Crown Width Research Articles

Assessing the effects of forest gaps on beech (Fagus orientalis L.) trees traits in the logged temperate broad-leaf forest

Silvicultural operations, including single-tree selection create gaps in forest canopies and these gaps impact on the forests structure. This study examines the influences of different harvest-created gap sizes on the oriental beech (Fagus orientalis L.) trees traits in temperate Hyrcanian forest, northern Iran. We selected three gap sizes (small, medium and large) and the adjacent unlogged closed canopies with five replications for each and measured some features of beech trees in overstory at the gaps-edge and closed stands. The results showed that gap size significantly influenced on crown length, crown surface area, crown ratio, bole, height/diameter (H/D) and minimum radius / maximum radius (CA) ratios of beech trees six years following gap creation (P < 0.05). Many beech tree traits in adjacent closed forest had no significant difference with gaps, except for crown asymmetric (P < 0.01).Statistically significant differences were observed in beech trees regarding to the clear bole, crown ratio, and CA among the four cardinal points of gaps. A significantly positive correlation was observed between crown ratio with crown length, crown width, crown area, crown volume, and DBH for trees. We found that crown ratio increased significantly with decreasing the bole and total height of beech trees. Results indicated that H/D ratio and total height, DBH, crown length and bole for beech trees were significantly negatively correlated. The CA ratio increased significantly with increasing the bole of trees. The crown radii of border beech trees towards gap center were significantly larger than those of forest-facing side of trees (P < 0.01). This study demonstrates that beech trees in overstory and at the edge of gaps respond differently to artificial gaps after 6 years of formation in oriental beech stand in temperate Hyrcanian forest.

Symmetry of crown widths in subjects with unilateral maxillary lateral incisor agenesis

The aim of this study was to compare mesiodistal width and symmetry of maxillary and mandibular teeth in subjects with and without unilateral maxillary lateral incisor agenesis. The study group consisted of 31patients with unilateral maxillary lateral incisor agenesis (19females, 12males, mean age: 16.55 ± 5.24years), and acontrol group of 31patients (19females, 12males, mean age: 16.58 ± 4.41years) without agenesis. Mesiodistal dimensions of all teeth except second molars were measured. Paired samples t‑test and Wilcoxon signed-rank test were used for intragroup comparisons. Independent samples t‑test was used for intergroup comparisons. In the study group, mesiodistal dimensions of maxillary canine, second premolar, first molar, mandibular second premolar and first molar teeth on the agenesis side were significantly smaller than on the contralateral side (p < 0.05). In the control group, no significant difference was seen in mesiodistal dimensions between right and left sides. In the study group, mesiodistal dimensions of all teeth on the lateral agenesis side were significantly smaller than on the control side (p < 0.05). On the side without lateral agenesis, all teeth except the maxillary and mandibular first molars and mandibular second premolar teeth were significantly smaller than on the control side (p < 0.05). Total mesiodistal dimensions of the maxillary teeth were significantly smaller on the lateral agenesis side than on the contralateral side (p = 0.001). Total tooth size of the study group was significantly smaller than for the control group (p < 0.05). Patients with unilateral maxillary lateral incisor agenesis might have asymmetries in tooth width and have smaller teeth than individuals without agenesis.

The Role of Green Infrastructure in Enhancing Microclimate Conditions: A Case Study of a Low-Rise Neighborhood in Abu Dhabi

Urban heat islands are characterized by the increased temperature in urban areas compared with the rural surroundings due to human-made interventions that replace natural lands with buildings and roads. This study focuses on the assessment and utilization of using local nature-based solutions such as trees, sensitive landscaping types and design strategies to enhance microclimate in neighborhood streets and the public realm in desert areas, taking Abu Dhabi as a case study. The research utilizes a design-based approach to propose landscaping and layouts of urban street trees in low-rise residential urban areas. In this study, two methods namely an on-site measurement using citizen science, and a numerical simulation model in the ENVI-met software are used. Site-measurements included the tree physical characteristics such as tree height, crown width (crown spread/diameter), and trunk height, and the use of technology (photography and the Fulcrum mobile application, Nikon Forestry pro Laser Rangefinder) and air temperature around trees. ENVI-met included four scenarios: 1—“no-vegetation”, 2—“grass-only”, 3—“existing conditions” and 4—“proposed landscape design”. Grass and three types of local street trees are used in the proposed scenarios including Ghaf, Poinciana, and Temple tree. In addition, a standard of 6 and 8 m spacing between each tree is applied to determine the effect of varying vegetation densities on the outdoor temperature. The combined results using citizen science and the model allowed the identification of particular urban tree species that show substantial cooling effects. This is the case of Poinciana trees, which decreased the air temperature up to 0.9 °C when spaced every six meters in pathways and open unshaded areas amongst alleys, improving the overall thermal conditions in neighborhoods of hot-arid landscapes.

