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1
Goelz, J. C. G. "Open-Grown Crown Radius of Eleven Bottomland Hardwood Species: Prediction and Use in Assessing Stocking." Southern Journal of Applied Forestry 20, no. 3 (August 1, 1996): 156–61. http://dx.doi.org/10.1093/sjaf/20.3.156.
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Abstract Equations were prepared to predict crown radius for eleven species of open-grown bottomland hardwood trees. Crown radius was predicted as a function of diameter at breast height (dbh) and as a function of dbh, total height, and crown ratio. Equations were prepared for individual species and species groups. Pecan (Carya illinoensis (Wangenh.) K. Koch) has the largest crowns over a broad range of dbh. Eastern cottonwood (Populus deltoides Bartr. ex Marsh.) has the smallest crowns for most levels of dbh. Sweetgum (Liquidambar styraciflua L.) has relatively small crowns for trees of small dbh, but crown radius is comparable to most species at the largest dbh. The crown radius predictions may be used to calculate crown competition factor. B-lines of stocking may be calculated that represent a stand of one species as well as a mixed-species stand of any particular species proportion. South. J. Appl. For. 20(3):156-161.
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Umeki, Kiyoshi. "A comparison of crown asymmetry between Piceaabies and Betulamaximowicziana." Canadian Journal of Forest Research 25, no. 11 (November 1, 1995): 1876–80. http://dx.doi.org/10.1139/x95-202.
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Morphological plasticity in terms of asymmetric display of crowns was compared between Piceaabies (L.) Karst. and Betulamaximowicziana Regel. To evaluate crown asymmetry in relation to local environment, a model that predicts crown asymmetry from topography and configuration of neighbors was applied to data derived from a mixed forest in Hokkaido, northern Japan. Betulamaximowicziana had greater crown asymmetry than P. abies in absolute value. However, observed crown asymmetry of both species was determined by local environment to similar degrees. Some other differences were found between the two species. Crowns of P. abies were more influenced by neighbors than topography, while crowns of B. maximowicziana were more influenced by topography than neighbors. Crowns of P. abies were influenced mainly by larger neighbors, while crowns of B. maximowicziana were influenced by large and by relatively small neighbors.
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Bykova, Iuliia Igorevna. "Small crowns of Russian empresses in the XVIII – early XIX centuries: creation, presence, artistic attributes." Культура и искусство, no. 9 (September 2020): 15–29. http://dx.doi.org/10.7256/2454-0625.2020.9.33829.
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The object of this research is the small crowns of Russian empresses of the XVIII – early XIX century. The goal of this work consists in specification of circumstances of the creation and presence of small imperial crowns in Russia of that time, description of their artistic attributes, and analysis of these regalia as the works of jewelry art, considering stylistic evolution. For achieving the designated goal, the author applied comprehensive method of research based on the combination of art criticism and historical-cultural approach, referring to a range of sources: from unpublished archival documents and memoirs of contemporaries to visual material. The article clarifies the term “small” crown. Based on the archival documents, the author introduces into the scientific discourse the records on a number previously unknown small crowns, as well as specifies the circumstances of their creation along with names of the craftsmen. The artistic image of small Imperial crowns was analyzed for the first time. The conducted research demonstrates that in the XVIII century this image transformed under the influence of stylistic preferences in Russian artistic culture and due to the change of court jewelers who belonged to different schools of jewelry art. In the XIX century, influenced by the national ideas and according to the already established state ceremonial, which tends to traditionalism, the exterior of small crowns was fully oriented towards the small crown of 1797.
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Warmund, Michele R. "Ice Distribution in `Earliglow' Strawberry Crowns and Tissue Recovery following Extracellular Freezing." Journal of the American Society for Horticultural Science 118, no. 5 (September 1993): 644–48. http://dx.doi.org/10.21273/jashs.118.5.644.
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`Earliglow' strawberry (Fragaria xananassa Duchesne) plants were frozen to -5 or -50C to examine the distribution of ice in the crowns. Anatomical studies were also performed to characterize tissue growth in a greenhouse at 4, 8, and 15 weeks after freezing to -5C. Ice masses observed in fresh crown tissue corresponded to the presence of extracellular tissue voids in specimens fixed for scanning electron microscopy (SEM). Voids were present near the peduncle and adjacent to the vascular system in crown tissue. After plants were grown in the greenhouse, cell division and enlargement were observed near the voids in crowns subjected to -5C. By 15 weeks after freezing, a few small extracellular voids remained in the crowns. Tissue voids were also present in crowns of plants frozen rapidly to -50C and subsequently thawed. Cells in the crown of these plants were intact and did not appear collapsed after exposure to -50C, a lethal temperature.
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Warmund, Michele R. "STRAWBERRY GROWTH FOLLOWING A SUB-LETHAL FREEZE." HortScience 27, no. 6 (June 1992): 654f—654. http://dx.doi.org/10.21273/hortsci.27.6.654f.
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`Earliglow' strawberry (Fragaria × ananassa Duch.) plants were frozen to -5C to examine the distribution of ice in the crowns. Anatomical studies were also performed to characterize tissue growth in a greenhouse at 4, 8, and 16 weeks after freezing to -5C. Ice masses observed in fresh crown tissue corresponded to the presence of extracellular tissue voids in specimens fixed for scanning electron microscopy (SEM). Voids were present near the peduncle and adjacent to the vascular system in crown tissue. After plants were grown in the greenhouse, cell division and enlargement were observed near the voids in crowns subjected to -5C. By 15 weeks after freezing, a few small extracellular voids remained in the crowns.
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Engle, David M., Jimmy F. Stritzke, and P. Larry Claypool. "Effect of Paraquat Plus Prescribed Burning on Eastern Redcedar (Juniperus virginiana)." Weed Technology 2, no. 2 (April 1988): 172–74. http://dx.doi.org/10.1017/s0890037x00030347.
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Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) was evaluated as a pretreatment for eastern redcedar (Juniperus virginiana L. # IUPVI) before spring burning in tallgrass prairie. Wetting sprays of paraquat at 0.3 g ai/L or 0.6 g/L were applied to crowns of small (0.8 to 1.5 m), medium (1.5 to 2.5 m), and large (2.5 to 5.0 m) eastern redcedar trees in August 1983 and 1984 before prescribed burns in the springs of 1984 and 1985. Paraquat alone at the 0.6 g/L concentration killed about 90% of the crown of small trees but as little as 30% of the crown of large trees. Paraquat pretreatments increased post-fire damage to small- and medium-size trees and partially compensated for light fine fuel loading.
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Gao, Huilin, Jian Feng, You Yin, Wanjin Hu, Yang Qu, and Mingguo Liu. "Effect of strip shelterwood-cuts on the crown morphology plasticity of natural regenerated Pinus tabuliformis saplings in northeastern China." PeerJ 8 (August 26, 2020): e9826. http://dx.doi.org/10.7717/peerj.9826.
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The study analysed the effect of shelterwood-cut strips on the outermost crown profiles and crown characteristics of naturally regenerated Pinus tabuliformis saplings in northeastern China. A total of 49 regenerated saplings from shelterwood-cut strips and 30 from uncut strips were collected. Nonlinear quantile regression was used to develop the outermost crown profile model for the saplings from the shelterwood-cut and uncut strips. The quantile value suitable for describing the outermost crown profiles of the two types of strips was selected using nonparametric boundary regression. The difference in crown morphologies between the shelterwood-cut strips and uncut strips was compared. The results showed that with the same diameter at breast height, the crown radii of the uncut strip saplings were larger than those of the shelterwood-cut strip saplings within the range of 0.2–1.0 for the relative depth into the crown. The largest crown radius of the saplings from the uncut strips was larger than that of the saplings from the shelterwood-cut strips. The inflection points of the shelterwood-cut strip sapling crowns were larger than those of the uncut strip sapling crowns. The crown volume of the small uncut strip saplings was larger than that of the shelterwood-cut strip saplings, and the difference in crown volume decreased with increasing sapling size. The saplings in the early stage of the uncut strips showed a greater growth rate than those of the shelterwood-cut strips, but their growth rate slowed over the long term according to branch-length annual growth. The present study provides a reference for forest management strategy decision making in promoting natural regeneration.
