1,721,007 research outputs found
APPLICATION OF TOMOGRAPHIC ALGORITHMS TO SCHLIEREN OPTICAL DATA FOR THE STUDY OF CONVECTION HEAT TRANSFER
No full textIn this paper, optical data obtained by the schlieren technique for the air natural convective heat transfer from a horizontal, upward-facing, isothermal surface, are processed by using different tomographic algorithms. Optical data are collected over a 180 deg angle of view; however, particular emphasis is given to the reconstruction from data recorded over a limited angle of view, this in order to assess the capability of methods to provide a reliable reconstruction when the optical access to the test section is limited
S. Maria ad Cryptas (L’Aquila): un esempio di diagnostica termografica preventiva per il consolidamento
No full textStatistical inferential techniques for approaching forest mapping. A review of methods
No full textThe increasing availability of remote sensing data at no or low costs can be used as ancillary data in order to spatialize and improve the estimation of forest attributes and without increasing the sampling effort and costs. In this review paper, a description of the main statistical inferential techniques for approaching forest mapping is proposed. This article reviews the most used forest mapping methods based on the sole spatial information as well as techniques exploiting auxiliary information from remotely sensed data. The advantages and drawbacks of each method have been described on the basis of several factors, such as the aims of the investigation and the area under examination. Two main groups were here discussed with model-based methods on one side and model-assisted methods on the other, moving the attention from the model used to interpolate surfaces to the sampling scheme. Model-based methods include kriging, locally weighted regression, K-NN, decision trees and neural networks, while the inverse distance weighting interpolator is presented in the model-assisted group.Reliable and up-to-date information on forest characteristics are mandatory tools for any decisional process. The main input data of such systems are wall-to-wall maps depicting the spatial structures of forests and additional elements. Actually, if the original aim of forest inventories was to estimate harvestable timber amounts, a general interest towards multipurpose surveys is mandatory. Such information must deal with increased costs and more time-consuming procedures
A monte carlo appraisal of tree abundance and stand basal area estimation in forest inventories based on terrestrial laser scanning
Full text linkNon-detection of trees is an important issue when using single-scan TLS in forest inventories. A hybrid inference approach is adopted. Quoting from distance sampling, a detection function is assumed, so that the inclusion probability of each tree included within each plot can be determined. A simulation study is performed to compare the TLS-based estimators corrected and uncorrected for non-detection with the Horvitz–Thompson estimator based on conventional plot sampling, in which all the trees within plots are recorded. Results show that single-scan TLS provides more efficient estimators with respect to those provided by the conventional plot sampling in the case of low-density forests when no distance sampling correction is performed. In low-density forests, uncorrected estimators lead to a small bias (1%–6%), increasing with plot size. Therefore, care must be taken in enlarging the plot radius too much. The bias increases in forests with clustered spatial structures and in dense forests, where the bias levels (30%–50%) deteriorate the performance of uncorrected estimators. Even if the bias-corrected estimators prove to be effective in reducing the bias (below 15%), these reductions are not sufficient to outperform conventional plot sampling. Therefore, there is no convenience in using TLS-based estimation in high-density forests
Per-Pixel Forest Attribute Mapping and Error Estimation: The Google Earth Engine and R dataDriven Tool
