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1
Back, Merri, e A. K. Dobrenz. "Increasing the Leaf Area of Alfalfa". College of Agriculture, University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/200495.
Testo completo
2
Malone, Sean M. "Assessment of Soybean Leaf Area for Redefining Management Strategies for Leaf-Feeding Insects". Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29252.
Testo completoAbstract (sommario):
Commercially available leaf area index (LAI) meters are tools that can be used in making insect management decisions. However, proper technique must be determined for LAI estimation, and accuracy must be validated for the meters. Full-season soybean require LAI values of at least 3.5 to 4.0 by early to mid-reproductive developmental stages to achieve maximum yield potential, but the relationship between double-crop soybean LAI and yield is unknown. This research (1) evaluated minimum plot size requirements for mechanically defoliated soybean experiments using the LAI-2000 Plant Canopy Analyzer, (2) compared LAI estimates among LAI-2000 detector types which respond to different wavelengths of light, (3) compared LAI-2000 estimates with directly determined LAI values for 0, 33, 66, and 100% mechanical defoliation levels, (4) used linear and non-linear models to describe the response of full-season and double-crop soybean yields to reductions in LAI through mechanical defoliation, and (5) evaluated the response of double-crop soybean yields to reductions in LAI through insect defoliation.
The minimum plot size for obtaining accurate LAI estimates of defoliated canopies in soybean with 91 cm row centers is four rows by 2 m, with an additional 1 m at the ends of the two middle rows also defoliated. The wide-blue detector, which is found in newer LAI-2000 units and responds to wavelengths of light from 360 to 460 nm, gave higher LAI estimates than the narrow-blue detector, which responds to light from 400 to 490 nm. The unit with the narrow-blue detector gave estimates equal to directly determined LAI in two of three years for 0, 33, and 66% defoliation levels, while the units with the wide-blue detectors gave estimates higher than directly determined LAI in the two years that they were studied, except for a few accurate 33% defoliation estimates. Therefore, the LAI-2000 usually provides reasonable estimates of LAI. Yield decreased linearly with LAI when LAI values were below 3.5 to 4.0 by developmental stages R4 to R5 in both full-season and double-crop soybean. Usually, there was no relationship between yield and LAI at LAI values greater than 4.0. There was an average yield reduction of 820 ± 262 kg ha-1 for each unit decrease in LAI below the critical 3.5 to 4.0 level; maximum yields ranged from 1909 to 3797 kg ha-1. Insect defoliators did not defoliate double-crop soybean plots to LAI levels less than 4.0, and there was no yield difference between insect-defoliated and control plots. Therefore, double-crop soybean that maintains LAI values above the 3.5 to 4.0 critical level during mid-reproductive developmental stages is capable of tolerating defoliating pestPh. D.
3
Duffy, Natasha Michelle. "Design limitations to potential leaf area in urban forests". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ46004.pdf.
Testo completo
4
Ebodaghe, Denis Abumere. "Estimating daily green leaf area index for corn in Virginia". Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/74731.
Testo completoAbstract (sommario):
A model to predict the daily green leaf area index (GLAI) for corn has been developed for Indiana conditions. Using daily maximum and minimum temperatures the GLAI was predicted for the vegetative stage, reproductive and grain filling stage, and the leaf senescing stage of corn. Predictions of GLAI for corn can be made on a daily basis from the day corn is planted until it is harvested for grain.
The GLAI model was tested under Virginia conditions using green leaf area measurements collected from corn plants grown on Davidson silty clay loam, Davidson silty clay, and Mayodan sandy loam soils in the Piedmont region of the State. Maximum and minimum temperature data were also collected at the three sites. Measurements were made for two growing seasons using corn hybrid Pioneer 3369A, three plant population densities and two irrigation schedules. Short duration temperature data were also collected to compare with the daily maximum and minimum temperature data for the Mayodan site. Also a combination of soil temperature at 10 cm depth and air temperatures were used for the temperature functions accumulated from date of planting at the Mayodan site.
Results of this study show that the predicted and measured GLAI values compare favorably under irrigated conditions on the Davidson soil. The results were not as favorable on the irrigated corn on the Mayodan soil. When the corn is subjected to severe moisture stress on either soil, GLAI cannot be predicted with this model. Short duration temperature data resulted in a better prediction of GLAI on the Mayodan soil. When applying nitrogen fertilizer to the corn through the irrigation system through the grain filling stage, the measured GLAI values compared favorably with the predicted GLAI values. However, the application of nitrogen and sulfur fertilizer together resulted in GLAI being maintained above that predicted for a longer period of time during the grain filling stage before its decline.Ph. D.
5
Coker, Graham William Russell. "Leaf Area Index in Closed Canopies: An indicator of site quality". Thesis, University of Canterbury. School of Forestry, 2006. http://hdl.handle.net/10092/1128.
Testo completoAbstract (sommario):
This study examined leaf area index (LAI) and relationships with corresponding tree growth, climate and soil characteristics across New Zealand forest plantations. The aim of this study was to determine if quick measures of projected leaf area across environmental gradients of New Zealand were an accurate indicator of site quality. Projected leaf areas of Pinus radiata D Don and Cupressus lusitanica Mills seedlings were measured using a Li-Cor LAI-2000 plant canopy analyser at 22 locations representing the soil and climatic diversity across New Zealand plantation forests. Seedlings planted at 40 000 stems per hectare were used to test treatment effects of fertiliser, site disturbance and species over a 4 year period. It was hypothesised that collected climate and soil information would explain differences in LAI development patterns across sites as the canopies approached site and seasonal maxima. Averaged across sites Cupressus lusitanica 7.28 (± 2.59 Std.) m2 m-2 had significantly (p = 0.0094) greater projected LAIs than Pinus radiata 6.47 (± 2.29) m2m-2. Maximum site LAI (LAImax) varied from 2.9 to 11.8 m2 m-2 for Pinus radiata and from 3.1 to 12.6 m2 m-2 for Cupressus lusitanica. LAImax of both species was significantly and positively correlated with vapour pressure deficit, soil carbon, nitrogen, phosphorous and CEC, but negatively with solar radiation, temperature and soil bulk density. A seasonal model of LAI across sites illustrated an 8.5% fluctuation in LAI of established canopies over the course of a year. Despite considerable variation in climate and soil characteristics across sites the combined effects of LAI at harvest and temperature were significantly correlated with site productivity (r2 = 0.84 and 0.76 for Pinus radiata and Cupressus lusitanica respectively). A national model of LAImax (r2 = 0.96) was proposed for Pinus radiata across climate and soil environments and the significance of LAImax as a component of site quality monitoring tools is discussed.
6
Johnson, Ryan L., e University of Lethbridge Faculty of Arts and Science. "Airborne remote sensing of forest leaf area index in mountainous terrain". Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2000, 2000. http://hdl.handle.net/10133/90.
Testo completoAbstract (sommario):
Leaf area index (LAI) provides forestry information that is important for regional scale ecological models and in studies of global change. This research examines the effects of mountainous terrain on the radiometric properties of multispectral CASI imagery in estimating ground-based optical measurements of LAI, obtained using the TRAC and LAI- 2000 systems. Field and image data were acquired summer 1998 in Kananaskis, Alberta, Canada. To account for the influence of terrain a new modified approach using the Li and Strahler Geometric Optical Mutual Shadowing (GOMS) model in 'multiple forward mode' (MFM) was developed. This new methodology was evaluated against four traditional radiometric corrections used in comination with spectral mixture analysis (SMA) and NDVI. The MFM approach provided the best overall predictions of LAI measured with ground-based optical instruments, followed by terrain normalized SMA, SMA without terrain normalization and NDVI.xiv, 151 leaves : ill. (some col.), map ; 29 cm.
