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Influence of a narrow depth gradient and season on the morphology, phenology, and epibiosis of the brown alga Sargassum cymosum

JACOBUCCI, G. B.; GUETH, A. Z.; TURRA, A.; LEITE, F. P. P.
Fonte: CAMBRIDGE UNIV PRESS Publicador: CAMBRIDGE UNIV PRESS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.39%
Temporal and spatial fluctuations of environmental parameters are normally assigned as causes of variations in morpho-phenological characters of seaweeds and in their epibionts, but formal tests of such hypotheses are lacking, especially in narrow gradients. The present study evaluated the influence of a very small depth gradient (1 to 3 m) and of subtle seasonality characteristic of tropical areas on morpho-phenological traits and on the occurrence of sessile epiphytic organisms using a controlled orthogonal sampling design in a sublittoral population of the tropical brown alga Sargassum cymosum. Four temporal samples were obtained over a one-year period at three depths using nine replicates. The wet weight, maximum length, number of primary and secondary branches, and proportion of secondary branches with receptacles were recorded. Epibiosis was estimated by visual evaluation of percentage cover on secondary branches. Algal morphology varied as a function of the period of the year (weaker effect) and depth (stronger effect) but in different ways for each variable analysed. In general, fronds tended to be shorter, heavier, and more ramified in shallower areas. In relation to time, the morphological characters tended mostly to present higher values in January (summer) and/or April (autumn). Frequency of receptacles did not depend on algal morphology and depth at all but varied in time...

Resistência ao cisalhamento de sistemas adesivos autocondicionantes e de condicionamento total aplicados em dentina, em profundidades diferentes; Shear bond of different self etch and total etch adhesive systems applied in different dentin depth

Rosa, Ana Carolina Maito Villela
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 12/08/2009 PT
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36.42%
Objetivos: O propósito deste estudo foi o de avaliar, quanto à resistência ao cisalhamento, o comportamento de quatro sistemas adesivos, Adper Single Bond 2, Adper Prompt L-Pop, Magic Bond DE e Self Etch Bond em função das faces vestibulares e linguais e da profundidade da dentina. Material e Método: Quarenta terceiros molares extraídos tiveram suas raízes removidas e as coroas seccionadas no sentido mésio-distal. As faces vestibulares e linguais foram incluídas em anel de PVC/resina acrílica e divididas em grupos, um vestibular e um lingual para cada adesivo selecionado. Para se avaliar as diferentes profundidades de dentina, os mesmos corpos-de-prova preparados para a avaliação da resistência adesiva da camada superficial foram utilizados. Os espécimes foram então identificados e desgastados, posterior e seqüencialmente, para as profundidades de 0,5, 1,0, 1,5, 2,0mm. Cada profundidade foi avaliada por meio do método de cisalhamento ISO TR 11405, usando uma máquina universal de testes (EMIC-2000), regulada a 0,5mm/minuto e célula de carga de 200 Kgf. Os resultados foram submetidos à análise estatística de variância (Testes ANOVA, Tukey e Scheffé). Resultados: Houve diferença estatística significante (p<0...

Influence of a narrow depth gradient and season on the morphology, phenology, and epibiosis of the brown alga Sargassum cymosum

JACOBUCCI, G. B.; GUETH, A. Z.; TURRA, A.; LEITE, F. P. P.
Fonte: CAMBRIDGE UNIV PRESS Publicador: CAMBRIDGE UNIV PRESS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.39%
Temporal and spatial fluctuations of environmental parameters are normally assigned as causes of variations in morpho-phenological characters of seaweeds and in their epibionts, but formal tests of such hypotheses are lacking, especially in narrow gradients. The present study evaluated the influence of a very small depth gradient (1 to 3 m) and of subtle seasonality characteristic of tropical areas on morpho-phenological traits and on the occurrence of sessile epiphytic organisms using a controlled orthogonal sampling design in a sublittoral population of the tropical brown alga Sargassum cymosum. Four temporal samples were obtained over a one-year period at three depths using nine replicates. The wet weight, maximum length, number of primary and secondary branches, and proportion of secondary branches with receptacles were recorded. Epibiosis was estimated by visual evaluation of percentage cover on secondary branches. Algal morphology varied as a function of the period of the year (weaker effect) and depth (stronger effect) but in different ways for each variable analysed. In general, fronds tended to be shorter, heavier, and more ramified in shallower areas. In relation to time, the morphological characters tended mostly to present higher values in January (summer) and/or April (autumn). Frequency of receptacles did not depend on algal morphology and depth at all but varied in time...

