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Gebauer, Tobias. "Water turnover in species-rich and species-poor deciduous forests xylem sap flow and canopy transpiration /." Göttingen : Georg-August-Universität, 2010. http://webdoc.sub.gwdg.de/diss/2010/gebauer/gebauer.pdf.
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Price, David Thomas. "Some effects of variation in weather and soil water storage on canopy evapotranspiration and net photosynthesis of a young douglas-fir stand." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27511.
Повний текст джерелаАнотація:
Measurements of the energy balances and net photosynthesis rates of two low productivity coniferous forest canopies (12 and 22 years old), were made successfully during both wet and dry growing seasons, using a modified Bowen Ratio method. Canopy conductances (gc) were calculated from canopy evaporation rates (E) using the Penman-Monteith equation. A model was developed to predict canopy growth and evaporation rates from basic soil and weather data, and compared with the measured data. The photosynthesis model was physiologically based, derived from recent work of Farquhar and coworkers. The canopy conductance model used an empirical approach, based on simple relationships with recorded environmental variables, while canopy E was predicted from the Penman-Monteith equation. Findings were:
(1) Daytime E and canopy net photosynthesis rates (Fc) were generally lower in the younger canopy.
(2) In the old canopy, E was more strongly decoupled from net irradiance (Rn) and more dependent on the atmospheric vapour pressure deficit (D) in accordance with the predictions of McNaughton and Jarvis (1983).
(3) In the old canopy, Fc was significantly reduced by low soil water potential (Ψs) within the range of soil water storages at which measurements
were made, while gc was less dependent on Ψs. From consideration of changes in intercellular C0₂ concentration, gc was not found normally limiting to Fc. (4) No simple relationship was apparent between solar irradiance (S) and F at the canopy level. However highest Fc and canopy water use efficiency ratios occurred on cloudy days with low air temperature and low D.
(5) Night-time Fc measurements indicated that canopy respiration rates are generally very high and hence air temperature was a major factor limiting overall forest productivity.
(6) The computer model could predict gc from four variables (D,
S, root-zone soil water storage, W and time since dawn, t) with reasonable 2
success (r² 0.75). However, on days when gc was low, due to high D, E was occasionally significantly in error, because the Penman-Monteith equation is more sensitive to gc when the latter is low. Best agreement between measured and modelled E occurred on cloudy days when D was low and gc consequently high.
(7) Values for the maximum rates of carboxylation, as limited by foliar carboxylase activity and electron transport rate, were set at one third of those reported by Farquhar and coworkers, in order to obtain best overall agreement between measured and modelled data. This requirement indicated that poor nutrition was also limiting to stand productivity.
(8) Model prediction of canopy net photosynthesis was not satisfactory (r² 0.50), attributed mainly to using too simple an approach to estimating irradiance at the individual leaf level, and partly to unexplained variation in the measurements of Fc. In spite of its limitations, the model was found to respond realistically to changes in weather and Ψs, suggesting the approach was valid, and might be more successful with further development.Forestry, Faculty of
Graduate
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Zanelli, Carolina Brandão 1986. "Florística e fotossociologia da comunidade lenhosa no sub-bosque de um cerradão em Assis, SP." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/315521.
Повний текст джерелаАнотація:
Orientador: Ricardo Ribeiro RodriguesDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
Made available in DSpace on 2018-08-22T23:57:55Z (GMT). No. of bitstreams: 1 Zanelli_CarolinaBrandao_M.pdf: 11021724 bytes, checksum: 074f594a75e3131636ec29a9f0cdbc07 (MD5) Previous issue date: 2013
Resumo: A regeneração consiste no processo de reconstrução e reorganização da composição e estrutura de uma comunidade vegetal, e vem sendo bem estudada em florestas ombrofilas e estacionais sob a ótica da dinâmica de clareiras e da sucessão ecológica. No entanto, a regeneração de espécies lenhosas no cerrado ainda e pouco compreendida, e são poucos os estudos que avaliam conjuntamente o dossel e o sub-bosque em áreas de cerrado. O objetivo deste trabalho foi avaliar a floristica e a fitossociologia da comunidade lenhosa do dossel e do sub-bosque de um cerradão em Assis, SP. O trabalho foi realizado na Estação Ecológica de Assis, em uma parcela permanente de 10,4 ha, parte do "Projeto Parcelas Permanentes" do Programa BIOTA/FAPESP. Essa parcela permanente e subdividida em 256 subparcelas contiguas de 20 m x 20 m, das quais 100 foram sorteadas para amostragem. Para avaliar o dossel, foram considerados os dados já coletados no Projeto Parcelas Permanentes, referentes aos indivíduos lenhosos com perímetro na altura do peito (PAP) ? 15 cm, para as 100 subparcelas sorteadas. Para analisar o sub-bosque, foi delimitado um setor de avaliação de 2 m x 2 m em cada subparcela sorteada, onde foram medidos e identificados todos os indivíduos de espécies lenhosas com altura > 20 cm e PAP < 15 cm. Todas as espécies do dossel e do sub-bosque foram classificadas de acordo com o habitat, com base em estudos regionais de fitossociologia, em categorias não excludentes: floresta (F), quando ha registro da espécie em formações florestais não pertencentes ao cerrado sensu lato; cerradão (C), quando ha registro da espécie em cerradão; e cerrado sensu lato (c), quando ha registro da espécie nas demais fisionomias de cerrado sensu lato. Alem disso, foram calculados os parâmetros fitossociologicos usuais para todas as espécies no dossel e no sub-bosque. Tanto o dossel quanto o sub-bosque do cerradão em Assis foram compostos por espécies intermediarias entre diferentes habitats, a maior parte (46% das espécies no dossel e 36% no sub-bosque) constituída de espécies de cerrado/cerradão, incluindo espécies de ampla distribuição no domínio (como Bowdichia virgilioides, Machaerium acutifolium, Plathymenia reticulata, Pouteria ramiflora, Qualea grandiflora, Roupala montana e Xylopia aromática) e comuns em cerrados da província Meridional (como Eriotheca gracilipes, Eugenia pluriflora, Gochnatia polymorpha, Machaerium brasiliense, Myrcia venulosa e Ocotea corymbosa). Regenerantes das espécies do dossel constituíram a maior parte do sub-bosque do cerradão, tanto em numero de espécies (81% do total, n=60) quanto em valor de importância (221 do total de 300). O cerradão apresentou um conjunto de espécies de sub-bosque composto por arvores de pequeno porte e arbustos heliofitos que também ocorrem nas fisionomias mais abertas de cerrado, incluindo: Lacistema hasslerianum, Miconia albicans, Miconia langsdorffii, Miconia stenostachya, Palicourea marcgravii, Piptocarpha rotundifolia, Psychotria hoffmannseggiana e Psychotria vellosiana. Esse resultado e consistente com as características estruturais do dossel do cerradão, que possibilitam maior entrada de luz ao sub-bosque; e contrasta com o relatado para outras fisionomias florestais, onde as espécies de sub-bosque são tipicamente tolerantes a sombra
Abstract: Regeneration consists on the process of reconstruction and reorganization of the structure and composition of a plant community, and has been intensively studied in ombrophilous and seasonal forests according to the paradigm of gap dynamics and ecological succession. However, regeneration of woody plant species in the cerrado is still poorly understood, and few studies evaluate both the overstory and the understory in cerrado areas. The aim of this study was to investigate the floristics and phytosociology of the woody community of the overstory and understory in a cerradao fragment at Assis, Sao Paulo State, southeastern Brazil. Field work was conducted at Assis Ecological Station, in a 10,4 ha permanent plot, part of the Permanent Plots Project from the BIOTA/FAPESP Program. This plot is divided in 256 contiguous subplots of 20 m x 20 m, of which 100 subplots were randomly selected and analyzed. To study the overstory, we used data collected at the Permanent Plots Project, regarding all woody individuals with perimeter at breast height (PBH) ? 15 cm, for these 100 subplots. To study of the understory, we delimited a sector of 2 m x 2 m within each selected subplot, in which all woody individuals with height > 20 cm and PBH < 15 cm were measured and identified. All overstory and understory species were categorized according to their habitat, based in regional phytosociological studies, into non excluding groups: forest (F), when there is record of the species in forest formations that do not belong to cerrado sensu lato; cerradao (C), when there is record of the species in cerradao; and cerrado sensu lato (c), when there is record of the species in the remaining cerrado sensu lato physiognomies. We also calculated the usual phytosociological parameters for all overstory and understory species. Both the overstory and the understory in the study site were composed of species of intermediate distribution between habitats, the majority (46% of overstory species and 36% of understory species) occurring in cerrado/cerradão, including widely distributed Cerrado species (such as Bowdichia virgilioides, Machaerium acutifolium, Plathymenia reticulata, Pouteria ramiflora, Qualea grandiflora, Roupala montana e Xylopia aromatica) and common southern Cerrado species (such as Eriotheca gracilipes, Eugenia pluriflora, Gochnatia polymorpha, Machaerium brasiliense, Myrcia venulosa e Ocotea corymbosa). Regenerating individuals belonging to overstory species accounted for most of the cerradão understory, both in number of species (81%, n=60) and importance value (221 of the total of 300). At the cerradão, we observed a group of understory species composed of heliophyte and small sized trees and shrubs that also occur in the open cerrado physiognomies, such as: Lacistema hasslerianum, Miconia albicans, Miconia langsdorffii, Miconia stenostachya, Palicourea marcgravii, Piptocarpha rotundifolia, Psychotria hoffmannseggiana e Psychotria vellosiana. This result is consistent with the structural characteristics of the cerradão overstory, which enable light penetration to the understory; and differs from data reported in other forest formations, where understory species are typically shade tolerant
Mestrado
Biologia Vegetal
Mestre em Biologia Vegetal
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Pinard, Denis Joseph Jean-Paul. "Numerical simulation of wind in plant canopies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ60486.pdf.
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Burgess, Alexandra Jacquelyn. "The variable light environment within complex 3D canopies." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/38967/.
Повний текст джерелаАнотація:
With an expanding population and uncertain consequences of climate change, the need to both stabilise and increase crop yields is important. The relationship between biomass production and radiation interception suggests one target for improvement. Under optimal growing conditions, biomass production is determined by the amount of light intercepted and the efficiency with which this is converted into dry matter. The amount of light at a given photosynthetic surface is dependent upon solar movement, weather patterns and the structure of the plant, amongst others. Optimising canopy structure provides a method by which we can improve and optimise both radiation interception and also the distribution of light among canopy layers that contribute to net photosynthesis. This requires knowledge of how canopy structure determines light distribution and therefore photosynthetic capacity of a given crop species. The aim of this thesis was to assess the relationships between canopy architecture, the light environment and photosynthesis. This focused on two core areas: the effect of varietal selection and management practices on canopy structure and the light environment and; the effect of variable light on select photosynthetic processes (photoinhibition and acclimation). An image-based reconstruction method based on stereocameras was employed with a forward ray tracing algorithm in order to model canopy structure and light distributions in high-resolution. Empirical models were then applied using parameterisation from manually measured data to predict the effects of variable light on photosynthesis. The plasticity of plants means that the physical structure of the canopy is dependent upon many different factors. Detailed descriptions of canopy architecture are integral to predicting whole canopy photosynthesis due to the spatial and temporal differences in light profiles between canopies. This inherent complexity of the canopy means that previous methods for calculating light interception are often not suitable. 3-dimensional modelling can provide a quick and easy method to retain this complexity by preserving small variations. This provides a means to more accurately quantify light interception and enable the scaling of cellular level processes up to the whole canopy. Results indicate that a canopy with more upright leaves enables greater light penetration to lower canopy layers, and thus higher photosynthetic productivity. This structural characteristic can also limit radiation-induced damage by preventing exposure to high light, particularly around midday. Whilst these features may lead to higher photosynthetic rates per unit leaf area, per unit ground area, photosynthesis is usually determined by total leaf area of the canopies, and within this study, the erect canopies tended to have lower total leaf areas than the more horizontal canopies. The structural arrangement of plant material often led to low levels of light within the lower canopy layers which were punctuated by infrequent, high light events. However, the slow response of photosynthesis to a change in light levels meant that these sun flecks cannot be used by the plant and thus the optimal strategy should be geared towards light harvesting and efficient photosynthesis under low light conditions. The results of this study contribute to our understanding of photosynthetic processes within the whole canopy and provide a foundation for future work in this area.