7
Wang, Dongdong. "Improving satellite Leaf Area Index estimation based on various integration methods". College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9872.
Testo completoAbstract (sommario):
Thesis (Ph. D.) -- University of Maryland, College Park, 2009.Thesis research directed by: Dept. of Geography. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
8
Johnson, Ryan L. "Airborne remote sensing of forest leaf area index in mountainous terrain". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ49131.pdf.
Testo completo
9
Winkler, Tobias. "Empirical models for grape vine leaf area estimation on cv. Trincadeira". Master's thesis, ISA-UL, 2016. http://hdl.handle.net/10400.5/13008.
Testo completoAbstract (sommario):
Mestrado Vinifera Euromaster - Viticulture and Enology - Instituto Superior de Agronomia - UL / Institut National D'Etudes Superieures Agronomiques de MontpellierEstimating a Vineyard’s leaf area is of great importance when evaluating the productive and quality potential of a vineyard and for characterizing the light and thermal microenvironments of grapevine plants. The aim of the present work was to validate the Lopes and Pinto method for determining vineyard leaf area in the vineyards of Lisbon’s wine growing region in Portugal, with the typical local red grape cultivar Trincadeira, and to improve prediction quality by providing cultivar specific models. The presented models are based on independent datasets of two consecutive years 2015 and 2016. Fruiting shoots were collected and analyzed during all phenological stages. Primary leaf area of shoots is estimated by models using a calculated variable obtained from the average of the largest and smallest primary leaf area multiplied by the number of primary leaves, as presented by Lopes and Pinto (2005). Lateral Leaf area additionally uses the area of the biggest lateral leaf as predictor. Models based on Shoot length and shoot diameter and number of lateral leaves were tested as less laborious alternatives. Although very fast and easy to assess, models based on shoot length and diameter were not able to predict variability of lateral leaf area sufficiently and were susceptible to canopy management. The Lopes and Pinto method is able to explain a very high proportion of variability, both in primary and lateral leaf area, independently of the phenological stage, as well as before and after trimming. They are inexpensive, universal, practical, non-destructive methods which do not require specialized staff or expensive equipment
N/A
10
Phinopoulos, Victoras Georgios. "Estimation of leaf area in grapevine cv. Syrah using empirical models". Master's thesis, ISA/UL, 2014. http://hdl.handle.net/10400.5/8631.
Testo completoAbstract (sommario):
Mestrado Vinifera EuroMaster - Instituto Superior de AgronomiaEmpirical models for the estimation of the Area of single Primary and Lateral leaves, and total Primary and Lateral Leaf Area of a shoot, are presented for the grapevine cv. Syrah (Vitis vinifera L.). The Area of single Leaves is estimated with models using the sum of the lengths of the two lateral veins of each leaf, with logarithmic transformation of both variables. Separate models are proposed for Primary and Lateral Leaves. Models based on the Lopes and Pinto (2005) method, using Mean Leaf Area multiplied by the number of Leaves as predictors, are proposed for the estimation for Total Primary and Lateral Leaf Area. It is suggested, that failure to locate the Largest Leaf of a Primary or Lateral shoot, would not significantly impair the accuracy of the models. All models explain a very high proportion of variability in Leaf Area and they can by applied in research and viticulture for the frequent estimation of Leaf Area in any phase of the growing cycle. They are inexpensive, practical, non-destructive methods which do not require specialised staff or expensive equipment
11
Hailemariam, Temesgen. "Leaf area distribution and alternative sampling designs for hybrid spruce tree crowns". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ27153.pdf.
Testo completo
12
Fang, Hongliang. "Improving the estimation of leaf area index from multispectral remotely sensed data". College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/304.
Testo completoAbstract (sommario):
Thesis (Ph. D.) -- University of Maryland, College Park, 2003.Thesis research directed by: Geography. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
13
Bowyer, P. "Estimating leaf area index in savanna vegetation using remote sensing and inverse modelling". Thesis, University of Salford, 2005. http://usir.salford.ac.uk/2234/.
Testo completoAbstract (sommario):
Leaf area index (LAI), defined as the one sided green leaf area per unit ground area, is a key parameter in ecosystem process models. Owing to the large area of the earth's surface that they occupy, savanna ecosystems represent the third largest terrestrial carbon sink. There is considerable uncertainty however, as to the functioning of these ecosystems, particularly as they respond to land cover changes. Consequently, ecosystem process models constitute one of the best methods available for investigating the effect this may have on terrestrial carbon cycling. If these models are to be used over large areas however, they need to be parameterised. This thesis develops a methodology to estimate LAI in savanna ecosystems, using remotely sensed earth observation (EO) data, laboratory bidirectional reflectance measurements (BRDF), physically based canopy reflectance models (CRMs), and artificial neural networks (ANN). First, the scattering behaviour of Kalahari soils was characterised, by making laboratory BRDF measurements. Soils were shown to be highly non-Lambertian. These measurements were then used to parameterise three different CRMs. Modelled reflectances were assessed with respect to Landsat ETM+ and Terra-MODIS reflectances. Results showed that a 1-D turbid medium provided the closest fit to the measurements. A series of model sensitivity analyses (SA) were performed, and it was shown that reflectance in the red and shortwave infrared displayed greatest sensitivity to LAI, sensitivity in the near-infrared was negligible. Model inversions were performed with ANN and different waveband combinations, and LAI was estimated. The results showed that LAI could be estimated with high accuracy, an RMSE of 0.3 1, and 0.18, from ETM+ and MODIS measurements, respectively. These results were promising, and with further improvements to models, coupled with more accurate input data, will see the use of EO data play an increasingly important role in understanding the functioning of these savanna ecosystems.
14
Chalfant, Patricia. "Responses of Grapevines to Timing and Method of Leaf Removal". The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337628161.
Testo completo
15
Aqeel, Abdullah Mohammad. "USING MANUAL DEFOLIATION TO SIMULATE SOYBEAN RUST: EFFECT ON GROWTH AND YIELD FORMATION". UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/223.
Testo completoAbstract (sommario):
Field experiments were conducted in Kentucky and Louisiana in 2008 and 2009 (split-plot in a randomized complete block design with four replications) to investigate it is possible to simulate with manual defoliation the effect of soybean rust (SBR) (Phakopsora pachyrhizi Syd. and P. Syd) injury on a healthy soybean [Glycine max, (L.) Merr.] canopy, understand how defoliation affects the growth dynamics and canopy light interception, and if defoliation affectsleaf senescence and nitrogen remobilization during the seed-filling period. Two manual defoliation treatments based on changes in effective leaf area index (ELAI) (calculated as the reduction in leaf area equivalent to SBR-induced premature leaf abscission, loss in green leaf area, and reduction in photosynthetic capacity of diseased leaves) in infected canopies in Brazil were used to simulate SBR infection at growth stage R2 (full flowering) and R5 (beginning of seed-fill). Both defoliation treatments reduced yield in all experiments and the reduction was larger for the treatments at growth stage R2. The yield losses were equivalent to that observed in infected soybean canopies in Brazil. This suggests that a system of manual defoliation to simulate changes in effective leaf area duration shows promise as a tool to simulate the impact of SBR on soybean yield. The radiation use efficiency and crop growth rate from growth stage R2 to R5 were not influenced by defoliation. Defoliation started at growth stage R2 reduced seed number per unit area, while defoliation started at growth stage R5 reduced seed size due to shortening the seed-fill duration and a lower seed growth rate. There is no evidence that manual defoliation affected leaf senescence or nitrogen redistribution to the seed. This study found that the reduction of light interception by SBR was the main reason for the reductions in soybean growth and yield.