Analysis of test methods for texture depth evaluation applied in Portugal

Freitas, Elisabete F.; Pereira, Paulo A. A.; Antunes, M. L.; Domingos, P.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em /11/2008 ENG
Relevância na Pesquisa
36.46%
Texture is a surface characteristic which has a very wide influence on pavements functional quality. It is currently assessed by a number of test methods. Road Administrations face the problems of dealing with data acquired by different methods and, in addition to that, the repeatability and reproducibility of the results. This paper presents an analysis of test methods used for texture depth evaluation in Portugal: the volumetric patch method and two methods based on surface profiles. Hence, three roads with low (dense asphalt), medium (“open texture asphalt”) and high (porous asphalt) texture depths were selected, where five profilometers made five runs. Two subsections of 150 m length were also selected to carry out the volumetric patch test. The texture indicators analysed were: the mean texture depth, the mean profile depth and the sensor measured texture depth. The average and the standard deviation were the statistical parameters used for the analysis. The results obtained for each method are significantly different and a good correlation between the mean profile depth and the sensor measured texture depth was established.

The effect of depth and sediment type on the spatial distribution of shallow soft-bottom amphipods along the southern Portuguese coast

Carvalho, Susana; Cunha, Marina R.; Pereira, Fábio; Pousao-Ferreira, P.; Santos, M. N.; Gaspar, M. B.
Fonte: Springer Verlag Publicador: Springer Verlag
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.44%
The present study provides updated information on amphipod assemblages of the southern Portuguese coast, the most south-western part of continental Europe. The influence of depth and sediment type on the spatial distribution of shallow soft-bottom amphipods was tested by means of univariate and multivariate methods. Samples were collected down to 40 m depth within areas ranging from very fine sand to gravel. The ratio between density and diversity was found to increase with depth and from coarser to finer sediments. Both physical variables tested were found to play a major role in structuring amphipod assemblages. However, some dominance of depth was evident as samples were mainly separated according to this variable. Moreover, while only 15 taxa were common to all depth levels, 35 were collected from all sediment types. Both depth and sediment type may override the potential effects of geographical location, as samples from different areas along the southern Portuguese coast were biologically related. A peculiar habitat was sampled in this study: a maerl bed, which was confirmed to be a hotspot of density. Nevertheless, this habitat did not harbor a distinct amphipod assemblage but some taxa such as Caprella spp., Lembos websteri...

Intermediate depth and deep earthquakes: complexity of the Ibero-Magrhebian region

Buforn, E.; Cesca, S.; Bezzeghoud, M.; del Fresno, C.; Udias, A.
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Aula
POR
Relevância na Pesquisa
36.39%
The Ibero-Magrhebian region is located at the plate boundary between Eurasia and Africa and it is a tectonically complex region. A sign of the complexity, is the occurrence of intermediate depth earthquakes (40

Perceptual atoms: proximal motion vector-structures and the perception of object motion in depth

Hershenson,Maurice
Fonte: Conselho Brasileiro de Oftalmologia Publicador: Conselho Brasileiro de Oftalmologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2003 EN
Relevância na Pesquisa
36.42%
A framework is proposed for analyzing the perception of motion in depth produced by simple proximal motion patterns of two to four points. The framework includes input structure, perceptual system constraints, and a depth scaling mechanism. The input is relational stimulation described by two proximal dimensions, orientation and separation, that can change or remain constant over the course of a motion pattern. Combinations of change or no-change in these dimensions yield four basic patterns of proximal stimulation: parallel, circular, perspective, and parallax. These primary patterns initiate automatic processing mechanisms - a unity constraint that treats pairs of points as connected and a rigidity constraint that treats the connection as rigid. When the constraints are activated by perspective or parallax patterns, the rigid connection between the points also appears to move in depth. A scaling mechanism governs the degree to which the objects move in depth in order to maintain the perceived rigidity. Although this framework is sufficient to explain perceptions produced by three- and four-point motion patterns in most cases, some patterns require additional configurational factors to supplement the framework. Nevertheless, perceptual qualities such as shrinking...