Estimation of Genetic Parameters and Wood Yield Selection Index in a Clonal Trial of Korean Pine (Pinus koraiensis) in Northeastern China

In order to determine suitable traits for selecting high-wood-yield Korean pine materials, eleven morphological characteristics (tree height, basal diameter, diameter at breast height, diameter at 3 meter height, stem straightness degree, crown breadth, crown height, branch angle, branch number per node, bark thickness, and stem volume) were investigated in a 38-year-old Korean pine clonal trial at Naozhi orchard. A statistical approach combining variance and regression analysis was used to extract appropriate traits for selecting elite clones. Results of variance analysis showed significant difference in variance sources in most of the traits, except for the stem straightness degree, which had a p-value of 0.94. Moderate to high coefficients of variation and clonal repeatability ranged from 10.73% to 35.45% and from 0.06% to 0.78%, respectively. Strong significant correlations on the phenotypic and genotypic levels were observed between the straightness traits and tree volume, but crown breadth was weakly correlated to the volume. Four principal components retaining up to 80% of the total variation were extracted, and stem volume, basal diameter, diameter at breast height, diameter at 3 meter height, tree height, and crown height displayed high correlation to these components (r ranged from 0.76 to 0.98). Based on the Type III sum of squares, tree height, diameter at breast height, and branch number showed significant information to explain the clonal variability based on stem volume. Using the extracted characteristics as the selection index, six clones (PK105, PK59, PK104, PK36, PK28, and K101) displayed the highest Qi values, with a selection rate of 5% corresponding to the genetic gain of 42.96% in stem volume. This study provides beneficial information for the selection of multiple traits for genetically improved genotypes of Korean pine.

Measuring loblolly pine crowns with drone imagery through deep learning

In modeling forest stand growth and yield, crown width, a measure for stand density, is among the parameters that allows for estimating stand timber volumes. However, accurately measuring tree crown size in the field, in particular for mature trees, is challenging. This study demonstrated a novel method of applying machine learning algorithms to aerial imagery acquired by an unmanned aerial vehicle (UAV) to identify tree crowns and their widths in two loblolly pine plantations in eastern Texas, USA. An ortho mosaic image derived from UAV-captured aerial photos was acquired for each plantation (a young stand before canopy closure, a mature stand with a closed canopy). For each site, the images were split into two subsets: one for training and one for validation purposes. Three widely used object detection methods in deep learning, the Faster region-based convolutional neural network (Faster R-CNN), You Only Look Once version 3 (YOLOv3), and single shot detection (SSD), were applied to the training data, respectively. Each was used to train the model for performing crown recognition and crown extraction. Each model output was evaluated using an independent test data set. All three models were successful in detecting tree crowns with an accuracy greater than 93%, except the Faster R-CNN model that failed on the mature site. On the young site, the SSD model performed the best for crown extraction with a coefficient of determination (R2) of 0.92, followed by Faster R-CNN (0.88) and YOLOv3 (0.62). As to the mature site, the SSD model achieved a R2 as high as 0.94, follow by YOLOv3 (0.69). These deep leaning algorithms, in particular the SSD model, proved to be successfully in identifying tree crowns and estimating crown widths with satisfactory accuracy. For the purpose of forest inventory on loblolly pine plantations, using UAV-captured imagery paired with the SSD object detention application is a cost-effective alternative to traditional ground measurement.