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Savoie, Rodrique, André Rodrigue, Marie Pigeon-Gosselin, and Robert Chênevert. "Synthesis and vibrational spectra of complexes of small carboxylic acids with 18-crown-6." Canadian Journal of Chemistry 63, no. 7 (July 1, 1985): 1457–62. http://dx.doi.org/10.1139/v85-249.
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The neutral-component complexes (HCOOH)3•(18-crown-6)2, (CH3COOH)2•18-crown-6, and various halogenated CH3COOH/18-crown-6 adducts have been isolated and studied by infrared and Raman spectroscopy. The halogenated (F, Cl, and Br) derivatives, which occur as (acid•water)x•18-crown-6(x = 1 or 2) adducts, probably have a structure which is similar to that of the known CH2(CN)COOH•H2O•18-crown-6 complex.
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Rodríguez y Silva, Francisco, Mercedes Guijarro, Javier Madrigal, Enrique Jiménez, Juan R. Molina, Carmen Hernando, Ricardo Vélez, and Jose A. Vega. "Assessment of crown fire initiation and spread models in Mediterranean conifer forests by using data from field and laboratory experiments." Forest Systems 26, no. 2 (July 24, 2017): e02S. http://dx.doi.org/10.5424/fs/2017262-10652.
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Aims of study: To conduct the first full-scale crown fire experiment carried out in a Mediterranean conifer stand in Spain; to use different data sources to assess crown fire initiation and spread models, and to evaluate the role of convection in crown fire initiation.Area of study: The Sierra Morena mountains (Coordinates ETRS89 30N: X: 284793-285038; Y: 4218650-4218766), southern Spain, and the outdoor facilities of the Lourizán Forest Research Centre, northwestern Spain.Material and methods: The full-scale crown fire experiment was conducted in a young Pinus pinea stand. Field data were compared with data predicted using the most used crown fire spread models. A small-scale experiment was developed with Pinus pinaster trees to evaluate the role of convection in crown fire initiation. Mass loss calorimeter tests were conducted with P. pinea needles to estimate residence time of the flame, which was used to validate the crown fire spread model.Main results: The commonly used crown fire models underestimated the crown fire spread rate observed in the full-scale experiment, but the proposed new integrated approach yielded better fits. Without wind-forced convection, tree crowns did not ignite until flames from an intense surface fire contacted tree foliage. Bench-scale tests based on radiation heat flux therefore offer a limited insight to full-scale phenomena.Research highlights: Existing crown fire behaviour models may underestimate the rate of spread of crown fires in many Mediterranean ecosystems. New bench-scale methods based on flame buoyancy and more crown field experiments allowing detailed measurements of fire behaviour are needed.
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Ashton, P. Mark S., Lydia P. Olander, Graeme P. Berlyn, Rajesh Thadani, and Ian R. Cameron. "Changes in leaf structure in relation to crown position and tree size of Betula papyrifera within fire-origin stands of interior cedar-hemlock." Canadian Journal of Botany 76, no. 7 (July 1, 1998): 1180–87. http://dx.doi.org/10.1139/b98-128.
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Dimensions of anatomical and morphological attributes of leaves can influence physiological response to changes in environment over time. Linking structural attributes of leaves to crown position and tree size within naturally developing cohorts of trees can provide a clearer understanding of changes in crown morphology for a species. This study examined leaf anatomy and morphology of Betula papyrifera Marsh. growing in two stages of stand development of interior cedar-hemlock forest, northern British Columbia. Anatomical and morphological measurements of leaves located at six different positions within the crown were made on trees selected from stands that originated 15 years (small tree size) and 145 years (large tree size) after catastrophic fire. Leaf area and mass were measured in the field. Microscopic measures were made in the laboratory of thicknesses of leaves, cuticle, upper and lower epidermis, palisade, and spongy mesophyll. Stomatal density and stomatal aperture lengths were also determined. Leaf anatomy and morphology varied significantly with position in the crown and among size-classes of trees. Changes in leaf anatomy observed among positions within the crown reflect the changing availability of light and moisture experienced during crown development. For both size-classes of tree the largest anatomical dimensions of leaves were at the outer and uppermost parts of the crown, whilst the smallest were at the lower and innermost parts. Foliage of large trees (145 years) exhibit leaf attributes characteristic of the sun-shade dichotomy reported in the literature, but this was not shown for foliage of young saplings (15 years). For the small trees (15 years) the largest leaves were located at the top of the crown while the smallest were located at the bottom. This has been reported for many tropical pioneers but is in contrast to the usual sun-shade dichotomy of temperate pioneers. The large trees (145 years) followed the typical pattern with the smallest leaves at the top of the crown. Information from this study contributes to our understanding of foliar development of tree crowns by demonstrating how leaf structure changes with crown position and tree size under stand competition.Key words: Betula papyrifera, British Columbia, crown development, cuticle thickness, leaf area, palisade mesophyll, paper birch, stand dynamics.
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Pugia, Michael J., Brian E. Knudsen, and Richard A. Bartsch. "Lithium-selective, lipophilic, small-ring bis(crown ethers)." Journal of Organic Chemistry 52, no. 12 (June 1987): 2617–19. http://dx.doi.org/10.1021/jo00388a057.
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Kortegaard, H. E., T. Anthony Knudsen, S. Dahl, J. F. G. Agger, and T. Eriksen. "Consequences of crown shortening canine teeth in Greenland sled dogs." Journal of Small Animal Practice 56, no. 4 (January 13, 2015): 264–69. http://dx.doi.org/10.1111/jsap.12314.
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Rizzo, D. M., and T. C. Harrington. "Root movement and root damage of red spruce and balsam fir on subalpine sites in the White Mountains, New Hampshire." Canadian Journal of Forest Research 18, no. 8 (August 1, 1988): 991–1001. http://dx.doi.org/10.1139/x88-152.
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Crown dieback and mortality of red spruce and balsam fir in the subalpine zone of the northern Appalachian Mountains have been attributed to wind-induced crown and root damage. Vertical root movements, damage to roots and crowns, and growth rate were measured on wind-exposed spruce and fir trees near canopy gaps at Kancamagus Pass (875 m elevation) and Wildcat Mountain (1160 m) in the White Mountain National Forest, New Hampshire. Root movements were significantly correlated with windspeed, crown exposure, and depth of soil to rock. Woody roots that had made movements in excess of 10 mm had fewer small (1–3 mm diameter) roots, more abrasion wounds, and a greater amount of nonconducting (dry or discolored) xylem than roots that had made smaller movements. Hydraulic conductivity was significantly reduced in roots with greater than 40% xylem cross-sectional area that was nonconducting. Spruce and fir trees at gap margins grew slower and had more root and crown damage than trees sheltered within the canopy. Decreases in growth rate of spruce and fir trees at both sites during the past 20 years were significantly correlated with wind exposure and some of the root and crown damage variables.
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Franklin, Steven E. "Pixel- and object-based multispectral classification of forest tree species from small unmanned aerial vehicles." Journal of Unmanned Vehicle Systems 6, no. 4 (December 1, 2018): 195–211. http://dx.doi.org/10.1139/juvs-2017-0022.