Intracranial depth electrodes implantation in the era of image-guided surgery

Centeno,Ricardo Silva; Yacubian,Elza Márcia Targas; Caboclo,Luis Otávio Sales Ferreira; Carrete Júnior,Henrique; Cavalheiro,Sérgio
Fonte: Academia Brasileira de Neurologia - ABNEURO Publicador: Academia Brasileira de Neurologia - ABNEURO
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2011 EN
Relevância na Pesquisa
36.39%
The advent of modern image-guided surgery has revolutionized depth electrode implantation techniques. Stereoelectroencephalography (SEEG), introduced by Talairach in the 1950s, is an invasive method for three-dimensional analysis on the epileptogenic zone based on the technique of intracranial implantation of depth electrodes. The aim of this article is to discuss the principles of SEEG and their evolution from the Talairach era to the image-guided surgery of today, along with future prospects. Although the general principles of SEEG have remained intact over the years, the implantation of depth electrodes, i.e. the surgical technique that enables this method, has undergone tremendous evolution over the last three decades, due the advent of modern imaging techniques, computer systems and new stereotactic techniques. The use of robotic systems, the constant evolution of imaging and computing techniques and the use of depth electrodes together with microdialysis probes will open up enormous prospects for applying depth electrodes and SEEG both for investigative use and for therapeutic use. Brain stimulation of deep targets and the construction of "smart" electrodes may, in the near future, increase the need to use this method.

Insights into the Mechanism of Intermediate-Depth Earthquakes from Source Properties as Imaged by Back Projection of Multiple Seismic Phases

Langmuir, Charles H.; Ishii, Miaki; Kiser, E.; Shearer, P. M.; Hirose, H.
Fonte: American Geophysical Union Publicador: American Geophysical Union
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.39%
This study investigates the spatial and temporal distribution of energy release of large, intermediate-depth earthquakes using a modified back projection technique first used to study the 2004 Sumatra-Andaman megathrust event. Multiple seismic phases are included in the back projection analysis, which provides the capability to determine the energy distribution with respect to depth and time. A total of 22 intermediate-depth earthquakes with moment magnitudes greater than or equal to 6.5 are investigated with hypocentral depths between 100 and 300 km. For most of these events, the vertical extent of energy release is either below the resolution of this study ((leq5 km)) or slightly above ((leq15 km)). This observation agrees with previous studies that find large, intermediate-depth earthquakes have subhorizontal rupture planes. The results also show a significant portion of the events have multiple rupture planes that are well separated in depth. The closeness in time of the ruptures on separate planes and the distance between the planes suggest dynamic triggering where the P waves from the first rupture initiate rupture on the second plane. We propose that a dehydration embrittlement mechanism combined with preferentially hydrated subhorizontal faults can explain the observations of dominant subhorizontal rupture planes and the frequent occurrence of rupture complexity involving multiple subevents.; Earth and Planetary Sciences

Global Depth Perception from Familiar Scene Structure

Torralba, Antonio; Oliva, Aude
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Formato: 22 p.; 40226611 bytes; 7425856 bytes; application/postscript; application/pdf
EN_US
Relevância na Pesquisa
36.42%
In the absence of cues for absolute depth measurements as binocular disparity, motion, or defocus, the absolute distance between the observer and a scene cannot be measured. The interpretation of shading, edges and junctions may provide a 3D model of the scene but it will not inform about the actual "size" of the space. One possible source of information for absolute depth estimation is the image size of known objects. However, this is computationally complex due to the difficulty of the object recognition process. Here we propose a source of information for absolute depth estimation that does not rely on specific objects: we introduce a procedure for absolute depth estimation based on the recognition of the whole scene. The shape of the space of the scene and the structures present in the scene are strongly related to the scale of observation. We demonstrate that, by recognizing the properties of the structures present in the image, we can infer the scale of the scene, and therefore its absolute mean depth. We illustrate the interest in computing the mean depth of the scene with application to scene recognition and object detection.