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Zoecklein, Bruce. "Effect of canopy manipulation on rot incidence and rot metabolites of White Riesling (Vitis vinifera L.) grapes /." This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06302009-040443/.
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Jack, Steven B. "Forest Canopies: Form and Functional Relationships." DigitalCommons@USU, 1990. https://digitalcommons.usu.edu/etd/6484.
Повний текст джерелаАнотація:
Forest canopy structure is strongly influenced by stand density due to changing competitive interactions among the individual trees and in turn directly influences stemwood volume production. The structure and dynamics of forest canopies, particularly in relation to the production of stemwood, were examined in unmanaged, even-aged stands of two dissimilar tree species, Pinus contorta var. latifolia Engelm. and Abies lasiocarpa (Hook.) Nutt. The analysis of structure-production relationships was guided by a conceptual model which generated hypotheses and led to examination of assumptions incorporated in the model.
Mean crown dimensions were related to stand density through a negative exponential function for both species, but because of differing shade-tolerances, mean crown size of lodgepole pine was affected more by increasing density than was mean crown size of subalpine fir. More importantly, examination of the model assumptions indicated that adequate characterization of canopy structure should account for the influence of both crown shyness and stand height.
Stand density also influenced the amount and distribution of leaf area in these forest stands. The more plastic mean leaf area of lodgepole pine led to a constant leaf area index over a range of density and, thus, was consistent with conventional wisdom which assumes closed canopied forest stands support stable leaf area indices across a wide range of densities. The less plastic mean leaf area of subalpine fir, however, led to positive correlation between leaf area index and density.
Changes in mean crown dimensions and mean leaf area influenced the production of stemwood volume such that large mean crown sizes were less efficient than small mean crown sizes. The decrease in efficiency was attributed to accumulation of large branch biomass in large crowns to support foliage far from the stem. Increased support costs were indicated by the increasing proportion of crown volume which was nonfoliated as mean crown size increased. The assumption that accumulated branch biomass was responsible for the observed declines in efficiency for forest trees was reinforced by a comparison of structure-production relationships for lodgepole pine and the annual Helianthus annuus L.
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Key, Thomas Lee. "An evaluation of the relative value of spectral and phenological information for tree crown classification of digital images in the eastern deciduous forest /." Morgantown, W. Va. : [West Virginia University Libraries], 1998. http://etd.wvu.edu/templates/showETD.cfm?recnum=107.
Повний текст джерелаАнотація:
Thesis (M.A.)--West Virginia University, 1998.Title from document title page. Document formatted into pages; contains viii, 51 p. : col. ill., col. map. Vita. Includes abstract. Includes bibliographical references (p. 32-34).
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Zoecklein, Bruce W. "Effect of canopy manipulation on rot incidence and rot metabolites of White Riesling (Vitis vinifera L.) grapes." Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/43505.
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Khdair, Adnan Ibraheem. "Effects of air jets on deposition of charged spray in plant canopies." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1298903382.
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Furfaro, Roberto. "Radiative transport in plant canopies: Forward and inverse problem for UAV applications." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280700.
Повний текст джерелаАнотація:
This dissertation deals with modeling the radiative regime in vegetation canopies and the possible remote sensing applications derived by solving the forward and inverse canopy transport equation. The aim of the research is to develop a methodology (called "end-to-end problem solution") that, starting from first principles describing the interaction between light and vegetation, constructs, as the final product, a tool that analyzes remote sensing data for precision agriculture (ripeness prediction). The procedure begins by defining the equations that describe the transport of photons inside the leaf and within the canopy. The resulting integro-differential equations are numerically integrated by adapting the conventional discrete-ordinate methods to compute the reflectance at the top of the canopy. The canopy transport equation is also analyzed to explore its spectral properties. The goal here is to apply Case's method to determine eigenvalues and eigenfunctions and to prove completeness. A model inversion is attempted by using neural network algorithms. Using input-outputs generated by running the forward model, a neural network is trained to learn the inverse map. The model-based neural network represents the end product of the overall procedure. During Oct 2002, an Unmanned Aerial Vehicles (UAVs) equipped with a camera system, flew over Kauai to take images of coffee field plantations. Our goal is to predict the amount of ripe coffee cherries for optimal harvesting. The Leaf-Canopy model was modified to include cherries as absorbing and scattering elements and two classes of neural networks were trained on the model to learn the relationship between reflectance and percentage of ripe, over-ripe and under-ripe cherries. The neural networks are interfaced with images coming from Kauai to predict ripeness percentage. Both ground and airborne images are considered. The latter were taken from the on-board Helios UAV camera system flying over the Kauai coffee field. The results are compared against hand counts and parchment data to evaluate the network performances on real applications. In ground images, the error is always less than 11%. In airborne image, the error bound is 20%. The results are certainly adequate and show the tremendous potential of the methodology.
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Affeld, Kathrin. "Spatial complexity and microclimatic responses of epiphyte communities and their invertebrate fauna in the canopy of northern rata (Metrosideros robusta A. Cunn.: Myrtaceae) on the West Coast of the South Island, New Zealand." Diss., Lincoln University, 2008. http://hdl.handle.net/10182/771.
Повний текст джерелаАнотація:
Rain forest canopies are renowned for their very high biodiversity and the critical role they play in key ecological processes and their influence on global climate. Despite that New Zealand supports one of the most diverse and extensive epiphyte flora of any temperate forest system, few studies have investigated epiphyte communities and their invertebrate fauna along with factors that influence their distribution and composition. This thesis represents the first comprehensive study of entire epiphyte communities and their resident invertebrate fauna in the canopy of New Zealand’s indigenous forests. The aim of this study was to determine spatial patterns of epiphyte and invertebrate species richness, abundance and community composition in relation to abiotic variables, and in particular, the responses of these communities to elevated temperature and rainfall. This study was carried out in coastal lowland podocarp-broadleaved forests at two sites on the West Coast of the South Island of New Zealand. Samples from 120 mat-forming epiphyte assemblages located on inner canopy branches of 40 northern rata (Metrosideros robusta) trees were studied to characterise the component flora and fauna. Additionally, biomass, branch and tree characteristics and community responses to treatments designed to elevate temperature and rainfall to simulate predicted climate change were measured. This investigation revealed astonishing diversity and functional complexity of epiphyte and invertebrate life in this ecosystem. The 30.6 kg (dry weight) of epiphyte material collected contained a total of 567 species, 170 epiphyte and 397 invertebrate (excluding immature specimens and mites) species, including at least 10 species new to science and many undescribed species Epiphyte communities were found to be dominated by non-vascular plants (80 % of the total species richness), particularly liverworts and invertebrate communities were dominated with respect to abundance (~ 80 % of the total individuals) by Acari, Collembola and Hymenoptera (primarily ants) and functionally by scavengers and ants. Epiphyte and invertebrate communities were highly variable with respect to spatial patterning of species richness, abundance and composition across sites, among trees within sites and among branches within trees. Overall, a highly significant proportion, > 75 %, of the variance could be attributed to differences at the branch level, but these differences could not be explained by the environmental factors measured. There were no consistent relationships between the spatial pattern of epiphytes and invertebrates, or between vascular and non-vascular plants. However, there were significant positive correlations between epiphyte biomass and invertebrate species richness (r = 0.472; p < 0.0001) and abundance (r = -0.395; p < 0.0001), as well as non-living epiphyte biomass and scavenger species richness (r = 0.4; p < 0.0001). Microclimatic measurements taken on epiphyte mats were also highly variable with respect to temperature and relative humidity at similar physical locations within the same tree as well as across trees within sites. There was also considerable variation in the intensity and frequency of climatic extremes, although potentially harmful climatic conditions were experienced by all the epiphyte mats for which weather variables were measured. Negative correlations existed between both epiphyte and invertebrate community composition and increased temperatures expressed as cumulative degree days above 5˚C. However, variability was such that there was no direct evidence that increased temperature and rainfall treatments had an effect on invertebrate species richness, abundance or diversity. Northern rata host trees harbour an astonishingly diverse and complex canopy flora and fauna that is characterised by high spatial variability. Such variability highlights that to determine species distribution and community dynamics in canopy habitats in response to disturbance caused either by climate change or invasive species the structure of entire communities at different taxonomic and spatial scales, along with their responses to microclimatic factors, need to be studied. If such complexities are not taken into account, inappropriate interpretation may result in poor decisions concerning the conservation status, vulnerability and subsequent management of such unique ecosystems.
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Copeland, Nichola. "Fluxes and mixing ratios of biogenic volatile organic compounds in temperate plant canopies." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8003.
Повний текст джерелаАнотація:
Biogenic volatile organic compounds (BVOC) are a wide-ranging group of trace gas components in the atmosphere which are emitted naturally from Earth’s surface. It is now recognised that biogenically sourced VOCs are far more significant on a global scale than those from anthropogenic sources, with up to 10 times greater emissions. Very few field-based studies of fluxes from plant canopies have been undertaken, particularly for non-terpenoid compounds. This thesis presents mixing ratio and flux measurements of BVOC from a range of temperate plant canopies: Douglas fir, short-rotation coppice willow, Miscanthus and mixed peatland vegetation. The virtual disjunct eddy covariance technique (vDEC) using a proton transfer reaction mass spectrometer (PTR-MS) as a fast VOC sensor was used for all measurements except for peatlands, where grab samples were collected on adsorbent sampling tubes for later chromatographic analysis. The PTR-MS was also utilised for measuring the rate of degradation of VOCs during laboratory chamber experiments. Mixing ratios and fluxes of VOCs measured within and above a Douglas fir forest were the first canopy-scale measurements for this species. Fluxes of monoterpenes were comparable to previous studies while isoprene was also detected (standard emissions factors up to 1.15 μg gdw -1 h-1 and 0.18 μg gdw -1 h-1, respectively). Emissions of oxygenated VOCs were also found to be significant, highlighting the importance of quantifying a wider variety of VOCs from biogenic sources, other than isoprene and monoterpenes. Results for bioenergy crops Miscanthus and willow showed that willow was a high isoprene emitter (20 μg gdw -1 h-1), but no measureable VOCs were detected from Miscanthus. This indicates that future expansion of bioenergy crops, and hence species selection, should take resultant air quality and human health impacts – due to changing VOC emissions – into account. Fluxes of BVOC from a Scottish peatland are the first reported measurements for this ecosystem in a temperate climate. Additionally, to assess the impact of nitrogen deposition on VOC fluxes, BVOC measurements were taken from sample plots in a pre-existing, long-term field manipulation study to assess impacts of wet nitrate or ammonium deposition on peatland. The peatland was found to be a significant source of isoprene and monoterpenes (590 and 1.5 μg m-2 h-1 respectively) and there was evidence that emissions were affected by wet nitrogen treatment. Isoprene emissions were reduced by both nitrate and ammonium treatment, while nitrate increased β- pinene fluxes. Increasing atmospheric nitrogen concentrations are therefore predicted to have an impact on VOC emission. Chamber studies showed that the rate of loss of α-pinene from the gas-phase during oxidation – and hence potential formation of secondary organic aerosol (SOA) – decreased with increasing isoprene mixing ratio. This was not observed for limonene. These results show that as isoprene mixing ratios increase with increasing global temperatures, negative feedback on radiative forcing from SOA particles may be suppressed. Results from this thesis provide valuable experimental data for a range of temperate plant canopies, which will help constrain modelled predictions of future VOC emissions. Additionally, the importance of understanding the effects of land use and environmental change on VOC emissions was demonstrated.
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Styles, Julie M. "A wind tunnel study of the velocity field above a model plant canopy." [Canberra] : CSIRO Land and Water, 1997. http://nla.gov.au/nla.arc-13482.
Повний текст джерелаАнотація:
Thesis (B.Sc. (Honours)) - Australian National University, 1997.Title from title screen (viewed on May 20, 2002). "A thesis submitted in partial fulfilment of the requirements for the Degree of Bachelor of Science (Honours)"--Title screen. Bibliography: p. 64-66. Available full text via the internet.
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Tanino, Yukie 1980. "Flow and solute transport in random cylinder arrays : a model for emergent aquatic plant canopies." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/46787.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 159-166).
