Search results for "soil"
showing 10 items of 3493 documents
A Mixture Modeling Approach to Estimate Vegetation Parameters for Heterogeneous Canopies in Remote Sensing
2000
In this article, we describe a reflectance model which parametrizes the reflectance of vegetation canopies from optical properties of leaves and soil, and dominant canopy structural parameters. The model assumes certain principles of geometric models, for example, that sensor integrates the radiance reflected from three components, plant, shaded soil, and illuminated soil. Its inversion provides compositional information of the ground surface that is linked with the interpretation of the linear spectral mixture modeling (LSMM). This model also offers the potential for retrieving other meaningful biophysical properties such as LAI. The model has been tested on simulated spectra of spectral m…
Prototyping of Land-SAF leaf area index algorithm with VEGETATION and MODIS data over Europe
2009
Abstract The Satellite Application Facility on Land Surface Analysis (Land-SAF) aims to provide land surface variables for the meteorological and environmental science communities from EUMETSAT satellites. This study assesses the performance of a simplified (i.e. random distribution of vegetation is assumed) version of the Land-SAF algorithm for the estimation of Leaf Area Index (LAI) when prototyped with VEGETATION (processed in CYCLOPES program) and MODIS reflectances. The prototype estimates of LAI are evaluated both by comparison with validated CYCLOPES and MODIS LAI products derived from the same sensors and directly through comparison with ground-based estimates. Emphasis is given on …
Assessment of MODIS imagery to track light-use efficiency in a water-limited Mediterranean pine forest
2012
Abstract Daily values of gross primary production ( GPP ) derived from an eddy-covariance flux tower have been used to analyze the information content of the MODIS Photochemical Reflectance Index ( PRI ) on the light-use efficiency ( e ). The study has been conducted in a Mediterranean Pinus pinaster forest showing summer water stress. Advanced processing techniques have been used to analyze the effect of various external factors on e and PRI temporal variations. The intra-annual correlation between these two variables has been found to be mostly attributable to concurrent variations in sun and view zenith angles. The PRI has been normalized from these angular effects ( NPRI ), and its abil…
The effect of soil volume on the growth of roots and canopy of Opuntia ficus-indica
2019
The influence of soil volume on root development and canopy growth rates of cactus pear (Opuntia ficus-indica) was studied at Palermo University, Italy, in 2014-2016. In November 2014, 60 1-year-old O. ficus-indica cladodes were planted in pots containing five different soil volumes, 50, 33, 18, 9 or 5 L, in a complete randomized design with three replications. Root dry mass, total number of cladodes and canopy dry mass were measured after 6, 12, 18 and 24 months. The results revealed a significant effect of soil volume and sampling time and their interaction (P<0.01) on root dry mass, total number of cladodes and canopy dry mass. Root dry mass ranged between 23 and 206 g, with the highe…
CO2 uptake of Opuntia ficus-indica (L.) Mill. whole trees and single cladodes, in relation to plant water status and cladode age
2013
Most of net photosynthesis determinations in Opuntia ficus-indica come from measurements on individual cladodes. However, they have limitations when used to scale up to whole canopy gas exchange, because a large variability of carbon assimilation may occur within the canopy, due to, among others, differences in cladode age and intercepted radiation or individual cladode response to abiotic stresses. The aim of this work was to evaluate the application of open gas exchange chambers, simultaneously applied around the whole canopy, to measure net CO 2 uptake, continuously over a 24 h period, in single Opuntia ficus-indica (L.) Mill. potted trees and in relation with their water status. Net CO2…
Evaluating carbon fluxes in orange orchards in relation to planting density
2009
SUMMARYOrange (Citrus sinensis L.) is one of the main fruit crops worldwide and its evergreen orchards may have a great potential for carbon (C) sequestration, but no data are currently available. In order to understand carbon fluxes in orange orchards, an experiment was undertaken on traditional and intensive planting systems.The experiment used C. sinensis scions grafted onto Citrus aurantium (bitter orange) rootstock. One orchard contained 14-year-old trees of the cv. Tarocco Scirè (a blood orange) grown in a traditional system with 494 trees/ha. The second orchard contained 12-year-old trees of the cv. Newhall (a seedless navel orange) grown in an intensive system with 1000 trees/ha. Ne…
The scattering and re-absorption of red and near-infrared chlorophyll fluorescence in the models Fluspect and SCOPE
2019
Scattering and re-absorption have been recognized as relevant aspects for the interpretation of solar induced chlorophyll fluorescence (SIF) in vegetation remote sensing. In an earlier study [Yang and Van der Tol, RSE 215, 97–108, 2018] we addressed the problem of scattering and re-absorption of near-infrared fluorescence in the vegetation canopy. In this study we analyse within-leaf re-absorption of both red and near-infrared fluorescence using the radiative transfer model Fluspect. The leaf scattering determines the ratio of backward to total leaf fluorescence emission Fb/(Fb + Ff). Fluspect reproduces this ratio with an RMSE of less than 0.1, and explains the observed dependence of the s…
Assessing Canopy PRI for Water Stress detection with Diurnal Airborne Imagery
2008
Soil Moisture Experiments 2004 (SMEX04) Special Issue
L-band vegetation optical depth seasonal metrics for crop yield assessment
2018
Attenuation of surface microwave emission due to the overlying vegetation is proportional to the density of the canopy and to its water content. The vegetation optical depth (VOD) parameter measures this attenuation. VOD could be a valuable source of information on agroecosystems, especially at lower frequencies for which greater portion of the vegetation canopy contributes to the observed brightness temperature. In the past, visible-infrared indices have been used to provide yield estimates based on measuring the photosynthetic activity from the surface canopy layer. These indices are affected by clouds and apply only in the presence of solar illumination. In this study we instead use the …
Remote sensing of sunlight-induced chlorophyll fluorescence and reflectance of Scots pine in the boreal forest during spring recovery
2005
A measurement campaign to assess the feasibility of remote sensing of sunlight-induced chlorophyll fluorescence (ChlF) from a coniferous canopy was conducted in a boreal forest study site (Finland). A Passive Multi-wavelength Fluorescence Detector (PMFD) sensor, developed in the LURE laboratory, was used to obtain simultaneous measurements of ChlF in the oxygen absorption bands, at 687 and 760 nm, and a reflectance index, the PRI (Physiological Reflectance Index), for a month during spring recovery. When these data were compared with active fluorescence measurements performed on needles they revealed the same trend. During sunny days fluorescence and reflectance signals were found to be str…