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Forest inventory, monitoring, and assessment requires accurate tree species identification and mapping. Recent experiences with multispectral data from small fixed-wing and rotary blade unmanned aerial vehicles (UAVs) suggest a role for this technology in the emerging paradigm of enhanced forest inventory (EFI). In this paper, pixel-based and object-based image analysis (OBIA) methods were compared in UAV-based tree species classification of nine commercial tree species in mature eastern Ontario mixedwood forests. Unsupervised clustering and supervised classification of tree crown pixels yielded approximately 50%–60% classification accuracy overall; OBIA with image segmentation to delineate tree crowns and machine learning yielded up to 80% classification accuracy overall. Spectral response patterns and tree crown shape and geometric differences were interpreted in context of their ability to separate tree species of interest with these classification methods. Accuracy assessment was based on field-based forest inventory tree species identification. The paper provides a brief summary of future research issues that will influence the growth of this geomatics innovation in forest tree species classification and forest inventory.
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Wang, B., and S. N. Jeffers. "Effects of Cultural Practices and Temperature on Fusarium Root and Crown Rot of Container-Grown Hostas." Plant Disease 86, no. 3 (March 2002): 225–31. http://dx.doi.org/10.1094/pdis.2002.86.3.225.
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Fusarium root and crown rot of hosta plants grown in containers is caused primarily by Fusarium hostae. In an effort to develop an integrated strategy for managing this disease at nurseries, the effects of wounding, container mix content, watering schedule, and temperature on disease development were investigated. Plants were not wounded or were wounded by severing the roots, severing the roots and making incisions in the crown, or severing the roots and removing a small piece of the crown. Plants were inoculated by dipping roots and crowns into a suspension of conidia from one of two isolates of F. hostae. In addition, some plants were inoculated by wounding crowns with a scalpel dipped in a conidium suspension. Disease development was examined on plants grown at different temperatures (18, 25, or 32°C), grown in different container mixes (100% Canadian sphagnum peat, 100% aged and processed pine bark, or a mixture of 50% peat and 50% bark), and watered on different schedules (which kept the container mix wet, moist, or dry). Significant levels of disease occurred only on plants that were wounded when inoculated. Fusarium root and crown rot was more severe when both the roots and crowns were wounded than when only the roots were wounded. Disease symptoms developed when crowns of plants were wounded with a scalpel infested with conidia, suggesting that contaminated tools used for vegetative propagation may transfer F. hostae. Disease development also was affected significantly by container mix content, watering schedule, and temperature. In separate experiments, disease was most severe on plants grown in 100% aged pine bark, in dry container mix, or at 18 to 25°C. Disease development was significantly less when plants were grown in 100% peat, in wet container mix, or at 32°C. These results suggest that altering or manipulating cultural practices used to produce hostas in containers at nurseries can reduce the impact from Fusarium root and crown rot.
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Duan, Baofu, Weizeng Gong, Guoshan Ta, Xuxu Yang, and Xuewei Zhang. "Influence of Small, Clear Distance Cross-Tunnel Blasting Excavation on Existing Tunnel below." Advances in Civil Engineering 2019 (October 31, 2019): 1–16. http://dx.doi.org/10.1155/2019/4970269.
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The vibration effect generated during tunnel excavation can influence or damage adjacent tunnels. Studying and controlling the blasting vibration effect has important theoretical and practical significance, especially for new tunnels. This paper takes the tunnel project of Gao Jiu Lu-Jia Hua Cross Tunnel in Chongqing as the research background and assesses the blasting vibration influence in the up-down cross-tunnel. Onsite monitoring and numerical simulation were used to analyze peak particle velocity (PPV) changes, stress distribution, and crown settlement during the excavation process of Gao Jiu Lu I Tunnel at Jia Hua Tunnel Left Line in the cross-section. Influence laws of blasting excavation in a small, clear distance cross-tunnel on an existing tunnel below were obtained. Results show that new tunnel blasting vibrations exerted the largest influence on the crown of the existing tunnel below in the cross-section. The maximum tensile stress of the secondary lining of the existing tunnel below was mainly concentrated in the crown area. The maximum compressive stress during excavation was concentrated in the crown foot, and the stress value was less than the tensile and compressive strength of the concrete. The loosening of the surrounding rock from blasting excavation of the new tunnel caused secondary settlement of the existing tunnel crown below. The cumulative settlement value at the cross-section of the two tunnels was the largest. With an increase in axial distance from the cross-section of the existing tunnel crown, the settlement value gradually declined and became stable. These research results have reference value for the construction of a small, clear distance cross-tunnel and provide theoretical guidance for similar tunnel excavation projects in the future.
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Funada, R., T. Kubo, M. Tabuchi, T. Sugiyama, and M. Fushitani. "Seasonal Variations in Endogenous Indole-3-Acetic Acid and Abscisic Acid in the Cambial Region of Pinus densiflora Sieb. et Zucc. Stems in Relation to Earlywood-Latewood Transition and Cessation of Tracheid Production." Holzforschung 55, no. 2 (February 21, 2001): 128–34. http://dx.doi.org/10.1515/hf.2001.021.
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Summary Seasonal changes in the total amount (measured as ng cm−2) of endogenous indole-3-acetic acid (IAA) and abscisic acid (ABA) in the cambial region of Pinus densiflora Sieb. et Zucc. trees with crowns of different sizes were determined at different stem heights. The total amount of IAA varied seasonally in all trees and at all stem positions, being maximal in early summer (May or July). In a tree with a large crown, the total amount of IAA remained high after peaking and declined in autumn, whereas in a tree with small crown it decreased rapidly after peaking, in particular in the lower stem. The transition from earlywood to latewood occurred concurrently with the decrease in the total amount of IAA after it had peaked, suggesting the involvement of IAA in the control of latewood formation. Cessation of the production of tracheids also paralleled the decline in the total amount of IAA early in the growing season in the lower stem of the tree with a small crown, but not in the tree with a large crown. Thus, other factors in addition to declining IAA seem to be involved in halting the production of the tracheids. The total amount of ABA was lower than that of IAA in all trees and at all stem heights, and changes were not correlated with specific changes during the annual cycle of cambial activity and dormancy.
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Fearne, Janice M., and Alan H. Brook. "Small primary tooth-crown size in low birthweight children." Early Human Development 33, no. 2 (June 1993): 81–90. http://dx.doi.org/10.1016/0378-3782(93)90203-7.
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da Fonsêca-Genevois, Veronica, Virág Venekey, Wilfrida Decraemer, and Nic Smol. "Bernardius lineatus gen. n., sp. n. (Enoplida: Enchelidiidae), a remarkable nematode with ornamented cuticle from a Brazilian tropical sandy beach." Nematology 11, no. 2 (2009): 275–87. http://dx.doi.org/10.1163/156854109x429600.
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AbstractBernardius lineatus gen. n., sp. n. is described from a sandy beach at Tamandaré Bay, Brazil. It possesses the main characteristics of the family Enchelidiidae (Nematoda: Enoplida), but is unique by the presence of a body cuticle ornamented with longitudinal ridges formed by small rods, an entirely different character to all other members of the order Enoplida. The new genus is also characterised by a long, subdivided, buccal cavity with two subventral teeth and numerous denticles and the arrangement of the anterior sensilla in two crowns, the anterior crown being papilliform and the posterior crown consisting of six external labial and four cephalic sensilla, setiform. The relationships of the genera within the Enchelidiidae are discussed and an emended family diagnosis provided.
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Velisevich, Svetlana, Alexander Popov, and Sergei Goroshkevich. "Crown structure of 25-year-old Siberian stone pine grafts from mother trees of different ages." BIO Web of Conferences 11 (2018): 00043. http://dx.doi.org/10.1051/bioconf/20181100043.