Odontometric analysis using CBCT for sexual dimorphism in Egyptian-Fayoum population in case of normal occlusion

Objectives of this study was to evaluate odontometric linear measurements obtained from CBCT software including mesiodistal, tooth length dimensions and enamel thickness of the mandibular canine and mandibular first molar and arch measurements for sexual dimorphism in Egyptian population sample. Material and Methods: The study was carried out on 100 patients who visited the department of oral and maxillofacial radiology, Fayoum University for dental treatments. The study sample were grouped into two groups, group A (50 males) and group B (50 females) aged between 18-25 years old. The teeth which were selected for linear measurements using CBCT in the present study were 100 mandibular permanent canines (Lower 3) and 100 mandibular permanent 1st molar (Lower 6), for each group respectively. The linear measurements were taken on crown width and height, Enamel thickness, arch depth and width. Results: There was a highly significant difference between Male and Female for odontometric measurements of mandibular right and left canines and 1st molars including (CWL3, CLL3, CWL6 and CLL6) while enamel thickness measurements showed non-significant differences between males and females including (ETL3 at cusp tip, ETML6, ETDL6 and ETL6 at mesio-lingual cusp tip). Arch measurements including (ICW, IMW through fossa and IMW through contact) showed high significant differences between males and females. Conclusion: Odontometric parameters including mandibular canine, mandibular first molar crown width and length, inter-canine width and inter-molar width measurements based on CBCT imaging show highly significant gender difference. Thus, the parameters can be simple and reliable sexual dimorphism for medicolegal purpose.

Determination of the Thickness of the Safe Enamel for Laminate Veneer Preparation and Orthodontic Stripping by CBCT

The purpose of this study is to determine the thickness and limitation of the safe enamel for laminate veneers and orthodontic stripping applications. Enamel thickness (ET) was determined in detail for each tooth and also it was examined whether there was a relationship between the mesiodistal crown width of the teeth and the thickness of the enamel and whether there was a sexual dimorphism. CBCT records of 101 subjects (mean age: 20.88 ± 2.48 years) were examined. ET was measured both mesial and distal region of maxillary and mandibular incisors, canines, and premolars in different levels as cervical, middle, and incisal (occlusal) 1/3. Paired t-test, student t-test, Mann-Whitney U-test and Pearson correlation coefficients a simple linear regression analysis used for statistical analysis. ET of mandibular first premolars and canines was thicker at right side. Mesial enamel of maxillary first premolars, canines, lateral incisors and mandibular premolars and canines were significantly thicker than distal enamel. The mesial enamel of mandibular first premolars was significantly thicker in females. Also, males' maxillary laterals were significantly larger. All premolars had a correlation between mesio-distal crown widths and ET. Mesial and distal ET was unique for each one tooth at different levels. The relationship between ET and crown dimensions of all premolar teeth was also determined.

The Effect of Crown Dimensions on Stem Profile for Dahurian Larch, Korean Spruce, and Manchurian Fir in Northeast China

Crown architecture has long been evaluated for its impact on taper modeling. However, most of the research has focused on a limited number of crown dimensions. This study examined the effect of adding several crown dimensions in improving the diameter and volume estimates of Dahurian larch, Korean spruce, and Manchurian fir in northeast China. The crown dimensions included crown length, crown ratio, crown width, height to live crown base, diameter at the crown base, and crown shape. A well-known taper model of Clark et al. (1991) was fitted to the data of 276 trees from natural stands. To adjust the inherent autocorrelation in the data, we added a third-order continuous-time error structure in the model fit. Model fitting was carried out with the NLMIXED procedure (Non-linear Mixed Procedure), followed by the MODEL procedure of SAS using the generalized nonlinear least-squares method. Fit statistics and graphical assessments were used to evaluate the original and modified models. Above 98% of the total variance of d was explained by the models for all species. The addition of crown variables showed slight improvements for root mean square error (RMSE) values in the analyzed species. The RMSE plots indicated that the models with crown variables slightly improved the diameter and volume predictions for the species but only for the upper stem (&gt;50%–90%). The study demonstrated that crown dimensions influence the stem taper, but the original model of Clark et al. (1991) reasonably realized that effect.