Full text linkRemote sensing products are typically assessed using a single accuracy estimate for the entire map, despite significant variations in accuracy across different map areas or classes. Estimating per-pixel uncertainty is a major challenge for enhancing the usability and potential of remote sensing products. This paper introduces the dataDriven open access tool, a novel statistical design-based approach that specifically addresses this issue by estimating per-pixel uncertainty through a bootstrap resampling procedure. Leveraging Sentinel-2 remote sensing data as auxiliary information, the capabilities of the Google Earth Engine cloud computing platform, and the R programming language, dataDriven can be applied in any world region and variables of interest. In this study, the dataDriven tool was tested in the Rincine forest estate study area—eastern Tuscany, Italy—focusing on volume density as the variable of interest. The average volume density was 0.042, corresponding to 420 m3 per hectare. The estimated pixel errors ranged between 93 m3 and 979 m3 per hectare and were 285 m3 per hectare on average. The ability to produce error estimates for each pixel in the map is a novel aspect in the context of the current advances in remote sensing and forest monitoring and assessment. It constitutes a significant support in forest management applications and also a powerful communication tool since it informs users about areas where map estimates are unreliable, at the same time highlighting the areas where the information provided via the map is more trustworthy. In light of this, the dataDriven tool aims to support researchers and practitioners in the spatially exhaustive use of remote sensing-derived products and map validation
Kiwifruit plant physiological behavior to different levels of soil water depletion under semi-arid environmental conditions
Full text linkKiwifruit crop is known to be extremely sensitive to unbalanced soil water content, both excess and deficit, and irrigation is therefore a key factor to be properly managed. A field experiment was conducted in a commercial kiwifruit orchard (Actinidia chinensis var. chinensis ‘Zesy 002’) located in Metaponto (southern Italy) to evaluate the variation of vine water status, leaf transpiration and stomatal conductance under different water deficit levels, by increasing depletion of soil water content in the top soil layers (0-35 cm). Reduced soil water availability was achieved gradually, by imposing an irrigation treatment of water restriction (7 0 % of full crop requirements, ETc) for a limited period of the growing season (15 days), which was monitored by multi-profile soil moisture probes. Stem water potential (Ψ), leaf transpiration (E) and stomatal conductance (gsw) were evaluated during the water stress phase and the subsequent recovery phase (7 days) and compared to the control, in which irrigation supply was aimed at ensuring the soil water content in the volume of soil affected by irrigation remained between the field capacity (FC) and the lower readily available water (RAW) level. Leaf transpiration and gsw decreased during the water stress phase, reaching minimum values at midday approximately 60 and 7 0 % lower compared to control. Stem water potential became more negative due to the reduction in the soil water content, showing midday values of -14 bars at the end of the water stress phase. The prompt decline in E in response to Ψ lowering, occurring in the first days after the change in irrigation volumes, confirms a high sensitivity of kiwifruit vines to water deficit. During the recovery phase, a quick re-establishment of Ψ and a slow restoration of leaf activity and functionality were observed, making these parameters important indicators of the vine physiological status
Mapping the diversity of forest attributes: a design-based approach
No full textForest attributes such as volume or basal area are concentrated at tree locations and are absent elsewhere. It is, therefore, more meaningful to consider the amount of forest attributes at a prefixed spatial grain, within regular plots of prefixed size centered at the points of the study area. In this way, the diversity of attributes within plots also can be considered and quantified by suitable indexes, giving rise to a diversity surface defined on the continuum of points constituting the area. We analyze the estimation of diversity surfaces when a sample of plots is selected by a probabilistic sampling scheme and diversity within nonsampled plots is estimated using an inverse distance weighting interpolator. We discuss the design-based asymptotic properties of the resulting maps when the survey area remains fixed and the number of sampled points increases. Because diversity surfaces share suitable mathematical properties, if the schemes adopted to select sample points ensure an even coverage of the study areas avoiding large portions of non-sampled zones, it can be proven that the estimated maps approach the true maps.Les attributs de la forêt comme le volume ou la surface terrière sont concentrés à l’emplacement des arbres et sont absents ailleurs. Par conséquent, il