Search results for " Sensing"
showing 10 items of 1517 documents
In vivo photoprotection mechanisms observed from leaf spectral absorbance changes showing VIS–NIR slow-induced conformational pigment bed changes
2019
Abstract Regulated heat dissipation under excessive light comprises a complexity of mechanisms, whereby the supramolecular light-harvesting pigment–protein complex (LHC) shifts state from light harvesting towards heat dissipation, quenching the excess of photo-induced excitation energy in a non-photochemical way. Based on whole-leaf spectroscopy measuring upward and downward spectral radiance fluxes, we studied spectrally contiguous (hyperspectral) transient time series of absorbance A(λ,t) and passively induced chlorophyll fluorescence F(λ,t) dynamics of intact leaves in the visible and near-infrared wavelengths (VIS–NIR, 400–800 nm) after sudden strong natural-like illumination exposure. …
Positive density-dependent growth supports costs sharing hypothesis and population density sensing in a manipulative parasite.
2017
SUMMARYParasites manipulate their hosts’ phenotype to increase their own fitness. Like any evolutionary adaptation, parasitic manipulations should be costly. Though it is difficult to measure costs of the manipulation directly, they can be evaluated using an indirect approach. For instance, theory suggests that as the parasite infrapopulation grows, the investment of individual parasites in host manipulation decreases, because of cost sharing. Another assumption is that in environments where manipulation does not pay off for the parasite, it can decrease its investment in the manipulation to save resources. We experimentally infected rainbow trout Oncorhynchus mykiss with the immature larva…
How Realistically Does Outdoor UV-B Supplementation with Lamps Reflect Ozone Depletion: An Assessment of Enhancement Errors
2010
Limitations in the realism of currently available lamps mean that enhancement errors in outdoor experiments simulating UV-B radiation effects of stratospheric ozone depletion can be large. Here, we assess the magnitude of such errors at two Finnish locations, during May and June, under three cloud conditions. First we simulated solar radiation spectra for normal, compared with 10% and 20% ozone depletion, and convoluted the daily integrated solar spectra with eight biological spectral weighting functions (BSWFs) of relevance to effects of UV on plants. We also convoluted a measured spectrum from cellulose-acetate filtered UV-B lamps with the same eight BSWFs. From these intermediate results…
Comparison of different methods to assess the distribution of alien plants along the road network and use of Google Street View panoramas interpretat…
2021
The survey by foot in the field is compared to the survey from a car, the photo-interpretation of Google Street View (GSV) panoramas continuously and at intervals of 1.5 km and the photo-interpretation of Google Earth aerial images on a 10 km stretch of road in Sicily. The survey by foot was used as reference for the other methods. The interpretation of continuous GSV panoramas gave similar results as the assessment by car in terms of the number of species identified and their location, but with lower cost. The interpretation online of aerial photos allowed the identification of a limited number of taxa, but gave a good localisation for them. Interpretation of GSV panoramas, each of 1.5 km,…
Optimized Application of Biome-BGC for Modeling the Daily GPP of Natural Vegetation Over Peninsular Spain
2018
A methodology for improving the application of Biome-BGC in peninsular Spain was developed focusing on the optimization of the rooting depth (zroot), which is not available for the study area on a spatially distributed basis. The optimal zroot was identified by comparing daily gross primary production (GPP) simulations with varying zroot to GPP estimations from a production efficiency model previously optimized for and validated in the study area. The methodology was first tested in four eddy covariance (EC) sites representative of Mediterranean ecosystems and next applied at a regional scale to the whole study area. As a result, daily GPP simulated maps for the 2005-2012 period and an opti…
Environment-sensitivity functions for gross primary productivity in light use efficiency models
2022
International audience; The sensitivity of photosynthesis to environmental changes is essential for understanding carbon cycle responses to global climate change and for the development of modeling approaches that explains its spatial and temporal variability. We collected a large variety of published sensitivity functions of gross primary productivity (GPP) to different forcing variables to assess the response of GPP to environmental factors. These include the responses of GPP to temperature; vapor pressure deficit, some of which include the response to atmospheric CO2 concentrations; soil water availability (W); light intensity; and cloudiness. These functions were combined in a full fact…
Data synergy between leaf area index and clumping index Earth Observation products using photon recollision probability theory
2018
International audience; Clumping index (CI) is a measure of foliage aggregation relative to a random distribution of leaves in space. The CI can help with estimating fractions of sunlit and shaded leaves for a given leaf area index (LAI) value. Both the CI and LAI can be obtained from global Earth Observation data from sensors such as the Moderate Resolution Imaging Spectrometer (MODIS). Here, the synergy between a MODIS-based CI and a MODIS LAI product is examined using the theory of spectral invariants, also referred to as photon recollision probability ('p-theory'), along with raw LAI-2000/2200 Plant Canopy Analyzer data from 75 sites distributed across a range of plant functional types.…
Chlorophyll fluorescence as a tool for management of plant resources
1994
Abstract Light-induced chlorophyll fluorescence has become a tool which has ever-increasing potential application to experimental plant physiology. The effects of frost, heat, and drought have been analyzed using the kinetics of individual leaves of two representative types of life form: an evergreen tree (holm oak) dominant in the Mediterranean Basin and an annual cultivated legume (soybean). Various indices were used to quantify their response to environmental stress. Canopy fluorescence for the two types of plants was simulated. For two levels of measurement, leaf or canopy, light-induced fluorescence appears to be helpful for forest or crop management in the Mediterranean area.
Seguimiento del fenómeno blanco de la laguna de la Cruz (Cuenca, España)
2020
[EN] In the present study, a five-year follow-up was performed by remote sensing of the calcium carbonate precipitation in La Gitana karstic lake also known as La Cruz (located on the province of Cuenca, Spain). The important role that calcium carbonate precipitation plays in the ecology of the lake is well known for its influence on the vertical migrations of phytoplankton, the concentration of bioavailable phosphorus and, therefore, the eutrophication and quality of the waters. Whiting take place between the months of July and August, and it can be studied at this time through its optical properties, with the main objective of offering updated data on a phenomenon traditionally studied an…
Chlorophyll fluorescence emission spectrum inside a leaf
2008
International audience; Chlorophyll a fluorescence can be used as an early stress indicator. Fluorescence is also connected to photosynthesis so it can be proposed for global monitoring of vegetation status from a satellite platform. Nevertheless, the correct interpretation of fluorescence requires accurate physical models. The spectral shape of the leaf fluorescence free of any re-absorption effect plays a key role in the models and is difficult to measure. We present a vegetation fluorescence emission spectrum free of re-absorption based on a combination of measurements and modelling. The suggested spectrum takes into account the photosystem I and II spectra and their relative contributio…