With wetlands constituting about 6% of earth's land surface, aquatic vegetation plays a significant role in defining mean flow patterns and in the transport of dissolved and particulate material in the environment. However, the dependence of the hydrodynamic and transport processes on fundamental properties of an aquatic plant canopy has not been investigated systematically over the wide range of conditions that are observed in the field. A laboratory investigation was conducted to describe flow and solute transport in idealized emergent plant canopies. This thesis presents laboratory measurements of the mean drag, turbulence structure and intensity, and lateral dispersion of passive solute in arrays of randomly-distributed cylinders, a model for emergent, rigid aquatic plants. Mean drag per cylinder length normalized by the mean interstitial fluid velocity and viscosity increases linearly with cylinder Reynolds number. In contrast to the dependence previously reported for sparse arrays at Reynolds numbers greater than 1000, the drag coefficient increases with increasing cylinder density in intermediate and high cylinder densities. In dense arrays, turbulent eddies are constrained by the interstitial pore size such that the integral length scale is equal to the mean surface-to-surface distance between a cylinder in the array and its nearest neighbor. The classic scale model for mean turbulence intensity, which is a function of the inertial contribution to the drag coefficient, the solid volume fraction, and the integral length scale of turbulence normalized by d, is then confirmed with our laboratory measurements. Our laboratory experiments demonstrate that Kyy/ (d), the asymptotic (Fickian) lateral dispersion coefficient normalized by the mean interstitial fluid velocity and d, is independent of Reynolds number at sufficiently high Reynolds number.
(cont.) Although previous models predict that asymptotic lateral dispersion increases monotonically with cylinder density, laboratory measurements reveal that lateral dispersion at high Reynolds number exhibits three distinct regimes. In particular, an intermediate regime in which Kyy/ (d) decreases with increasing cylinder density is observed. A scale model for turbulent diffusion is developed with the assumption that only turbulent eddies with integral length scale greater than d contribute significantly to net lateral dispersion. The observed dependence of asymptotic dispersion on cylinder density is accurately described by a linear superposition of this turbulent diffusion model and existing models for dispersion due to the spatially-heterogeneous velocity field that arises from the presence of the cylinders. Finally, laboratory measurements support the conjecture that Kyy/ (d) is not strongly dependent on Reynolds number in dense arrays at any Red. However, the distance required to achieve asymptotic dispersion is shown to depend strongly on the Reynolds number.
by Yukie Tanino.
Ph.D.
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Chen, Zhengxiao. "Microwave remote sensing of vegetation : Stochastic Lindenmayer systems, collective scattering effects, and neural network inversions /." Thesis, Connect to this title online; UW restricted, 1994. http://hdl.handle.net/1773/5854.
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Strydom, Janéne. "Canopy manipulation practices for optimum colour of redglobe (V.Vinifera L.) /." Link to the online version, 2006. http://hdl.handle.net/10019/1228.
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Bohlman, Stephanie Ann. "The relationship between canopy structure, light dynamics and deciduousness in a seasonal tropical forest in Panama : a multiple scale study using remote sensing and allometry /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5509.
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Storck, Pascal. "Trees, snow, and flooding : an investigation of forest canopy effects on snow accumulation and melt at the plot and watershed scales in the Pacific Northwest /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/10103.
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Ishii, Hiroaki. "A canopy perspective of community dynamics of an old-growth Pseudotsuga-Tsuga forest /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/5573.
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Meek, David B. "The Relationship Between Leaf Area Index and Photosynthetic Temperature Response in Wheat (Triticum aestivum L.) Canopies." DigitalCommons@USU, 1990. https://digitalcommons.usu.edu/etd/6764.
Повний текст джерелаАнотація:
The objective of this study was to determine the effect of increasing leaf area index on the photosynthetic temperature response of a wheat canopy. Hard red spring wheat (Triticum aestivum L. cv. Veery-10) was grown hydroponically in a growth chamber, which also served as the gas-exchange chamber. Gas-exchange parameters were measured on single leaves and on wheat canopies at various leaf area indices. The temperature response curves of the canopy shifted from being steeper with a high temperature optimum to being flatter with a lower temperature optimum as leaf area index increased from 0 to 20.0 m2m-2. Single-leaf and canopy measurements show that this shift was primarily a result of increasing respiration from accumulating stems and reproductive structures and, to a lesser extent, from lower temperature optimums associated with lower light levels within the canopy.
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Campbell, Richard J. "Canopy light environment influences apple leaf physiology and fruit quality." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/39857.
Повний текст джерелаАнотація:
Several experiments were conducted to determine: the influence of canopy position, girdling, and defoliation on nectar production; whether instantaneous light measurements yield reliable estimates of cumulative seasonal light levels within the canopy; and the effect of the canopy light environment on spur leaf physiology and fruit quality. Defoliation of nongirdled flowering spurs had no effect on nectar production or composition, while defoliation of girdled spurs n~duced nectar sugar concentration by 24%. Canopy position had no influence on nectar production or composition. At full bloom there were differences in photosynthe~tic potential of spur leaves from different canopy positions. Exterior leaves had a greater maximum photosynthetic rate and an unique photosynthetic light response curve compared to the intermediate and interior leaves. Differences among positions persisted throughout the season. Stomatal conductance, specific leaf weight, dark respiration, and light levels were greater for the exterior leaves throughout the season.
Instantaneous light measurements made on a single uniformly overcast day after the canopy was fully-developed (average of four times during the day) provided reliable estimates (predictive R2 > 0.90, n = 30) of total cumulative seasonal photosynthetic photon density (PPD). There was a I-to-l relationship between instantaneous and cumulative PPD after canopy development was complete providing both measures were expressed as a percentage. The relationships were equal over multiple dates for two consecutive years. Cloudless conditions provided poor estimates (predictive R2 = 0.49 to 0.80, n = 30). Light environment and harvest date influenced fruit quality characteristics within the canopy. Fruit red color, intensity of red color, and soluble solids concentration were all positively related to light level, with the highest R 2 on the early harvest dates. Fruit weight, firmness,
length/ diameter ratio, starch index, and seed number were not consistently influenced by the light environment. The number of hours above an average photosynthetic photon flux density threshold of 250 I-£mol. m-2• sec'! explained slightly more of the variation in fruit quality characteristics than any other expressions of light.Ph. D.
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Kershaw, John A. "Crown structure and stem form development in young stands of western hemlock /." Thesis, Connect to this title online; UW restricted, 1993. http://hdl.handle.net/1773/5523.
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Balduzzi, Mathilde. "Plant canopy modeling from Terrestrial LiDAR System distance and intensity data." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20203.
Повний текст джерелаАнотація:
Le défi de cette thèse est de reconstruire la géométrie 3D de la végétation à partir des données de distance et d'intensité fournies par un scanner de type LiDAR. Une méthode de « shape-from-shading » par propagation est développée pour être combinée avec une méthode de fusion de données type filtre de Kalman pour la reconstruction optimale des surfaces foliaires.-Introduction-L'analyse des données LiDAR nous permet de dire que la qualité du nuage de point est variable en fonction de la configuration de la mesure : lorsque le LiDAR mesure le bord d'une surface ou une surface fortement inclinée, il intègre dans sa mesure une partie de l'arrière plan. Ces configurations de mesures produisent des points aberrants. On retrouve souvent ce type de configuration pour la mesure de feuillages puisque ces derniers ont des géométries fragmentées et variables. Les scans sont en général de mauvaise qualité et la quantité d'objets présents dans le scan rend la suppression manuelle des points aberrants fastidieuse. L'objectif de cette thèse est de développer une méthodologie permettant d'intégrer les données d'intensité LiDAR aux distances pour corriger automatiquement ces points aberrants. -Shape-From-Shading-Le principe du Shape-From-Shading (SFS) est de retrouver les valeurs de distance à partir des intensités d'un objet pris en photo. La caméra (capteur LiDAR) et la source de lumière (laser LiDAR) ont la même direction et sont placés à l'infini relativement à la surface, ce qui rend l'effet de la distance sur l'intensité négligeable et l'hypothèse d'une caméra orthographique valide. En outre, la relation entre angle d'incidence lumière/surface et intensité est connue. Par la nature des données LiDAR, nous pourrons choisir la meilleure donnée entre distance et intensité à utiliser pour la reconstruction des surfaces foliaires. Nous mettons en place un algorithme de SFS par propagation le long des régions iso-intenses pour pouvoir intégrer la correction de la distance grâce à l'intensité via un filtre de type Kalman. -Design mathématique de la méthode-Les morceaux de surface correspondant aux régions iso-intenses sont des morceaux de surfaces dites d'égales pentes, ou de tas de sable. Nous allons utiliser ce type de surface pour reconstruire la géométrie 3D correspondant aux images d'intensité.Nous démontrons qu'à partir de la connaissance de la 3D d'un bord d'une région iso-intense, nous pouvons retrouver des surfaces paramétriques correspondant à la région iso-intense qui correspondent aux surfaces de tas de sable. L'initialisation de la région iso-intense initiale (graine de propagation) se fait grâce aux données de distance LiDAR. Les lignes de plus grandes pentes de ces surfaces sont générées. Par propagation de ces lignes (et donc génération du morceau de la surface en tas de sable), nous déterminons l'autre bord de la région iso-intense. Puis, par itération, nous propagerons la reconstruction de la surface. -Filtre de Kalman-Nous pouvons considérer cette propagation des lignes de plus grande pente comme étant le calcul d'une trajectoire sur la surface à reconstruire. Dans le cadre de notre étude, la donnée de distance est toujours disponible (données du scanner 3D). Ainsi il est possible de choisir, lors de la propagation, quelle donnée (distance ou intensité) utiliser pour la reconstruction. Ceci peut être fait notamment grâce à une fusion de type Kalman. -Algorithme-Pour procéder à la reconstruction par propagation, il est nécessaire d'hiérarchiser les domaines iso-intenses de l'image. Une fois que les graines de propagation sont repérées, elles sont initialisées avec l'image des distances. Enfin, pour chacun des nœuds de la hiérarchie (représentant un domaine iso-intense), la reconstruction d'un tas de sable est faite. C'est lors de cette dernière étape qu'une fusion de type Kalman peut être introduiteThe challenge of this thesis is reconstruct the 3D geometry of vegetation from distance and intensity data provided by a 3D scanner LiDAR. A method of “Shape-From-Shading” by propagation is developed to be combined with a fusion method of type “Kalman” to get an optimal reconstruction of the leaves. -Introduction-The LiDAR data analysis shows that the point cloud quality is variable. This quality depends upon the measurement set up. When the LiDAR laser beam reaches the edge of a surface (or a steeply inclined surface), it also integrate background measurement. Those set up produce outliers. This kind of set up is common for foliage measurement as foliages have in general fragmented and complex shape. LiDAR data are of bad quality and the quantity of leaves in a scan makes the correction of outliers fastidious. This thesis goal is to develop a methodology to allow us to integrate the LiDAR intensity data to the distance to make an automatic correction of those outliers. -Shape-from-shading-The Shape-from-shading principle is to reconstruct the distance values from intensities of a photographed object. The camera (LiDAR sensor) and the light source (LiDAR laser) have the same direction and are placed at infinity relatively to the surface. This makes the distance effect on intensity negligible and the hypothesis of an orthographic camera valid. In addition, the relationship between the incident angle light beam and intensity is known. Thanks to the LiDAR data analysis, we are able to choose the best data between distance and intensity in the scope of leaves reconstruction. An algorithm of propagation SFS along iso-intense regions is developed. This type of algorithm allows us to integrate a fusion method of type Kalman. -Mathematical design of the method-The patches of the surface corresponding to the iso-intense regions are patches of surfaces called the constant slope surfaces, or sand-pile surfaces. We are going to use those surfaces to rebuild the 3D geometry corresponding to the scanned surfaces. We show that from the knowledge of the 3d of an iso-intensity region, we can construct those sand-pile surfaces. The initialization of the first iso-intense regions contour (propagation seeds) is done with the 3D LiDAR data. The greatest slope lines of those surfaces are generated. Thanks to the propagation of those lines (and thus of the corresponding sand-pile surface), we build the other contour of the iso-intense region. Then, we propagate the reconstruction iteratively. -Kalman filter-We can consider this propagation as being the computation of a trajectory on the reconstructed surface. In our study framework, the distance data is always available (3D scanner data). It is thus possible to choose which data (intensity vs distance) is the best to reconstruct the object surface. This can be done with a fusion of type Kalman filter. -Algorithm-To proceed a reconstruction by propagation, it is necessary to order the iso-intensity regions. Once the propagation seeds are found, they are initialized with the distances provided by the LiDAR. For each nodes of the hierarchy (corresponding to an iso-intensity region), the sand-pile surface reconstruction is done. -Manuscript-The thesis manuscript gathers five chapters. First, we give a short description of the LiDAR technology and an overview of the traditional 3D surface reconstruction from point cloud. Then we make a state-of-art of the shape-from –shading methods. LiDAR intensity is studied in a third chapter to define the strategy of distance effect correction and to set up the incidence angle vs intensity relationship. A fourth chapter gives the principal results of this thesis. It gathers the theoretical approach of the SFS algorithm developed in this thesis. We will provide its description and results when applied to synthetic images. Finally, a last chapter introduces results of leaves reconstruction
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Figliolia, Marcia Balistiero [UNESP]. "Ecologia da germinação de sementes e desenvolvimento de plantas de Platymiscium floribundum Vog. (Sacambu) - Fabaceae em viveiro e sob dossel de floresta ombrófila densa, São Paulo, SP." Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/100674.