Comparison between the mesiodistal crown dimensions of second primary molar with stainless steel crowns from different companies

Background: Due to the variations in tooth anatomy and size among different populations, this study aimed to compare the mesiodistal width of primary second molars in Iraqi children with the mesiodistal width of stainless-steel crowns from different companies. Materials and Methods: This cross-sectional study was conducted on 220 intact maxillary and mandibular primary second molars selected from boys and girls’ Iraqi children aged 8-9 years collected from different primary schools in Baghdad city. The mesiodistal dimensions of the selected teeth and the available maxillary and mandibular stainless-steel crowns from three different companies were measured by using a 3-D scanner, and then the whole measurements were calculated using 3 shape Ortho-analyzer software program. Results: Data were analyzed statistically via SPSS V 26 software and the results showed that there’s non-significant difference between the MD measurements of second primary molars between right and left sides, and high significant difference were recorded with higher mean values for boys than girls. When comparing the same mesiodistal measurement between molars with that of stainless-steel crowns, only limited sizes of stainless steel crowns were found to be fitted to the molars of Iraqi children. Conclusion: more studies need to be applied using other stainless steel crown companies to find the relation in the mesiodistal measurement of Iraqi populations.&#x0D; &#x0D;

A Genetic Linkage Map of BC2 Population Reveals QTL Associated with Plant Architecture Traits in Lagerstroemia

Plant architecture improvement is of great significance in influencing crop yield, harvesting efficiency and ornamental value, by changing the spatial structure of the canopy. However, the mechanism on plant architecture in woody plants is still unclear. In order to study the genetic control of plant architecture traits and promote marker-assisted selection (MAS), a genetic linkage map was constructed, and QTL mapping was performed. In this study, using 188 BC2 progenies as materials, a genetic map of Lagerstroemia was constructed using amplification fragment length polymorphisms (AFLP) and simple sequence repeats (SSR) markers, and the QTLs of four key plant architecture traits (plant height, crown width, primary lateral branch height and internode length) were analyzed. The genetic map contains 22 linkage groups, including 198 AFLP markers and 36 SSR markers. The total length of the genome covered by the map is 1272 cM, and the average distance between markers is 6.8 cM. Three QTLs related to plant height were located in LG1, LG4 and LG17 linkage groups, and the phenotypic variation rates were 32.36, 16.18 and 12.73%, respectively. A QTL related to crown width was located in LG1 linkage group, and the phenotypic variation rate was 18.07%. Two QTLs related to primary lateral branch height were located in the LG1 and LG7 linkage groups, and the phenotypic variation rates were 20.59 and 15.34%, respectively. Two QTLs related to internode length were located in the LG1 and LG20 linkage groups, and the phenotypic variation rates were 14.86 and 9.87%. The results provide a scientific basis for finely mapping genes of plant architecture traits and marker-assisted breeding in Lagerstroemia.

Urban Green Areas and Woody Plant Composition: Dwelling Space Quality Factor in the Klokočina Housing Estate

Abstract The environment of a city is influenced by global and local climate changes, pollution load from transport, industry and local heat sources. Green spaces as part of the urban green infrastructure fulfil multiple ecosystem services and improve the environmental and residential quality of a city. The level of positive effects of green spaces depends on their area, distribution within the city and the proportion of trees. The aim of the paper was to evaluate land cover structure in a selected segment of the housing estate Klokočina in Nitra, Slovakia. The evaluation focused on the share of biologically active and inactive surfaces, as well as the parameters of woody plant structure in green spaces. Green areas account for 58.70%, while built-up areas, parking lots and roads cover in total 41.30%. Biologically inactive anthropogenic horizontal and of building envelope areas represent 67.30%. Biologically active green areas represent 32.70%. The share of areas with tree crown overlap on horizontal areas is 20.82%, other areas are paved surfaces or grassland. We calculated the indices of the quality of green spaces from the individual categories of areas: proportional green area index (PGAI), effective green area index (EGAI) and tree shade index (TSI). The tree species composition consists of 36 deciduous and 11 coniferous tree species, and 20 shrub species. We evaluated the biometric traits of trees as the tree height, crown width, stem girth and tree vitality class (TVC). The correlations between tree traits were statistically tested with a significant result. In the group of biologically active areas of greenery, we propose to increase the proportion of trees, to establish more natural lawns and xerophyte flower beds. In the category of inactive areas, we propose the reconstruction of parking lots to grass paved surfaces.

Comparison of Lateral Tooth Volume and Morphology Between Buccally and Palatally Localised Unilateral Impacted Maxillary Canine Cases on Cone-Beam Computed Tomography.