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Inheritance of the age-specific traits of the Siberian stone pine crown structure by vegetative progeny was analyzed. Studies were carried out on 25-year-old grafts onto the same species seedlings as rootstocks. Scions for grafting were sampled from two groups of trees: young-mature (YM) and old growth (OG) trees in the southeast of the West Siberian Plain. The analysis of graft development showed that the YM trees had a significantly higher and thicker trunk, and their crowns were broader and denser due to a larger number of shoots. They multiplied by means of the branching feature due to the predominance of axes 2-3 branching orders. The OG trees formed small and transparent crowns that visually resembled separate branches from the upper parts of the crown of ontogenetically old trees. It was suggested that in the vegetative progeny of trees of a different ontogenetic state, the growth potential was epigenetically inherited.
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Lyons, Betsy, Nalini M. Nadkarni, and Malcolm P. North. "Spatial distribution and succession of epiphytes on Tsuga heterophylla (western hemlock) in an old-growth Douglas-fir forest." Canadian Journal of Botany 78, no. 7 (July 1, 2000): 957–68. http://dx.doi.org/10.1139/b00-064.
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We examined the distribution and abundance of nonvascular epiphytes on western hemlock trees in an old-growth coniferous forest focusing on patterns of epiphyte distribution at different spatial scales, epiphyte abundance amongst trees differing in size, and crown structures associated with epiphyte abundance. Total epiphyte cover was greatest in four canopy microhabitats: the upper canopy strata, crowns of large trees, lower crown branches, and inner branch plots. Epiphyte functional groups were stratified vertically within the stand and horizontally within branches. Alectorioid and "other" lichens were most abundant in the upper canopy and outer branch plots. Cyanolichens and Sphaerophorus globosus (Huds.) Vain. were most abundant in the lower to mid canopy. Although cyanolichens were most abundant in middle branch plots, Sphaerophorus was most abundant in inner branch plots. Bryophytes were most abundant in the lower canopy and inner branch plots. At the stand level, canopy height and tree size were the main influences on epiphytes. Within trees, plots closer to the tree trunk and lower in the crown had the greatest abundance of epiphytes. In this forest, understory trees were colonized first by bryophytes, not by alectorioid and "other" lichens as is common for small trees in young stands.Key words: epiphyte succession, lichens, western hemlock, old growth, forest canopy, crown structure.
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He, Qi Sheng, and Na Li. "Estimation of Individual Tree Parameters Using Small-Footprint LiDAR with Different Density in a Coniferous Forest." Advanced Materials Research 518-523 (May 2012): 5320–23. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.5320.
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In this paper, the effects of different LiDAR point density on individual tree parameters including tree height and crown diameter were investigated for the coniferous tree species in the Qilian Mountain area within Gansu province, western China. 10 different density data were acquired in field survey area, with the minimum density of 0.234 points/m2 and the maximum density of 0.6941 points/m2 for per flight. By summing up the different flight data, the different density LIDAR data from 0.234 points/m2 to 5.226 points/m2 for extracting tree height and crown diameter can be analyzed. The result showed that the number of extraction points and the extraction accuracy of tree height and crown width arrived at relative high level in point density of about 2.5 points per m2. When the point density increased, the increased extraction points and the extraction accuracy of tree height and crown width became slow. It means that about 2.5 points per m2 of LiDAR data density may provide relative high accurate individual tree parameters estimation.
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Holdaway, Margaret R. "Modeling Tree Crown Ratio." Forestry Chronicle 62, no. 5 (October 1, 1986): 451–55. http://dx.doi.org/10.5558/tfc62451-5.
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The crown ratio (the ratio of live crown length to total height) of an individual tree in a stand can be predicted from commonly measured stand and tree variables. For example, the ratio can be estimated using a nonlinear model combining stand basal area (BA) and initial tree diameter (DBH). The first term reflects the importance of competition on crown ratio; the second term differentiates among trees of different sizes.Biologically reasonable behavior is exhibited by the crown ratio model. The core model, with only two parameters, is very flexible; the full model, with four parameters, is capable of describing a full range of logical crown ratio growth patterns. When extrapolated, this nonlinear model continues to be biologically reasonable. In addition, the parameters are capable of theoretical interpretation.When tested on a Lake States data base of over 150 000 trees, the moan crown ratio estimation error was small, −2% for softwoods and +3% for hardwoods. Variation in weather and survey crew effects did not appear to contribute to errors in crown ratio estimation, although errors in crown ratio prediction did vary by region.
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Chmura, Daniel J., Mark G. Tjoelker, and Timothy A. Martin. "Environmental and genetic effects on crown shape in young loblolly pine plantations." Canadian Journal of Forest Research 39, no. 3 (March 2009): 691–98. http://dx.doi.org/10.1139/x08-200.
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Tree crown shape is an important trait affecting the light environment in forest canopies. We examined genetic and environmental effects on outer crown shape of young single-family stands of loblolly pine ( Pinus taeda L.). Crown diameter profiles were measured after canopy closure at four experimental sites in the southeastern US. The two examined families of contrasting aboveground productivity differed in crown length but not in their outer crown shapes or crown shape ratios, defined as the ratio of crown diameter to crown length. Within each site, intensive silvicultural treatment, consisting of fertilization and control of competing vegetation, had little effect upon crown shape. A strongly significant effect of site on crown shape parameters was found in the family grown at all four experimental sites; however, density differences among the experimental series likely accounted for a part of the across-sites variation in crown shape. In contrast to other studies on crown shape in trees, and to findings at age 2 years in the same stands, we conclude that family effects on the outer crown shape were small compared with the environmental effects in these 5-year-old pine plantations, following canopy closure.
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Campbell, Terry W. "Crown Vetch (Coronilla varia) Poisoning in a Budgerigar (Melopsittacus undulatus)." Journal of Avian Medicine and Surgery 20, no. 2 (June 2006): 97–100. http://dx.doi.org/10.1647/2005-009.1.
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Larocque, Guy R., and Peter L. Marshall. "Crown development in red pine stands. I. Absolute and relative growth measures." Canadian Journal of Forest Research 24, no. 4 (April 1, 1994): 762–74. http://dx.doi.org/10.1139/x94-101.
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The crown development of red pine (Pinusresinosa Ait.) plantations originating from different initial spacings was studied between 13 and 33 years of age. First, the effect of spacing on models used to predict crown width and crown ratio from diameter at breast height (DBH) and height was examined. Models for trees of different ages that included all the spacings were found to predict crown growth measures as well as separate models derived for each spacing. Second, the following crown relative growth measures were studied: crown width/crown length (crown shape ratio), crown surface/crown volume, and foliage biomass/crown volume. The way such measures changed over time under different initial spacings was studied; these findings were compared with changes in relative growth rate (RGR), which can be used to evaluate the effect of competitive stress. Crown shape ratio decreased with an increase in DBH in the absence of severe competition, and increased with DBH under severe competitive stress. The other two crown relative growth measures were always negatively correlated with DBH; this shows that large trees use their aerial growing space less efficiently than small trees at all stages of stand development. Only crown shape ratio changed in the same way as RGR.
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Schmid-Haas, Paul. "Zur Waldinventur gehört die Überwachung der Vitalität | Monitoring vitality is an important task for forest inventories." Schweizerische Zeitschrift fur Forstwesen 153, no. 2 (February 1, 2002): 68–75. http://dx.doi.org/10.3188/szf.2002.0068.