Повний текст джерелаАнотація:
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figliolia_mb_dr_rcla.pdf: 2811984 bytes, checksum: b1692752dd1e7065b3f766c9d1ca22a9 (MD5)O objetivo geral da pesquisa foi estudar aspectos da germinação de sementes de Platymiscium floribundum Vog. em laboratório e viveiro e desenvolvimento das mudas em condições de viveiro e natural sob o dossel, com vistas a estabelecer indicadores biológicos quanto à fisiologia e ecologia da germinação e desenvolvimento das plantas para subsidiar projetos de conservação, de manejo e de revegetação de áreas alteradas ou desprotegidas. Tendo como enfoque o estudo das temperaturas cardeais de germinação das sementes e o estabelecimento de padrões tecnológicos de análise foram testadas, em condições controladas de laboratório, temperaturas no intervalo de 10 a 40ºC, com presença contínua e ausência total de luz branca. Verificou-se que a faixa limite de germinação está entre 10 e 12,5 e 37,5 e 40ºC; a 10ºC iniciou-se somente a protrusão radicular, sem emissão da raiz primária e, a 40ºC, houve morte total das sementes. A faixa ótima de temperatura para a germinação, na presença contínua de luz, está entre 15 a 25ºC, com maiores índices de velocidades de germinação a 20 e 25ºC. Para o estudo ecofisiológico foram testadas as interações entre diferentes regimes de temperatura, quantidades de água e luz. As temperaturas onde a germinação das sementes se mostrou superior foram 25, 20 e 15ºC. Os resultados de germinação com as quantidades de água do ii substrato de 30 e 60mL foram superiores à de 90mL. Os percentuais de germinação foram inferiores à medida que se associaram elevadas quantidades de água e temperatura. As sementes da espécie apresentaram insensibilidade à luz, germinando tanto na presença quanto na ausência de luz, não apresentando variação significativa entre os espectros de luz testados. Os resultados indicam que P. floribundum apresenta plasticidade...
The purpose of the present work was the study of germination under laboratory and nursery conditions and seedling development under nursery and field conditions for getting biological indicators of ecophysiology of germination and establishment of Platymiscium floribundum Vog for conservation, management and reforestation projects. Determination of cardinal, and optimum temperatures was done by isothermic incubations in the range of 10 to 40°C, under continuous white light and darkness. The minimum temperature was 12.5°C and the maximum 37.5°C. At 10°C, only radicle protrusion was observed and at 40°C the seeds have died. The optimum temperature range from 15 to 25°C with highest germination rate at 20 to 25°C. For ecophysiological study, different temperatures were tested under different conditions of substrate humidity and light. The germination under low humidity (30mL) and moderate humidity (60mL) of the substrate was higher than high humidity (90mL). Seeds of P. floribundum were light insensitive. The seedling emergence capacity under nursery conditions were high under both natural light (NL) and far red light (FR) in all tested shading percentage (10, 18, 30, 50 and 80 shading), with high seedling survival under 30 and 80% shading NL and 18, 30 and 50% shading FR. Seedling development was high under FR at 18, 30 and 50% and in stem diameter at all WL treatments. Plants accumulated more root and aerial dry matter under NL. By aerial to root dry matter ratio, highest aerial development was observed under 0, 30, 18 and 80% shading WL and 18 and 80% shading FR. Analysis of seedling development was carried out under natural conditions under two shading intensities under canopy at Serra da Cantareira, São Paulo... (Complete abstract, click electronic address below)
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Gräfe, Jan. "Prediction of aerodynamic parameters of plant canopies and of soil heating in ridges covered with plastic mulch as contributions to SVAT modelling." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=982159277.
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Berry, Stephanie C. Carleton University Dissertation Biology. "The influence of vegetation and soil carbon dioxide exchange on the concentration and isotopic composition of atmospheric carbon dioxide within plant canopies." Ottawa, 1994.
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Gräfe, Jan. "Prediction of aerodynamic parameters of plant canopies and of soil heating in ridges covered with plastic mulch as contributions to SVAT modelling." Doctoral thesis, Humboldt-Universität zu Berlin, Landwirtschaftlich-Gärtnerische Fakultät, 2006. http://dx.doi.org/10.18452/15553.
Повний текст джерелаАнотація:
Die Implementierung und Anwendung von Soil-Vegetation-Atmosphere-Transport-Modellen (SVAT) in der Landwirtschaft erfordert die Kenntnis der aerodynamischen Eigenschaften der Unterlage. Diese sind die Verschiebungslänge d, die Rauhigkeitslänge z0 und weitere Parameter welche den Effekt der Rauhigkeitsschicht unmittelbar über dem Pflanzenbestand beschreiben, wie die Schichthöhen für den Transfer von Impuls Zm* und Skalaren Zs*. Umfangreiche Literaturangaben über einen weiten Bereich von Bestandsmerkmalen wurden zur Entwicklung und Ableitung neuer Schätzfunktionen der genannten Parameter genutzt. Ein neues Modell wird für d als Funktion der Bestandeshöhe hc und dem Plant Area Index PAI vorgeschlagen. Ein semi¬empirisches Vorhersagemodell wird für die Längenskale Ls in Abhängigkeit von hc, PAI, der relativen Kronenhöhe und dem mittleren Abstand zwischen Rauhigkeitselementen entwickelt. Mit Schätzwerten für d, Ls, Zm* und anderen Inputs wurde eine Gleichung für z0 entwickelt und geprüft. Unter Berücksichtigung der Rauhigkeitsschicht werden geschlossene analytische Lösungen für die Schubspannungsgeschwindigkeit, das Windprofil und den aerodynamischen Widerstand präsentiert. Es wird ein Energiebilanzmodell für teilweise mit Folien bedeckten Erddämmen vorgestellt. Bekannte Vorgehensweisen aus der Literatur wurden hinsichtlich der Effekte des peripheren Strahlungsanteils der Sonne, der Modifizierung des kurzwelligen und langwelligen Strahlungstransfers durch den Damm selbst und der winkelabhängigen Transmission und Reflexion von Folien erweitert. Nur 3 Parameter mussten aus stündlichen Messwerten der Bodentemperatur über einen Monat bestimmt werden. Beim Gesamttest des Modells zeigte sich eine mittlere quadratische Abweichung zwischen Simulationen und Messungen der Dammtemperatur von 1.5-1.9 K in Abhängigkeit vom Standort. Testsimulationen zeigten, dass für strahlungsundurchlässige Folien eine präzise Darstellung der winkelabhängigen Reflexion nicht notwendig ist. Für transparente Folien sind zur Beschreibung von Transmission und Reflexion auch einfache Ansätze ausreichend. Nur wenige Inputs sind zur Simulation erforderlich wie die Gehalte an Humus, Sand und Ton, die Dammgeometrie und die Transmissions- und Reflexionsgrade der eingesetzten Folien.Implementation and application of Soil Vegetation Atmosphere Transport Models (SVAT) in agriculture require knowledge of aerodynamic properties of the exchanging surface. These are the zero plane displacement d, the roughness length for momentum z0, and additional parameters describing the roughness layer just above the canopy as the height of the roughness layer for momentum and scalars (Zm*, Zs*), and parameters of the modified diffusivity profile functions. Several data summaries from the literature on aerodynamic properties over a broad range of plant canopies are used to develop and test predictive models for a number of needed aerodynamic parameters. A new model for d is presented as a function of canopy height hc and Plant Area Index PAI. A semi-empirical equation for the canopy length scale Ls is derived from hc, PAI, fractional crown height, and inter-element spacing of roughness elements. Having estimates of d, Ls, Zm* and other inputs one can derive predictive equations for z0. Closed form analytical expressions are given for the friction velocity, the horizontal wind speed profile and the aerodynamic resistance, which account for both stability and roughness layer effects. An energy balance model for a two-dimensional ridge surface partly covered by a plastic mulch is presented. Previous approaches are modified and extended to include (1) the circumsolar part of diffuse radiation and (2) the altered interception of diffuse short- and long-wave radiation due to horizon obstructions and surface slope and (3) the directional dependence of transmissivity and reflectivity of plastic mulches. Only three parameters had to be estimated from data taken over one month at one site. Overall, simulated data fitted with the whole data set on soil temperatures, with root mean square errors of 1.5 K and 1.9 K for both sites, respectively. Test simulations established that for opaque plastics, detailed analysis of directional radiative properties is not necessary, and for transparent plastics, rather simpler approaches are sufficient. Only a few inputs have to be provided to apply the model: the soil humus content and texture, the shape of the ridge, and the transmissivities and reflectivities of the used plastic mulches in the short-wave and long-wave range.
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Figliolia, Marcia Balistiero. "Ecologia da germinação de sementes e desenvolvimento de plantas de Platymiscium floribundum Vog. (Sacambu) - Fabaceae em viveiro e sob dossel de floresta ombrófila densa, São Paulo, SP /." Rio Claro : [s.n.], 2005. http://hdl.handle.net/11449/100674.
Повний текст джерелаАнотація:
Orientador: Massanori TakakiResumo: O objetivo geral da pesquisa foi estudar aspectos da germinação de sementes de Platymiscium floribundum Vog. em laboratório e viveiro e desenvolvimento das mudas em condições de viveiro e natural sob o dossel, com vistas a estabelecer indicadores biológicos quanto à fisiologia e ecologia da germinação e desenvolvimento das plantas para subsidiar projetos de conservação, de manejo e de revegetação de áreas alteradas ou desprotegidas. Tendo como enfoque o estudo das temperaturas cardeais de germinação das sementes e o estabelecimento de padrões tecnológicos de análise foram testadas, em condições controladas de laboratório, temperaturas no intervalo de 10 a 40ºC, com presença contínua e ausência total de luz branca. Verificou-se que a faixa limite de germinação está entre 10 e 12,5 e 37,5 e 40ºC; a 10ºC iniciou-se somente a protrusão radicular, sem emissão da raiz primária e, a 40ºC, houve morte total das sementes. A faixa ótima de temperatura para a germinação, na presença contínua de luz, está entre 15 a 25ºC, com maiores índices de velocidades de germinação a 20 e 25ºC. Para o estudo ecofisiológico foram testadas as interações entre diferentes regimes de temperatura, quantidades de água e luz. As temperaturas onde a germinação das sementes se mostrou superior foram 25, 20 e 15ºC. Os resultados de germinação com as quantidades de água do ii substrato de 30 e 60mL foram superiores à de 90mL. Os percentuais de germinação foram inferiores à medida que se associaram elevadas quantidades de água e temperatura. As sementes da espécie apresentaram insensibilidade à luz, germinando tanto na presença quanto na ausência de luz, não apresentando variação significativa entre os espectros de luz testados. Os resultados indicam que P. floribundum apresenta plasticidade... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The purpose of the present work was the study of germination under laboratory and nursery conditions and seedling development under nursery and field conditions for getting biological indicators of ecophysiology of germination and establishment of Platymiscium floribundum Vog for conservation, management and reforestation projects. Determination of cardinal, and optimum temperatures was done by isothermic incubations in the range of 10 to 40°C, under continuous white light and darkness. The minimum temperature was 12.5°C and the maximum 37.5°C. At 10°C, only radicle protrusion was observed and at 40°C the seeds have died. The optimum temperature range from 15 to 25°C with highest germination rate at 20 to 25°C. For ecophysiological study, different temperatures were tested under different conditions of substrate humidity and light. The germination under low humidity (30mL) and moderate humidity (60mL) of the substrate was higher than high humidity (90mL). Seeds of P. floribundum were light insensitive. The seedling emergence capacity under nursery conditions were high under both natural light (NL) and far red light (FR) in all tested shading percentage (10, 18, 30, 50 and 80 shading), with high seedling survival under 30 and 80% shading NL and 18, 30 and 50% shading FR. Seedling development was high under FR at 18, 30 and 50% and in stem diameter at all WL treatments. Plants accumulated more root and aerial dry matter under NL. By aerial to root dry matter ratio, highest aerial development was observed under 0, 30, 18 and 80% shading WL and 18 and 80% shading FR. Analysis of seedling development was carried out under natural conditions under two shading intensities under canopy at Serra da Cantareira, São Paulo... (Complete abstract, click electronic address below)
Doutor
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Suhayda, Brett. "The effect of sanding and pruning on yield and canopy microclimate in 'Stevens' cranberry." Connect to this title, 2008. http://scholarworks.umass.edu/theses/162/.
