Crown Size Research Articles

Forest stand and canopy development unaltered by 12years of CO2 enrichment.

Canopy structure—the size and distribution of tree crowns and the spatial and temporal distribution of leaves within them—exerts dominant control over primary productivity, transpiration and energy exchange. Stand structure—the spatial arrangement of trees in the forest (height, basal area and spacing)—has a strong influence on forest growth, allocation and resource use. Forest response to elevated atmospheric CO2 is likely to be dependent on the canopy and stand structure. Here, we investigated elevated CO2 effects on the forest structure of a Liquidambar styraciflua L. stand in a free-air CO2 enrichment experiment, considering leaves, tree crowns, forest canopy and stand structure. During the 12-year experiment, the trees increased in height by 5 m and basal area increased by 37%. Basal area distribution among trees shifted from a relatively narrow distribution to a much broader one, but there was little evidence of a CO2 effect on height growth or basal area distribution. The differentiation into crown classes over time led to an increase in the number of unproductive intermediate and suppressed trees and to a greater concentration of stand basal area in the largest trees. A whole-tree harvest at the end of the experiment permitted detailed analysis of canopy structure. There was little effect of CO2 enrichment on the relative leaf area distribution within tree crowns and there was little change from 1998 to 2009. Leaf characteristics (leaf mass per unit area and nitrogen content) varied with crown depth; any effects of elevated CO2 were much smaller than the variation within the crown and were consistent throughout the crown. In this young, even-aged, monoculture plantation forest, there was little evidence that elevated CO2 accelerated tree and stand development, and there were remarkably small changes in canopy structure. Questions remain as to whether a more diverse, mixed species forest would respond similarly.

Use of LiDAR technology for quantification and design of park, garden and urban tree structure

It is essential to know the parameters of trees making up a city’s green infrastructure for evaluating the functions of its ecosystems and ecosystem services being provided. Traditional methods of creating tree inventories proved to be slow and costly, while not being able to provide sufficient data for ecosystem services mapping. Laser scanning methods can be used to obtain accurate measurements of tree dimensions, crown size measurements and overall tree structure details. They can be used to analyze large forested areas at a fraction of the time needed to measure each tree individually by hand. The goal of this study was to conduct an approbation of ground-based 3D scanning methods and test their capabilities of obtaining tree parameters for use in green infrastructure inventories. The research is based on scans and analysis of sites of the green fund of Moscow, Russia, during the vegetation periods of the years 2019-2020. LiDAR scanning allows automatic georeferencing of data and creates detailed 3D geometry of tree objects. This enables previously impossible measurements of tree dimensions to be taken and calculated: aboveground biomass and crown area. Such methods can automate the process of creating tree inventory databases, while eliminating subjective bias when recording measurements.

CROWN MORPHOMETRY FOR TWO VALUABLE TIMBER SPECIES FROM MIOMBO WOODLAND IN MOZAMBIQUE

Pterocarpus angolensis DC and Bobgunnia madagascariensis (Desv.) J. H. Kirkbr. & Wiersema are two hardwood species found in Miombo woodland. Crown size, being closely related to the photosynthetic capacity of a tree, is an important parameter in studies of the growth of individual trees. In this sense, the present study aimed to study the morphometric relationships of P. angolensis and B. madagascariensis as a resource to describe the morphometric features of these species. Data were sampled in 60 rectangular plots of 20 x 50 m, systematically distributed within the forest. In each plot, the diameter at breast height (DBH), height (h), crown insertion point (cih) and four crown radii of all trees with DBH ≥ 10 cm were measured. Results indicated that crown diameter and crown length of P. angolensis grow as DBH and height increase, the larger the crown, the greater the trees dimensions; as for B. madagascariensis, crown features have shown low correlation when considering DBH. It was concluded that crown features influence on tree growth and are important measures of description and planning of silvicultural activities to be performed in natural forests. The results are of interest to forest managers since they make decisions about silvicultural operations. Keywords: crown dimensions; prediction models; umbila; pau-ferro; forest management.