Full textAbstract:
We are interested in a continuous and healthy forest cover. Therefore vitality and stability of trees should be taken into account in most inventories. These factors influence the future development of the forest and are indispensable for economical as well as ecological planning. Forecasts on the basis of models that do not make use of this information are not always reliable. Increment is one of the best indicators of vitality. In addition,crown defoliation should be estimated, even though this estimator has a large random error and it is well known that only heavy crown defoliations cause an essential loss of productivity. On the other hand, it has also been known for some time that even small crown defoliation rates are correlated with subsequent mortality. Moreover, for Norway spruce and silver fir in the range 0–25% crown defoliation is strongly correlated with diameter increment, if trees are compared strictly within sample plots. Surprisingly, crown defoliation is also an indicator of diminished storm stability. No other quantitative estimator for crowns is as reliable and, despite the initial difficulties in its estimation,crown defoliation is an important indicator for vitality. Changes over time are even more valuable than the absolute value. It is alarming that the number of trees with crown defoliation of more than 25% tripled in Switzerland between 1985 and 2000 – a statistically highly significant increase. Storm damage analysis has shown that infections in butt and roots considerably increase future storm risk. A relatively simple examination of the supporting roots for infections now turns out to be an efficient method to assess tree stability. Further investigation shows strong correlations between infections in the supporting roots of Norway spruce and silver fir and increment and crown defoliation. Evidently, infections in the roots may show the cause of the correlations of crown defoliation and the rate of mortality, increment and storm stability. It is, of course, not possible to monitor vitality and stability in a comprehensive way. However, decisive information on the sustainability of the growing stock can be gained with clearly justifiable costs. These possibilities have not been fully exploited.
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Yan, Shijie, Linhai Jing, and Huan Wang. "A New Individual Tree Species Recognition Method Based on a Convolutional Neural Network and High-Spatial Resolution Remote Sensing Imagery." Remote Sensing 13, no. 3 (January 29, 2021): 479. http://dx.doi.org/10.3390/rs13030479.
Full textAbstract:
Tree species surveys are crucial to forest resource management and can provide references for forest protection policy making. The traditional tree species survey in the field is labor-intensive and time-consuming, supporting the practical significance of remote sensing. The availability of high-resolution satellite remote sensing data enable individual tree species (ITS) recognition at low cost. In this study, the potential of the combination of such images and a convolutional neural network (CNN) to recognize ITS was explored. Firstly, individual tree crowns were delineated from a high-spatial resolution WorldView-3 (WV3) image and manually labeled as different tree species. Next, a dataset of the image subsets of the labeled individual tree crowns was built, and several CNN models were trained based on the dataset for ITS recognition. The models were then applied to the WV3 image. The results show that the distribution maps of six ITS offered an overall accuracy of 82.7% and a kappa coefficient of 0.79 based on the modified GoogLeNet, which used the multi-scale convolution kernel to extract features of the tree crown samples and was modified for small-scale samples. The ITS recognition method proposed in this study, with multi-scale individual tree crown delineation, avoids artificial tree crown delineation. Compared with the random forest (RF) and support vector machine (SVM) approaches, this method can automatically extract features and outperform RF and SVM in the classification of six tree species.
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Lilieholm, Robert J., and Shih-Chang Hu. "Effect of Crown Scorch on Mortality and Diameter Growth of 19-Year-Old Loblolly Pine." Southern Journal of Applied Forestry 11, no. 4 (November 1, 1987): 209–11. http://dx.doi.org/10.1093/sjaf/11.4.209.
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Abstract Various levels of crown scorch on 19-year-old loblolly pine (Pinus taeda L.) were examined. Scorching and mortality were greatest for small-diameter, suppressed trees. Diameter growth one year after scorching was not diminished for lightly scorched trees but decreased with increasing crown scorch. During the second and third growing seasons after scorching, only trees receiving complete crown scorch exhibited significantly less diameter growth. South. J. Appl. For. 11(4):209-211.
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Szücs-Csillik, Iharka, and Zoia Maxim. "Simbolistica „cununii” - între cer și pământ." Anuarul Muzeului Etnograif al Transilvaniei 31 (December 20, 2017): 300–308. http://dx.doi.org/10.47802/amet.2017.31.18.
Full textAbstract:
From the cycle of the constellation symbolism we will approach the „Corona-Crown” constellation. The origin of these dress accessories gets lost in the darkness of time, standing testimony of the „Prehistoric Art”. The "Corona- Crown" is the small constellation Corona Borealis, visible in early summer, its brightest stars form a semicircular arc. The "crown" is a symbol and sign of belonging to the celestial world bearer, supernatural, divine, being worn at rituals of passage; of magic; of gratitude to heroes, to victors, to geniuses and to wise; of martyrdom; of coronation of kings, being a sign of immortality, honor, victory, greatness and joy. Archaeological discoveries will complete the mythological and ritualistic picture of these hairy ornaments, represented by „Moon Goddess” from Turdaș and „Bride of Trușești”. The story behind these clothing accessories represented in the Prehistoric Art and in the stars makes that the man to be closer to sky (heaven, deity), the microcosmic Earth merging with the macrocosmic Universe.
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Podoprigora, Vladimir, Anotoly Sorokin, Daniil Makarov, and Dmitry Kharlamov. "Crown’s anisotropy of a tree and scattering the signals of navigation satellites frequency band L1." E3S Web of Conferences 149 (2020): 02005. http://dx.doi.org/10.1051/e3sconf/202014902005.
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The model of interaction of signals from navigation satellites with the tree crown is considered. The contribution of the anisotropy of the dielectric constant to the cross section of radio wave scattering due to the orientational ordering of the branches is shown. The calculation of the scattering cross sections for small and large elements is presented. The tensor of orientational ordering of tree branches with division into tiers differing in the size and orientation of elements is introduced. Test measurements of navigation satellite signals passed through the crowns of spruce trees were carried out.
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Dehmlow, Eckehard V., and Sabine Schrader. "Notizen: Influence of Counter Ion Structure on the Direction of the Phase Transfer Catalytic Methylation of an Enol [1]." Zeitschrift für Naturforschung B 45, no. 3 (March 1, 1990): 409–12. http://dx.doi.org/10.1515/znb-1990-0320.
Full textAbstract:
Phase transfer catalytic (PTC) methylations of deoxybenzoin by dimethyl sulfate can be steered towards enol ether formation by large, sterically shielded ammonium ions or – more strongly – by large highly delocalized phospho-iminium (and presumably other large) cations. The C-alkylation direction is favoured by small, hard ammonium ions of the type RNMe3+ and by crown ethers, particularly benzo-crowns. O/C ratios can be varied between 0,75 and 63, the largest effects so far reported for ambident anions. These results should give guide-lines for alkylations of other ambident ions.
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Larocque, Guy R., and Peter L. Marshall. "Crown development in red pine stands. II. Relationships with stem growth." Canadian Journal of Forest Research 24, no. 4 (April 1, 1994): 775–84. http://dx.doi.org/10.1139/x94-102.
Full textAbstract:
The development of red pine (Pinusresinosa Ait.) stands originating under different initial spacings was examined using three measures of growth efficiency that are similar in concept to relative growth rate: diameter at breast height (DBH) increment/crown width, DBH increment/crown projection, and DBH increment/foliage biomass. These three measures of efficiency decreased with increasing DBH in the absence of severe competition and increased with increasing DBH under severe competitive stress. This indicates that small trees occupied their aerial growing space better and utilized their foliage to produce stemwood more efficiently than large trees in the absence of competition, and that the effect of competition was to reverse this trend. Absolute and relative growth rates for DBH and the three measures of growth efficiency were related very significantly to absolute (e.g., crown width) and relative (e.g., crown width/crown length) measures of crown development.
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Loghin, Ana-Maria, Johannes Otepka-Schremmer, and Norbert Pfeifer. "Potential of Pléiades and WorldView-3 Tri-Stereo DSMs to Represent Heights of Small Isolated Objects." Sensors 20, no. 9 (May 9, 2020): 2695. http://dx.doi.org/10.3390/s20092695.
