Search results for "Canopy"
showing 10 items of 221 documents
Beyond APAR and NPQ: Factors Coupling and Decoupling SIF and GPP Across Scales
2021
The connection between solar-induced fluorescence (SIF) and vegetation gross primary productivity is being widely investigated across spatial, temporal, and biological scales, including: a) studies at the leaf [1], [2], plant canopy [2]–[4] or satellite pixel scale [5], [6], b) temporally with studies spanning from diurnal [7] to seasonal scales [1], [3], [5], and b) biologically with studies covering various plant functional types (PFTs), e.g., crops [4], [7], deciduous [8] or evergreen forests [1], [3], in response to different sources of stress.
Optimal modalities for radiative transfer-neural network estimation of canopy biophysical characteristics: Evaluation over an agricultural area with …
2011
International audience; Neural networks trained over radiative transfer simulations constitute the basis of several operational algorithms to estimate canopy biophysical variables from satellite reflectance measurements. However, only little attention was paid to the training process which has a major impact on retrieval performances. This study focused on the several modalities of the training process within neural network estimation of LAI, FCOVER and FAPAR biophysical variables. Performances were evaluated over both actual experimental observations and model simulations. The SAIL and PROSPECT radiative transfer models were used here to simulate the training and the synthetic test dataset…
Empirical and physical estimation of Canopy Water Content from CHRIS/PROBA data
2013
20 páginas, 4 tablas, 7 figuras.
Transcriptional responses to pre-flowering leaf defoliation in grapevine berry from different growing sites, years, and genotypes
2017
Leaf removal is a grapevine canopy management technique widely used to modify the sourceâsink balance and/or microclimate around berry clusters to optimize fruit composition. In general, the removal of basal leaves before flowering reduces fruit set, hence achieving looser clusters, and improves grape composition since yield is generally curtailed more than proportionally to leaf area itself. Albeit responses to this practice seem quite consistent, overall vine performance is affected by genotype, environmental conditions, and severity of treatment. The physiological responses of grape varieties to defoliation practices have been widely investigated, and just recently a whole genome trans…
Nest-mediated parental care in a marine fish: Are large-scale nesting habitats selected and do these habitats respond to small-scale requirements?
2018
Fishes have evolved various reproductive strategies including mechanisms that involve parental care and demersal eggs laid into nests. Symphodus ocellatus has a seasonal reproduction period during which large, dominant males become territorial and build nests with fragments of algae, where they attract females to spawn and provide care to the developing eggs. Based on the hypothesis that the S. ocellatus males choose the reproductive habitat based on some characteristics of the substrate, here we assessed whether, on a coastal area scale, the distribution of this species changes during the reproductive period because of the selection of some suitable sites or substrates, and whether the nes…
Toward the valorization of olive (Olea europaea var. europaea L.) biodiversity: horticultural performance of seven Sicilian cultivars in a hedgerow p…
2019
Abstract An intense survey of the Sicilian’s olive growing areas for autochthonous germplasm, mainly represented by centennials olive trees (Olea europaea var. europaea L.) apparently older then III centuries, started at the beginning of the 1980s and resulted in the selection of more than 150 cultivars and accessions. This germplasm was propagated in a nursery, by grafting onto seedlings of Olea europaea L., and planted in an experimental orchard, in an olive district located in the South-west of the Island, where they were evaluated for over 30 years and selected for their early bearing, high and constant productivity, as well as high oil content of the fruits and excellent chemical (olei…
Ultraviolet radiation accelerates photodegradation under controlled conditions but slows the decomposition of senescent leaves from forest stands in …
2019
Depending on the environment, sunlight can positively or negatively affect litter decomposition, through the ensemble of direct and indirect processes constituting photodegradation. Which of these processes predominate depends on the ecosystem studied and on the spectral composition of sunlight received. To examine the relevance of photodegradation for litter decomposition in forest understoreys, we filtered ultraviolet radiation (UV) and blue light from leaves of Fagus sylvatica and Bettda pendula at two different stages of senescence in both a controlled-environment experiment and outdoors in four different forest stands (Picea abies, Pagus sylvatica, Acer platanoides, Betula pendula). Co…
Spatial distribution of saplings in heavily worn urban forests: Implications for regeneration and management
2012
Abstract We studied the spatial distribution of saplings in the vicinity of other saplings and mature trees in heavily worn urban forests. Our aim was to identify favorable microsites for saplings to regenerate under different levels of wear. We hypothesized that these safe microsites were situated close to tree trunks that might offer shelter from trampling caused by humans and their pet dogs. The distribution of saplings was explored at 0.1–0.6 m to the nearest sapling and 0.1–2 m to the nearest mature tree. Sorbus aucuparia was the most abundant sapling species, followed by Populus tremula , Betula pubescens and Picea abies . These species all tended to cluster with their conspecific sap…
Canopy status modulates formation of wood rays in scots pine under hemiboreal conditions
2021
Abstract Non-structural carbohydrates (NSC) reserves are crucial for trees to cope with weather extremes, thus to ensure their survival and ecological plasticity. The NSC reserves can depend on social status, suggesting uneven plasticity of trees at the stand level. In stemwood of Scots pine (Pinus sylvestris L.), which is a widespread and important species, NSC reserves are stored in parenchyma in wood rays (WR). The quantity of WRs is adjusted intra-annually, allowing retrospective analysis of factors affecting their formation. Accordingly, the differences in WR quantity in stemwood of dominant and intermediate (canopy trees with reduced and narrow crowns) maturing Scots pine were assesse…
A unified vegetation index for quantifying the terrestrial biosphere
2021
[EN] Empirical vegetation indices derived from spectral reflectance data are widely used in remote sensing of the biosphere, as they represent robust proxies for canopy structure, leaf pigment content, and, subsequently, plant photosynthetic potential. Here, we generalize the broad family of commonly used vegetation indices by exploiting all higher-order relations between the spectral channels involved. This results in a higher sensitivity to vegetation biophysical and physiological parameters. The presented nonlinear generalization of the celebrated normalized difference vegetation index (NDVI) consistently improves accuracy in monitoring key parameters, such as leaf area index, gross prim…