est plus significatif de considérer la quantité des attributs de la forêt à une résolution spatiale prédéterminée, dans des parcelles régulières de taille prédéterminée, centrées sur les points de la zone d’étude. De cette manière, la diversité des attributs au sein des parcelles peut également être prise en compte et quantifiée à l’aide d’indices appropriés, donnant lieu à une surface de diversité définie sur le continuum de points constituant la superficie à l’étude. Nous analysons l’estimation des surfaces de diversité lorsqu’un échantillon de parcelles est sélectionné au moyen d’un plan d’échantillonnage probabiliste et que la diversité au sein de parcelles non échantillonnées est estimée à l’aide d’un interpolateur pondéré par l’inverse de la distance. Nous discutons des propriétés asymptotiques des cartes obtenues, qui résultent du plan d’expérience, lorsque la zone d’inventaire demeure fixe et que le nombre de points échantillonnés augmente. Puisque les surfaces de diversité partagent des propriétés mathématiques appropriées, si les plans d’échantillonnage adoptés pour sélectionner les points d’échantillonnage assurent une couverture uniforme des zones d’étude, en évitant de laisser de larges portions non échantillonnées, on peut démontrer que les cartes estimées se rapprochent des vraies cartes
Adoption of nature-based solutions and orchard sustainable management to face kiwifruit vine decline syndrome (KVDS)
No full textItaly, the third largest producers of kiwifruit in the world, lost 10% of its production in recent years because of the spread of the kiwifruit vine decline syndrome (KVDS) (Bardi, 2020). Although the etiology of KVDS is still not clear, it is often associated with water excess and stagnation. We hypothesize that soil compaction and hypoxia could have a priming effect in the emergence of KVDS. To investigate the causal factors and potential solutions to counter KVDS, a multi-disciplinary experimental trial was undertaken in a kiwifruit orchard (Actinidia chinensis var. chinensis ‘Zesy002’) affected by KVDS in Latina (Italy). Soils from two areas were sampled: a) vines showing severe symptoms of KVDS, and b) healthy vines as control (CTRL). Soils showed different levels of compaction, clay/silt content and water content, with higher values in KVDS field, compared to CTRL. The topsoil (0-30 cm) redox potential was significantly lower in KVDS field than in the CTRL (256 vs 327 mV), so indicating low soil oxygen content. Higher soil CO2 and CH4, two greenhouse gases that also are indicators of hypoxic conditions, were found in KVDS field (Sofo et al., 2022). The analysis of topsoil (0-30 cm) thin sections showed KVDS soils had fewer macropores than CTRL (8.5 vs 11.5%, v/v). Macroscopically, the roots affected by KVDS were rotting, showing a loss of rhizodermis and cortical parenchyma. Microscope analysis revealed damage to the root system, with tissue breakdown and decomposition (D'Ippolito et al., 2022). Genomic analysis identified some abundant fungal species in KVDS roots (Ilyonectria vredenhoekensis, Fusarium oxysporum and Paraphaeosphaeria michotii), but further investigation is required to determine the eventual role of these fungi in KVDS emergence. A metagenomic/metatranscriptomic analysis of rhizosphere-associated microorganisms was carried out for detecting a) eventual beneficial microorganisms and biocontrol microbial agents for KVDS control isolated from healthy plants, and b) the hypothetical role of pathogenic microorganisms detected in KVDS plants, able to compromise roots functionality. Nature-based solutions were applied, such as planting decompacting crops (e.g., Rafanus spp.) for increasing water permeability and agroecosystem diversification, the application of compost and bio-fertilizers containing plant-growth-promoting microorganisms and mycorrhiza (Saccharomyces cerevisiae, Bacillus megaterium, Bacillus pumilus, Pseudomonas striata, Azospirillum brasilense, Candida tropicalis, Glomus intraradices, and Trichoderma harzianum), the amelioration of water drainage into the soil, and root pruning for improving root regeneration. Implementing novel management strategies can improve kiwifruit growth and vine productivity, also reducing KVDS symptoms in impacted vineyards, contributing to the socio-economic sustainability of farms, and increasing the ecosystem services, according to a sustainable, modern and multifactorial concept of agriculture
Convezione naturale in canali verticali con sporgenze conduttrici e non conduttrici: uno studio sperimentale
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