Full textAbstract:
High-resolution stereo and multi-view imagery are used for digital surface model (DSM) derivation over large areas for numerous applications in topography, cartography, geomorphology, and 3D surface modelling. Dense image matching is a key component in 3D reconstruction and mapping, although the 3D reconstruction process encounters difficulties for water surfaces, areas with no texture or with a repetitive pattern appearance in the images, and for very small objects. This study investigates the capabilities and limitations of space-borne very high resolution imagery, specifically Pléiades (0.70 m) and WorldView-3 (0.31 m) imagery, with respect to the automatic point cloud reconstruction of small isolated objects. For this purpose, single buildings, vehicles, and trees were analyzed. The main focus is to quantify their detectability in the photogrammetrically-derived DSMs by estimating their heights as a function of object type and size. The estimated height was investigated with respect to the following parameters: building length and width, vehicle length and width, and tree crown diameter. Manually measured object heights from the oriented images were used as a reference. We demonstrate that the DSM-based estimated height of a single object strongly depends on its size, and we quantify this effect. Starting from very small objects, which are not elevated against their surroundings, and ending with large objects, we obtained a gradual increase of the relative heights. For small vehicles, buildings, and trees (lengths <7 pixels, crown diameters <4 pixels), the Pléiades-derived DSM showed less than 20% or none of the actual object’s height. For large vehicles, buildings, and trees (lengths >14 pixels, crown diameters >7 pixels), the estimated heights were higher than 60% of the real values. In the case of the WorldView-3 derived DSM, the estimated height of small vehicles, buildings, and trees (lengths <16 pixels, crown diameters <8 pixels) was less than 50% of their actual height, whereas larger objects (lengths >33 pixels, crown diameters >16 pixels) were reconstructed at more than 90% in height.
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Kim, Chun-Geun, So-Young Lee, and Hee-Myung Park. "Staged Orthodontic Movement of Mesiolinguoversion of the Mandibular Canine Tooth in a Dog." Journal of the American Animal Hospital Association 51, no. 1 (January 1, 2015): 49–55. http://dx.doi.org/10.5326/jaaha-ms-6041.
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A 10 mo old Sapsaree dog presented for evaluation and treatment of malocclusion causing palatal trauma. A class III malocclusion with mesiolinguoversion of the 404 and enamel hypoplasia was diagnosed based on oral examination. It was decided to attempt orthodontic correction of the mesiolinguoverted tooth using an elastic chain and inclined bite plane technique with crown restoration of the enamel hypoplasia teeth. One year after the orthodontic correction and composite removal, the mesiolinguoverted right mandibular canine tooth was moved to an acceptable location within the dental arch and the locally discolored right maxillary canine tooth was vital.
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Koike, S. T. "Sclerotinia Stem and Crown Rot of Corn-Salad Caused by Sclerotinia minor in California." Plant Disease 87, no. 10 (October 2003): 1264. http://dx.doi.org/10.1094/pdis.2003.87.10.1264a.
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Corn-salad or lamb's lettuce (Valerianella locusta) is a specialty leafy green vegetable that is grown commercially in California and is harvested fresh for use in salads. In 2001, field plantings of corn-salad in coastal California showed symptoms and signs of a previously undescribed disease. Initial symptoms consisted of a light tan discoloration at the crown and lower leaf attachment areas. Once this discoloration was observed, the crown rapidly developed a soft rot, attached leaves wilted, and the entire plant collapsed. White mycelium and small (0.5 to 3.0 mm in diameter), irregularly shaped, black sclerotia formed on the crowns and lower leaves. Isolations from symptomatic crowns, mycelium, and sclerotia produced colonies of Sclerotinia minor (1). Seven-week-old corn-salad plants grown in a peat moss-based rooting medium in pots were used to test pathogenicity. Sclerotia from six corn-salad isolates from the Salinas Valley were inserted into slots made in the potting mix adjacent to the crowns of plants. Sclerotia were not placed in slots for control corn-salad. All test plants were incubated in a greenhouse at 21 to 23°C. After 4 weeks, inoculated corn-salad plants wilted and collapsed, and S. minor was reisolated from necrotic crown and stem tissues. Uninoculated plants were asymptomatic. Using the same method, sclerotia from one lettuce (Lactuca sativa) isolate were used to inoculate corn-salad plants that produced similar symptoms. All experiments were repeated and results were similar. To our knowledge, this is the first report of corn-salad as a host of S. minor in California and the United States. The susceptibility of corn-salad to S. minor from lettuce indicates that this crop might contribute to inoculum levels and lettuce drop incidence for the extensive lettuce plantings in the Salinas Valley. Reference: (1) C. L. Patterson and R. G. Grogan. Plant Dis. 72:1046, 1988.
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Lin, Chenxi, Zhenong Jin, David Mulla, Rahul Ghosh, Kaiyu Guan, Vipin Kumar, and Yaping Cai. "Toward Large-Scale Mapping of Tree Crops with High-Resolution Satellite Imagery and Deep Learning Algorithms: A Case Study of Olive Orchards in Morocco." Remote Sensing 13, no. 9 (April 30, 2021): 1740. http://dx.doi.org/10.3390/rs13091740.
Full textAbstract:
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., >3 m) and small tree spacings (e.g., <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.
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Keane, Robert E., Elizabeth D. Reinhardt, Joe Scott, Kathy Gray, and James Reardon. "Estimating forest canopy bulk density using six indirect methods." Canadian Journal of Forest Research 35, no. 3 (March 1, 2005): 724–39. http://dx.doi.org/10.1139/x04-213.
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Canopy bulk density (CBD) is an important crown characteristic needed to predict crown fire spread, yet it is difficult to measure in the field. Presented here is a comprehensive research effort to evaluate six indirect sampling techniques for estimating CBD. As reference data, detailed crown fuel biomass measurements were taken on each tree within fixed-area plots located in five important conifers types in the western United States, using destructive sampling following a series of four sampling stages to measure the vertical and horizontal distribution of canopy biomass. The six ground-based indirect measurement techniques used these instruments: LI-COR LAI-2000, AccuPAR ceptometer, CID digital plant canopy imager, hemispherical photography, spherical densiometer, and point sampling. These techniques were compared with four aggregations of crown biomass to compute CBD: foliage only, foliage and small branchwood, foliage and all branchwood (no stems), and all canopy biomass components. Most techniques had the best performance when all canopy biomass components except stems were used. Performance dropped only slightly when the foliage and small branchwood canopy biomass aggregation (best approximates fuels available for crown fires) was employed. The LAI-2000, hemispherical photography, and CID plant canopy imager performed best. Regression equations that predict CBD from gap fraction are presented for all six techniques.
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King, David A., and Deborah A. Clark. "Allometry of emergent tree species from saplings to above-canopy adults in a Costa Rican rain forest." Journal of Tropical Ecology 27, no. 6 (September 30, 2011): 573–79. http://dx.doi.org/10.1017/s0266467411000319.
Full textAbstract:
Abstract:Relations between crown width and tree height and trunk diameter and tree height were measured for trees of all sizes of six large emergent species (Balizia elegans, Dipteryx panamensis, Hieronyma alchorneoides, Hymenolobium mesoamericanum, Lecythis ampla and Terminalia oblonga) in the lowland tropical wet forest at La Selva, Costa Rica. Thirty to 45 individuals were chosen per species to provide a relatively even height distribution from 1 m up to the maximum encountered height. Among small juveniles, the crown widths of the two species with the smallest leaves and horizontally spreading branches were greater than those of the four large-leaved species. On reaching and exceeding the canopy, all but one species showed pronounced increases in crown width with increasing height. These patterns are linked to leaf size and first branching height in small juveniles and low densities of emergent trees at La Selva and other tropical forests, where crown expansion in all directions enhances light interception under the equatorial sun in trees that are not crowded by neighbours of similar height.