Partition lenses for extended depth of field

Chu, Kaiqin (1972 - ); George, Nicholas
Fonte: University of Rochester. Publicador: University of Rochester.
Tipo: Tese de Doutorado Formato: Number of Pages:xxv, 193 leaves
ENG
Relevância na Pesquisa
36.39%
Thesis (Ph. D.)--University of Rochester. Institute of Optics, 2010.; In the thesis we describe a topic in the field of integrated computational imaging systems, where we seek to establish considerable improvement in extending the depth of field over the well-known classical limit established by Lord Rayleigh in the late 1870’s. Theory, computer simulation and experiment are given for a new type of lens where the correlation among different segments of the aperture of the lens is broken. Three examples of these lenses are given. One is a lens partitioned into two parts by polarization. The second example is an all glass lens partitioned by optical path lengths. And the third is a combination of two logarithmic lenses, where the correlation between the lenses is broken by means of controlled optical path difference. For a conventional lens partitioned by polarization or optical path length, we describe the partitioning methods from the view point of physical optics and random process theory. Through numerical and laboratory studies of the partitioned lens we find that the depth of field will be extended to be twice the Rayleigh limit. When combined with the Metric Parameter Maximum Entropy method for digital processing...

Patterns in diatom assemblages across a gradient of water depth in an Adirondack lake: Are patterns across regions reproducible?

McGowan, Mollie Sinead
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN
Relevância na Pesquisa
36.46%
Diatoms have been used as indicators of depth in paleolimnological studies but their consistency has recently been challenged. It was suggested that, for diatoms to be strengthened as a depth proxy, their distributions must be reproducible across regions. To assess this proposition, surface-sediment samples were collected along a transect in Wolf Lake, Adirondacks, New York, an oligotrophic lake located in a relatively pristine environment, to evaluate the consistency of diatom species across a depth gradient. The diatom distribution found at Wolf Lake was qualitatively compared to changes in diatom species from oligotrophic lakes in northwest Ontario (Kingsbury, 2012). In Wolf Lake, diatoms changed with depth and can be broadly grouped into three zones: a nearshore benthic zone (B1), a mid-depth zone (B2) and a planktonic zone (P). The near shore, B1 zone, was mainly characterized by species in the genera Achnanthes, Brachysira, and Eunotia. The mid-depth, B2 zone, was composed of a variety of species with peaks in Navicula submuralis and Fragilaria construens. The planktonic zone was dominated by Cyclotella stelligera and Tabellaria flocculosa v. linearis. The transition of the P to B2 zone was located at ~8.5 m which is close to the limit of light...

Three Essays on Market Depth in Futures Markets

Aidov, Alexandre
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Relevância na Pesquisa
36.53%
Liquidity is an important market characteristic for participants in every financial market. One of the three components of liquidity is market depth. Prior literature lacks a comprehensive analysis of depth in U.S. futures markets due to past limitations on the availability of data. However, recent innovations in data collection and dissemination provide new opportunities to investigate the depth dimension of liquidity. In this dissertation, the Chicago Mercantile Exchange (CME) Group proprietary database on depth is employed to study the dynamics of depth in the U.S. futures markets. This database allows for the analysis of depth along the entire limit order book rather than just at the first level. The first essay examines the characteristics of depth within the context of the five-deep limit order book. Results show that a large amount of depth is present in the book beyond the best level. Furthermore, the findings show that the characteristics of five-deep depth between day and night trading vary and that depth is unequal across levels within the limit order book. The second essay examines the link between the five-deep market depth and the bid-ask spread. The results suggest an inverse relation between the spread and the depth after adjusting for control factors. The third essay explores transitory volatility in relation to depth in the limit order book. Evidence supports the relation between an increase in volatility and a subsequent decrease in market depth. Overall...

Diversity and depth-related patterns of mobile invertebrates associated with kelp forests

Coleman, M.; Vytopil, E.; Goodsell, P.; Gillanders, B.; Connell, S.
Fonte: C S I R O Publishing Publicador: C S I R O Publishing
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
36.39%
It is remarkable that although the importance of depth is firmly rooted in the discipline of marine ecology, so little is understood about depth-related patterns of invertebrates in kelp forests, particularly in temperate Australia. We tested for the existence of broad scale patterns in depth-related diversity and abundance of mobile invertebrates in kelp holdfasts (Ecklonia radiata) across several spatial scales along 500 km of coastline. There was a greater abundance and richness of common taxa in holdfasts from shallow relative to deep waters. Strikingly, a disproportionately large percentage (60%) of species was unique to holdfasts from shallow reefs, suggesting that shallow environments create conditions that facilitate a rich biodiversity of invertebrate fauna. We conclude that depth-related variation in kelp forests may not be completely idiosyncratic, and coherent research programs of a broader scale and scope may unify subsets of fragmented knowledge that previously provided little insight into general depth-related patterns of invertebrate assemblages.; Melinda A. Coleman, Elaine Vytopil, Paris J. Goodsell, Bronwyn M. Gillanders and Sean D. Connell; © CSIRO 2007