16
Hirooka, Yoshihiro. "Evaluation of Rice Growth Characteristics Based on Non-destructive Measurements of Leaf Area Index". Kyoto University, 2016. http://hdl.handle.net/2433/215581.
Testo completoAbstract (sommario):
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第19755号
農博第2151号
新制||農||1038(附属図書館)
学位論文||H28||N4971(農学部図書室)
32791
京都大学大学院農学研究科農学専攻
(主査)教授 白岩 立彦, 教授 奥本 裕, 教授 稲村 達也
学位規則第4条第1項該当
17
Bravo, Avila Catherine Heidy. "Root:Shoot Ratio and Specific Leaf Area Along an Elevational Gradient in the Peruvian Andes". FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/884.
Testo completoAbstract (sommario):
Andean montane forests are one of the most diverse ecosystems on Earth, but are also highly vulnerable to climate change. Therefore, the link between plant distribution and ecosystem productivity is a critical point to investigate in these ecosystems. Are the patterns in productivity observed in montane forest due to species turnover along the elevational gradients? Methodological constraints keep this question unanswered. Also, despite their importance, belowground biomass remains poorly quantified and understood. I measured two plant functional traits in seedlings, root:shoot ratio and specific leaf area, to identify different strategies in growth and biomass allocation across elevations. A tradeoff in specific leaf area with elevation was found in only one species, and no generalized directional change was detected with elevations for root:shoot ratio. Lack of information for the ontogeny of the measured plant traits could confounding the analysis.
18
May, David Z. "A MULTISPECTRAL REMOTE SENSING INVESTIGATION OF LEAF AREA INDEX AT BLACK ROCK FOREST, NY". Ohio University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1157569101.
Testo completo
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Neumann, John A. P. "Variability in the relationship between leaf area and selected stem measures in Douglas fir". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28819.
Testo completoAbstract (sommario):
Variability in the relationship between tree leaf area (TLA) and selected stem measurements was examined in three Douglas-fir stands (Pseudotsuga menziesii (Mirb.) Franco, var. menziesii) that were less than 50 years-old, spaced to approximately 550 to 650 stems/ha, and differed in soil moisture and nutrients. Attention was given to the effect of mean annual ring width (MARW), cross-sectional area of the live bark (ALB - a surrogate measure of relative nutrient storage in the stem), and cross-sectional area of the most recent annual rings equal in number to the number of whorls in the live crown (ALC), on variability in the relationship between TLA and cross-sectional area of sapwood (ASW).
At breast height, basal area, ASW, and cross-sectional area of sapwood plus live bark (ASWLB) were not linearly related to TLA, and linear regression equations using log transformed variables varied significantly between sites. Nonlinear regression equation for ASW at breast height was: TLA = 0.064ASẆ¹•³³ (I² = 0.856). Including D (the distance between breast height and the center of the live crown) in the nonlinear equation, did not significantly improve the regression.
Tree leaf area prediction models using stem measures from the base of live crown (blc) had higher adjusted R² values than models using stem measures from breast height.
At the blc, basal area, ASW, and ASWLB were linearly related to TLA (adjusted R² = 0.926, 0.908, and 0.934, respectively).
Multiplying ASW by MARW did not improve the fit of the regression models. Multiplying ASW by ALB improved the linearity of the relationship of ASW at breast height to TLA. The best fitting TLA model overall used the product of ASW at blc and ALB at blc as the independent variable (adjusted R² = 0.967).
The results indicate that research into the allometric relationship of TLA to stem measures should give consideration to more than hydraulic measures and include measures of bark function. At breast height and the blc, the independent variable ALC was linearly related to tree leaf area and had higher adjusted R² values than did ASW. In most trees the ALC stem measure was found to include a portion of heartwood area. The strong relationship between TLA and ALC suggests that a given transpiring leaf mass or area is related to a proportional amount of conducting stemwood and physical support stemwood.
A quick alternative approach for estimating individual tree leaf area using photographs taken at fixed distance and angle from the target tree did not result in a reliable tree leaf area prediction technique. The difficulty of obtaining views of the tree crown which were not obstructed by adjacent tree crowns was the major obstacle. Using a fixed distance and camera angle was a problem because of variable
tree heights. However, altering these fixed positions introduced additional variation into the tree leaf area estimation.
Mean specific leaf area (SLA) varied significantly by site, needle age class, and crown position. Mean SLA per needle age class per branch can be predicted with 95% confidence and a 10% allowable error using six 10-needle samples.Forestry, Faculty of
Graduate
20
Bobeva, Albena. "Quantifying the distribution of forest functional types and forest leaf area index in the Alps". [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969685106.
Testo completo
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Shah, Kushendra Narayan. "MULTI-SCALE MAPPING AND ACCURACY ASSESSMENT OF LEAF AREA INDEX FOR VEGETATION STUDY IN SOUTHERN ILLINOIS". OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1234.
Testo completoAbstract (sommario):
The increasing interest of modeling global carbon cycling during the past two decades has driven this research to map leaf area index (LAI) at multiple spatial resolutions by combining LAI field observations with various sensor images at local, regional, and global scale. This is due to its important role in process based models that are used to predict carbon sequestration of terrestrial ecosystems. Although a substantial research has been conducted, there are still many challenges in this area. One of the challenges is that various images with spatial resolutions varying from few meters to several hundred meters and even to 1 km have been used. However, a method that can be used to collect LAI field measurements and further conduct multiple spatial resolution mapping and accuracy assessment of LAI is not available. In this study, a pilot study in a complex landscape located in the Southern Illinois was carried out to map LAI by combining field observations and remotely sensed images. Multi-scale mapping and accuracy assessment of LAI using aerial photo, Landsat TM and MODIS images were explored by developing a multi-scale sampling design. The results showed that the sampling design could be used to collect LAI observations to create LAI products at various spatial resolutions and further conduct accuracy assessment. It was also found that the TM derived LAI maps at the original and aggregated spatial resolutions successfully characterized the heterogeneous landscape and captured the spatial variability of LAI and were more accurate than those from the aerial photo and MODIS. The aerial photo derived models led to not only over- and under-estimation, but also pixilated maps of LAI. The MODIS derived LAI maps had an acceptable accuracy at various spatial resolutions and are applicable to mapping LAI at regional and global scale. Thus, this study overcame some of the significant gaps in this field.
22
HAGIHARA, Akio, 秋男 萩原, Kazuyoshi YAMAJI e 和義 山路. "Dimension Relations of Branches in Hinoki (Chamaecyparis obtusa (Sieb. et Zucc.)Endl.)". 名古屋大学農学部付属演習林, 1993. http://hdl.handle.net/2237/8693.