The aim of this study was to compare the lateral tooth volume and morphology differences between buccally and palatally localized unilateral impacted maxillary canine (IMC) patients with volumetric and linear measurements on cone-beam computed tomography (CBCT) records. CBCT records of 48 individuals with 24-buccally and 24-palatally localized unilateral IMCs were included to the study. The patients comprised 34 females, 14 males, with a mean age of 17.71 (±SD 6.63 years). This split-mouth, retrospective case-control, study consisted of buccally and palatally IMC group, and each group was categorized into 2 sub-groups as impacted and erupted side. Lateral tooth volume, tooth length, mesiodistal-buccolingual crown widths, mesiodistal- buccolingual root widths at cemento-enamel junction (CEJ), at 4 mm apical to CEJ, at 8 mm apical to CEJ, mesiodistal crown-root angle, arch perimeter measurements were performed on CBCT images. The data were analyzed by factorial design repeated measures ANOVA. Bonferroni test was used for post-hoc analysis. The total volume, mesiodistal - buccolingual crown widths, buccolingual root width of lateral incisor at CEJ were statistically smaller in palatally IMC group. The lateral incisor's length, and arch perimeter were statistically shorter, mesiodistal, buccolingual root widths at 8 mm apical to CEJ, and crown-root angle of the lateral were narrower on impacted side than erupted side. The volume and crown widths of lateral incisor are effective in sagittal localization of IMC. The shorter length, narrower apical root morphology and mesially inclined crown-root angle of lateral incisor are noteworthy on impacted sides, regardless of sagittal position of IMC.

Laser-impact-induced splashing: an analysis of the splash crown evolution after Nd:YAG ns-pulse laser impact on a liquid tin pool

The splash created by intense laser pulse impact onto a liquid tin layer is studied experimentally using time-delayed stroboscopic shadowgraphy. An 8-ns infrared (1064 nm) laser pulse is focused onto a deep liquid tin pool. Various laser spot sizes (70, 120, and 130 upmum in diameter) and various laser pulse energies (ranging 2.5–30 mJ) are used, resulting in laser fluences of sim 10–1000 J/cm^2 inducing pronounced splashing. Specifically, we study the time evolution of the splash crown-width. The crown width expansion velocity is found to be linearly dependent on the laser energy, and independent of the focal spot size. A collapse of all crown width evolution data onto a single master curve confirms that the hydrodynamic evolution of our laser-impact-induced splash is equivalent to droplet-impact-induced splashing. Laser-impact splashing is particularly relevant, e.g. for high-brightness laser-assisted discharge-produced plasma and laser-produced plasma sources of extreme ultraviolet light for nanolithography.

Genetic Diversity on Phenotypes of Blumea balsamifera Germplasms

Objective The diversified phenotypic characteristics of Blumea balsamifera (L.) DC. germplasms were classified to facilitate the breeding program. Method Nine quantifiable and 13 quality phenotypic traits of the plant were used to describe the 159 germplasm samples of B. balsamifera. Genetic diversity, correlation, principal component, and cluster analyses were applied for the study. Result The genetic diversity on phenotypic characteristics of the collected germplasms was rich. Among the quantifiable traits, plant height had the highest genetic diversity index of 2.072; and, number of flowering branches topped the coefficient of variation at 32.76%. The crown breadth of the plants was found significantly correlated with the height, leaf width, petiole length, length of flower branch, and opening angle of flower branch (P＜0.01). On the quality traits, the highest genetic diversity index of 1.201 was the leaf shape. And, the color intensity of anthocyanin in leaf vein and that in main stem, as well as, those in leaf edge and petiole were significantly correlated. The cumulative contribution rate of the first eight principal components reached 64.32%. They included the factors associated with yield, color-intensity, leaf smoothness, leaf edge, leaf shape, leaf greenness, and flower-branch angle. Based on the phenotypic traits, the sum of squares deviations method using the genetic distance of 10 on the germplasms divided the 159 varieties into Group Ⅰ of 39 that accounted for 24.53% of the total, Group Ⅱ of 38 that accounted for 23.90% of the total, and Group Ⅲ of 82 that accounted for 51.57% of the total. Conclusion Genetically, the phenotypic characteristics of the 159 B. balsamifera germplasms appeared richly diversified. The leaf width of the plants could be the most outstanding trait for breeding selection of high-yield B. balsamifera varieties.