Depth Relationships in Porosity and Permeability in the Mount Simon Sandstone (Basal Sand) of the Midwest Region: Applications for Carbon Sequestration

Medina, Cristian R.; Barnes, David A.; Rupp, John A.
Fonte: Universidade de Indiana Publicador: Universidade de Indiana
Tipo: Conferência ou Objeto de Conferência Formato: 4833209 bytes; application/pdf
EN_US
Relevância na Pesquisa
36.44%
This poster was presented at the 2008 Annual Meeting of the American Association of Petroleum Geologists (AAPG) and the Society of Petroleum Engineers (SPE), held in Pittsburgh, Pennsylvania, from October 11-15, 2008.; Porosity and permeability values collected from core analyses in the Upper Cambrian Mount Simon sandstone indicate a predictable relationship with depth owing to diagenetic changes in the pore structure. This predictive relationship is useful for evaluating the geological carbon sequestration capacity in the Midwestern region. Porosity logs from wells in the study area provide additional sources of petrophysical data. The regional trend of decreasing porosity with depth is described by the equation: φ(d) = 16.36 * e-0.00012*d (r2=0.41), where φ equals porosity and d is depth in feet. The correlation between burial depth and porosity can help predict the petrophysical character of the Mount Simon sandstone in more deeply buried and largely undrilled portions of the basin. Understanding the relationship among porosity, permeability, and depth also provides information for use in numerical models that simulate supercritical carbon dioxide flow within the Mount Simon sandstone. The decrease of porosity and permeability with depth generally holds true on a basinwide scale. However...

Spatial depth-based classification for functional data

Sguera, Carlo; Galeano, Pedro; Lillo, Rosa E.
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: info:eu-repo/semantics/draft; info:eu-repo/semantics/workingPaper Formato: application/pdf
Publicado em /05/2012 ENG
Relevância na Pesquisa
36.44%
Functional data are becoming increasingly available and tractable because of the last technological advances. We enlarge the number of functional depths by defining two new depth functions for curves. Both depths are based on a spatial approach: the functional spatial depth (FSD), that shows an interesting connection with the functional extension of the notion of spatial quantiles, and the kernelized functional spatial depth (KFSD), which is useful for studying functional samples that require an analysis at a local level. Afterwards, we consider supervised functional classification problems, and in particular we focus on cases in which the samples may contain outlying curves. For these situations, some robust methods based on the use of functional depths are available. By means of a simulation study, we show how FSD and KFSD perform as depth functions for these depth-based methods. The results indicate that a spatial depthbased classification approach may result helpful when the datasets are contaminated, and that in general it is stable and satisfactory if compared with a benchmark procedure such as the functional k-nearest neighbor classifier. Finally, we also illustrate our approach with a real dataset.; This research was partially supported by Spanish Ministry of Education and Science grant 2007/04438/001...

Studies on submarine control for periscope depth operations

Tolliver, John V.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xiv, 139 p.
EN_US
Relevância na Pesquisa
36.42%
Approved for public release; distribution in unlimited.; Requirements for submarine periscope depth operations have been increased by integration with carrier battle groups, littoral operations, and contributions to joint surveillance. Improved periscope depth performance is therefore imperative. Submarine control personnel rely on a large number of analog gauges and indications. An integrated digital display system could enhance the ergonomics of the human control interface and display additional parameters. This thesis investigates the required feedbacks for robust automatic depth control at periscope depth, and thus indirectly determines the additional parameters desired for an integrated display. A model of vertical plane submarine dynamics is coupled with first and second order wave force solutions for a particular submarine hull form. Sliding mode control and several schemes of state feedback are used for automatic control. Head and beam seas at sea states three and four are investigated. The automatic control effectiveness provides insight into the indications used by the ship's control party in operations at periscope depth. One possible display system is proposed, with several additional enhancements to improve ship's safety...

