Search results for "SOI"
showing 10 items of 4823 documents
Latent heat flux variability and response to drought stress of black poplar: A multi-platform multi-sensor remote and proximal sensing approach to re…
2022
Abstract High-throughput mapping of latent heat flux (λET) is critical to efforts to optimize water resources management and to accelerate forest tree breeding for improved drought tolerance. Ideally, investigation of the energy response at the tree level may promote tailored irrigation strategies and, thus, maximize crop biomass productivity. However, data availability is limited and planning experimental campaigns in the field can be highly operationally complex. To this end, a multi-platform multi-sensor observational approach is herein developed to dissect the λET signature of a black poplar (Populus nigra) breeding population (“POP6”) at the canopy level. POP6 comprised more than 4600 …
Sensitivity of L-band vegetation optical depth to carbon stocks in tropical forests: a comparison to higher frequencies and optical indices
2019
Supplementary data to this article can be found online at https://doi.org/10.1016/j.rse.2019.111303. Monitoring vegetation carbon in tropical regions is essential to the global carbon assessment and to evaluate the actions oriented to the reduction of forest degradation. Mainly, satellite optical vegetation indices and LiDAR data have been used to this purpose. These two techniques are limited by cloud cover and are sensitive only to the top of vegetation. In addition, the vegetation attenuation to the soil microwave emission, represented by the vegetation optical depth (VOD), has been applied for biomass estimation using frequencies ranging from 4 to 30¿GHz (C- to K-bands). Atmosphere is t…
Bidirectional sun-induced chlorophyll fluorescence emission is influenced by leaf structure and light scattering properties : a bottom-up approach
2015
Abstract Sun-induced chlorophyll fluorescence (SIF) at leaf level is emitted in both upward and downward directions in the red and far-red part of the spectrum (650–850 nm) when a leaf is illuminated from the upper leaf surface. Hence, total SIF is represented by the sum of the upward and downward emission components. Nevertheless, the downward component of leaf SIF is often not considered despite that downward fluorescence yield (↓FY) can amount up to 40% of the total fluorescence yield (FYtot). Downward SIF is mainly emitted in the far-red, since this part of fluoresced light is highly scattered within leaves, unlike red Chl fluorescence, which is mostly reabsorbed. While total FY can be …
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…