Competition Effects on Growth and Crown Dimensions of Shortleaf and Loblolly Pine in Mature, Natural-Origin, Pine–Hardwood Mixtures of the Upper West Gulf Coastal Plain of Arkansas, USA: A Neighborhood Analysis

The need for a comprehensive and mechanistic understanding of competition has never been more important as plants adapt to a changing environment and as forest management evolves to focus on maintaining and enhancing complexity. With the recent decline in shortleaf pine (Pinus echinata Mill.) land area, it is critical to determine the effects of competition on shortleaf pine and its performance against loblolly pine (Pinus taeda L.), the preferred planted replacement. We evaluate differences in shortleaf and loblolly pine 10 year mean basal area increment (BAI) and crown dimensions across a gradient of neighborhoods. Linear mixed-effects regression models were developed using BAI and several crown metrics as responses and crowding, competitor species abundance and identity, and initial size and species identity of focal tree as predictors. Crowding of focal trees negatively impacted BAI and crown size (p < 0.001, respectively). Although loblolly pine had three times higher BAI as compared to shortleaf pine within similar neighborhoods, BAI was variable, and the crowding effect did not differ between shortleaf and loblolly pine (p ranged from 0.51–0.99). Competitive impacts on focal trees did not differ by competitor identity (p ranged from 0.07–0.70). Distance-independent competition indices better explained the variation in BAI and horizontal crown metrics, while distance-dependent size ratios were more effective at evaluating vertical crown metrics. These findings highlight shortleaf pine competitive potential in mature, natural-origin stands and provide support for the restoration of pine–hardwood and hardwood–pine stratified mixtures as well as management of shortleaf pine at long rotations.

The Prevalence and Morphology of Supernumerary Teeth in Children With Nonsyndromic Cleft Lip and Palate

Cleft lip with or without cleft palate (CL/P) is congenital deformity associated with hyperdontia. To determine the prevalence and characteristics of supernumerary teeth in patients with CL/P. Retrospective descriptive and correlation clinical study. One hundred thirteen children with cleft (age ranged 9.3-19.2; 67 males and 46 females) treated in Clinic of Congenital Facial Deformities Medical University of Lublin were included in the study. Records evaluation was conducted regarding age, gender, cleft type (Q36, Q37-International Classification of Diseases 10th revision), cleft side, and incidence of supernumeraries. In all supernumerary teeth, size, shape, and developmental degree were analyzed and correlation between the incidence of hyperdontia with different variables was checked. Correlations were detected using chi-square and the Yates correction. The majority of the examined group were males-59.29% with Q37 (67.26%) and the cleft on the left side (62.83%). Hyperdontia was noted in 26.55%. Only upper lateral incisors were affected. They usually had atypical shape (56.67%), reduced size (83.33%), and delayed development (56.67%). The prevalence of supernumerary permanent teeth in patients with cleft was higher than in the general population. Anomaly was more frequent in male patients and occurred mainly on the cleft side. The severity of the cleft did not influenced the frequency of supernumerary teeth, their shape, size, and developmental degree. Supernumerary teeth were characterized by reduced crown size, abnormal structure, incorrect inclination, and delayed development phase.