Guidelines for building a detailed elastic depth model

Dunne, J; Beresford, G; Kennett, Brian
Fonte: Society of Exploration Geophysicists Publicador: Society of Exploration Geophysicists
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.44%
We developed guidelines for building a detailed elastic depth model by using an elastic synthetic seismogram that matched both prestack and stacked marine seismic data from the Gippsland Basin (Australia). Recomputing this synthetic for systematic variations upon the depth model provided insight into how each part of the model affected the synthetic. This led to the identification of parameters in the depth model that have only a minor influence upon the synthetic and suggested methods for estimating the parameters that are important. The depth coverage of the logging run is of prime importance because highly reflective layering in the overburden can generate noise events that interfere with deeper events. A depth sampling interval of 1 m for the P-wave velocity model is a useful lower limit for modeling the transmission response and thus maintaining accuracy in the tie over a large time interval. The sea-floor model has a strong influence on mode conversion and surface multiples and can be built using a checkshot survey or by testing different trend curves. When an S-wave velocity log in unavailable, it can be replaced using the P-wave velocity model and estimates of the Poisson ratio for each significant geological formation. Missing densities can be replaced using Gardner's equation...

Dynamics of leaf litter humidity, depth and quantity: two restoration strategies failed to mimic ground microhabitat conditions of a low montane and premontane forest in Costa Rica

Barrientos,Zaidett
Fonte: Revista de Biología Tropical Publicador: Revista de Biología Tropical
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2012 EN
Relevância na Pesquisa
36.42%
Little is known about how restoration strategies affect aspects like leaf litter’s quantity, depth and humidity. I analyzed leaf litter’s quantity, depth and humidity yearly patterns in a primary tropical lower montane wet forest and two restored areas: a 15 year old secondary forest (unassisted restoration) and a 40 year old Cupressus lusitanica plantation (natural understory). The three habitats are located in the Río Macho Forest Reserve, Costa Rica. Twenty litter samples were taken every three months (April 2009-April 2010) in each habitat; humidity was measured in 439g samples (average), depth and quantity were measured in five points inside 50x50cm plots. None of the restoration strategies reproduced the primary forest leaf litter humidity, depth and quantity yearly patterns. Primary forest leaf litter humidity was higher and more stable (x=73.2), followed by secondary forest (x=63.3) and cypress plantation (x=52.9) (Kruskall-Wallis=77.93, n=232, p=0.00). In the primary (Kruskal-Wallis=31.63, n=78, p<0.001) and secondary (Kruskal-Wallis=11.79, n=75, p=0.008) forest litter accumulation was higher during April due to strong winds. In the primary forest (Kruskal-wallis=21.83, n=78, p<0.001) and the cypress plantation (Kruskal-wallis=39.99...

Effect of Weed Competition, Planting Time and Depth on Pistacia atlantica Seedlings in a Mediterranean Nursery in Iran

Hosseini,Seyed Mohsen; Gholami,Shaiesteh; Sayad,Ehsan
Fonte: Unidade de Silvicultura e Produtos Florestais Publicador: Unidade de Silvicultura e Produtos Florestais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2007 EN
Relevância na Pesquisa
36.46%
The effect of weed competition, Planting time and Depth on growth and survival of Pistacia atlantica seedlings was evaluated in nursery conditions. Pistacia atlantica is a deciduous tree species that belongs to the Anacardiaceae family. It is valuable for soil conservation and therefore suitable for plantation in dry lands. Regeneration of Pistacia atlantica in western part of Iran presents problems due to much destruction of its natural habitats. Two levels of weed treatment (weed competition was removed several times by hand or the weeds permitted to grow) and three levels of sowing date (9 January, 29 January, 18 February) were used. In addition, seeds were sown at three different depths (0.4 and 8 cm) but no seedlings emerged when seeds were sown at 0 cm sowing depth. At the end of the first growing season on September 2004, survival, height above the soil surface, collar diameter, shoot/root length ratio and shoot/root dry weight ratio were measured. Survival was significantly affected by sowing depth but not by sowing date and weed treatment. Survival was greater at 4 cm than at 8 cm sowing depth. Collar diameter was significantly greater at 4 cm than at 8 cm sowing depth and in 9 January and 29 January than in 18 February sowing date but was not different between weed treatments. Shoot/root length ratio and height was not affected by sowing date...