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Antos, Joseph A., Audrey E. McPherson, and Heidi J. Guest. "Growth rates and crown morphology of Abies amabilis in the seedling bank of an ancient subalpine conifer forest." Canadian Journal of Forest Research 50, no. 11 (November 2020): 1124–30. http://dx.doi.org/10.1139/cjfr-2020-0087.
Full textAbstract:
The population dynamics of shade-tolerant tree species often includes a seedling bank — small trees persisting in the understory until canopy opening allows increased height growth. We studied the growth and morphology of 0.1–1.3 m tall Abies amabilis Douglas ex J. Forbes trees in the seedling bank of an ancient (>1300 years old) subalpine conifer forest on Vancouver Island, western Canada. We determined rates of height growth by counting growth rings at 10 cm intervals along the main stem and assessed crown morphology by measuring the length and location of each branch along the main stem. These small trees were very old (mean basal ring count, 112 years) and grew very slowly, taking on average 170 years to reach a height of 1 m. Instead of the typical conical form of open-grown Abies Mill., seedling bank individuals had flat crowns. Most branches were near the top of the main stem. The maximum distance along the main stem plus a branch was 1.6 times the main stem length, indicating that resource allocation is focused on lateral growth. The ability to grow slowly and adjust crown morphology allows seedling bank trees to persist for decades to centuries and to retain the possibility of release and growth into the canopy.
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Kirk, W. W., P. S. Wharton, R. L. Schafer, P. Tumbalam, S. Poindexter, C. Guza, R. Fogg, et al. "Optimizing Fungicide Timing for the Control of Rhizoctonia Crown and Root Rot of Sugar Beet Using Soil Temperature and Plant Growth Stages." Plant Disease 92, no. 7 (July 2008): 1091–98. http://dx.doi.org/10.1094/pdis-92-7-1091.
Full textAbstract:
Azoxystrobin is applied early in the sugar beet growing season in north-central United States for control of Rhizoctonia damping-off and Rhizoctonia crown and root rot caused by Rhizoctonia solani anastomoses groups (AGs) 4 and 2-2, respectively. Fungicide application timings based on crop growth stage and soil temperature thresholds were evaluated in inoculated small-scale trials and in commercial fields with a history of Rhizoctonia crown and root rot. Soil temperature thresholds of 10, 15, and 20°C were selected for fungicide application timings and used to test whether soil temperature could be used to better time applications of azoxystrobin. In both small- and large-plot trials, timing applications after attainment of specific soil temperature thresholds did not improve efficacy of azoxystrobin in controlling damping-off or Rhizoctonia crown and root rot compared with application timings based on either planting date, seedling development, or leaf stage in a susceptible (E-17) and a resistant (RH-5) cultivar. Application rate and split application timings of azoxystrobin had no significant effect on severity of crown and root rot. Other environmental factors such as soil moisture may interact with soil temperature to influence disease development. Cv. RH-5 had higher sugar yield attributes than the susceptible cultivar (E-17) in seasons conducive and nonconducive to crown and root rot development. All isolates recovered from both small- and large-plot trials in all years were AG 2-2. R. solani AG 4 was not identified in any samples from any year.
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Ao, Mingrui, Miaocao Wang, and Fulong Zhu. "Investigation of the Turbulent Drag Reduction Mechanism of a Kind of Microstructure on Riblet Surface." Micromachines 12, no. 1 (January 6, 2021): 59. http://dx.doi.org/10.3390/mi12010059.
Full textAbstract:
With the k-ε renormalization group turbulence model, the drag reduction mechanism of three- dimensional spherical crown microstructure of different protruding heights distributing on the groove surface was studied in this paper. These spherical crown microstructures were divided into two categories according to the positive and negative of protruding height. The positive spherical crown micro-structures can destroy a large number of vortexes on the groove surface, which increases relative friction between water flow and the groove surface. With decreasing the vertical height of the spherical crown microstructure, the number of rupture vortexes gradually decreases. Due to the still water area causes by the blocking effect of the spherical crown microstructure, it was found that the shear stress on the groove surface can be reduced, which can form the entire drag reduction state. In another case, the spherical crown microstructures protrude in the negative direction, vortexes can be generated inside the spherical crown, it was found that these vortexes can effectively reduce the resistance in terms of pressure and friction. In a small volume, it was shown that the surface drag reduction rate of spherical crown microstructures protrudes in negative directions can be the same as high as 24.8%.
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Krajnc, Luka, and Jožica Gričar. "The Effect of Crown Social Class on Bark Thickness and Sapwood Moisture Content in Norway Spruce." Forests 11, no. 12 (December 10, 2020): 1316. http://dx.doi.org/10.3390/f11121316.
Full textAbstract:
The research study examined the effect of tree properties (crown social class, diameter at breast height (DBH), and tree height) on bark thickness (BT) and sapwood moisture content (SMC) in Norway spruce (Picea abies (L.) H. Karst.). Both examined variables were shown to be positively affected by DBH and tree height. The relationship between DBH and SMC varied among crown social classes, while the relationship between DBH and BT was relatively constant across crown social classes. Crown social class had a relatively small effect on BT and SMC, having a more pronounced effect on SMC than on BT. The relationship between tree height and BT did not vary across crown social classes, while the relationship between SMC and tree height was found to change slightly across crown social classes. Measurements of BT and SMC in the field are affordable, fast, and easy to use. Both variables could potentially be used to improve predictions of bark beetle attacks, as they reflect the physiological state of an individual tree.
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NEDELEA, Raluca Ioana, Adrian TOMA, and Andreea MARINCUS. "The Conservative Approach to Dental Crown Fractures in Dogs and Cats." Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Veterinary Medicine 76, no. 2 (November 25, 2019): 201. http://dx.doi.org/10.15835/buasvmcn-vm:2019.0023.
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Dental crown fractures in small animal pathology are common dental issues in every day practice. The most frequently performed procedure is extraction with all the negative consequences.The conservative approach to dental crown fractures involves endodontic treatment and coronal reconstruction in order to keep the fractured teeth on the dental arch.They were taken into study 74 dental crown fractures involving the pulp chamber, leaving the root undamaged.Clinical and radiological one-year check-up revealed us that the conservative approach to dental crown fractures in dogs and cats, when the selection criteria correspond to the indications of the specialized literature and when it is performed by latest protocols, is a reliable alternative to veterinary dental extractions.
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Herschede, Sarah R., Hassan Gneid, Taylor Dent, Ellen B. Jaeger, Louise B. Lawson, and Nathalie Busschaert. "Bactericidal urea crown ethers target phosphatidylethanolamine membrane lipids." Organic & Biomolecular Chemistry 19, no. 17 (2021): 3838–43. http://dx.doi.org/10.1039/d1ob00263e.
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In this manuscript we report a small molecule that can selectively bind to the bacterial lipid phosphatidylethanolamine and consequently functions as an antibacterial agent against certain Gram-positive bacteria.
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Moore, T. L., L. E. Valentine, M. D. Craig, G. E. St J. Hardy, and P. A. Fleming. "Does woodland condition influence the diversity and abundance of small mammal communities?" Australian Mammalogy 36, no. 1 (2014): 35. http://dx.doi.org/10.1071/am13007.
