2,522 research outputs found

    Single-picture reconstruction and rendering of trees for plausible vegetation synthesis

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    State-of-the-art approaches for tree reconstruction either put limiting constraints on the input side (requiring multiple photographs, a scanned point cloud or intensive user input) or provide a representation only suitable for front views of the tree. In this paper we present a complete pipeline for synthesizing and rendering detailed trees from a single photograph with minimal user effort. Since the overall shape and appearance of each tree is recovered from a single photograph of the tree crown, artists can benefit from georeferenced images to populate landscapes with native tree species. A key element of our approach is a compact representation of dense tree crowns through a radial distance map. Our first contribution is an automatic algorithm for generating such representations from a single exemplar image of a tree. We create a rough estimate of the crown shape by solving a thin-plate energy minimization problem, and then add detail through a simplified shape-from-shading approach. The use of seamless texture synthesis results in an image-based representation that can be rendered from arbitrary view directions at different levels of detail. Distant trees benefit from an output-sensitive algorithm inspired on relief mapping. For close-up trees we use a billboard cloud where leaflets are distributed inside the crown shape through a space colonization algorithm. In both cases our representation ensures efficient preservation of the crown shape. Major benefits of our approach include: it recovers the overall shape from a single tree image, involves no tree modeling knowledge and minimal authoring effort, and the associated image-based representation is easy to compress and thus suitable for network streaming.Peer ReviewedPostprint (author's final draft

    On the angular dependency of canopy gap fractions in pine, spruce and birch stands

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    The angular profiles of canopy gap fraction curves are influenced by canopy structure, and are commonly expected to vary with stand- and crown-level variables such as tree pattern, crown shape and leaf orientation. In this study, measurements of canopy structure, gap fractions and effective LA! in 986 plots of Scots pine, Norway spruce and Silver birch stands in Finland were used to assess how similar the angular canopy gap fraction profiles are for common boreal tree species. The profiles were characterized with help of the shape function psi(theta), defined as the normalized value of the canopy light extinction coefficient at zenith angle (theta). Variation in psi(theta) would be induced not only by a non-spherical leaf orientation, but also by differences in the directional clumping indices, such as could result from species-specific differences in crown shape. Our results showed that there is wide variation in the shape of psi in the individual plots of the three different species. The species-specific mean curves psi(theta), however, showed relatively small variation with theta, except for a sudden drop at large zenith angles, and the shape of the curves was similar for the different tree species. Results indicate that differences in crown shape of the study species do not significantly affect the angular profiles of canopy gap fraction. (C) 2015 The Authors. Published by Elsevier B.V.Peer reviewe

    Notch Signaling Pathway in Tooth Shape Variations throughout Evolution

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    Evolutionary changes in vertebrates are linked to genetic alterations that often affect tooth crown shape, which is a criterion of speciation events. The Notch pathway is highly conserved between species and controls morphogenetic processes in most developing organs, including teeth. Epithelial loss of the Notch-ligand Jagged1 in developing mouse molars affects the location, size and interconnections of their cusps that lead to minor tooth crown shape modifications convergent to those observed along Muridae evolution. RNA sequencing analysis revealed that these alterations are due to the modulation of more than 2000 genes and that Notch signaling is a hub for significant morphogenetic networks, such as Wnts and Fibroblast Growth Factors. The modeling of these tooth crown changes in mutant mice, via a three-dimensional metamorphosis approach, allowed prediction of how Jagged1-associated mutations in humans could affect the morphology of their teeth. These results shed new light on Notch/Jagged1-mediated signaling as one of the crucial components for dental variations in evolution

    Neandertal Mandibular Molars from Hortus Cave, France: A Comparison of Crown Shapes Using Elliptical Fourier Analysis