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Prosperi, Juliana. "Biologie du développement des hémi-épiphytes ligneux." Montpellier 2, 1998. http://www.theses.fr/1998MON20240.
Повний текст джерелаАнотація:
Par une approche architecturale, cette etude explore les modalites de croissance des hemi-epiphytes ligneux d'amerique du sud (guyane et venezuela), appartenant a 4 genres : ficus (moraceae), coussapoa (cecropiaceae), clusia (clusiaceae) et blakea (melastomaceae). L'auteur montre le role de la reiteration caulinaire et racinaire dans l'edification de la plante, et dans ses relations spatiales avec la cime de l'arbre hote. Les modalites reiteratives conduisent a la formation de differents formes de croissance : arborescente, buissonnante et lianescente, permettant aux hemi-epiphytes d'occuper differemment l'espace aerien. La survie de l'organisme dans la canopee, est resolue par la reiteration differee qui permet a la plante de se maintenir et de se propager vegetativement, notamment en cas de stress. Quelques reflexions sont emises par rapport au concept classique du type biologique et a la valeur selective de la reiteration dans l'evolution des angiospermes vers l'hemi-epiphytisme.
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Stephan, Jean. "Architecture 3D et microclimat lumineux de l'arbre." Phd thesis, Clermont-Ferrand 2, 2007. http://www.theses.fr/2007CLF21754.
Повний текст джерелаАнотація:
L'effet de deux méthodes de conduite contrastées (Central Leader vs. Conduite Centrifuge) est étudié sur trois cultivars de pommiers architecturalement distincts ; 'Scarletspur Delicious' , 'Golden Delicious' et 'Granny Smith'. Les arbres sont digitalisés en 3D en utilisant un outil électromagnétique à l'échelle des pousses deux fois en cours de première année et avant la récolte en deuxième année. Les pousses sont décrites et classifiées selon leur longueur et leur typologie (fructifères vs. Végétatives). Le bois porteur est également décrit en deuxième année en mettant l'accent sur la stratégie de taille (bois porteur taillé vs. Non taillé). Des expérimentations virtuelles sont réalisées à travers la reconstruction du feuillage, la création de maquettes 3D et la simulation de l'interception de la lumière, à l'échelle de l'arbre, des types de pousses et des pousses individuelles. Un modèle simplifié pour l'estimation de l'interception de la lumière par les arbres isolés est proposé, en utilisant des paramètres de structure du feuillage. La démographie et la séquence des pousses sont principalement affectées par le cultivar, avec une faible influence du mode de conduite. Une tendance similaire est observée à l'échelle de l'arbre pour les paramètres de structure du feuillage et de la lumière. La distribution spatiale des pousses et la densité de surface foliaire se différencient selon le mode de conduite. 'Scarletspur Delicious' est un arbre de forme réduite et compacte par rapport aux deux autres cultivars qui possèdent des arbres plus ouverts et plus grands. L'effet des systèmes de conduite se traduit par une plus grande proportion de pousses végétatives longues et réitérées (R-LVS) sur les arbres en Central Leader. Ces derniers présentent une distribution hétérogène de la surface foliaire et de l'interception de la lumière des deux types de pousses causées par les R-LVS qui augmentent l'ombrage mutuel des pousses. Ces différences varient en fonction des cultivars et sont plus tranchées chez Granny Smith. Les paramètres étudiés montrent que le système de conduite pourrait avoir un impact direct sur le développement et le positionnement spatial des pousses. Ceci affecte notablement la floraison et la production, même si la croissance et la structure de l'arbre dépendent essentiellement du cultivar
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Gerber, Fanny. "Estimation du contenu en eau de la végétation par télédétection hyperspectrale dans le infrarouge." Paris, Institut de physique du globe, 2011. http://www.theses.fr/2011GLOB0006.
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Fort, Tania. "Functions, transmission and emission of the canopy microbiota." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0338.
Повний текст джерелаАнотація:
Les arbres interagissent avec des communautés microbiennes diversifiées qui influencent leur fitness et le fonctionnement des écosystèmes terrestres. Contrairement aux micro-organismes associés aux racines et au sol, les micro-organismes qui colonisent la canopée forestière sont encore mal connus. L’objectif de cette thèse est de mieux comprendre les fonctions des micro-organismes associés aux parties aériennes des arbres (feuilles, tiges, graines) ainsi que leur dynamique de transmission verticale (de l’arbre à ses descendants) et horizontale (émission de l’arbre vers l’atmosphère), en combinant des analyses d’écologie moléculaire et d’écophysiologie végétale. Le premier chapitre [P1] montre une stratification verticale des communautés fongiques et bactériennes foliaires au sein de la canopée du hêtre (Fagus sylvatica). Cette stratification est plus marquée chez les micro-organismes épiphytes que chez les endophytes, elle s’atténue au cours de la saison végétative chez les bactéries et semble être liée à la morphologie plutôt qu’à la physiologie foliaire. La stratification verticale des fonctions microbiennes est en cours d’analyse. Le deuxième chapitre [P2] met en évidence la présence de champignons dans les tissus internes des glands du chêne sessile (Quercus petraea), y compris l’embryon, suggérant que le microbiote peut être transmis verticalement de l’arbre mère à ses descendants et influencer la régénération forestière. Les glands contiennent en particulier plusieurs espèces de champignons pathogènes, en association avec leurs mycoparasites. Ces communautés fongiques varient significativement en fonction de l’arbre mère et de la population de chêne. Enfin, le troisième chapitre [P3] teste un prototype de mesure des flux d’émissions bactériennes au-dessus des couverts végétaux. Il montre que la moitié des espèces capturées dans l’atmosphère est présente sur la surface des feuilles et suggère que la composition des bioaérosols est fortement influencée par la plante cultivée dominante localement, la vigne (Vitis Vinifera). Des mesures complémentaires, incluant une plus large gamme d’habitats forestiers et non-forestiers, devront être réalisées pour mieux cerner l’origine des émissions, qui sont connues pour influencer le cycle de l’eau. Cette thèse apporte donc des éléments pour modéliser la dynamique et l’évolution du système arbre-microbiote-atmosphère, qu’il conviendra de renforcer et d’intégrer aux connaissances sur le système sol afin de répondre aux défis posés par le changement climatiqueTrees interact with diverse microbial communities that influence their fitness and the functioning of terrestrial ecosystems. Unlike microorganisms associated with roots and soil, microorganisms that colonize the forest canopy are still poorly understood. The objective of this thesis is to better understand the functions of microorganisms associated with the aerial parts of trees (leaves, stems, seeds) as well as their vertical (from the plant to its offspring) and horizontal (emission from the plant to the atmosphere) transmission dynamics, by combining molecular ecology and plant ecophysiology analyses. The first chapter [P1] shows a vertical stratification of fungal and foliar bacterial communities within the beech canopy (Fagus sylvatica). This stratification is more pronounced for epiphytic microorganisms than for endophytes. It also decreases during the growing season in bacteria and appears to be related to morphology rather than foliar physiology. Vertical stratification of microbial functions is being analyzed. The second chapter [P2] highlights the presence of fungi in the internal tissues of the acorns of sessile oak (Quercus petraea), including the embryo, suggesting that the microbiota can be transmitted vertically from the mother tree to its offsprings and influence forest regeneration. Acorns contain in particular several fungal pathogens, in association with their mycoparasites. These fungal communities vary significantly depending on the mother tree and the oak population. Finally, the third chapter [P3] tests a prototype for measuring bacterial emission fluxes over plant cover. It shows that half of the species captured in the atmosphere are present on the leaf surface and suggests that the composition of bioaerosols is strongly influenced by the locally dominant cultivated plant, the grapevine (Vitis vinifera). Complementary measures, including a wider range of forest and non-forestry habitats, will have to be carried out to better understand the origin of emissions, which are known to influence the water cycle. This thesis therefore provides elements for modelling the dynamics and evolution of the tree-microbiota-atmosphere system, which will need to be strengthened and integrated into knowledge of the soil system in order to respond to the challenges raised by climate change
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Yetzer, Kenneth H. "Modeling the interaction between Plant Canopies and the Planetary Boundary Layer using a new 1D Multi-Layer Soil-Vegetation-Atmosphere Transfer (SVAT) Scheme combined with a Non-Local Turbulence Closure Model /." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu148819327206972.
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Bixby, Mitchell. "Interception in Open-grown Douglas-fir (Pseudotsuga menziesii) Urban Canopy." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/37.
Повний текст джерелаАнотація:
I hypothesized that Douglas-fir trees (Pseudotsuga menziesii) standing apart from other trees ('open-grown') will intercept more rainfall than Douglas-fir trees standing near other trees ('closed-canopy'). Open-grown trees differ structurally and are more common in urban settings, yet have been infrequently studied. Existing literature, based primarily on closed-canopy trees, suggests Douglas-fir trees in Pacific Northwest forests intercept approximately 25% of rainfall annually. Because open-grown trees have more vertical leaf area than individual trees in closed-canopy forests, I expected to find higher interception by open-grown trees. I collected throughfall under four open-grown Douglas-firs using six static collectors ('buckets') per tree, and two closed-canopy Douglas-firs using six buckets per tree. I compared their throughfall to the incident rainfall in two adjacent open-field buckets. Gross interception was measured in 53 collections during rainy weather from 16Nov07 to 31Mar08. Over the same period, rainfall per hour, wind speed, gust speed, wind direction, temperature and relative humidity were collected at a weather station located within 1 km of the site. For comparison, average hourly rainfall at Portland International Airport from 1950 to 2005, for the same months of the collection period, showed a comparable number of medium- to high-intensity storms, but more low-intensity storms. I found that incident rainfall for the adjacent open-field buckets totaled 65.6cm and 71.6cm over the study period. Interception values for closed-canopy trees averaged 26%, corresponding to the literature, with results of 22 and 30%. Interception values for open-grown trees averaged 31%, with results ranging from 15 to 45%. Three of the 24 buckets returned overall negative interception rates over five months. Given the lower storm intensity of 2007-08, interception rates may be somewhat high, compared to the historical average. The negative interception rates at three buckets were likely due to their locations under high drip points, as has been observed in other studies. Considering the wide range of canopy architecture among open-grown trees, the high variability in interception was not surprising. My hypothesis was supported by the data, but requires more testing to better generalize these results. Future studies that link open grown tree canopy morphological characteristics to interception are warranted.
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Gavinet, Jordane. "Installation d'espèces feuillues en forêt de pins d'Alep : interactions avec les strates arborées et arbustives." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4371.
