Search results for "leaf area"
showing 10 items of 124 documents
Growth and physiological responses of young olive trees affected by Olive leaf yellowing associated virus
2017
We studied the effect of Olive leaf yellowing associated virus (OLYaV) on biometric and physiological changes in olive. The trial was carried out on 32 two-yearold virus-free trees of 'Frantoio' grafted on virus-free olive seedlings and grown in 32-L pots. Half of the trees were inoculated with OLYaV in the fall of 2007. At 6, 18, and 24 months after inoculation, tree height, basal trunk diameter and total leaf number were determined, and leaf area tree-1 was estimated from a 50-leaf subsample. Twigs of various order were also counted and measured. At the end of the experiment, dry matter partitioning, leaf gas exchange and water potential were also measured. Total twig length and number, t…
Assessing Non-Photosynthetic Cropland Biomass from Spaceborne Hyperspectral Imagery
2021
Non-photosynthetic vegetation (NPV) biomass has been identified as a priority variable for upcoming spaceborne imaging spectroscopy missions, calling for a quantitative estimation of lignocellulosic plant material as opposed to the sole indication of surface coverage. Therefore, we propose a hybrid model for the retrieval of non-photosynthetic cropland biomass. The workflow included coupling the leaf optical model PROSPECT-PRO with the canopy reflectance model 4SAIL, which allowed us to simulate NPV biomass from carbon-based constituents (CBC) and leaf area index (LAI). PROSAIL-PRO provided a training database for a Gaussian process regression (GPR) algorithm, simulating a wide range of non…
Multiple Cost Functions and Regularization Options for Improved Retrieval of Leaf Chlorophyll Content and LAI through Inversion of the PROSAIL Model
2013
Abstract: Lookup-table (LUT)-based radiative transfer model inversion is considered a physically-sound and robust method to retrieve biophysical parameters from Earth observation data but regularization strategies are needed to mitigate the drawback of ill-posedness. We systematically evaluated various regularization options to improve leaf chlorophyll content (LCC) and leaf area index (LAI) retrievals over agricultural lands, including the role of (1) cost functions (CFs); (2) added noise; and (3) multiple solutions in LUT-based inversion. Three families of CFs were compared: information measures, M-estimates and minimum contrast methods. We have only selected CFs without additional parame…
On the semi-automatic retrieval of biophysical parameters based on spectral index optimization
2014
Abstract: Regression models based on spectral indices are typically empirical formulae enabling the mapping of biophysical parameters derived from Earth Observation (EO) data. Due to its empirical nature, it remains nevertheless uncertain to what extent a selected regression model is the most appropriate one, until all band combinations and curve fitting functions are assessed. This paper describes the application of a Spectral Index (SI) assessment toolbox in the Automated Radiative Transfer Models Operator (ARTMO) package. ARTMO enables semi-automatic retrieval and mapping of biophysical parameters from optical remote sensing observations. The SI toolbox facilitates the assessment of biop…
Quantifying Irrigated Winter Wheat LAI in Argentina Using Multiple Sentinel-1 Incidence Angles
2022
Synthetic aperture radar (SAR) data provides an appealing opportunity for all-weather day or night Earth surface monitoring. The European constellation Sentinel-1 (S1) consisting of S1-A and S1-B satellites offers a suitable revisit time and spatial resolution for the observation of croplands from space. The C-band radar backscatter is sensitive to vegetation structure changes and phenology as well as soil moisture and roughness. It also varies depending on the local incidence angle (LIA) of the SAR acquisition’s geometry. The LIA backscatter dependency could therefore be exploited to improve the retrieval of the crop biophysical variables. The availability of S1 radar time-series data at d…
Global sensitivity analysis of the A-SCOPE model in support of future FLEX fluorescence retrievals
2014
In support of ESA's Earth Explorer 8 candidate mission FLEX (FLuorescence EXplorer), a Photosynthesis Study has been initiated to quantitatively link fluorescence to photosynthesis. This led to the development of A-SCOPE, a graphical user interface software package that integrates multiple biochemical models into the soil-vegetation-atmosphere-transfer model SCOPE. Its latest version (v1.53) has been successfully verified and was subsequently evaluated through a global sensitivity analysis. By using the method of Saltelli [4], the relative importance of each input variable to model outputs was quantified through first order and total effect sensitivity indices. Variations in leaf area index…
EFFECT OF TIPPING AND TOPPING ON SHOOT UNIFORMITY: PRELIMINARY RESULTS ON SINGLE CORDON TRAINED CABERNET SAUVIGNON AND MERLOT
2007
The study was carried out in a two year old Merlot/140 Ru and Cabernet Sauvignon/140 Ru vineyards during the 2004 growth season. Vines were spaced 2.4 m x 0.9 m in North-South orientated rows. Each vine had five to six shoots. The vineyards were drip irrigated (800 m3/Ha/season). Shoots more than 100 cm were tipped or topped at pea berry size development stage. Tipping of Merlot vines reduced shoot growth and variability of all vegetative parameters. Topping of Cabernet Sauvignon reduced variability of shoot Diameter and increased lateral shoot growth.
MANUAL AND MECHANICAL LEAF REMOVAL IN THE BUNCH ZONE (VITIS VINIFERA L. 'NERO D'AVOLA'): EFFECTS ON PLANT PHYSIOLOGY, VEGETATIVE PARAMETERS, YIELD AN…
2013
Mechanical and manual leaf removal of Nero d Avola vines were carried out in a commercial vineyard in Sclafani Bagni area, Sicily (South Italy), in the 2007 growing season. Rows were North East-South West oriented and vines were spur pruned and non-irrigated. The aim was to investigate the effects of two different ways of defoliation on plant physiology, vegetative parameters, yield and grape quality in a warm temperature area. Fruit zone defoliation consisted of mechanical (MLR) and hand leaf removal (HLR), applied either to both sides of the canopy (Northweast and Southeast). These treatments were applied when the berries had reached pea size and compared to a non-defoliated treatment (co…
Effect of rootstock vigor and in-row spacing on stem and root growth, conformation, and dry-matter distribution of young apple trees
2003
The effects of M.9 and MM.106 rootstocks and in-row spacing (0.4, 0.7, and 1 m) on the vegetative behavior of three-year-old apple (Malus domestica Borkh) trees were studied. Analysis of digital images was used to estimate canopy and root growth and conformation (shape and size), whereas dry matter distribution was used to determine partitioning to various plant parts. Trees on less vigorous M.9 rootstocks showed reduced stem and root growth as they produced less and/or shorter shoots and less and/or shorter and thinner roots. Canopy spread area (CSA) and volume were similar for trees on both rootstocks and differences in stem length density (stem length per unit canopy volume; SLD) compens…
Green roofs for smart cities: experimental determination of the “fractional vegetation coverage” of six vegetated species
2015
Towards a de-carbonization of European countries, green roofs are becoming popular, due not only to aesthetic reasons but also to energy and environmental issues. Indeed, especially in summer periods, the building cooling demand might be sensibly cut thanks to such passive components often chosen for planning smart cities. To properly model the energy performances of buildings equipped with these components, a particular attention must be paid to radiative exchanges occurring among soil surface, leaves and outdoor surroundings. These thermal exchanges depend on parameters, like the “fractional vegetation coverage” whose literature data do not seem particularly suitable for the simulation ne…