FEATURES OF DIAGNOSIS AND TREATMENT OF PATIENTS WITH REDUCED BITE HEIGHT

Aesthetic and hygienic requirements of patients with reduced bite height necessitate the use of modern orthopedic constructions. The main cause of this disease is pathological abrasion of the hard tissues of the teeth, the prevalence of which ranges from 4 to 57% at a young age, reaches 91% in the elderly and is accompanied by both morphological and functional disorders of the dental-maxillary system.
 The aim of the research. Research the features of the diagnosis of dental status in patients with reduced bite height and timing of their treatment.
 Materials and methods of research. Determine the degree of reduction in the height of the bite in persons with pathological abrasion of the hard tissues of the teeth of varying severity compared with the norm and features of its recovery.
 Research results and their discussion. In order to prepare for orthopedic treatment, we determined the height of the bite in 123 patients. Accordingly, they were divided into three groups. Group 1 consisted of 32 patients with included dentition defects with reduced bite height up to 2 mm (n = 32), group 2 - examined with included dentition defects with reduced bite height 2-4 mm (n = 31), group 3 are patients with included dentition defects with reduced bite height of 4-6 mm (n = 30). All persons of the main groups belonged to the second and third age groups according to the WHO, aged 35-55 years, who required orthopedic treatment with fixed constructions of dentures.
 The control group (n = 30) are young people who belonged to the 1st WHO age group (age - 18-34 years) with intact dentition, without concomitant somatic and dental pathology, were examined in one visit.
 In order to study the degree of dependence of bite height reduction between incisors, canines, premolars and molars, we studied 30 gypsum models of supergypsum of the upper and lower jaws without reduction of bite height and 93 - with varying degrees of pathological abrasion of tooth hard tissues of all examined people.
 The models were fixed in a standard articulator in the central occlusion position. Using a caliper, we determined the size of the tooth crowns and compared it with standard sizes.
 In this research, we found the dependence of the degree of reduction in the height of the bite in the area of molars - premolars - incisors and canines in the ratio 1: 1,25: 1,5.
 We performed orthopedic treatment and subsequent clinical observation for each patient for 6 months, examining their condition after fixation of prostheses in 1 week and in 1, 3 and 6 months after orthopedic treatment.
 Based on the diagnosis of bite height reduction, we provided practical recommendations on the terms of use of fixed pharmacy bridges prostheses according to the degree of bite height reduction in the examined people.
 In the case of patients with a decrease in bite height by 3-4 mm, permanent orthopedic treatment is possible in 90 days after fixation of temporary orthopedic constructions in the oral cavity, and in patients with a reduced bite height of more than 4 mm - in 180 days.
 Conclusions. According to the results of the research, a high efficiency of determining the degree of reduction in bite height in preparing patients for permanent orthopedic treatment depending on the severity of the pathological process.

Identification of the most preferred topographic elevation characteristics for the wild olive trees in Al-Baha Region, Saudi Arabia

The aim of this research was to identify the topographical elevation characteristics most preferred by wild olive trees in the Al-Baha region. This study successfully identified the elevation preferred by wild olives. The results show that the majority (81.6%) of wild olives are located at an elevation range of 1,750–2,500m. However, in the Al-Mandaq sub-region, many wild olive trees can also be found at a lower elevation of 1,250–1,500m, while wild olive presence at a higher elevation of 2000–2,500m can be found in the Al-Baha sub-region. It was observed that at a lower elevation of 1500–1750m, most wild olive crown sizes are small, indicating that the wild olive prefers a higher elevation to grow well. These findings can be regarded as theoretically indicating landforms suitable for olive plantation. As a basis for the suitability of olive plantation sites, these topographical characteristics factors are the essential prerequisites. However, it is obvious that site suitability is subject to the temporal dynamics of environmental variables.

Effects of Canopy and Multi-Epoch Observations on Single-Point Positioning Errors of a GNSS in Coniferous and Broadleaved Forests

Global navigation satellite systems (GNSS) can quickly, efficiently, and accurately provide precise coordinates of points, lines, and surface elements, plus complete surveys and determine various boundary lines in forest investigations and management. The system has become a powerful tool for dynamic forest resource investigations and monitoring. GNSS technology plays a unique and important role in estimating timber volume, calculating timber cutting area, and determining the location of virgin forest roads and individual trees in forests. In this study, we quantitatively analyzed the influence of crown size and observation time on the single-point positioning accuracy of GNSS receivers for different forest types. The GNSS located single points for different forest types and crown sizes, enabling the collection of data. The locating time for each tree was more than 10 min. Statistical methods were used to analyze the positioning accuracy of multi-epoch data, and a model was developed to estimate the maximum positioning errors under different forest conditions in a certain positioning time. The results showed that for a continuous positioning time of approximately 10 min, the maximum positioning accuracies in coniferous and broadleaf forests were obtained, which were 12.13 and 15.11 m, respectively. The size of a single canopy had no obvious influence on the single-point positioning error of the GNSS, and canopy density was proven to be closely related to the positioning accuracy of a GNSS. The determination coefficients (R2) in the regression analysis of the general model, coniferous forest model, and broadleaved forest model that were developed in this study were 0.579, 0.701, and 0.544, respectively. These results indicated that the model could effectively predict the maximum positioning error in a certain period of time under different forest types and crown conditions at middle altitudes, which has important guiding significance for forest resource inventories and precise forest management.