Повний текст джерелаАнотація:
L’installation de plantules est une phase critique fortement influencée par les interactions avec la végétation établie, compétition ou facilitation. Dans cette thèse, nous montrons que l’effet du pin d’Alep ou d'arbustes sur l’installation d’espèces feuillues dépend de la densité du couvert, de la stratégie des espèces cibles et nurses et des conditions locales. Sous couverts très denses, la survie et la croissance des plantules sont drastiquement limitées par compétition lumineuse et hydrique, le stress hydrique étant renforcé par une faible allocation de biomasse aux racines. À l’autre extrémité du gradient, en milieu ouvert, la photoinhibition et la concurrence avec les herbacées peuvent limiter l'installation des plantules. Les espèces sclérophylles sempervirentes sont peu sensibles aux fortes irradiances, températures et demandes évaporatives et peuvent profiter de conditions favorables momentanées par polycyclisme en milieu ouvert. L’effet d’un couvert végétal sur ces espèces est principalement compétitif, tandis que les espèces décidues à fort SLA bénéficient d’un couvert modéré. En pépinière, la litière des principales espèces ligneuses modifie les propriétés physico-chimiques et microbiologiques du sol sous-jacent mais sans effet sur des plantules de chêne au bout de 2 ans, montrant un faible effet allélopathique. L’éclaircie des peuplements de pin d’Alep denses est une stratégie pour faciliter l’installation d’espèces feuillues et ainsi améliorer la diversité et la résilience au feu des forêts. L’optimum de couvert semble se déplacer vers des couverts plus denses dans des sites à conditions climatiques ou édaphiques plus sévères et pour les espèces déciduesSeedling establishment is a critical demographic phase, strongly influenced by plant-plant interactions. This thesis shows that the effect of Aleppo pine and shrubs on broadleaved seedling establishment depends on vegetation cover density, target and nurse species strategies and local conditions. A dense vegetation cover strongly limits seedling establishment by light and water competition, seedlings water stress being worsened by a low biomass allocation to roots. At the other extreme, in the open, photoinhibition and competition with grasses can limit seedling establishment. Sclerophyllous species are poorly sensitive to high temperature, irradiance and evaporative demand and can take advantage of favorable conditions at any time of the year by polycyclism in the open: interactions with pine are thus mostly competitive. In contrast, deciduous species with high SLA are more sensitive to photo-inhibition and benefit from the protection of a moderate cover, under which they are able to grow faster. In a nursery experiment, pine and shrub litters modified soil chemical and microbiological properties but without feedback on oak seedlings, indicating a poor allelopathic effect. Pine thinning is a strategy to enhance broadleaved seedling establishment and increase Mediterranean forest diversity and fire-resilience. However, the optimum thinning intensity seems to decrease in harsher climatic or edaphic conditions and for deciduous species
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Strydom, Janene. "Canopy manipulation practices for optimum colour of redglobe (V.Vinifera L.)." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/2784.
Повний текст джерелаАнотація:
Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2006.Under certain South African conditions, Redglobe develops a colour that is too dark and thus unacceptable for the Far Eastern markets. These markets require a pink colour instead of a dark red colour. The cultivation of grapes with an acceptable colour involves amongst other, canopy management practices. This generally includes the removal of leaves and/or lateral shoots. Hereby, the leaf area and the microclimatic conditions in the canopy are altered. The aim of this study was to test the usefulness of leaf and lateral shoot removal at different defoliation times after anthesis in order to obtain a pink coloured Redglobe crop. Other quality aspects, namely total soluble solids (TSS), total titratable acidity (TTA), berry mass and total yield, were also evaluated. A canopy management trial was conducted on six year old Redglobe vines with moderate vigour. The treatment design was a 2 x 3 x 4 factorial and involved two leaf removal (L) levels (L0 = 0% leaf removal; L33 = 33% leaf removal) in combination with three lateral shoot removal (LS) levels (LS0 = 0 % lateral shoot removal; LS50 = 50% lateral shoot removal; LS100 = 100% lateral shoot removal). Four defoliation times (DT) were selected: 36 (pea berry size), 69 (véraison), 76 (one week after véraison) and 83 (two weeks after véraison) days after anthesis (DAA). A total of 24 treatment combinations, replicated in four blocks, were applied. Generally, treatment combinations involving 33% leaf removal lowered the main shoot leaf area. Likewise, the lateral shoot leaf area was decreased by increasing levels of lateral shoot removal at any defoliation time. As expected, 33% leaf removal applied in combination with any level of lateral shoot removal, always resulted in a lower total vine leaf area compared to where 0% leaf removal was part of the treatment combination. Compensation reactions occurred and in this regard the main shoot leaf size increased due to 33% leaf removal applied at 1 week after véraison and 2 weeks after véraison. Treatment combinations involving lateral shoot removal increased the ratio of main shoot leaf area to the total leaf area. On the other hand, the main shoot leaf area percentage was lowered by the application of 33% leaf removal at 2 weeks after véraison compared to no leaf removal at the same defoliation time. It can therefore be assumed that the contribution of lateral shoot leaves to grape composition might have increased in cases where the main shoot leaf area was lowered at a later stage (e.g. 2 weeks after véraison). The bunches were visually evaluated and divided into classes from dark (class one) to light (class nine). This visual bunch evaluation showed that the mean bunch colour was in class three (lighter than class two) due to the defoliation time. The lateral shoot removal x leaf removal interaction resulted in a mean bunch colour that was in classes 2 and 3. However, within these classes, there was a tendency that bunch colour decreased for defoliation times later than pea berry size. The lateral shoot removal x leaf removal interactions showed that bunch colour was darker when the treatment combinations involved 0% leaf removal. The percentage of bunches with the desired colour was increased by application of the treatments at véraison, compared to the other defoliation times, and also with 50% lateral shoot removal and 100% lateral shoot removal compared to 0% lateral shoot removal. Biochemical analyses confirmed that increased levels of lateral shoot removal generally lowered the anthocyanin concentration regardless of defoliation time. A similar effect on TSS was observed, i.e. from véraison onwards, the application of 50% lateral shoot removal and 100% lateral shoot removal tended to lower TSS. The effect of these levels of lateral shoot removal at véraison was significant. The role of the lateral shoots in colour development and sugar accumulation is therefore emphasized. Furthermore, the special role that lateral shoots also play in berry development is illustrated in that berry mass tended to decrease when 100% lateral shoot removal in combination with 33% leaf removal and 100% lateral shoot removal in combination with 0% leaf removal were applied at véraison. This, together with the positive relationship obtained between grape colour and the lateral shoot leaf area:fruit mass ratio, accentuates the role of active leaf area during the ripening period. The possible effect of the microclimatic light environment on colour must also be considered. However, although the light intensity increased with increased levels of LS, the colour that was obtained was probably not associated with the differences in light intensity. It was found that it is possible to manipulate the colour of Redglobe grapes with defoliation treatments. However, the treatments that have a decreasing effect on grape colour also affected other quality parameters like TSS and berry size negatively. Although, it is possible to reduce the colour of Redglobe through the application of leaf and lateral shoot removal at different defoliation times, the question arises whether the treatment combinations used in this study are worthwhile to pursue because the mean bunch colour that was obtained was still too dark. However, it was possible to increase the percentage of bunches with the desired colour. Therefore, if such treatments are applied, it must be approached cautiously, keeping in mind that assimilate supply has to be sustained throughout the ripening period.
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Monnier, Yogan. "Stratégies d'acclimatation à l'ombre et rôle des interactions plantes-plantes dans la dynamique pin-chêne en milieu méditerranéen." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10045.
Повний текст джерелаАнотація:
Lors de ce travail de thèse nous avons adopté une approche fonctionnelle de la dynamique forestière méditerranéenne. L'objectif principal est de comprendre comment les réponses fonctionnelles à la disponibilité de la lumière et aux interactions biotiques vont conditionner la régénération des trois principales espèces impliquées dans cette dynamique : Pinus halepensis, Quercus ilex, Quercus pubescens. Une première expérimentation en pots a été menée en conditions contrôlées afin de déterminer progressivement : les différences de stratégies d'acclimations à l'ombre du pin d'Alep et du chêne pubescent, les compromis fonctionnels et les limites ontogéniques et nutritionnelles de ces stratégies, et l'impact de l'allélopathie et de la compétition sur cette réponse à l'ombre. Une expérimentation de terrain a ensuite permis de créer un gradient d'éclaircie dans une pinède de pin d'Alep, pour comprendre les principaux effets positifs et négatifs de la canopée sur les facteurs abiotiques et le développement du chêne pubescent et du chêne vert à différentes échelles de temps. Les résultats obtenus montrent que le pin d'Alep présente une stratégie d'évitement de l'ombre par une forte réponse plastique qui implique des compromis fonctionnels, des coûts nutritionnels élevés, et un temps d'expression limité. Cette stratégie présente un désavantage dans le cas d'une régénération sous canopée. A l'inverse, le chêne pubescent montre une stratégie plus conservatrice grâce à une réponse plastique à l'ombre limitée, mais une forte sensibilité aux interactions plantes-plantes. En conditions naturelles, le chêne pubescent et le chêne vert en régénération présentent des réponses différentes au gradient d'éclaircie de la canopée, le chêne pubescent montrant cette fois ci une moins forte tolérance à l'ombre. Cette thèse permet de mettre en évidence les liens entre limites fonctionnelles de la plasticité phénotypique, tolérance à l'ombre, et réussite d'installation sous couvert forestierDuring this work we studied the Mediterranean forest dynamic through a functional approach. Our main goal consisted to know how functional responses to light availability and biotic interactions determine the regeneration of three main species involved in this dynamic : Pinus halepensis, Quercus ilex and Quercus pubescens.A nursery experiment was set up to determine specific shade acclimatation strategies of the Aleppo pine and the Downy oak, functional tradeoffs and nutritional and ontogenetic limits of these stratgies, and the competitive and allélopathic impact on the shade induced response.Then a field experiment was set up to make a light gradient in an Aleppo pins pinewood in order to know the main positive and negative canopy effects on abiotic factors and oak seedlings development at different scales of time. Results showed that Aleppo pine exhibits a shade avoiding strategy through a strong plastic response involving functional tradeoffs, high nutritional costs, and time-limited expression. This strategy is considered as maladaptive in case of regeneration under unovercome forest canopy. Reversly, the downy oak shows a more conservative strategy through a limited plastic response to shade but a strong vulnerability to plant-plant interactions. In field conditions, Quercus pubescens and Quercus ilex seedlings showed different responses to the canopy cover, with a fewer shade tolerance in Quercus pubescens. This work help to highlight relationships between functional limits of phenotypic plasticity, shade tolerance, and regenerative success in Aleppo pine understory
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Nazrala, Jorge José Bautista. "Influencia de las coberturas vegetales en el microclima de la canopia de la vid y en las características de la uva y el vino." Master's thesis, Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias - École Nationale Supérieure Agronomique (Montpellier, Francia), 2004. http://bdigital.uncu.edu.ar/1115.
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Bonal, Damien. "Variabilité interspécifique de l'efficience d'utilisation de l'eau en forêt tropicale humide guyanaise : groupes fonctionnels, interprétation écophysiologique, intégration à l'échelle du couvert." Nancy 1, 2000. http://docnum.univ-lorraine.fr/public/SCD_T_2000_0006_BONAL.pdf.
Повний текст джерелаАнотація:
Ce travail avait pour objectif la caractérisation de la diversité fonctionnelle des espèces d'arbres de la forêt tropicale humide guyanaise à l'aide des méthodologies basées sur la composition isotopique du carbone ([delta]13C) et sur des approches écophysiologiques complémentaires. Une très forte variabilité interspécifique de [delta]13C (amplitude de 6. 0 ‰) a été mise en évidence, traduisant des variations du simple au triple de l'efficience d'utilisation de l'eau intrinsèque (WUE int = A/gs). Cette amplitude de variations est nettement plus forte que celle observée dans d'autres écosystèmes terrestres. Un regroupement des espèces sur la base de critères écophysiologiques [delta]13C et écologiques (tolérance à l'ombre) a pu être effectué, constituant une étape préalable intéressante à la modélisation du fonctionnement intégré de l'écosystème forestier tropical. L'analyse écophysiologique comparée sur le terrain et en chambre phytotronique de quatre espèces différant par leurs valeurs de [delta]13C montre que les valeurs très négatives de [delta]13C sont associées à des valeurs élevées de gs et de [psi]wm ainsi qu'à une sensibilité stomatique très forte au dessèchement du sol. Un modèle de régulation homéostatique du potentiel hydrique foliaire est proposé pour interpréter le comportement atypique des deux espèces de virola (absence de réponse du potentiel hydrique foliaire à la sécheresse atmosphérique ou édaphique). Un objectif additionnel était de caractériser le fonctionnement intégré du couvert forestier en estimant la discrimination isotopique du carbone à l'échelle du couvert ([delta]a). Un modèle de [delta]a intégrant la diversité fonctionnelle des espèces de la canopée est proposé. Les valeurs de [delta]a des peuplements étudiées sont nettement supérieures à celles précédemment obtenues à l'aide d'autres modèles. Ces résultats trouvent des applications majeures dans l'étude du rôle des différents écosystèmes terrestres dans les échanges de Co2 avec l'atmosphère.
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Ploton, Pierre. "Amélioration des estimations de biomasse en forêt tropicale : apport de la structure et de l’organisation spatiale des arbres de canopée." Thesis, Paris, AgroParisTech, 2017. http://www.theses.fr/2017AGPT0005.