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The paper deals with the sex and age composition of the population of primitive bison from the Upper Palaeolithic site of Anetovka II. This evidence is used to shed light on the hunting strategy of the site inhabitants The studied M3 sample consists of specimens. The minimum number of individuals is of which are identified as semi adult as adult as mature and as old. The studied sample looks homogeneous in every respect. The most variable characteristics of М3 are tooth crown width and talonid length while tooth crown length seems the least variable. The length to width ratio of teeth crowns suggests that many females were removed from the population. Hunting was focused on semi adult and young adult animals. This hunting strategy had an impact on the population size of the primitive bison. Animals that did not reach the desired body weight young were obtained less often which is indicative of selectivity of hunting.

Nitrogen addition affects eco-physiological interactions between two tree species dominating in subtropical forests

Nitrogen (N) deposition affects plant growth and interspecific interaction. This study aimed to explore the effect of N deposition on the growth and eco-physiological interactions between two tree species dominating in subtropical forests. A greenhouse experiment was conducted for 6 months in which the conifer Cunninghamia lanceolata and the broadleaved Phoebe chekiangensis were grown in monocultures and in a mixture under two levels of N addition: 0 and 45 kg ha−1 yr−1. The plant growth, root architecture, biomass distribution, element contents in plants and soil, and photosynthetic physiology were determined. The height and crown width of both seedlings tended to be higher in the mixture than in the monoculture when grown without N addition. P. chekiangensis was superior to C. lanceolata in resource acquisition and showed a greater net photosynthetic rate, plant height, crown width, total biomass, and belowground biomass distribution. In the mixture, N addition increased the net photosynthetic rate and decreased the height, ground diameter, and crown width of both species. Belowground biomass distribution was decreased in C. lanceolata but increased in P. chekiangensis under N addition. The P contents in both seedlings were higher in the mixture than in monocultures. Results showed N addition aggravated the competition and weakened the growth of both species in the mixture, largely determined by the competition for resources through the changing root architecture and biomass allocation. Our results provide new insights into the mechanisms of interspecific interaction in response to increasing N deposition in silvicultural practice.

Influence of strata-specific forest structural features on the regeneration of the evergreen broad-leaved forest in Tianmu Mountain.

The vertical stratification of the stand may lead to a high heterogeneity of microenvironment in the forest, which further influences the understory regeneration and succession of the forest. Most relevant previous studies emphasized the overall effects of the Whole-stand structural characteristics on understory regeneration, while the strata-specific impacts of the overstory should be explored especially for those forests with a complicated combination of overstory species and heights. In this study, a subtropical evergreen broad-leaved forest in Tianmu Mountain of China was intensively investigated within 25 plots of 20 m × 20 m, aiming to find out how significant the stratified overstory (trees with diameter at breast height (DBH) ≥ 5 cm) structure and non-structure characteristics impact the understory (trees with DBH < 5 cm) regeneration. Regardless of species composition, the studied overstory was evenly divided into three strata (i.e. upper, middle and lower strata) according to their heights. Redundancy analysis was applied to explore both overall and strata-specific forest structure on characteristics (height, DBH, species diversity, and density) of tree regeneration. We found that the overall effect of the whole overstory on the forest regeneration depended mostly on diameter at breast height (DBH), tree species richness index and crown width. However, when analyzing with the strata-specific characteristics, the most pronounced impact factors for the regeneration were tree height of the upper and lower forest strata, tree species richness index and crown width of the middle and lower forest strata, and the competition index impact of the lower forest stratum. Among the three strata, the lower forest stratum showed the most significant impact with three characteristics on the understory regeneration, which may be attributed to their direct competition within the overlapping near-ground niches. Among the new generations, seedlings and saplings were more sensitive to the overstory structural characteristics than young trees. Our results suggest that the overstory showed strata-specific effects on the understory regeneration of evergreen broad-leaved forests in subtropical China, which provides theoretical basis for strata-specific forest management in similar forests.