Evaluating the Endophytic Activities of Beauveria bassiana on the Physiology, Growth, and Antioxidant Activities of Extracts of Lettuce (Lactuca sativa L.).

Endophytic entomopathogens have growth promoting, nutrient fortifying, and anti-insect properties that could improve the yield and quality of lettuce (Lactuca sativa L.). Lactuca sativa is a vegetable crop with high demand; however, it is susceptible to aphid infestations. This study’s objectives were to assess the pathogenicity of Beauveria bassiana (strain: SM3) (Bals.) Vuil. (Hypocreales) against Myzus persicae Sulzer, tissue colonization of lettuce by conidia of B. bassiana, as well as the effects of fungal inoculation on growth, tissue nutrient content, and proximate composition of the lettuce plants. Furthermore, the involvement of tissue nutrients in mediating the influence of endophytic fungus on the plant traits was examined. Insects and plants were exposed to four fungal conidial concentrations: 0, 1 × 106, 1 × 107 and 1 × 108 conidia mL−1 in an anti-insect bioassay and a greenhouse experiment, respectively. The B. bassiana strain was pathogenic against M. persicae, inducing mean insect mortality of 78% at the highest concentration (1 × 108 conidia mL−1). The B. bassiana endophytically colonized up to 76% of plants exposed to 1 × 108 conidia mL−1. Crown size and plant height varied significantly among treatments. However, the plant fresh and dry weights and nutrient elements N, P, K, Ca, and Mg did not vary significantly among treatments. Among the plant macronutrients assessed, only tissue carbon content was significantly (p < 0.01) affected by conidial treatments. The tissue C and Cu contents significantly correlated with the antioxidant capacity of the lettuce plants. Most of the micronutrients, viz. Mn, Fe, Cu, and B were remarkably higher (p < 0.05) in the fungus-treated plants than in the control plants. The antioxidant capacity (FRAP and TEAC) of plant extracts varied significantly (p < 0.001) among treatments, with the highest conidial treatment yielding the most increased antioxidant activity. In conclusion, the B. bassiana strain was endophytic to lettuce, pathogenic against M. persicae, and induced increased micro-nutrient tissue contents and antioxidant activities. This study demonstrated that B. bassiana could be potentially used in the biofortification of nutritive and medicinal qualities of plants.

Укрепление и защита берегов в Калачевском районе Волгоградской области с помощью кустарниковой растительности

The critical abrasion situation manifests itself on the coastal part of the Kalachevsky district due to the increasing anthropogenic load. The most important element of the complex of measures to combat silting of reservoirs and coastal abrasion, as well as an effective measure to strengthen the banks is forest vegetation. The objectives of the research were to study the soil, forest and climatic conditions of the object under study, to develop an assortment of shrubs and features of the formation of protective forest stands, as well as criteria for selecting an adapted assortment of tree and shrub vegetation and methods of caring for the soil and plantings. During the research, the most promising types of shrubs for creating upper protective forest stands were identified: Ligustrum vilgare L., Berberis vulgaris L., Cotoneaster lucidus Schltdl., Amelanchier Medik., Ribes aureum Pursh., Rosa canina L. It was found that the useful role of forest stands is manifested in their ability to convert surface runoff into subsurface runoff, to clean surface stock water from fine-grained soil, to weaken the speed of movement and to extinguish the energy of waves, binding the soil with roots. Recommendations are given for the creation and placement of anti-abrasion plantings, depending on the steepness and height of the slope. It is stated that one of the main measures for the care of the aboveground part of the plantings is the pruning of the crown, carried out taking into account the biological characteristics of their growth and development, including the removal of dry and damaged branches, thinning of the crown, preservation of the previously given crown size, rejuvenation of the crown. It is recommended to place shrubs depending on the landscape, soil and climatic conditions and features of abrasive processes in areas of constant, periodic, episodic flooding and strong moderate and weak flooding of the coastline.