Повний текст джерелаАнотація:
Les forêts tropicales séquestrent plus de la moitié du carbone forestier mondial et sont particulièrement menacées par les processus de déforestation et de dégradation, qui représentent la deuxième source d’émissions anthropogéniques de CO2. De fait, les forêts tropicales sont au centre de politiques climatiques internationales (i.e. Reducing emissions from deforestation and forest degradation, REDD) visant à réduire ces émissions. L’initiative REDD repose sur notre capacité à cartographier les stocks de carbone forestier (dynamique spatiale) et à détecter la déforestation et la dégradation (dynamique temporelle) à large échelle spatiale (e.g. nationale, bassin forestier), avec exactitude et précision. Dans ce cadre, la télédétection apparait comme un outil crucial, mais les nombreuses sources d’erreur dans la chaîne de cartographie du carbone font des objectifs du REDD un challenge ambitieux. Dans cette thèse, nous avons évalué les erreurs associées aux estimations de carbone forestier (quantifié au travers de la biomasse épigée, AGB) (1) aux échelles de l’arbre et du peuplement en utilisant un modèle pantropical largement employé et (2) à l’échelle du paysage en utilisant une méthode de télédétection basée sur les caractéristiques texturales d’images optiques à très haute résolution spatiale. Notre objectif général était de mieux comprendre et de réduire l’erreur d’estimation de l’AGB à chaque échelle par une meilleure prise en compte de la structure, de la distribution et de l’organisation spatiale des arbres de canopée.Malgré l’importance des grands arbres dans la dynamique du carbone forestier, ils sont sous-représentés dans les jeux de données destructifs et soumis à un biais de sous-estimation dans le modèle d’AGB pantropical. Nous avons assemblé une base de données pantropicale et étudié l’influence de la forme de l’arbre sur le patron d’erreur du modèle. Nos résultats montrent que la source de biais du modèle est une augmentation de la masse de l’arbre dans la couronne chez les arbres de canopée. Un modèle d’AGB prenant ce phénomène en compte a été proposé. Nous avons aussi propagé le biais du modèle à l’échelle du peuplement et montré que l’interaction entre la structure du peuplement et l’erreur du modèle, qui est souvent négligée, peut en fait être substantielle. Une analyse des propriétés structurelles des couronnes a également été menée au regard des hypothèses de la Théorie Métabolique de l’Ecologie Des déviations ont été observées, notamment à la loi de Léonardo (i.e. principe de conservation des aires), qui, toutes choses égales par ailleurs, pourraient justifier la grande proportion de masse trouvée dans les couronnes des arbres de canopée.Une seconde partie de la thèse porte sur l’extrapolation des estimations d’AGB des parcelles de terrain via les caractéristiques de texture des canopées extraites par transformée de Fourier (i.e. méthode FOTO). Un obstacle majeur au développement d’une méthode d’estimation de l’AGB à large échelle basée sur la texture tient au fait que la relation texture – paramètres de structure du peuplement varie entre types de forêt et régions du monde. Nous avons investigué cette question en simulant des scènes de canopées virtuelles pour 279 parcelles de 1 ha établies dans des types de forêts tropicales contrastés. Nous montrons qu’en complémentant les indices de texture FOTO avec d’autres descripteurs structuraux, notamment sur l’ouverture de la canopée (via une analyse de lacunarité) et l’élancement des arbres (via un proxy bioclimatique), il devrait être possible de développer un cadre d’inversion stable de l’AGB à large échelle. Un premier cas d’étude empirique dans une mosaïque forestière du bassin du Congo a donné des résultats prometteurs.Globalement, ce travail met en évidence le besoin de mieux prendre en compte les patrons de variation de structure de l’arbre (e.g. ontogénétique) et de la forêt afin d’améliorer les modèles génériques d’AGBTropical forests store more than half of the world’s forest carbon and are particularly threatened by deforestation and degradation processes, which together represent the second largest source of anthropogenic CO2 emissions. Consequently, tropical forests are the focus of international climate policies (i.e. Reducing emissions from deforestation and forest degradation, REDD) aiming at reducing forestrelated CO2 emissions. The REDD initiative lies on our ability to map forest carbon stocks (i.e. spatial dynamics) and to detect deforestation and degradations (i.e. temporal dynamics) at large spatial scales (e.g. national, forested basin), with accuracy and precision. Remote-sensing is as a key tool for this purpose, but numerous sources of error along the carbon mapping chain makes meeting REDD criteria an outstanding challenge. In the present thesis, we assessed carbon (quantified through aboveground biomass, AGB) estimation error at the tree- and plot-level using a widely used pantropical AGB model, and at the landscape-level using a remote sensing method based on canopy texture features from very high resolution (VHR) optical data. Our objective was to better understand and reduce AGB estimation error at each level using information on large canopy tree structure, distribution and spatial organization.Although large trees disproportionally contributed to forest carbon stock, they are under-represented in destructive datasets and subject to an under-estimation bias with the pantropical AGB model. We destructively sampled 77 very large tropical trees and assembled a large (pantropical) dataset to study how variation in tree form (through crown sizes and crown mass ratio) contributed to this error pattern. We showed that the source of bias in the pantropical model was a systematic increase in the proportion of tree mass allocated to the crown in canopy trees. An alternative AGB model accounting for this phenomenon was proposed. We also propagated the AGB model bias at the plot-level and showed that the interaction between forest structure and model bias, although often overlooked, might in fact be substantial. We further analyzed the structural properties of crown branching networks in light of the assumptions and predictions of the Metabolic Theory of Ecology, which supports the power-form of the pantropical AGB model. Important deviations were observed, notably from Leonardo’s rule (i.e. the principle of area conservation), which, all else being equal, could support the higher proportion of mass in large tree crowns.A second part of the thesis dealt with the extrapolation of field-plot AGB via canopy texture features of VHR optical data. A major barrier for the development of a broad-scale forest carbon monitoring method based on canopy texture is that relationships between canopy texture and stand structure parameters (including AGB) vary among forest types and regions of the world. We investigated this discrepancy using a simulation approach: virtual canopy scenes were generated for 279 1-ha plots distributed on contrasted forest types across the tropics. We showed that complementing FOTO texture with additional descriptors of forest structure, notably on canopy openness (from a lacunarity analysis) and tree slenderness (from a bioclimatic proxy) allows developing a stable inversion frame for forest AGB at large scale. Although the approach we proposed requires further empirical validation, a first case study on a forests mosaic in the Congo basin gave promising results.Overall, this work increased our understanding of mechanisms behind AGB estimation errors at the tree-, plot- and landscape-level. It stresses the need to better account for variation patterns in tree structure (e.g. ontogenetic pattern of carbon allocation) and forest structural organization (across forest types, under different environmental conditions) to improve general AGB models, and in fine our ability to accurately map forest AGB at large scale
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Caillon, Robin. "Biogéographie du microclimat foliaire : mécanismes et conséquences sur les relations plantes-insectes." Thesis, Tours, 2016. http://www.theses.fr/2016TOUR4006/document.
Повний текст джерелаАнотація:
Les performances du végétal et des arthropodes dont il constitue le microhabitat dépendent des températures de surface foliaire. Celles-ci peuvent dévier fortement de la température de l’air et présenter des niveaux d’hétérogénéité différents selon l'échelle spatiale considérée. La feuille atténue les températures extrêmes en rapprochant son amplitude de variation journalière de celle de la température de l’air. Cependant, cette réponse diminue l’hétérogénéité des températures de surface foliaire et les capacités de thermorégulation comportementale des arthropodes à l'échelle de la feuille. Les températures moyennes de surface foliaire atténuent peu le réchauffement, et déterminent localement la performance photosynthétique du végétal. De l’échelle de la feuille à celle de la canopée, les plantes montrent des réponses différentes au réchauffement. Ce type de changement d'échelle est primordial pour améliorer notre compréhension de l'impact des changements climatiquesPlant performance and leaf-dwelling arthropods are impacted by leaf surface temperatures. Leaf surface temperatures can show important deviation from air temperature and present different levels of heterogeneity depending on the spatial scale. The leaf buffers temperature extremes by getting closer in amplitude to air temperature. However, this physiological response decreases the heterogeneity of temperatures at the leaf surface and the opportunities for arthropods to behavioraly thermoregulate in this microclimate. Mean temperatures at the leaf surface show low buffering abilities in response to warming and locally determine photosynthetic performance. From the leaf to the canopy scale, plants show different responses to warming and scaling is crucial to increase our understanding of the impact of global warming
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Levionnois, Sébastien. "Diversité et variabilité de l’architecture vasculaire et hydraulique de la pousse feuillée chez des arbres de canopée d’une forêt tropicale humide Scaling of petiole anatomies, mechanics, and vasculatures with leaf size in the widespread Neotropical pioneer tree species Cecropia obtusa Trécul (Urticaceae) Linking drought-induced embolism resistance in stem xylem tissue to multi-scale wood anatomical traits of Neotropical trees." Thesis, Guyane, 2019. http://www.theses.fr/2019YANE0011.
Повний текст джерелаАнотація:
Les traits hydrauliques sont reliés aux fonctions fondamentales du transport de l’eau dans la plante et de la résistance à la sécheresse, déterminant l’écologie, l’évolution, et les processus en lien avec le changement climatique pour les plantes. Cependant, ces traits restent que peu documentés pour les forêts tropicales humides, empêchant de mieux comprendre l’écologie des arbres tropicaux et le futur des forêts tropicales. À partir d’une approche générale s’intéressant à la structure (morphologie et anatomie) et au fonctionnement (physiologie) de la pousse feuillée au sein des arbres, cette thèse analyse la structure et le fonctionnement de la pousse feuillée des arbres, notamment dans la perspective de la résistance à la sécheresse. Cette thèse s’appuie sur un jeu de données général qui concerne 42 espèces d’arbres de canopée échantillonnées en forêt tropicale humide de Guyane, et qui illustre une large gamme de tailles de feuilles. Un second jeu de données, destiné à mieux comprendre les sources de variabilité intraspécifique, porte de l’espèce pionnière Cecropia obtusa Trécul (Urticaceae). Une première partie de la thèse vise à comprendre la coordination entre la feuille et la tige pour une large gamme de dimension foliaire, en analysant les changements morpho-anatomiques et fonctionnels soulignant la relation entre dimensions de la feuille et dimensions de la tige à l’échelle interspécifique. Ce cadre est aussi appliqué à l’échelle intraspécifique pour le modèle C. obtusa pour la relation pétiole-limbe. Comprendre les changements liés aux dimensions de la feuille permet ainsi d’investir correctement les effets ontogénétiques et saisonniers sur les traits foliaires vasculaires et hydrauliques pour C. obtusa. La seconde partie vise à mieux comprendre les mécanismes de résistance à la sécheresse de la pousse feuillée. En retenant 25 espèces, les déterminants anatomiques de la résistance à l’embolie par sécheresse des tiges et sont étudiés. Les différentes propriétés et mécanismes déjà connus pour des plantes tempérées sont abordés conjointement afin de conforter ou non leur existence et comprendre leurs contributions relatives. La segmentation de vulnérabilité (c.-a.d. la différenciation de résistance à l’embolie) à l’interface tige-feuille est également étudiée pour 20 espèces. Sa coordination avec la segmentation hydraulique (c.-à-d. différenciation de résistance hydraulique), qui est dérivée des études anatomiques réalisées dans la première partie, est étudiée. Je montre ainsi (i) un large spectre de variation pour la segmentation de vulnérabilité entre espèces, (ii) une relation positive avec la segmentation hydraulique, suggérant qu’il y a des espèces promouvant à la fois la segmentation hydraulique et la segmentation de vulnérabilité pour découpler le fonctionnement la feuille de la tige du point de vue hydraulique, et (iii) que la segmentation de vulnérabilité a un impact important sur le temps de dessiccation théorique de la pousse feuillée, confirmant que la segmentation de vulnérabilité est un mécanisme de résistance à la sécheresse. Dans une dernière partie, je teste le pouvoir prédictif des différents traits hydrauliques étudiés sur la distribution hydro-topographique des espèces, ainsi que l’impact du stress hydrique sur la croissance des arbres, à une échelle locale. Dans la Discussion générale, je discute de la signification fonctionnelle de la surface de la feuille et des traits de résistance à la sécheresse en forêt tropicale humide, ainsi que la relation potentielle entre la surface de la feuille et la résistance à la sécheresseHydraulic traits are related to the fundamental functions of conduction and drought resistance, driving plant ecology, evolution, and processes related to climate change. However, these traits are still poorly documented for tropical rainforest, hindering our understanding of tropical tree ecology and the future of tropical forests. Through a trait-based approach combining leaf and stem in-depth anatomy and physiology, this thesis analyses the structure and the functioning of tree leafy shoots, a compartment exposed to the most severe water stress within a tree. This thesis is based on a dataset of 42 canopy tree species sampled in a rainforest in French Guiana, exemplifying a large range of leaf size. A second dataset, aiming at better understanding the sources of intraspecific variability, focus on the pioneer tree species Cecropia obtusa Trécul (Urticaceae). The first part aims at understanding the coordination between leaf and stem across a large leaf size range, by analysing the morpho-anatomical and functional changes underlying the leaf size-stem size relationship for 42 tropical rainforest canopy trees. This framework is also applied at the intraspecific level for the model C. obtusa, for the petiole-lamina relationship. Understanding leaf size-related changes allows to properly investigate ontogenetic and seasonal effects on leaf vascular and hydraulic traits for C. obtusa. The second part aims at better understanding the drought resistance of the leafy shoot. By retaining 25 species, the anatomical determinants of drought-induced embolism resistance for stems are studied. The different properties and mechanisms already known for temperate plants are investigated jointly to consolidate or not their existence, and understand their relative contribution. Vulnerability segmentation (i.e. differentiation of embolism resistance) at the leaf-stem interface is investigated across 20 species. I further evidenced (i) a large spectrum of variation for vulnerability segmentation across species, (ii) a positive relation with hydraulic segmentation (i.e. differentiation of hydraulic resistance), suggesting that some species promote both hydraulic and vulnerability segmentations to decouple hydraulically leaf and stem, and (iii) that vulnerability segmentation has a massive role in enhancing the theoretical desiccation time of shoots, confirming vulnerability segmentation as a drought resistance mechanism for tropical trees. In a final part, all traits are merged to test their predictive power for species hydro-topographic distribution and growth-mediated response to water stress, at a local scale. In the general discussion, I discuss the functional signification of leaf size and drought resistance traits for tropical rainforest, as also potential relation between leaf size and drought resistance
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Dupont, Sylvain. "Modélisation de la micrométéorologie à l'échelle de paysages complexes." Habilitation à diriger des recherches, Université Paul Sabatier - Toulouse III, 2009. http://tel.archives-ouvertes.fr/tel-00443770.