Testo completo
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Thomas, Dana J. "Morphological Tradeoffs of American Chestnut (Castanea Dentata) and Co-Occurring Hardwoods in Varying Nutrient and Light Regimes". Miami University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=miami1134161439.
Testo completo
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Cardoso, Saulo Strazeio [UNESP]. "Crescimentos sucessivos de Capim-Marandu em diferentes solos submetidos à fertilização potássica". Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/138912.
Testo completoAbstract (sommario):
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Apesar de sua importância, ainda há uma escassez com relação a estudos relacionados à nutrição mineral de forrageiras, especialmente trabalhos sobre a adubação potássica. Assim, o objetivo desse trabalho foi avaliar os efeitos da adubação potássica em diferentes solos, nas concentrações de K na parte aérea, área foliar e produção de massa seca do capim-marandu. O delineamento experimental empregado foi inteiramente casualizado em esquema fatorial 5 x 5, constituído por cinco solos (Nitossolo Vermelho eutroférrico latossólico, Latossolo Vermelho distrófico típico, Chernossolo Argilúvico Órtico abrúptico saprolítico, Argissolo Vermelho-Amarelo eutrófico típico e Neossolo Quartzarênico Órtico típico) e cinco doses de K (0; 30; 60; 120 e 180 mg kg-1) aplicadas antes do plantio das forrageiras. Em intervalos de aproximadamente 30 dias (crescimento), a parte aérea das plantas eram colhidas, totalizando sete crescimentos sucessivos. Em cada crescimento foi avaliado a concentração de K na parte aérea, área foliar e produção de massa seca. Os solos estudados apresentaram capacidade diferenciada no fornecimento de K para as plantas, sendo maior nos MTor e menor no RQo. A adubação potássica promoveu incrementos significativos na concentração de K na parte aérea, na área foliar e na produção de massa seca do capim-marandu sendo mais evidente até o terceiro crescimento sucessivo das plantas.
Despite its importance, there is still a shortage of studies related to mineral nutrition of forage plants, especially on potassium fertilization. The aim of this study was to evaluate the effects of potassium fertilizer in different types of soils, the K concentrations in aerial part, leaf area and dry matter production of Marandu grass. The experimental design was completely randomized in a factorial 5 x 5 consisting of five soil types (Oxisol–Rhodic Eutrodox, Oxisol–Rhodic Hapludox, Argiluvic Chernosol Orthic Saprolite, Ultisol–Typic Hapladult and Typical Orthic Quartzarenic Neosol) and five K doses (0, 30, 60, 120 and 180 mg kg-1) applied before planting the forage plants. At intervals of approximately 30 days (growth), the shoots were harvested, making a total of seven consecutive growths. In each growth was evaluated the concentration of K in shoots, leaf area and dry matter production. The soils showed different ability in providing K for plants, being higher in mTOR and lower in RQo. Potassium fertilization promoted significant increases in the concentration of K in shoots, leaf area and dry matter production of Marandu grass, being more evident until the third successive plant growth.
25
Donaldson, Jason. "Do trees suppress grass fuel loads? : canopy cover effects in South African savannas". Bachelor's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/26376.
Testo completoAbstract (sommario):
Continental scale analysis of the savanna biome indicated that fire did not spread at tree canopy cover above 40%. This study investigates this relationship in a field study. It is possible that the type of tree (forest vs. savanna) may influence the amount of shade experienced by the understory and therefore this study also explores differences in LAI between congeneric pairs of forest and savanna tree species. Data were collected in two major South African savanna parks. Plots were set out to measure grass biomass in reference to canopy cover in both Kruger National Park (n=60) and the Hluhluwe-iMfolozi Game Reserve (n=82). Seven congeneric pairs were selected to compare leaf area and LAI between forest and savanna tree species using a destructive method. Against expectations, it was only when canopy cover reached 80% that grass fuel load was too low to support fire spread in all Kruger National Park plots (Pr=O) and 89% of the Hluhluwe-iMfolozi Game Reserve plots (Pr=0.11). No consistent, general relationships were evident with leaf area or LAI in comparisons between forest-savanna congeneric pairs. The significance of these findings and future direction is discussed.
26
Pfister, Lucas Federico. "Effect of canopy management practices - hedging vs curling shoot tips - on growth, yield and fruit composition of Merlot grapevines". Master's thesis, ISA, 2011. http://hdl.handle.net/10400.5/8583.
Testo completoAbstract (sommario):
Mestrado Vinifera EuroMaster - Instituto Superior de AgronomiaA study to compare the effects of hedging and curling the shoot tips (rolling) on the last wire of the trellising system was carried out in Saint Emilion (France) on Merlot grapevines in 2011. Vines were hedged or curled when shoots were 30 – 40 cm longer than the highest wire. The effects of the two canopy management strategies on vine performance, mainly vegetative growth, disease occurrence, phenology, water status, yield components and berry composition were compared. Curled, not hedged vines presented longer main shoots, more lateral shoots and higher potassium values on the petioles. Hedged plants had a higher percentage of shaded clusters and a higher leaf layer number at the cluster zone and ¾ of the canopy. Regarding leaf area, curled plants presented a bigger main leaf area but for lateral leaf area no differences were found. Although berries on hedged plants were prone to have a higher mass, no differences for berry composition were found. Hedging seems to be an appropriated technique for the Sain Emilion region as it is less time consuming, less expensive, possible to be mechanized and it has no detriment regarding quality of berries
27
Pasch, Ludwig Anselm. "The effect of leaf area to crop weight ratios on fruit quality and performance of grapevine (Vitis vinifera cv. Pinot Noir)". Master's thesis, ISA/UL, 2014. http://hdl.handle.net/10400.5/8635.
Testo completoAbstract (sommario):
Mestrado Vinifera EuroMaster - Instituto Superior de AgronomiaVine performance, fruit and wine composition were investigated on field grown Pinot Noir grapevines subjected to a range of leaf removal and cluster thinning treatments. Both treatments were applied in three levels (25 %, 50 % and 100 % of leaves and clusters retained, respectively) at the phenological stage of pea-size. New emerging leaves were removed as they appeared. Veraison was delayed when leaf area to fruit weight ratio (LA/Y) dropped below a certain threshold (13 cm2 g-1). On the contrary a high LA/Y ratio (> 26 cm2g-1) did not show any difference on fruit colouration. No significant differences in single leaf photosynthetic rate were observed between the treatments, however, there was a trend that vines from the 50 % leaf retained treatment tended to exhibit highest values for stomatal conductance and photosynthesis. Defoliated vines compensated for a restricted leaf area by increasing individual leaf size of the remaining leaves.The results of the present study suggest that fruit is produced at the expense of vegetative growth. High crop levels resulted in a decrease of individual leaf size. Moreover, pruning weight and LA/Y ratio were positively correlated. Sugar accumulation in grape berries were shown to follow a saturation curve. An increase of the source to sink ratio up to a certain point was accompanied by an increase in sugar accumulation. If this threshold was exceeded, additional leaf area did not promote higher sugar accumulation, indicating that the vine might be sink-limited. The most severe defoliation treatment significantly reduced berry size and berry weight. No consistent pattern between titratable acidity, pH and YAN and leaf area to fruit weight ratio could be found. Wine tannin content and wine colour parameters were not affected by the treatments
28
DeRose, Robert Justin. "Leaf Area Index - Relative Density Relationships in Even-Aged Abies Balsamea - Picea Rubens Stands in Maine". Fogler Library, University of Maine, 2004. http://www.library.umaine.edu/theses/pdf/DeRoseRJ2004.pdf.