Generic Additive Allometric Models and Biomass Allocation for Two Natural Oak Species in Northeastern China

Current models for oak species could not accurately estimate biomass in northeastern China, since they are usually restricted to Mongolian oak (Quercus mongolica Fisch. ex Ledeb.) on local sites, and specifically, no biomass models are available for Liaodong oak (Quercuswutaishanica Mayr). The goal of this study was, therefore, to develop generic biomass models for both oak species on a large scale and evaluate the biomass allocation patterns within tree components. A total of 159 sample trees consisting of 120 Mongolian oak and 39 Liaodong oak were harvested and measured for wood (inside bark), bark, branch and foliage biomass. To account for the belowground biomass, 53 root systems were excavated following the aboveground harvest. The share of biomass allocated to different components was assessed by calculating the ratios. An aboveground additive system of biomass models and belowground equations were fitted based on predictors considering diameter (D), tree height (H), crown width (CW) and crown length (CL). Model parameters were estimated by jointly fitting the total and the components’ equations using the weighted nonlinear seemingly unrelated regression method. A leave-one-out cross-validation procedure was used to evaluate the predictive ability. The results revealed that stem biomass accounts for about two-thirds of the aboveground biomass. The ratio of wood biomass holds constant and that of branches increases with increasing D, H, CW and CL, while a reverse trend was found for bark and foliage. The root-to-shoot ratio nonlinearly decreased with D, ranging from 1.06 to 0.11. Tree diameter proved to be a good predictor, especially for root biomass. Tree height is more prominent than crown size for improving stem biomass models, yet it puts negative effects on crown biomass models with non-significant coefficients. Crown width could help improve the fitting results of the branch and foliage biomass models. We conclude that the selected generic biomass models for Mongolian oak and Liaodong oak will vigorously promote the accuracy of biomass estimation.

Forest structure drives changes in light heterogeneity during tropical secondary forest succession.

Light is a key resource for tree performance and hence, tree species partition spatial and temporal gradients in light availability. Although light distribution drives tree performance and species replacement during secondary forest succession, we yet lack understanding how light distribution changes with tropical forest development.This study aims to evaluate how changes in forest structure lead to changes in vertical and horizontal light heterogeneity during tropical forest succession.We described successional patterns in light using a chronosequence approach in which we compared 14 Mexican secondary forest stands that differ in age (8–32 years) since agricultural abandonment. For each stand, we measured vertical light profiles in 16 grid cells, and structural parameters (diameter at breast height, height and crown dimensions) for each tree.During succession, we found a rapid increase in stand size (basal area, crown area and length) and stand differentiation (i.e. a gradual leaf distribution along the forest profile), which leads to fast changes in light conditions and more light heterogeneity. The inflection points of the vertical light gradient (i.e. the absolute height at which 50% relative light intensity is attained) rapidly moved towards higher heights in the first 20 years, indicating that larger amounts of light are intercepted by canopy trees. Light attenuation rate (i.e. the rate of light extinction) decreased during succession due to slower accumulation of the crown area with height. Understorey light intensity and heterogeneity slightly decreased during succession because of an increase in crown size and a decrease in lateral gap frequency. Understorey relative light intensity was 1.56% at 32 years after abandonment.Synthesis. During succession, light conditions changed linearly, which should lead to a continuous and constant replacement of species. Especially in later successional stages, stronger vertical light gradients can limit the regeneration of light‐demanding pioneer species and increase the proportion of shade‐tolerant late‐successional species under the canopy. These changes in light conditions were largely driven by the successional changes in forest structure, as basal area strongly determined the height where most light is absorbed, whereas crown area, and to a lesser extent crown length, determined light distribution.