Повний текст джерелаАнотація:
Les paysages ruraux et urbains sont caractérisés par une très forte hétérogénéité spatiale liée à la présence de végétation, bâtiments, clairières, routes, ..., ayant des propriétés physiques, des états hydriques et une résistance au vent très variables. Cette hétérogénéité locale des surfaces ajoutée à la topographie agissent sur les échanges entre la canopée et l'atmosphère, et donc sur les champs atmosphériques (vent, température, humidité), générant des conditions micrométéorologiques complexes sensibles à cette hétérogénéité. La modélisation des champs micrométéorologiques à l'échelle de paysages ruraux et urbains est important i) pour améliorer les prédictions météorologiques, en particulier les événements locaux, mais aussi ii) pour de nombreux domaines de la recherche environnementale liés par exemple à la climatologie urbaine, à la qualité de l'air, à la dissémination de grains de pollen transgéniques, à la stabilité des peuplements au vent, à la propagation des feux de forêt, aux échanges de CO2 entre la biosphère et l'atmosphère, etc. Ceci est d'autant plus vrai dans le contexte du changement climatique et notamment du possible accroissement des événements extrêmes aux conséquences environnementales, sanitaires et économiques lourdes. Bien que la modélisation des champs microméteorologiques ne puisse pas influer sur ce changement, elle peut être un outil pour comprendre l'impact du changement climatique sur les écosystèmes, pour explorer différents aménagements des surfaces rurales et urbaines, ou pour modifier les pratiques agricoles, afin de limiter les conséquences de ces événements extrêmes. Mes travaux de recherche au cours de ces dix dernières années ont principalement eu pour objectif de (i) développer et valider des modèles de canopées urbaine et rurale pour une meilleure simulation des champs micrométéorologiques à l'échelle paysages complexes, et (ii) d'étudier à partir de ces modèles l'impact des hétérogénéités de surface et de la petite topographie sur ces champs, sur la stabilité des arbres au vent, et sur la dispersion de pollen de maïs. Après une revue générale du contexte scientifique dans lequel mes travaux de recherche se situent, je décline mes principaux résultats de recherche suivant les quatre thématiques : 1) modélisation de la canopée urbaine, 2) dynamique du vent à l'échelle de couverts hétérogènes, 3) interaction vent-plante, et 4) dispersion environnementale de grains de pollen de maïs. Un bilan scientifique et académique est ensuite fait avant de présenter mon projet de recherche pour les années à venir.
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Brouard, Eloïse. "Effet de l'adaptation des pratiques culturales de la vigne en réponse au changement climatique (manipulation de la canopée, utilisation d'acide abscissique) sur le potentiel qualitatif de la baie de raisin : approches agronomique, analytique et transcriptomique : & Caractérisation fonctionnelle de VviAKR, enzyme potentiellement impliquée dans la voie de biosynthèse des méthoxypyrazines." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0408.
Повний текст джерелаАнотація:
Les changements climatiques mondiaux ont déjà affecté et continueront d’affecter la physiologie de la vigne, en particulier le rendement et la composition des baies à la récolte, et donc, en définitive, la qualité et la typicité des vins produits. Parmi les différentes stratégies possibles d’adaptation de la viticulture au changement climatique (modifications de l’encépagement, création de nouvelles variétés mieux adaptées aux conditions futures,...), le contrôle de la composition des baies à la récolte par le biais d’une modification des pratiques culturales et notamment par des manipulations de la canopée (rapport feuilles/fruits (Fe/Fr), manipulation de l’exposition des grappes, échardage) est certainement celle qui serait la plus rapide à mettre en œuvre.Ma thèse a pour but de rechercher le meilleur point de compromis entre diminution du taux de sucres et maintien de l’acidité, de l’accumulation des composés phénoliques et d’une complexité aromatique proche de l’actuelle, en réponse aux manipulations de canopée (rapport Fe/Fr, échardage) couplées ou non à l’application d’acide abscissique (ABA).Différents ratio Fe/Fr ont ainsi été étudiés sur le cépage d’étude Cabernet-Sauvignon en conditions semi-contrôlées en serre sur boutures fructifères puis au vignoble au sein d’une parcelle de production. L’analyse de la composition des baies en métabolites primaires et secondaires, réalisée lors de ces deux expériences, a permis de déterminer que le ratio 6 feuilles restantes par grappe était la valeur seuil en dessous de laquelle un effet sur les métabolites primaires est visible. Une diminution du taux de sucres a notamment été observée, également associée à la diminution de la concentration en anthocyanes totales qui sont particulièrement importantes dans la définition de la typicité des vins de Bordeaux. L’application d’ABA exogène sur les baies avant la véraison a permis de diminuer les effets négatifs de la modification du ratio Fe/Fr sur l’accumulation des anthocyanes et n’a pas montré d’impact sur la typicité des vins lors des dégustations des microvinifications réalisées au cours de cette étude. Ces résultats analytiques obtenus ont été couplés à des analyses transcriptomiques de type RNAseq et PCR quantitative en temps réel (Fluidigm) afin d’identifier les gènes clefs associés au voies métaboliques primaires et secondaires réagissant aux modulations du ratio Fe/Fr couplées ou non à l’ajout d’ABA. Ainsi, le couplage modulation du ratio Fe/Fr et application d’ABA exogène sur les baies serait une méthode potentiellement utilisable afin de réduire le taux de sucres et de maintenir une typicité bordelaise proche de l’actuelle.La caractérisation fonctionnelle d'un gène potentiellement associé à la voie de biosynthèse des méthoxypyrazines, impliquées dans le caractère végétal du raisin et du vin, a également été mise en œuvre. Différentes approches ont été testées et ont fourni des indices utiles, cependant les résultats obtenus sont encore en cours de confirmationGlobal climate changes have already affected and will continue to affect the physiology of grapevine, in particular the yield and berry composition at harvest, and thus ultimately the quality and typicality of the wines produced. Among the different possible strategies of adapting viticulture to climate change (changes varieties, creation of new varieties better adapted to future conditions,...), modulating berry composition at harvest through changing cultural practices, such as manipulations of the canopy (leaf / fruit ratio, grape exposure), may be a fast and efficient option as a short-term adaptation strategy.My thesis aims to find the best point of compromise between reducing the sugar level and, maintaining the acidity, phenolic compounds, and the aromatic complexity by the canopy manipulations (leaves / fruits ratio, secondary shoot removal), coupled or not with the application of abscisic acid.Different leaf / fruit ratios were studied on the Cabernet-Sauvignon cultivar in greenhouse and in vineyard within a plot of production. The berry composition analysis of primary and secondary metabolites, performed in these two experiments, made it possibleto determine that the ratio of 6 leaves remaining per cluster was the threshold value below which an effect on the primary metabolites is visible. A decrease in the sugar content was especially observed, also associated with a decrease in the concentration of total anthocyanins which are particularly important in the definition of the typicality of Bordeaux wines. The application of exogenous abscisic acid to the berries before veraison permitted to reduce the negative effects of the modification of the leaf-to-fruit ratio on the accumulation of anthocyanins and did not affect the typicality of the wines during the tastings of the microvinifications carried out during this study. These analytical results were coupled with transcriptomic analyses of RNAseq and real-time quantitative PCR (Fluidigm) to identify key genes associated with the primary and secondary metabolic pathways reacting to modulations of leaf-to-fruit ratio coupled or not with the addition of abscisic acid.Thus, the coupling modulation of the leaf-to-fruit ratio to the application of exogenous abscisic acid on the berries would be a usable method to reduce the sugar content and maintain a typicality of Bordeaux wines close to the current one.The functional characterization of a gene potentially associated with the biosynthetic pathway of methoxypyrazines, which are involved in vegetable character of grapes and wine, was also conducted. Different approaches have been tested and provided useful clues but the conclusive results are still under further confirmation
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Haeussler, Sybille. "Germination and first-year survival of red alder seedlings in the central Coast Range of Oregon /." 1987. http://hdl.handle.net/1957/10700.
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Zhang, Shu-Huan. "Manipulation of yield through source-sink changes in soybean (Glycine max (L.) Merrill) /." 1996. https://scholarworks.umass.edu/theses/3461.
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Biskup, Bernhard [Verfasser]. "Determination of structural parameters of single plants and canopies using 3D techniques / vorgelegt von Bernhard Biskup." 2009. http://d-nb.info/995718911/34.
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Lindh, Briana C. "Understory herb and shrub responses to root trenching, pre-commercial thinning, and canopy closure in Douglas-fir forest of the western Cascades, Oregon." Thesis, 2003. http://hdl.handle.net/1957/30049.
Повний текст джерелаАнотація:
This thesis examines factors limiting understory herb presence and flowering
in young second-growth Douglas-fir (Pseudotsuga menziesii) forests on the west side
of the Cascade Mountains, Oregon, USA. I studied the belowground effects of canopy
trees on understory herbs and shrubs in old-growth forests using trenched plots from
which tree roots were excluded. Effects of tree density and stand age were tested by
comparing the understory community composition of old-growth stands and pre-commercially
thinned and unthinned young second-growth stands. I also examined
the effect of conifer basal area on understory herb presence and flowering within one
young second-growth watershed. In young stands, I focused on three groups of
understory herb species: disturbance-responsive (release), forest generalist and old-growth
associated.
The effects of root trenching on vegetation and soil moisture were tested in
closed-canopy and gap locations in two old-growth Douglas-fir (Pseudotsuga
menziesii) forests. Ten years after installation, trenched plots averaged 92% total
understory cover while untrenched plots averaged 47% cover. Trenched plots under
closed canopies were moister than control plots throughout the growing season; the
trenching effect on soil moisture became apparent in the generally wetter gaps only at
the end of the growing season. Vegetation responses to trenching were concomitantly
larger under closed canopies than in gaps.
Stands that had been pre-commercially thinned 20 years earlier exhibited
understory composition more similar to old growth than did unthinned stands.
Thinned stands exhibited higher frequencies, abundances and density of flowering of
old-growth associated herbs than did unthinned stands, but lower than did old-growth
stands. Forest generalist and release species showed mixed responses to thinning.
I used both general linear models and classification and regression tree models
to explore the association of herb species presence and flowering with conifer basal
area and abiotic variables. Both modeling approaches yielded similar biological
insights. Flowering was more sensitive than presence to current stand basal area.
Flowering of old-growth associated and release species was negatively correlated with
conifer basal area. Linear models allowed clearer hypothesis tests, while tree-based
models had greater explanatory power and provided information about interactions
between variables.Graduation date: 2004