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Norris, Patricia E. "Factors influencing the adoption of soil conservation practices in Virginia's Piedmont Bright Leaf Erosion Control Area". Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/104521.
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30
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.
Testo completoAbstract (sommario):
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.
31
Kenefic, Laura. "Leaf Area, Stemwood Volume Growth, and Stand Structure in a Mixed-Species, Multi-Aged Northern Conifer Forest". Fogler Library, University of Maine, 2000. http://www.library.umaine.edu/theses/pdf/KeneficLS2000.pdf.
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32
McCurdy, Wyatt Conner. "Characterizing spatiotemporal variation in LAI of Virginia Pine Plantations". Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/96595.
Testo completoAbstract (sommario):
Loblolly pine is an important managed tree species within the southeastern United States, and better understanding spatial patterns in its productivity has potential to contribute to both modeling and management of the species. Using recently-created pine management maps specific to Virginia and empirical relationships predicting pine LAI from the Landsat satellite, we conducted a statewide analysis of temporal patterns in stand-level southern pine leaf area index (LAI) following clear-cut and planting. Here, using 28 years of Landsat time-series data for 13,140 stands that were clear-cut between 2014-2017, we examined 1) when LAI peaked over the rotation, and 2) how LAI in each stand compared to a recommended fertilization threshold of 3.5 LAI. We found that, on average, winter LAI reached a maximum of 2.02., which can be approximately doubled to give a summer LAI of 4.04, and within stand peak occurred between years 13 and 15. We also found that around 45.8% of stands achieved an LAI value higher than 3.5: a fertilization threshold recommended for managed stands in Virginia. The dataset produced by our analysis will bolster information required for modeling loblolly pines as a plant functional type in regional land simulations, and the finding that most stands are below the recommended LAI fertilization threshold will fuel further management-motivated research.Master of Science
Management of pines in the southeastern U.S. contributes to the region's economy and carbon sequestration potential. In this study, we used Virginia forest harvest maps to identify individual patches (stands) of pine forest which had each gone through a full harvest life cycle (rotation). With unique managed pine stands identified, we used satellite imagery to estimate growth of canopy leaf area over time within each stand, using a metric called leaf area index (LAI). We identified 13,140 separate stands, each with up to 28 years of available data. We took the first full-state census of areas of managed pines in Virginia, and their leaf area development. We acquired one LAI measurement from February of each year, for each stand in Virginia. Using February LAI for each of our stands, we found that an average stand in VA has a maximum winter LAI of 2.02 (meaning an approximate maximum summer LAI of 4.04), and that stands generally reached their peak LAI after around 14 years of growth. It is recommended, in VA, that a landowner fertilize their stand in the middle of a harvest rotation if summer peak LAI is under 3.5, at stand closure. We found that at ten years of stand age, 45.8% of stands were estimated to reach above this threshold. Since this study's dataset is the most comprehensive LAI dataset for managed pines in VA, it may be used to improve management outcomes as well as understand pine productivity for land surface modeling purposes.
33
Thomas, Dana Jeanette. "Morphological tradeoffs of American chesnut (Castanea dentata) and co-occurring hardwoods in varying nutrient and light regimes". Connect to this document online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1134161439.
Testo completoAbstract (sommario):
Thesis (M.S.)--Miami University, Dept. of Botany, 2005.Title from first page of PDF document. Document formatted into pages; contains [1], v, 38 p. : ill. Includes bibliographical references (p. 35-38).
34
Joel, Gräsman. "Effekten av gödsling på björkars (Betula pendula) specifika bladarea (SLA) och tillväxt". Thesis, Linnéuniversitetet, Institutionen för skog och träteknik (SOT), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-90151.
Testo completoAbstract (sommario):
The number one highest growth-limiting factor in Swedish forests is nitrogen, because of that fertilization often gives a significant growth increase, wherever you are in Sweden. Specific leaf area (SLA) can be used as a standard measurement of how much resources a tre has to use to build up light absorbing leaf area of needles/leaves. Since there is a strong linear relationship between tree growth and leaf area, there should also be a clear correlation between each leaf area of single trees and its diameter, basal area and volume growth (Xiao, 2005).The datamaterial for the study was collected at the forest estate, Toftaholm, near Ljungby in Kronoberg County (57 ° 0´N; 14 ° 3`E). Data were collected from birches growing in both in fertilized and unfertilized young stands of Birch during the growing season of 2018. The biomass sampling occured in May, July and August. At each occasion, samples were taken from 40 birches (a total of 120 samples were collected).The average value of SLA for all samples on the fertilized treatment was 17.33 m² / kg and 16.41 m² / kg for the non-fertilized treatment (Figure 4). The significance analysis obtained a p-value of 0.019 (Table 2), which confirms that there is a significant difference between the fertilized and the unfertilized treatment.In the significance analysis, it could be concluded that with a 95% probability, there is a significant difference between the comparison of all samples from the fertilized (G) and non-fertilized (OG) treatment.
35
Davidson, Diedre P., e University of Lethbridge Faculty of Arts and Science. "Sensitivity of ecosystem net primary productivity models to remotely sensed leaf area index in a montane forest environment". Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2002, 2002. http://hdl.handle.net/10133/155.
Testo completoAbstract (sommario):
Net primary productivity (NPP) is a key ecological parameter that is important in estimating carbon stocks in large forested areas. NPP is estimated using models of which leaf area index (LAI) is a key input. This research computes a variety of ground-based and remote sensing LAI estimation approaches and examines the impact of these estimates on modeled NPP. A relative comparison of ground-based LAI estimates from optical and allometric techniques showed that the integrated LAI-2000 and TRAC method was preferred. Spectral mixture analysis (SMA), accounting for subpixel influences on reflectance, outperformed vegetation indices in LAI prediction from remote sensing. LAI was shown to be the most important variable in modeled NPP in the Kananaskis, Alberta region compared to soil water content (SWC) and climate inputs. The variability in LAI and NPP estimates were not proportional, from which a threshold was suggested where first LAI is limiting than water availability.xii, 181 leaves : ill. ; 28 cm.
36
Alavi, Ghasem. "Climate, leaf area, soil moisture and tree growth in spruce stands in SW Sweden : field experiments and modelling /". Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5710-6.pdf.
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King, Nathan Todd. "The short-term effects of fertilization on loblolly pine (Pinus taeda L.) photosynthesis, dark respiration, and leaf area". Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/34476.
Testo completoAbstract (sommario):
The initial physiological processes leading to enhanced growth of loblolly pine subsequent to fertilization are not clearly understood. Much of the debate revolves around the temporal response of photosynthesis (Pn) to fertilization or even if Pn increases at all due to enhanced nutrition. This study tracked loblolly pine light-saturated photosynthesis (Asat), dark respiration (Rd), volume, height, basal diameter, and leaf area responses in eight clones to fertilization (112 kg/ha N) over the course of a growing season in the field. Measurements were conducted intensively before and after fertilization in order to track the initial physiological changes prior to any changes in growth in the fertilized seedlings.