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Loss of mammal species in Australia in the last 200 years has been attributed to many factors including habitat removal and altered fire regimes. Decline in tree condition could contribute further to the ongoing decline of mammals. Eucalyptus wandoo trees are currently undergoing a decline in condition that can result in a loss of canopy and other changes to the habitat. This paper examines the relationships between E. wandoo tree condition, habitat characteristics and small mammal species richness and abundance. Live-capture trapping was conducted at 24 E. wandoo sites at Dryandra State Forest and Wandoo Conservation Park, Western Australia. Condition and microhabitat variables of E. wandoo were recorded for each site. Generalised additive mixed models revealed a range of habitat and tree condition characteristics that influenced small mammal abundance and species richness, including site litter cover, crown dieback, understorey vegetation cover and tree density. The availability of coarse woody debris played a large role in explaining the abundance of Cercartetus concinnus and Antechinus flavipes, along with other microhabitat and tree condition variables, such as tree leaf litter and crown dieback. Epicormic growth, crown density and the distance to the drift fence from E. wandoo trees were the common variables in the best model for the abundance of Sminthopsis griseoventer. The decline in condition of E. wandoo and the subsequent modifications to the microhabitat are correlated with changes in the small mammal community. A better understanding of how the decline of E. wandoo impacts small mammal communities could improve management practices in E. wandoo woodlands.
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Tomita, Mizuki, Yoshihiko Hirabuki, Yuji Araki, Shinji Tsukawaki, Bora Ly, and Peou hang. "Potential of High-Resolution Satellite Imagery for Mapping Distribution and Evaluating Ecological Characteristics of Tree Species at the Angkor Monument, Cambodia." Journal of Landscape Ecology 7, no. 3 (January 29, 2015): 49–59. http://dx.doi.org/10.2478/jlecol-2014-0021.
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Abstract Large trees play several vital roles in the Angkor monuments landscape. They protect biodiversity, enhance the tourism experience, and provide various ecosystem services to local residents. A clear understanding of forest composition and distribution of individual species, as well as timely monitoring of changes, is necessary for conservation of these trees. using traditional field work, obtaining this sort of data is time-consuming and labour-intensive. This research investigates classification of very high resolution remote sensing data as a tool for efficient analyses. QuickBird satellite imagery was used to clarify the tree species community in and around Preah Khan temple, to elucidate differences in ecological traits among the three dominant species (Dipterocarpus alatus, Lagerstroemia calyculata and Tetrameles nudiflora), and to identify crowns of the dominant species. Population structures of trees were determined using a 14.26ha study plot. Species name, DBH, height, height under the crown and crown area were recorded for all trees over 40 cm in DBH. Tree locations were also recorded so as to provide references for the imagery analysis. Ecological traits of the dominant species were estimated using regressions by an expanded allometric equation for both large and small trees, based on DBH, height, height under the crown and crown width. The total number of species in the study plot was 45. From a spatial perspective, the three dominant species over 100 cm in DBH were segregated from each other. D. alatus, L. calyculata and T. nudiflora were concentrated, respectively, along the approach to the temple, near the centre of the complex, and on the walls of the monument. Object Based Image Analysis (OBIA) conducted using QuickBird satellite imagery, showed that crowns of D. alatus were largely determined by maximum of NIR layer and mean of digital number in panchromatic layer. Differences in the parameters for both asymptotic height and spatial distribution among the dominant species, result from differences in ecological traits, and enhance the value of the tourism resource by providing a dramatic shift of forest scenery that can be enjoyed by visitors to the monument.
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Zhao, Lei, Haijun Yang, Heng Xie, Jieli Duan, Mohui Jin, Han Fu, Jie Guo, Zeyu Xu, Tingting Jiang, and Zhou Yang. "Effects of Morphological and Anatomical Characteristics of Banana Crown Vascular Bundles on Cutting Mechanical Properties Using Multiple Imaging Methods." Agronomy 10, no. 8 (August 14, 2020): 1199. http://dx.doi.org/10.3390/agronomy10081199.
Full textAbstract:
To obtain the appropriate mechanized cutting region for banana dehanding, the methods of X-ray Computed Tomography (CT), Paraffin-embedded tissue section, and scanning electron microscopy (SEM) were adopted to observe the morphological and anatomical characteristics of vascular bundles of the banana crown. The results indicated that the crown can be divided into three regions, viz., the central stalk–crown transition region (CSCTR), the crown expansion region (CER), and the crown–finger transition region (CFTR). According to the obtained characteristics, the cutting mechanical properties are found to be affected by the relative angle between the vascular bundle and cutter (RAVBC) and the vascular bundle density. In CSCTR, due to the opposite change of RAVBC and density, the cutting mechanical properties become unstable and the cutting energy decreases gradually from 4.30 J to 2.57 J. While in CER, the cutting mechanical properties tend to be stable, and the cutting energy varies in a small range (2.83–2.92 J), owing to the small changes of RAVBC and density. When the vascular bundles cross from the CER to CFTR, the cutting energy increases with the increase of RAVBC and density, which varies from 3.37 to 4.84 J. Accordingly, the appropriate cutting region for dehanding, which can reduce the energy consumption and improve the cutting efficiency, is ascertained to be between CSCTR and CER.
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Kawamura, Koji, and Hiroshi Takeda. "Light environment and crown architecture of two temperate Vaccinium species: inherent growth rules versus degree of plasticity in light response." Canadian Journal of Botany 80, no. 10 (October 1, 2002): 1063–77. http://dx.doi.org/10.1139/b02-096.
Full textAbstract:
Light environment and crown architecture were investigated in two closely related species (deciduous Vaccinium hirtum and evergreen Vaccinium bracteatum) in a young and an old secondary forest. Light environment was determined by photographic estimation of light above ramets (30500 cm tall). Crown architecture was examined to determine the effects of ramet age and light level on several architectural traits. In the young secondary forest, both species were mainly found in large gaps. In the old secondary forest, V. bracteatum persisted in deep shade, whereas V. hirtum was concentrated in small gaps. Vaccinium hirtum had narrower crowns and thinner stems than V. bracteatum, indicating lower structural costs in V. hirtum. Older ramets had greater total shoot extension (only V. bracteatum) and shorter length of the current-year shoots (markedly so in V. hirtum) than younger ramets. In higher light levels, V. bracteatum had greater aboveground growth and higher leaf area indices, whereas V. hirtum had only greater flowering intensity. Architectural traits were highly correlated with ramet age in V. hirtum, whereas these were mainly affected by light in V. bracteatum, indicating higher architectural plasticity in the latter species. The differences in architecture and its plasticity can be relevant for the segregation of light habitats between the species.Key words: light environment, crown architecture, leaf display, morphological plasticity, current-year shoot.
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Fu, Chunqing, and Yuchun Gao. "Numerical Analysis on the Behavior of Existing Tunnels Subjected to the Undercrossed Shield Tunneling at a Small Proximity." Advances in Civil Engineering 2020 (December 31, 2020): 1–12. http://dx.doi.org/10.1155/2020/8823331.
Full textAbstract:
Shield excavation in a proximity to existing tunnels inevitably causes deformation and stress change of the adjacent tunnels. Based on the project of new metro line in Beijing where the shield tunnel was constructed under existing tunnel, a modified equivalent stiffness model for the existing tunnel is proposed. Based on this, a three-dimensional finite element is established, and subsequently the proposed modified equivalent stiffness model and the previous model are implemented into the finite element model (FEM), respectively, and then the effectiveness of it is verified through comparison with the field measurements. The results indicate that the modified equivalent stiffness model has excellent agreement with the monitoring value. The impacts of key parameters including undercrossing angle, vertical spacing, and soil parameters on the crown settlement of the existing tunnel are investigated. The maximum settlement of the existing tunnel crown decreases as the undercrossing angle increases. The decease of vertical spacing between the newly constructed tunnel and the existing tunnel leads to an increase of the peak value of crown settlement. As for the soil parameters, friction angle φ is the dominant parameter affecting crown settlement of the existing tunnel whereas the cohesion c is least influential. During the process of route selection, it is suggested to keep the vertical spacing between new tunnel and the existing tunnel greater than the external diameter of the new metro tunnel. For the situation of undercrossing an existing tunnel within an extremely small clearance, it is recommended to strengthen the soil as necessary.