1,720,969 research outputs found
Scaling-up of evapotranspiration measurements: The promising role of scintillometry
Full text linkThe assessment of evapotranspiration (ET) is of primary interest,especially for agricultural and environmental issues. Traditional micrometeorological techniques require homogenous surface and are characterized by limited footprint. Thus, they cannot be applied to assess ET over inhomogeneous and extensive surfaces, typical conditions at the catchment scale and of extensive farming systems. In this context, a suitable technique to measure turbulent fluxes is scintillometry, which can give measurements of sensible heat flux at larger scale, providing averages over heterogeneous surfaces. ET can then be estimated as residual of the energy budget. In this study, we present results from a one-week campaign held during summer 2016 in Southern Italy. We deployed a Large Aperture Scintillometer (LAS) in an extensive vineyard of 140 ha on a path length of 760 m. The site was characterized by gently slope terrain with uniform crop. In order to have reference measurements of local sensible heat flux, we deployed threesonic anemometers along the scintillometer path. The aim of the study was to test the ability of scintillometry to provide a spatially averaged flux, representative of the possibly diverse conditions in an extended footprint upwind to the measurement path. The relationship between sensible heat flux measured by EC and LAS showed to be very good for the EC station in the middle of the path, whereas off-centre areas were less represented
Evoluzione dinamica dell’evapotraspirazione del vigneto in condizioni di elevata aridità
No full textAssessing Carbon Flux Through Micrometeorological Method in a Mediterranean Grapevine
No full textAgriculture is indicted as both cause and part of the solution of the climate crisis. Increasing quantitative information on the capability of cropping systems to capture atmospheric carbon (C) is pivotal to assess crop ecological functions and services supporting the achievement of common agricultural strategies (e.g., carbon neutrality, Green Deal). The present study reports annual data on C flux measured with eddy covariance (EC) at a commercial vineyard located in Southern Italy. Results show that the seasonal Net Ecosystem Exchange (NEE) reflects phenological stages and environmental conditions. The highest monthly carbon capture (approx. -120g C m-2month-1) occurred in July corresponding to the period of maximum vine growth, while NEE was at its minimum or even positive during dormant season. The cumulated NEE reached about -400 g C m-2 per year confirming vineyards might act as C sink. The influence of certain practices (e.g., retention of pruning residues and cover crop) on NEE is discussed
Irrigation management in a Mediterranean vineyard under elevated atmospheric water demand
No full textCharacterization of microclimate and turbulent fluxes at a Mediterranean kiwi orchard covered with hail-protection net
Full text linkScreens and covers are increasingly used to protect crops from pests and extreme meteorological events. Their use affects plant microclimate and physiological responses as well, but this is only partly understood, particularly when considering the interaction among the cover and the training system. This study focuses on the microclimatic effects of the use of a hail protection net and an horizontal (pergola) kiwifruit canopy. The system splits the orchard environment in three distinct layers, determining a shaded understory, a space comprised between the canopy and the net, and the atmosphere above the net. To accent the effects, we considered a high-water demanding crop-kiwifruit, in an environment characterized by high evaporative demand (Bernalda, southern Italy).Three full eddy covariance and radiative balance equipment were used to assess fluxes (carbon dioxide, water vapor, and sensible heat) in the three layers and monitor meteorological variables (air temperature and relative humidity, wind, upward and downward short and long wave radiation, carbon dioxide and water vapor concentrations). Data from a typical clear-sky summer day are considered in this paper.While the net strongly reduced wind speed, it had a modest impact on all other variables. Conversely, the tick canopy layer had a major impact on all variables, determining a highly shaded, cooler and more humid understory, with very light wind. Nevertheless, the combination of high relative humidity and presence of the net was able to reduce the net loss of longwave radiation from the canopy during night, mitigating its cooling under these conditions.The reduction in wind speed and the increase in incoming longwave radiation around the crop, observed at night time, indicate potential valuable mechanisms that may be exploited to decrease water needs and prevent late frosts in the context of climate change, where extreme climatic events are more frequent and crop water requirements continue to increase
Protection net and the canopy layer decouple gas exchanges, affecting carbon and water fluxes: the case of a kiwifruit orchard in a Mediterranean environment
No full textCovers are increasingly used to protect crops from pests and extreme meteorological events. Their use affects plant microclimate and physiological responses as well, but this is only partly understood, particularly when considering the interaction among the cover and the training system. This study focuses on the microclimate effects of the concurrent use of a horizontal hail protection net and tree canopy. The system splits the orchard environment in three layers, giving a shaded understory, a volume comprised between the canopy and the net, and the atmosphere above the net. To accent the effects, we considered a high-water demanding crop – kiwifruit, in an environment characterized by high evaporative demand (Bernalda, southern Italy). Three full eddy covariance and radiative balance-equipments were used to synchronously monitor meteorological variables (air temperature and relative humidity, wind, upward and downward short and long wave radiation, carbon dioxide and water vapour concentrations) and infer fluxes (carbon dioxide, water vapour, and sensible heat) between the three layers. Data from a typical clear sky summer day, at different hours, are considered in this paper. While the net strongly reduced wind speed (-79%), it had a modest impact on all other variables. Conversely, the tick canopy layer had a major impact on all variables, determining a highly shaded, cooler and more humid understory, with very modest wind and higher carbon dioxide concentration. Most carbon assimilation and evapotranspiration were due to the tree canopy, while the understory played as a carbon source via respiration. The combination of the net and the pergola training system determined low energy understory conditions, which facilitate the buildup of water vapour and carbon dioxide and their recycling within the system. Given the large and increasing use of crop covers, a deeper understanding of their impacts on the drivers of climate change, such as the carbon, water and energy fluxes, is necessary
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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