The results showed that fertilization does increase Pn rates although there was no significant effect on Rd rates during the study. The fertilized seedlings mean Asat rates were significantly higher on three sampling dates and remained higher throughout most of the sampling period. At the end of the growing season, the fertilized seedlings had a 30.5% higher projected crown area than the controls and 48% greater mean volumes. Physiological and growth responses were significantly different among clones with some showing large and others showing little or no response to fertilization. These results support the hypothesis from Gough et al. (2004b) that post-fertilization increases in Pn create extra photoassimilate used in building larger leaf areas. These larger leaf areas contribute to higher canopy photosynthesis levels, which leads to an increase in dry matter production.Master of Science
38
Pacheco, Anna. "Contribution of hyperspectral remote sensing to the estimation of leaf area index in the context of precision agriculture". Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26734.
Testo completoAbstract (sommario):
The estimation of Leaf Area Index (LAI) is a key parameter controlling biophysical processes of the vegetation canopy, and ultimately yield. Defined as one half the total green leaf area per unit ground surface area, LAI is an essential component of precision crop management. Direct field techniques are tedious, time-consuming and labour-intensive. Indirect techniques, such as determining gap fraction with optical instruments have proven to be a good alternative, but their use is limited to rigid field sampling techniques. Vegetation indices have been useful to estimate LAI but are limited mostly due to its background reflectance noise. LAI can be estimated using different types of data, but only hyperspectral remote sensing has the potential to distinguish effectively the crop from other field components using spectral mixture analysis. Once the crop fraction has been derived, LAI is estimated using a crop fraction inversion technique. The application of this technique under agricultural field conditions has been very limited and not rigorously validated. The main objective of this study is to validate the crop fraction inversion technique for LAI estimation, and to examine the potential for LAI estimation using hyperspectral remote sensing data in the context of precision agriculture. This research will provide a unique scientific contribution to the field of hyperspectral remote sensing and greatly contribute to the advancement of remote sensing agriculture applications in Canada. (Abstract shortened by UMI.)
39
Banskota, Asim. "The discrete wavelet transform as a precursor to leaf area index estimation and species classification using airborne hyperspectral data". Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/39188.
Testo completoAbstract (sommario):
The need for an efficient dimensionality reduction technique has remained a critical challenge for effective analysis of hyperspectral data for vegetation applications. Discrete wavelet transform (DWT), through multiresolution analysis, offers oppurtunities both to reduce dimension and convey information at multiple spectral scales. In this study, we investigated the utility of the Haar DWT for AVIRIS hyperspectral data analysis in three different applications (1) classification of three pine species (Pinus spp.), (2) estimation of leaf area index (LAI) using an empirically-based model, and (3) estimation of LAI using a physically-based model. For pine species classification, different sets of Haar wavelet features were compared to each other and to calibrated radiance. The Haar coefficients selected by stepwise discriminant analysis provided better classification accuracy (74.2%) than the original radiance (66.7%). For empirically-based LAI estimation, the models using the Haar coefficients explained the most variance in observed LAI for both deciduous plots (cross validation R2 (CV-R2) = 0.79 for wavelet features vs. CV-R2 = 0.69 for spectral bands) and all plots combined (CV R2 = 0.71 for wavelet features vs. CV-R2 = 0.50 for spectral bands). For physically-based LAI estimation, a look-up-table (LUT) was constructed by a radiative transfer model, DART, using a three-stage approach developed in this study. The approach involved comparison between preliminary LUT reflectances and image spectra to find
the optimal set of parameter combinations and input increments. The LUT-based inversion was performed with three different datasets, the original reflectance bands, the full set of the wavelet extracted features, and the two wavelet subsets containing 99.99% and 99.0% of the cumulative energy of the original signal. The energy subset containing 99.99% of the cumulative signal energy provided better estimates of LAI (RMSE = 0.46, R2 = 0.77) than the original spectral bands (RMSE = 0.69, R2 = 0.42). This study has demonstrated that the application of the discrete wavelet transform can provide more accurate species discrimination within the same genus than the original hyperspectral bands and can improve the accuracy of LAI estimates from both empirically- and physically-based models.Ph. D.
40
Milla-Moreno, Estefania. "Structural properties related to mesophyll conductance and underlying variation in leaf mass area of balsam poplar (Populus balsamifera L.)". Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52158.
Testo completoAbstract (sommario):
In leaves, the ease with which CO₂ may diffuse from substomatal cavities to the sites of carboxylation (mesophyll conductance, gm) is inversely proportional to the pathway length in the gas phase and the structural resistances encountered in the liquid phase. Increased length of any pathway component should decrease gm, whereas increased area for diffusion should increase gm. There is evidence that within native balsam poplar (Populus balsamifera L.) populations, gm may increase with latitude of origin, as do leaf mass (LMA) and nitrogen per unit area. To investigate the internal structural characteristics that might limit maximum gm in leaves, a balsam poplar family (K4×C) known to have high variation in LMA was chosen. Several whole tissue properties (LMA, carbon-nitrogen ratio, chlorophyll concentration index), microanatomy traits (leaf thickness, intercellular air space, cell wall surface area, chloroplast counts), and ultrastructural attributes (cell wall thickness, thylakoid grana thickness, and cell wall area adjacent to chloroplasts) were measured.
There were significant genotypic differences in chlorophyll concentration index, numbers of chloroplasts per mesophyll cell, leaf thickness (tleaf), and thicknesses and cross-sectional areas of the palisade and spongy mesophyll layers. There were also differences in the fraction of intercellular air space (fias), as well as total and exposed cell wall surface areas of the mesophyll and its component tissues. Although genotypic differences in LMA were not significant, LMA varied as a function of tleaf (r=0.515, p<0.05) and fias (r=-0.510, p<0.05), which together explained considerable variation in this trait. The single best correlate of LMA was the cell wall area of the palisade (r=0.813, p<0.001), which accounted for well over half of the total cell wall area of the mesophyll. The areas of mesophyll cell walls and chloroplasts exposed to intercellular air space, both of which should contribute to gm, also increased with LMA. Along the same lines, but not correlated with LMA, there was a decrease in nitrogen density per unit exposed mesophyll surface area associated with thicker leaves (r=-0.481, p<0.05).Forestry, Faculty of
Graduate
41
Jones, Brian Paul. "Determination and Manipulation of Leaf Area Index to Facilitate Site-Specific Management of Double-Crop Soybean in the Mid-Atlantic, U.S.A". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/31566.
