquired the same year, was used to reconstruct a digital terrain model (DTM) and served as a reference for UAS-DAP-based ITCD. Marker-controlled watershed segmentation (MCWS) was used to delineate individual tree crowns. Accuracy index percentages between 55% (July 25) and 77.1% (September 22) were achieved. Omission errors were found to be relatively high for the first three DAP acquisitions (June 7, July 5, and July 25) and decreased gradually thereafter. The commission error was relatively high on July 25. Point cloud metrics were found to be predominantly consistent over the 4-month period, however, estimated tree heights gradually decreased over time, suggesting a trade-off between ITCD accuracies and measured tree heights. Our findings provide insight into the potential influence of seasonality on DAP-ITCD approaches to derive individual tree inventories. [ABSTRACT FROM AUTHOR]

Digital aerial photogrammetry (DAP) and unmanned aerial systems (UAS) have emerged as synergistic technologies capable of enhancing forest inventory information. A known limitation of DAP technology is its ability to derive terrain surfaces in areas with moderate to high vegetation coverage. In this study, we sought to investigate the influence of flight acquisition timing on the accuracy and coverage of digital terrain models (DTM) in a low cover forest area in New Brunswick, Canada. To do so, a multi-temporal UAS-acquired DAP data set was used. Acquired imagery was photogrammetrically processed to produce high quality DAP point clouds, from which DTMs were derived. Individual DTMs were evaluated for error using an airborne laser scanning (ALS)-derived DTM as a reference. Unobstructed road areas were used to validate DAP DTM error. Generalized additive mixed models (GAMM) were generated to assess the significance of acquisition timing on mean vegetation cover, DTM error, and proportional DAP coverage. GAMM models for mean vegetation cover and DTM error were found to be significantly influenced by acquisition date. A best available terrain pixel (BATP) compositing exercise was conducted to generate a best possible UAS DAP-derived DTM and outline the importance of flight acquisition timing. The BATP DTM yielded a mean error of −0.01 m. This study helps to show that the timing of DAP acquisitions can influence the accuracy and coverage of DTMs in low cover vegetation areas. These findings provide insight to improve future data set quality and provide a means for managers to cost-effectively derive high accuracy terrain models post-management activity. [ABSTRACT FROM AUTHOR]

Variations in species composition, diameter and height distributions, and quality make the management of hardwood-dominated stands difficult, particularly when considering mechanized forest operations. This study aimed to develop and field test a tool designed to improve the feasibility of forest operations in heterogeneous forest stands in Eastern Canada. To address inherent stand variability, a multitreatment approach was selected using conventional forest inventory (one inventory plot per hectare) and a silvicultural treatment decision key as main inputs. The Excel-based spreadsheet in combination with an ArcGIS model, referred to as the Multitreatment Planning Tool (MTPT), allowed to build operational maps identifying the type and spatial extent of silvicultural treatments to be performed. Once uploaded to positioning systems in harvesting machines, the operators were provided guidance on the silvicultural treatment to be performed and the location of the suggested machine trails. Field results obtained from nine harvest blocks (over 300 ha treated in total) showed the potential of using the MTPT until more mature and higher resolution-enhanced inventories become mainstream. Machine operators and operational managers both appreciated the straightforward and flexible method. Additional testing and refinement of the method is necessary, particularly when considering re-entry scheduling. [ABSTRACT FROM AUTHOR]