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    Neandertal permanent mandibular molars are well represented at Hortus Cave, France, Sub-Phase IVb and Vb, providing an opportunity to assess intrapopulation and intersite shape variation. We expected the mandibular molars from Hortus cave, comprising Hortus II, Hortus IV, Hortus V and Hortus VI to cluster together, compared to Neandertals close in proximity, such as Malarnaud and La Quina 5 as well as those more distantly located such as Arcysur- Cure 1, Engis 2 and Scladina 4A-1. A single Neolithic cave burial from Maurenne Caverne de la Cave, Belgium (n = 11) is used to contextualize the degree of variation in the Hortus assemblage. From photographic images of the permanent molars, crown shapes were digitized and binarized. The resulting images were processed in R using elliptical Fourier analysis and the resulting amplitudes of the harmonics were subjected to principal components analysis and hierarchical clustering. Hortus II and Hortus V, both from Sub-Phase Vb, are relatively similar to one another in M1 crown shape, and are secondarily grouped with Hortus IV from Sub-Phase IVb. Maurenne Caverne de la Cave has a larger degree of variation in crown shape than the Hortus assemblage, and the Neandertals imperfectly cluster together and apart from the Neolithic sample for some multivariate comparisons. Variance in Neandertal molar crown shape can be primarily explained as the result of chronology. Hortus consistently groups with other MIS 3 Neandertals such as La Quina 5 and Engis 2, while those from MIS 5, represented by Scladina 4A-1 and Malarnaud are distinct as is Arcy-sur-Cure 1 from late MIS 3. Across the molars, the Hortus assemblage is most similar to La Quina 5 from Charente, Southwest France

    Growth dynamics of crown shapes in stands of pedunculate oak and common hornbeam

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    Background and Purpose: Structure of crowns in forest stands is one of the main factors which determines growth and development of trees. Dynamic change occurs with the age of the stand due to silvicultural interventions or natural disturbances duringwhich trees are removed fromthe stand. The aim of this article is to analyse the structure of the crown shape of pedunculate oak and common hornbean trees with regard to diameter at breast height (DBH) and the age of the stand in one of the most important forest community in Croatia. Materials andMethods: The investigation is based on data collected on 47 permanent experimental plotswhichwere established as a chronosequence in a natural range of forests of pedunculate oak and common hornbeam in Croatia. The total surface of all plots amounts to 33.45 ha. Breast height diameter, tree height and stem height were measured on the trees in the experimental plots, and a detailed ground plan was made of horizontal crown projections, from which the crown diameters were calculated. In total 1505 pedunculate oak trees and 2026 common hornbeam trees were measured. For each tree the crown shape was calculated and trees were then grouped in age classes of 20 years, and the shape of the crown analysed according to species and age classes. Correlation between crown shapes and diameter at breast height was investigated for stands of the sixth age class (101 – 120 years) for each species by means of linear regression. Results and Discussion: The shape of the crown of pedunculate oak, although it shows a trend toward growth in relation to diameter at breast height, the regularity pattern of the shape indicates weak character (r=0.441), i.e. variability is explained with only 19%. Crown shapes of common hornbeam are almost constant in relation to diameter at breast height (r=114), and correlation between the examined values cannot be equated by any rational analytical term. Investigation of growth dynamics of crown shape structure was carried out according to the species of trees and age classes, and the interval inwhich 68%(x ± 1.0 s) and 95%of data (x ± 1.96 s)were included. Conclusions: The results of the investigation indicate that dependence on crown shape and diameter at breast height of pendunculate oak and common hornbeam cannot be described by any rational analytical term. Average values of the crown shapes according to age classes can be used as form factors for calculation of crown volume.Data are applicable in various applications, such as for example their integration in a simulator of growth and development of forest stands and examination of the effect of different silvicultural scenario

