Search results for "Geta"
showing 10 items of 3789 documents
NO signaling in cryptogein-induced immune responses in tobacco
2014
SPEIPM; International audience
Phytosociological remarks on residual woodlands of Laurus nobilis in Sicily
2010
A phytosociological study was done of Laurus nobilis woodlands in Sicily. The analysis, based on 18 relevés, supports the definition of a new syntaxon (Acantho mollis-Lauretum nobilis ass. nov.), considered as a vicariant of similar vegetation aspects described in other Mediterranean areas (Iberian and Italian peninsulas). The study mainly includes some unpublished sites where polycormic individuals of laurel, sometimes reaching 13-15 meters in height, dominates the tree layer. This vegetation is also characterized by some laurophyllous species (Hedera helix, Rhamnus alaternus, Smilax aspera and sometimes Viburnum tinus) and lianas (Rubia peregrina var. longifolia, Asparagus acutifolius, Ta…
Impact of changing forest management on soil organic matter in low mountain acid media
2002
The impacts of changes in vegetation cover from native deciduous forest to Douglas fir ( Pseudotsuga menziesii Franco) and of human activity on soil organic matter (SOM) characteristics were studied in two low mountain areas of east-central France. No striking difference in soil type (Dystric Cambisol) was found between the two sites. Humus-rich horizons were of the “Dysmull” and “Moder” types, regardless of the nature of the bedrock. Contrary to a common affirmation concerning other coniferous species, Douglas fir had no negative effect on soil pH and humification degree of SOM, with respect to the native beech vegetation. Pruning and partial clearing slightly improved humification, espect…
Two new natural begomovirus recombinants associated with the tomato yellow leaf curl disease co-exist with parental viruses in tomato epidemics in It…
2009
Two tomato geminivirus species co-exist in protected crops in Sicily, Tomato yellow leaf curl Sardinia virus (TYLCSV, found in 1989) and Tomato yellow leaf curl virus (TYLCV, found in 2002), and mixed infections have been detected. In a field survey conducted in 2004, the viral intergenic region (IR) was amplified from infected plants, and molecules apparently hybrid between the two species were found, but only in plants where one or both parental species were also present. Two of these hybrids, named 2/2 and 2/5, were isolated and infectious clones were obtained. They were both readily whitefly-transmitted to tomato plants; clone 2/5 produced symptoms typical of TYLCSV and TYLCV, while clo…
Remote sensing of vegetation dynamics in agro-ecosystems using smap vegetation optical depth and optical vegetation indices
2017
The ESA's SMOS and the NASA's SMAP missions, launched in 2009 and 2015, respectively, are the first two missions having on-board L-band microwave sensors, which are very sensitive to the water content in soils and vegetation. Focusing on the vegetation signal at L-band, we have implemented an inversion approach for SMAP that allows deriving vegetation optical depth (VOD, a microwave parameter related to biomass and plant water content) alongside soil moisture, without reliance on ancillary optical information on vegetation. This work aims at using this new observational data to monitor the phenology of crops in major global agro-ecosystems and enhance present agricultural monitoring and pre…
Quantitative global mapping of terrestrial vegetation photosynthesis
2017
Although traditional remote sensing systems based on spectral reflectance can already provide estimates of the 'potential' photosynthetic activity of terrestrial vegetation through the quantification of total canopy chlorophyll content or absorbed photosynthetic radiation, the determination of the 'actual' photosynthetic activity of terrestrial vegetation requires information about how the absorbed light is used by plants, such as vegetation fluorescence, using very high spectral resolution spectroscopy in the range 650-800 nm. The Fluorescence Explorer (FLEX) mission, selected in November 2015 as the 8th Earth Explorer by the European Space Agency (ESA), carries the FLORIS spectrometer, wi…
Quantifying the Robustness of Vegetation Indices through Global Sensitivity Analysis of Homogeneous and Forest Leaf-Canopy Radiative Transfer Models
2019
Vegetation indices (VIs) are widely used in optical remote sensing to estimate biophysical variables of vegetated surfaces. With the advent of spectroscopy technology, spectral bands can be combined in numerous ways to extract the desired information. This resulted in a plethora of proposed indices, designed for a diversity of applications and research purposes. However, it is not always clear whether they are sensitive to the variable of interest while at the same time, responding insensitive to confounding factors. Hence, to be able to quantify the robustness of VIs, a systematic evaluation is needed, thereby introducing a widest possible variety of biochemical and structural heterogeneit…
Evidence of low land surface thermal infrared emissivity in the presence of dry vegetation
2007
International audience; Land surface emissivity in the thermal infrared usually increases when the vegetation amount increases, reaching values that are larger than 0.98. During an experiment in Morocco over dry barley crops, it was found that emissivity may be significantly lower than 0.98 at full cover and that in some situations, it might decrease with increasing amount of vegetation, which was unexpected. Older data acquired in Barrax, Spain, over senescent barley also exhibited emissivity values lower than 0.98. The decrease of emissivity was also observed by means of Simulations done with our land surface emissivity model developed earlier. The main reason for such behavior might be f…
A global Canopy Water Content product from AVHRR/Metop
2020
Abstract Spatially and temporally explicit canopy water content (CWC) data are important for monitoring vegetation status, and constitute essential information for studying ecosystem-climate interactions. Despite many efforts there is currently no operational CWC product available to users. In the context of the Satellite Application Facility for Land Surface Analysis (LSA-SAF), we have developed an algorithm to produce a global dataset of CWC based on data from the Advanced Very High Resolution Radiometer (AVHRR) sensor on board Meteorological–Operational (MetOp) satellites forming the EUMETSAT Polar System (EPS). CWC reflects the water conditions at the leaf level and information related …
Estimation of volume fraction and gravimetric moisture of winter wheat based on microwave attenuation: a field scale study
2019
A considerable amount of water can be stored in vegetation, especially in regions experiencing large quantities of precipitation (mid-latitudes). In this context, an accurate estimate of the actual water status of the vegetation could lead to an improved understanding of the effect of plant water on the water budget. In this study, we developed and validated a novel approach to retrieve the vegetation volume fraction (δ) (i.e., volume percentage of solid plant material of a canopy in air) and the gravimetric vegetation water content (m g ) (i.e., amount of water per wet biomass) for winter wheat. The estimation was based on the attenuation of L-band microwave measurements through vegetation…