Competitive drivers of interspecific deviations of crown morphology from theoretical predictions measured with Terrestrial Laser Scanning

AbstractTree crown morphology is a key driver of forest dynamics, determining not only the competitiveness of an individual but also the competitive effect exerted on neighbouring trees. Multiple ecological theories, including metabolic scaling theory (MST), predict crown morphology from first principles, but typically lack consideration of competition. The accurate quantification of crown morphology to test theoretical predictions, and the canopy interactions that could alter them, has historically been limited by the simplicity and associated error of traditional crown measurements.In this study, we calculate high‐resolution two‐ and three‐dimensional crown metrics from Terrestrial Laser Scanning data for 1,441Pinus sylvestris,P.nigra,Quercus fagineaandQ. ilextrees from a water‐limited forest community in central Spain and test height‐crown metric scaling relationships. We demonstrate new TLS methods to define symmetric and asymmetric neighbourhood metrics based on tree height, crown size and neighbour projected crown area, and test the importance of neighbourhood genus diversity on crown morphology by separating competition from congeneric and heterogeneric neighbours.Competition negatively impacted all crown metrics except crown depth where onlyP.nigrashowed sensitivity. Asymmetric competition was the strongest driver of pine crown morphology, but oaks were more sensitive to symmetric competition, in line with shade tolerance expectations. Congeneric competition reducedQ.fagineacrown size and changed its shape, but we found no significant effects of heterogeneric neighbours. Most species and crown dimensions had height‐crown scaling exponents below those predicted by MST, which may be due to water limitation effects. Pines and oaks showed large differences in crown depth to height scaling, with the former shallower and the latter deeper, in contrast to theoretical predictions.Synthesis. Our study is the first to demonstrate the ability of TLS to characterise crown morphology from leaf‐wood separated clouds and competitive neighbour effects in a water‐limited forest community, and to use TLS metrics to test ecological crown scaling theory. Most crown metrics scaled below theoretical predictions. Pines were more sensitive to competition by larger neighbours and oaks to crowding from all neighbours, with competition from neighbours of the same genus having a consistent negative effect.

Including tree spatial extension in the evaluation of neighborhood competition effects in Bornean rain forest.

Classical tree neighborhood models use size variables acting at point distances. In a new approach here, trees were spatially extended as a function of their crown sizes, represented impressionistically as points within crown areas. Extension was accompanied by plasticity in the form of crown removal or relocation under the overlap of taller trees. Root systems were supposedly extended in a similar manner. For the 38 most abundant species in the focal size class (10–<100 cm stem girth) in two 4‐ha plots at Danum (Sabah), for periods P1 (1986–1996) and P2 (1996–2007), stem growth rate and tree survival were individually regressed against stem size, and neighborhood conspecific (CON) and heterospecific (HET) basal areas within incremented steps in radius. Model parameters were critically assessed, and statistical robustness in the modeling was set by randomization testing. Classical and extended models differed importantly in their outcomes. Crown extension weakened the relationship of CON effect on growth versus plot species’ abundance, showing that models without plasticity overestimated negative density dependence. A significant negative trend of difference in CON effects on growth (P2−P1) versus CON or HET effect on survival in P1 was strongest with crown extension. Model outcomes did not then support an explanation of CON and HET effects being due to (asymmetric) competition for light alone. An alternative hypothesis is that changes in CON effects on small trees, largely incurred by a drought phase (relaxing light limitation) in P2, and following the more shaded (suppressing) conditions in P1, were likely due to species‐specific (symmetric) root competition and mycorrhizal processes. The very high variation in neighborhood composition and abundances led to a strong “neighborhood stochasticity” and hence to largely idiosyncratic species’ responses. A need to much better understand the roles of rooting structure and processes at the individual tree level was highlighted.

Human Molar Size Variation: Wisdom Teeth Just Don't Care?