Effects of Aspen and Spruce Density on Size and Number of Lower Branches 20 Years after Thinning of Two Boreal Mixedwood Stands

This study examined branch diameter, number of whorls, and number of branches in the lower 2 m of the stems of white spruce growing in pure stands and in mixture with a range of densities of trembling aspen. Data were collected from two study sites located north of Big River Saskatchewan, which were regenerated following clearcutting in 1992 and thinned in 1996 to five aspen densities and two spruce densities. Results show significant decreases in spruce diameter at breast height (DBH), height, live crown ratio, maximum branch diameter in the lower 2 m, average branch diameter in the whorl closest to 1 m, and increases in tree slenderness with increases in aspen density. Increasing spruce density reduced the number of live branches and number of live branch whorls in the lower 2 m. Maximum branch diameter in the whorl closest to 1 m was influenced by both aspen and spruce density, with a significant interaction term resulting from effects of intraspecific competition being evident for aspen densities of 1500 stems ha−1 or lower. DBH and slenderness explained more than 49% of the variation in spruce crown width, maximum branch diameter in the lower 2 m, maximum live branch diameter in the whorl closest to 1 m, and average live branch diameter in the whorl closest to 1 m. DBH explained more variation in crown width and branch diameter than slenderness. This study demonstrates that growing spruce in mixture with aspen can lead to reductions in branch size and that early thinning to low aspen densities could lead to increases in size of knots and associated reductions in wood quality, particularly when spruce densities are low.

Experimental study on line-contact elastohydrodynamic grease lubrication properties of surface-textured rollers

Purpose This paper aims to study line-contact elastohydrodynamic grease lubrication properties of surface-textured rollers as well as the effect of different crown widths (dw) on oil film thickness under textured conditions. Design/methodology/approach The laser processing method was used to make the micro-texture on the surface of GCr15 steel rollers; lithium grease was used as the lubricant, and line-contact elastohydrodynamic grease lubrication experiments under pure sliding conditions were performed on light interference elastohydrodynamic-lubricated experimental table. Findings The results show that the line-contact elastohydrodynamic grease lubrication is closely related to the textured crown width of steel rollers. At low speeds and light loads, texturing has an inevitable inhibitory effect on the formation of the lubricating oil film, and the smaller the width of the crown area, the more obvious the inhibitory effect, which is not conducive to the improvement of the lubrication condition. At high speeds and high loads, the textured roller with dw = 1 mm has the largest oil film thickness and shows better lubrication performance. Originality/value At present, there is little research on the surface texture of line-contact friction pairs. This work explores the effect of different textured crown width on the lubricating properties of line-contact elastohydrodynamic grease lubrication by experiment. It provides a new theoretical basis for the subsequent practical application of surface texture technology.

Individual Tree Crown Segmentation Directly from UAV-Borne LiDAR Data Using the PointNet of Deep Learning

Accurate individual tree crown (ITC) segmentation from scanned point clouds is a fundamental task in forest biomass monitoring and forest ecology management. Light detection and ranging (LiDAR) as a mainstream tool for forest survey is advancing the pattern of forest data acquisition. In this study, we performed a novel deep learning framework directly processing the forest point clouds belonging to the four forest types (i.e., the nursery base, the monastery garden, the mixed forest, and the defoliated forest) to realize the ITC segmentation. The specific steps of our approach were as follows: first, a voxelization strategy was conducted to subdivide the collected point clouds with various tree species from various forest types into many voxels. These voxels containing point clouds were taken as training samples for the PointNet deep learning framework to identify the tree crowns at the voxel scale. Second, based on the initial segmentation results, we used the height-related gradient information to accurately depict the boundaries of each tree crown. Meanwhile, the retrieved tree crown breadths of individual trees were compared with field measurements to verify the effectiveness of our approach. Among the four forest types, our results revealed the best performance for the nursery base (tree crown detection rate r = 0.90; crown breadth estimation R2 &gt; 0.94 and root mean squared error (RMSE) &lt; 0.2m). A sound performance was also achieved for the monastery garden and mixed forest, which had complex forest structures, complicated intersections of branches and different building types, with r = 0.85, R2 &gt; 0.88 and RMSE &lt; 0.6 m for the monastery garden and r = 0.80, R2 &gt; 0.85 and RMSE &lt; 0.8 m for the mixed forest. For the fourth forest plot type with the distribution of crown defoliation across the woodland, we achieved the performance with r = 0.82, R2 &gt; 0.79 and RMSE &lt; 0.7 m. Our method presents a robust framework inspired by the deep learning technology and computer graphics theory that solves the ITC segmentation problem and retrieves forest parameters under various forest conditions.