Testo completoAbstract (sommario):
Double cropping soybean after small grain harvest does not always allow sufficient canopy growth to maximize photosynthesis and seed yield. This is due to a shorter growing season and moisture deficits common to the Mid-Atlantic USA. Leaf area index (LAI) is the ratio of unit leaf area of a crop to unit ground area and is a reliable indicator of leaf area development and crop biomass. An LAI of 3.5 to 4.0 by flowering is required to maximize yield potential. Soybean LAI will vary within and between fields due to soil differences, cultivar selection, and other cultural practices. Site-specific management strategies such as varying plant population may be used to manipulate LAI and increase yield in leaf area-limited systems. Furthermore, methods to remotely sense leaf area are in order to facilitate such management strategies in large fields. The objectives of this research were to: i) determine the effect of plant population density on soybean LAI and yield; ii) determine the relationship between LAI measured at different reproductive stages and yield; iii) investigate and validate relationships between LAI and yield for two cultivars in three crop rotations across varying soil moisture regimes; iv) validate relationships found in previous work between soybean LAI and yield across soil moisture regimes in grower fields; and v) determine if normalized difference vegetation index (NDVI) values obtained from aerial infrared images can be used to estimate LAI and soybean yield variability. Increasing plant population increased LAI for cultivars at Suffolk in 2000 and 2001, but LAI increased with plant populations on soils with lower plant available water holding capacity (PAWHC) at Port Royal in 2001. In 2000 at Suffolk, seed yield increased quadratically with increasing population and cultivar did not affect the response. In 2001, no relationship occurred between yield and plant population at either Suffolk or Port Royal, but the relationship of yield and LAI depended on soybean development stage at both sites. However, this relationship was not consistent between sites or years. In another study, crop rotation affected LAI and yield one out of two years. However, LAI and yield in both study years were negatively impacted on soil types with lower PAWHC. Where significant, a linear relationship was observed between yield and LAI for all soil types. Studies on grower fields showed similar linear relationships between yield and LAI. Remote sensing techniques showed promise for estimation of LAI and yield. When obtained at an appropriate development stage, vegetation indices correlated to both LAI and yield, and were observed to be effective as a predictor of LAI until plants achieved LAI levels of 3.5 to 4.0.Master of Science
42
Braun, Marko. "The Segmentation of Reflectances from Moderate Resolution Remote Sensing Data for the Retrieval of Land Cover Specific Leaf Area Index". Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-75863.
Testo completo
43
Pace, Micah D. "Effect of Stand Density on Behavior of Leaf Area Prediction Models for Eastern White Pine (Pinus strobus L.) in Maine". Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/PaceMD2003.pdf.
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Kandasamy, Sivasathivel. "Leaf Area Index (LAI) monitoring at global scale : improved definition, continuity and consistency of LAI estimates from kilometric satellite observations". Phd thesis, Université d'Avignon, 2013. http://tel.archives-ouvertes.fr/tel-00967319.
Testo completoAbstract (sommario):
Monitoring biophysical variables at a global scale over long time periods is vital to address the climatechange and food security challenges. Leaf Area Index (LAI) is a structure variable giving a measure of the canopysurface for radiation interception and canopy-atmosphere interactions. LAI is an important variable in manyecosystem models and it has been recognized as an Essential Climate Variable. This thesis aims to provide globaland continuous estimates of LAI from satellite observations in near-real time according to user requirements to beused for diagnostic and prognostic evaluations of vegetation state and functioning. There are already someavailable LAI products which show however some important discrepancies in terms of magnitude and somelimitations in terms of continuity and consistency. This thesis addresses these important issues. First, the nature ofthe LAI estimated from these satellite observations was investigated to address the existing differences in thedefinition of products. Then, different temporal smoothing and gap filling methods were analyzed to reduce noiseand discontinuities in the time series mainly due to cloud cover. Finally, different methods for near real timeestimation of LAI were evaluated. Such comparison assessment as a function of the level of noise and gaps werelacking for LAI.Results achieved within the first part of the thesis show that the effective LAI is more accurately retrievedfrom satellite data than the actual LAI due to leaf clumping in the canopies. Further, the study has demonstratedthat multi-view observations provide only marginal improvements on LAI retrieval. The study also found that foroptimal retrievals the size of the uncertainty envelope over a set of possible solutions to be approximately equal tothat in the reflectance measurements. The results achieved in the second part of the thesis found the method withlocally adaptive temporal window, depending on amount of available observations and Climatology as backgroundestimation to be more robust to noise and missing data for smoothing, gap-filling and near real time estimationswith satellite time series.
45
Harrington, John T. "Physiological effects of moisture stress, moisture stress conditioning, and leaf area manipulations on black alder seedlings (Alnus glutinosa (L.) Gaertn.)". Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/45674.
Testo completoAbstract (sommario):
This project consisted of three studies, two of which examined the effects of moisture deficits and moisture stress conditioning of black alder seedlings and the third examined the effects of shoot manipulations on the physiology of black alder seedlings and the nitrogenase activity of the seedlings' root nodules.
Endophyte strain was found to be nonsignificant in response to moisture deficit and moisture-stress conditioning (MSC). Using regression analysis MSC significantly decreased the impact of low water potentials on photosynthesis and acetylene reduction. There were no significant improvements in this response with increased MSC periods. Exposure of nodules to dry soil conditions while keeping the host plant hydrated did not significantly reduce acetylene reduction, nodule sugar content, transpiration or leaf conductance; however, photosynthesis was significantly reduced. Only defoliations of 100% significantly lowered acetylene reduction. Defoliations of 45% caused increases in photosynthesis and transpiration of residual leaves three days following defoliation. Nodule sugar content was unaffected by any level of defoliation.
Master of Science
46
Johnson, Bryan Fisher. "Influence of Several Herbicides on Visual Injury, Leaf Area Index, and Yield of Glyphosate-Tolerant Soybean (Glycine max)". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32295.
Testo completoAbstract (sommario):
The occasional failure of glyphosate to control all weeds throughout the entire growing season has prompted growers to sometimes use herbicides other than glyphosate on glyphosate-tolerant soybean. Field studies were conducted in 1999 and 2000 to investigate potential crop injury from several herbicides on glyphosate-tolerant soybean, and to determine the relationship between soybean maturity, planting date, and herbicide treatment on soybean injury, leaf area index (LAI), and yield. Three glyphosate-tolerant soybean cultivars representing maturity groups III, IV and V were planted at dates representing the full-season and double-crop soybean production systems used in Virginia. Within each cultivar and planting date, 15 herbicide treatments, in addition to a control receiving only metolachlor preemergence, were applied to cause multiple levels of crop injury. Results of this study indicate that glyphosate-tolerant soybean generally recovered from early-season herbicide injury and LAI reductions; however, reduced yield occurred with some treatments. Yield reductions were more common in double-crop soybean than in full-season soybean. In full-season soybean, most yield reductions occurred only in the early maturing RT-386 cultivar. These yield reductions may be attributed to the reduced developmental periods associated with early maturing cultivars and double-crop soybean that often lead to reduced vegetative growth and limited LAI. Additional reductions of LAI by some herbicide treatments on these soybean may have coincided with yield reductions; however, reduced LAI did not occur with all yield reducing treatments. Therefore, soybean LAI response to herbicide treatments does not always accurately indicate the potential detrimental effects of herbicides on soybean yield. Further, yield reductions associated with herbicide applications occurred, although soybean sometimes produced leaf area exceeding the critical LAI level of 3.5 to 4.0 which is the minimum LAI needed for soybean to achieve maximum yield.Master of Science
47
Hancock, Dennis Wayne. "SPECTRAL REFLECTANCE OF CANOPIES OF RAINFED AND SUBSURFACE IRRIGATED ALFALFA". UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_diss/332.