The inhibitory cascade model (ICM) is a tenet of mammalian molar morphogenesis that predicts that a larger developing first molar (M1) results in a smaller and later-forming adjacent second (M2) and third (M3) molar. Recently, we have shown that late-developing M3s are also at higher risk of impaction, a common dental health concern worldwide. The mechanisms delaying M3 onset time are unclear.Here we tested the hypothesis that M1 crown size predicts M3 developmental timing and M3 eruption, based on a sample of young Western Canadian dental patients. We also tested the extent to which contemporary modern human molars conform to the ICM. We sampled retrospective cone beam computed tomography scans and panoramic radiographs taken for clinical diagnostic purposes of multi-ethnic patients aged 13-24 years residing in four Western Canadian municipalities. We studied 99 patients, sampling 327 quadrants from 57 girls and 42 boys, at two distinct times that allowed us to know if an M3 had properly erupted. Using Horos and Xoran i-Cat software, we scored permanent molar development using a 9-stage classification after Demirjian's system. We measured mesiodistal lengths of M1, M2 and M3 crowns. In SPSS v.25, we calculated a Generalized Estimating Equation model through a multivariable linear regression to test if M1 crown length (“size”) predicted M3 developmental timing and eruption status. We also tested other variables including jaw type (maxillary; mandibular). Significance was set to p<0.05. Unexpectedly, we identified 13 molar size ratio patterns occurring at different frequencies (e.g., M1>M2>M3 in only 31.6% of cases) that reflected whether molars were located in the maxilla versus the mandible. This pattern diversity included up to four patterns in the same person's mouth. Further, M3 size was predicted not by M1 size (Wald Chi-Square [Wald X2]=0.701, p=0.40) but by M2/M1 ratio and absolute M2 size (Wald X2=14.04, p=0.000). Relative to M1 crown length, if M2 crown length increased by 10%, the adjacent M3 crown lengthened by 7% (±3%), indicating that M2 increases “faster” than M3. Crown length ratios (M3:M1, M2:M1) did not predict M3 impaction (Wald X2=0.124, p=0.73) or M3 developmental stage (M2:M1, Wald X2=0.228, p=0.63; M3:M1, Wald X2=3.253, p=0.07). We conclude that M1 crown length does not predict early versus late M3 development or M3 eruption status. Thus, the ICM does not appear to be useful for predicting M3 impaction risk. Contemporary modern humans present several distinct molar size ratio patterns, indicating that Homo sapiens molar size is subject to oral quadrant-specific and jaw type-specific effects beyond inhibition from a developing M1.

Toward Large-Scale Mapping of Tree Crops with High-Resolution Satellite Imagery and Deep Learning Algorithms: A Case Study of Olive Orchards in Morocco

Timely and accurate monitoring of tree crop extent and productivities are necessary for informing policy-making and investments. However, except for a very few tree species (e.g., oil palms) with obvious canopy and extensive planting, most small-crown tree crops are understudied in the remote sensing domain. To conduct large-scale small-crown tree mapping, several key questions remain to be answered, such as the choice of satellite imagery with different spatial and temporal resolution and model generalizability. In this study, we use olive trees in Morocco as an example to explore the two abovementioned questions in mapping small-crown orchard trees using 0.5 m DigitalGlobe (DG) and 3 m Planet imagery and deep learning (DL) techniques. Results show that compared to DG imagery whose mean overall accuracy (OA) can reach 0.94 and 0.92 in two climatic regions, Planet imagery has limited capacity to detect olive orchards even with multi-temporal information. The temporal information of Planet only helps when enough spatial features can be captured, e.g., when olives are with large crown sizes (e.g., &gt;3 m) and small tree spacings (e.g., &lt;3 m). Regarding model generalizability, experiments with DG imagery show a decrease in F1 score up to 5% and OA to 4% when transferring models to new regions with distribution shift in the feature space. Findings from this study can serve as a practical reference for many other similar mapping tasks (e.g., nuts and citrus) around the world.