    Growth dynamics of crown shapes in stands of pedunculate oak and common hornbeam

    Get PDF
    Background and Purpose: Structure of crowns in forest stands is one of the main factors which determines growth and development of trees. Dynamic change occurs with the age of the stand due to silvicultural interventions or natural disturbances duringwhich trees are removed fromthe stand. The aim of this article is to analyse the structure of the crown shape of pedunculate oak and common hornbean trees with regard to diameter at breast height (DBH) and the age of the stand in one of the most important forest community in Croatia. Materials andMethods: The investigation is based on data collected on 47 permanent experimental plotswhichwere established as a chronosequence in a natural range of forests of pedunculate oak and common hornbeam in Croatia. The total surface of all plots amounts to 33.45 ha. Breast height diameter, tree height and stem height were measured on the trees in the experimental plots, and a detailed ground plan was made of horizontal crown projections, from which the crown diameters were calculated. In total 1505 pedunculate oak trees and 2026 common hornbeam trees were measured. For each tree the crown shape was calculated and trees were then grouped in age classes of 20 years, and the shape of the crown analysed according to species and age classes. Correlation between crown shapes and diameter at breast height was investigated for stands of the sixth age class (101 – 120 years) for each species by means of linear regression. Results and Discussion: The shape of the crown of pedunculate oak, although it shows a trend toward growth in relation to diameter at breast height, the regularity pattern of the shape indicates weak character (r=0.441), i.e. variability is explained with only 19%. Crown shapes of common hornbeam are almost constant in relation to diameter at breast height (r=114), and correlation between the examined values cannot be equated by any rational analytical term. Investigation of growth dynamics of crown shape structure was carried out according to the species of trees and age classes, and the interval inwhich 68%(x ± 1.0 s) and 95%of data (x ± 1.96 s)were included. Conclusions: The results of the investigation indicate that dependence on crown shape and diameter at breast height of pendunculate oak and common hornbeam cannot be described by any rational analytical term. Average values of the crown shapes according to age classes can be used as form factors for calculation of crown volume.Data are applicable in various applications, such as for example their integration in a simulator of growth and development of forest stands and examination of the effect of different silvicultural scenario

    Change in drivers of mangrove crown displacement along a salinity stress gradient

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    1. Crown displacement in trees is an adaptive response driven by neighbours that optimizes space use and reduces competition. But it can also be the result of wind force. Although morphological responses to neighbours have been well studied, the interplay between neighbours and wind in driving crown shape, and the implications for plant interactions remain poorly understood. However, it is crucial to predict such changes in vegetation structure and function under the scope of global change. We test the hypothesis that aboveground interactions are reduced with increasing soil stress and that wind becomes the main driver of crown shape in mangrove forests. 2. We investigated the effect of neighbours and wind intensity and direction on crown displacement of mangrove canopy and below canopy trees along a salinity gradient, and assessed crown asymmetry for three mangrove tree species, as well as the contribution of crown displacement on reducing crown‐projected area overlap and thus neighbourhood competition. 3. Results show that crown displacement of canopy trees is strongly influenced by winds at all salinities. At low salinities, competition for space accounted for 48% of crown displacement away from neighbours, compared to 49% found for the synthetized effects of wind and neighbours. While trees below the canopy displace their crowns away from their neighbours, no response to wind could be detected. This can be due to the wind protection conferred by a dense canopy stand related to bigger crowns that effectively reduce wind drag. At higher salinities, there was a reduction in canopy overlap due to crown displacement, which suggests reduced aboveground plant interactions with increasing soil stress. 4. While neighbourhood avoidance is a fundamental strategy for optimal light foraging, this study shows that wind strength and directionality are main drivers of crown shape with increasing stress and highlights their potential influence in plant interactions and forest structure, pointing to an increased susceptibility of trees to disturbances that should be further studied

    W227 Tree Growth Characteristics

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    Trees are fascinating. The largest of all woody plants, they have well-defined stems that support a crown of leaves. The growth form varies by species and can be categorized. This publication has been created to provide professional foresters, arborists, students, Extension personnel, advanced homeowners and others a general understanding of how trees grow. Specifics will include primary vs. secondary growth, allocation of photosynthate, shoot growth patterns and crown shape
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