Testo completoAbstract (sommario):
The site-specific management of alfalfa has not been well-evaluated, despite the economic importance of this crop. The objectives of this work were to i) characterize the effects of soil moisture deficits on alfalfa and alfalfa yield components and ii) evaluate the use of canopy reflectance patterns in measuring treatment-induced differences in alfalfa yield. A randomized complete block design with five replicates of subsurface drip irrigation (SDI) and rainfed treatments of alfalfa was established at the University of Kentucky Animal Research Center in 2003. Potassium, as KCl, was broadcast on split-plots on 1 October 2004 at 0, 112, 336, and 448 kg K2O ha-1. In the drought year of 2005, five harvests (H1 - H5) were taken from each split-plot and from four locations within each SDI and rainfed plot. One day prior to each harvest, canopy reflectance was recorded in each plot. Alfalfa yield, yield components, and leaf area index (LAI) were determined. In 2005, dry matter yields in two harvests and for the seasonal total were increased (Pandlt;0.05) by SDI, but SDI did not affect crown density. Herbage yield was strongly associated with yield components but yields were most accurately estimated from LAI. Canopy reflectance within blue (450 nm), red (660 nm) and NIR bands were related to LAI, yield components, and yield of alfalfa and exhibited low variance (cv andlt; 15%) within narrow ( 0.125 Mg ha-1) yield ranges. Red-based Normalized Difference Vegetation Indices (NDVIs) and Wide Dynamic Range Vegetation Indices (WDRVIs) were better than blue-based VIs for the estimation of LAI, yield components, and yield. Decreasing the influence of NIR reflectance in VIs by use of a scalar (0.1, 0.05, or 0.01) expanded the range of WDRVI-alfalfa yield functions. These results indicate that VIs may be used to estimate LAI and dry matter yield of alfalfa within VI-specific boundaries.
48
Souza, Vanessa de Arruda. "Utilização de técnicas de sensoriamento remoto para a estimativa da evapotranspiração em uma cultura de arroz irrigado". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/72454.
Testo completoAbstract (sommario):
A evapotranspiração (ET) é um fenômeno natural que influencia diretamente mudanças no clima local e global, possuindo grande importância hidrológica e meteorológica. Este trabalho teve como objetivo estimar a ET através do método Penman-Monteith, e comparar com os resultados estimados pelo Método da Covariância de Vórtices Turbulentos. Os dados de IAF (Índice de Área Foliar) para descrição da vegetação foram obtidos a partir do sensor MODIS e de medições em campo da Rede SulFlux. A área de estudo desta pesquisa localizou-se no município de Cachoeira do Sul-RS, em uma propriedade de cultivo de arroz irrigado. O período de estudo referiu-se a safra que estendeu-se de outubro de 2010 a março de 2011. Os resultados mostraram que o IAF e as estimativas de ET apresentam um comportamento temporal semelhante. A comparação entre os resultados das estimativas de ET, utilizando dados obtidos em campo e estimados através de sensoriamento remoto, foram satisfatórios. No entanto, o resultado que apresentou os maiores valores para a ET foi proveniente do sensor MODIS. Sendo assim, pode-se concluir que a estimativa da ET, a partir de dados de vegetação, obtidos através de técnicas de sensoriamento remoto, constituem-se como uma alternativa para os métodos de ET que utilizam dados de vegetação medidos em campo.The Evapotranspiration (ET) is a natural phenomenon that directly causes changes in the local and global climate, having a great hydrologic and meteorological importance. This work has as objective to estimate ET through the Penman-Monteith method and compare with the estimated results by the Eddy Covariance Method. The LAI (Leaf Area Index) data for the vegetation description were obtained from the MODIS sensor and from field measurements of the SulFlux network. The field of study of this research had place in the city of Cachoeira do Sul – Rio Grande do Sul state, in a irrigated rice crop property. The study period is referred to the crop that extended from October 2010 to March 2011. The results showed that the LAI and the ET estimates have a similar temporal behavior. The comparison between the results of ET estimates, using data obtained in field and estimated through remote sensing, were satisfactory. However, the result that showed the highest values for ET was from the MODIS sensor. This way, it can be concluded that the ET estimate, through vegetation data, obtained by remote sensing techniques, are an alternative for the ET methods that use vegetation field measured data.
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Bazzano, Lorenza. "Basal leaf removal to reduce fruitset and induce smaller and looser clusters in variety Trincadeira with compact bunches". Master's thesis, ISA-UL, 2016. http://hdl.handle.net/10400.5/13006.
Testo completoAbstract (sommario):
Mestrado Vinifera Euromaster - Viticulture and Enology - Instituto Superior de Agronomia - UL / Institutt National D'Etudes Superieures Agronomiques de MontpellierThis paper studies whether pre-flowering basal leaf removal is able to modify the cluster compactness in Vitis vinifera L. cv Trincadeira, as well as its berry composition and canopy density, in order to avoid the incidence of diseases such as Botrytis bunch rot. The first six leaves were removed for an early defoliation treatment (ED) performed at pre-bloom, and this was compared with a control non-defoliated (ND). During the vegetative season, various analyses were performed: monitoring phenology development, leaf area measurements, radiations analysis, stem water potential, canopy dimensions and Point Quadrat assessments, fruitfulness, bunch compactness estimation and berry composition. Results seem to point out that early defoliated vines went through a prompt recovery, with a great lateral shoots and leaves regrowth. Despite no significant difference was proven in the analyses from the two treatments, leaf area and canopy dimension appears to be greater in ND vines all along the season up until ripening, when ED vines show higher values. Clusters affected by coulure and millerandage were found both in ED and in ND vines, demonstrating that fruitset was not optimal in the whole plot. Trincadeira’s high vigor and unsuitable environment conditions during 2016 season were found to have a greater impact than expected. Significance of the study: The goal is to provide viticulturists with tools to optimize the wine grape production, using a feasible field operation.
N/A
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Rubilar, Rafael Alejandro. "Environmental constraints on growth phenology, leaf area display, and above and belowground biomass accumulation of Pinus radiata (D. Don) in Chile". NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-12062005-135049/.
Testo completoAbstract (sommario):
Environmental site-specific constraints on shoot, branch, and leaf area growth and phenology were investigated during the third and fourth growing seasons in two-year-old radiata pine plantations established under a factorial combination of soil preparation, fertilization, and weed control at three contrasting textural and climatic soil-site conditions in the Central Valley of Chile. During October 2002 and June 2005, biweekly measurements of foliage accretion, branch, and stem growth were obtained together with periodical evaluations of foliage senescence. At each site, tree growth, aboveground biomass, belowground biomass, total biomass, aboveground:belowground biomass ratio, and leaf area index increased mainly by weed control (WC). The large gradient of tree growth and biomass accumulation among sites, and within sites varying in response to WC, was mainly attributed to large differences in soil water availability and possibly atmospheric water demand differences within sites. A linear relationship was established between LAI and stand growth across sites. The slope of the relationship (stemwood growth efficiency, GE) varied from 2.9 m3ha-1year-1 to 6.8 m3ha-1year-1 per unit of leaf area, with lower growth efficiencies found on sites with the greater water constraints. Phenology of growth was little affected by site or silvicultural treatments. Seasonal differences in the patterns of growth were mainly observed among sites for diameter, with longer growing seasons at sites with lower water limitations. In contrast, strong site and silvicultural treatments effects were observed on tree morphology. Trees where water limitations were more severe exhibited fewer and shorter flushes of height growth. The negative effects of soil water limitations, were at least partially ameliorated by silvicultural treatments that had been applied three years previously. Resource availability constraints during the mid to late growing season affected diameter growth more than height growth. Phenology of fascicle elongation indicated that sites with water and nutritional constraints ended fascicle elongation earlier during a growing season. Phenology of fascicle senescence indicated that maximum needlefall occurred during the summer and autumn seasons. No differences in silvicultural treatments were observed in foliage accretion or senescence patterns. Foliage longevity increased for sites with water and nutrient limitations.