Individual Tree Crown Detection Using UAV Orthomosaic

Unmanned Aerial Vehicles (UAVs) are increasingly used in forestry as they are economical and flexible. This study aims to present the advantages of the drone photogrammetry method in collecting individual tree crowns, as individual tree crown detection could deliver essential ecological and economic information. The referred accuracy for individual tree crown extraction is 79.2%. Only crowns that were clearly visible were selected and manually delineated on the image because the distribution of the true crown size is significantly different from the segmented crowns. The aim of this study is to investigate UAVs orthomosaics in individual tree crown detection. The objectives of this study are to produce the orthomosaic of tree crown extraction mapping using the Pix4D software and analyze the tree crowns using tree crown delineation and the OBIA algorithm. Data processing involves the processing of aerial images using Pix4Dmapper. Automatic tree crown detection involves a tree crown delineation algorithm and OBIA operations to process the tree crown extraction. The crown delineation algorithm and OBIA algorithm operation will be compared to the actual tree crown measurement in terms of diameter and area. The tree crown delineation method obtained a 0.347m mean diameter difference from the actual tree crown diameter, while the OBIA approach obtained 4.98m. The tree crown delineation method obtained 97.26% of the actual tree crown area, while OBIA obtained 91.74%.

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.

A Crown Morphology-Based Approach to Individual Tree Detection in Subtropical Mixed Broadleaf Urban Forests Using UAV LiDAR Data

Owing to the complex forest structure and large variation in crown size, individual tree detection in subtropical mixed broadleaf forests in urban scenes is a great challenge. Unmanned aerial vehicle (UAV) light detection and ranging (LiDAR) is a powerful tool for individual tree detection due to its ability to acquire high density point cloud that can reveal three-dimensional crown structure. Tree detection based on a local maximum (LM) filter, which is applied on a canopy height model (CHM) generated from LiDAR data, is a popular method due to its simplicity. However, it is difficult to determine the optimal LM filter window size and prior knowledge is usually needed to estimate the window size. In this paper, a novel tree detection approach based on crown morphology information is proposed. In the approach, LMs are firstly extracted using a LM filter whose window size is determined by the minimum crown size and then the crown morphology is identified based on local Gi* statistics to filter out LMs caused by surface irregularities contained in CHM. The LMs retained in the final results represent treetops. The approach was applied on two test sites characterized by different forest structures using UAV LiDAR data. The sensitivity of the approach to parameter setting was analyzed and rules for parameter setting were proposed. On the first test site characterized by irregular tree distribution and large variation in crown size, the detection rate and F-score derived by using the optimal combination of parameter values were 72.9% and 73.7%, respectively. On the second test site characterized by regular tree distribution and relatively small variation in crown size, the detection rate and F-score were 87.2% and 93.2%, respectively. In comparison with a variable-size window tree detection algorithm, both detection rates and F-score values of the proposed approach were higher.

Vascular epiphyte diversity and host tree architecture in two forest management types in the Himalaya

Epiphytes are one of the most diversified plant life forms, whose species richness peaks in the tropics and subtropics. Here we examined vertical distribution metrics (i.e., number of epiphyte individuals and epiphyte species richness) of vascular epiphytes (i.e., orchids and ferns) on two dominant host trees (i.e., Schima wallichii (DC.) Korth. and Quercus lanata Sm.) in sub-tropical forests of Nepal. We sampled a total number of 72 host trees of Q. lanata and S. wallichii from two forest sites: a government protected national park forest and community managed forest. We applied generalized linear mixed models and Kruskal-Wallis rank sum tests to explain epiphyte diversity by tree architecture (i.e., diameter at breast height, tree height, crown size, number of forks, bark rugosity, bark pH and tree layer), host species and forest management types. After variable selection via multi-model inference technique, we found diameter at breast height to be the most powerful and significant explanatory variable for the number of epiphyte individuals and epiphyte species richness across host tree species, tree layers, and forest management types. Interestingly, epiphyte diversity was on average higher in the community managed forest than in the national park forest, on S. wallichii than on Q. lanata and particularly on the trunk below forks. We conclude that effective conservation of epiphyte diversity in the Nepal Himalaya requires conservation of old-growth host trees through community approaches. If large and old tree stands are maintained, community managed forests can host high diversity of vascular epiphytes and provide ecosystem goods to local people alike.