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The Penman–Monteith equation for reference evapotranspiration (ETo) estimation cannot be applied in many situations, because climatic records are totally or partially not available or reliable.
In these cases, empirical equations that rely on few climatic variables are necessary. Nevertheless, the uncertainty associated
with empirical model estimations is often high. Thus, the improvement of methods relying on few climatic inputs as well as
the development of emergency estimation tools that demand no local climatic records turns into a task of great relevance.
The present study describes different approaches based on multiple linear regression, simple regression and artificial neural
networks (ANNs) to deal with ETo estimation exclusively from exogenous records from secondary stations. This cross-station approach is based on a continental
characterization of the study region, which enables the selection and hierarchization of the most suitable ancillary data
supplier stations. This procedure is compared with different traditional and cross-station approaches, including methodologies
that also consider local temperature inputs. The proposed methods are also evaluated as gap infilling procedures and compared
with a simple methodology, the window averaging. The artificial neural network and the multiple linear regression approaches
present very similar performance accuracies, considerably higher than simple regression and traditional temperature-based
approaches. The proposed input combinations allow similar performance accuracies as ANN models relying on exogenous ETo records and local temperature measurements. The cross-station multiple linear regression procedure is recommended due to
its higher simplicity. 相似文献
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Balaguer MP Gómez-Estaca J Gavara R Hernandez-Munoz P 《Journal of agricultural and food chemistry》2011,59(24):13212-13220
The aim of this work has been to study the modification of gliadin films with cinnamaldehyde as a potential cross-linker agent. The molecular weight profile and cross-linking density showed that cinnamaldehyde increased reticulation in the resulting films. The participation of free amino groups of the protein in the newly created entanglements could be a possible mechanism of connection between the polypeptidic chains. The combination of a Schiff base and a Michael addition is a feasible approach to understanding this mechanism. The protein solubility in different media pointed to lower participation by both noncovalent and disulfide bonds in stabilizing the structure of the cross-linked films. The new covalent bonds formed by the cinnamaldehyde treatment hampered water absorption and weight loss, leading to more water-resistant matrices which had not disintegrated after 5 months. The properties of this novel bioplastic could be modified to suit the intended application by using cinnamaldehyde, a naturally occurring compound. 相似文献
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Forest management policies in Mediterranean areas have traditionally encouraged land cover changes, with the establishment of tree cover (Aleppo pine) in natural or degraded ecosystems for soil conservation purposes: to reduce soil erosion and to increase the vegetation structure. In order to evaluate the usefulness of these management policies on reduced erosion in semi-arid landscapes, we compared 5 vegetation cover types (bare soil, dry grassland, shrublands, afforested dry grasslands and afforested thorn shrublands), monitored in 15 hydrological plots (8 × 2 m), in the Ventós catchment (Alicante, SE Spain), over 4 years (1996 to 1999). Each cover type represented a different dominant patch of the vegetation mosaic on the north-facing slopes of this catchment. The results showed that runoff coefficients of vegetated plots were less than 1% of the precipitation volume; whereas runoff in denuded areas was nearly 4%. Soil losses in vegetation plots averaged 0.04 Mg ha− 1 year− 1 and increased 40-fold in open-land plots. The evaluation of these forest management policies, in contrast with the natural vegetation communities, suggests that: (1) thorn shrublands and dry grassland communities with vegetation cover could control runoff and sediment yield as effectively as Aleppo pine afforestation in these communities, and (2) afforestation with a pine stratum improved the stand's vertical structure resulting in pluri-stratified communities, but reduced the species richness and plant diversity in the understorey of the plantations. 相似文献
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Pau Aragó Galindo Carlos Granell Paulo Guilherme Molin Joaquín Huerta Guijarro 《Precision Agriculture》2012,13(5):594-610
Site-specific agriculture has been adopted in a high-tech context using, for instance, in situ sensors, satellite images for remote sensing analysis, and some other technological devices. However, farmers and smallholders without the economic resources and required knowledge to use and to access the latest technology seem to find an impediment to precision agricultural practices. This article discusses the possibility of adopting precision agriculture (PA) principles for site-specific management but in a low technology context for such farmers. The proposed methodology to support PA combines low technology dependency and a participatory approach by involving smallholders, farmers and experts. The case studies demonstrate how the interplay of low technology and a participative approach may be suitable for smallholders for site-specific agriculture analysis. 相似文献
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Ancillary data supply strategies for improvement of temperature-based ETo ANN models 总被引:1,自引:0,他引:1
The development of new and more precise models for reference evapotranspiration (ETo) estimation from minimum climatic data is mandatory, since the application of existing methods that provide acceptable results is limited to those places where large amounts of reliable climatic data are available. The performance quality of empirical equations and their local calibrations is to be questioned in a large variety of climatic contexts. As an alternative to traditional techniques, artificial neural networks (ANNs) are highly appropriate for the modelling of non-linear processes, which is the case of evapotranspiration. Nevertheless, temperature-based ANN models do not always provide accurate enough ETo estimations and their performance depends highly on the specific relationships temperature-ETo of the studied continental context. This paper describes the performance improvement of temperature-based ANN models through the consideration of exogenous ETo records as ancillary inputs in different continental contexts of the autonomous Valencia region, on the Spanish Mediterranean coast. The influence on the model performance of the number of considered ancillary stations and the corresponding number of training patterns is also analysed. Finally, this performance is compared with existing empirical and ANN temperature-based models. The proposed models can be used with high accuracy not only for infilling purposes, but also for estimating ETo outside the training station. Concerning models which demand scant climatic inputs, the proposed model provides performances with lower associated errors than the currently existing temperature-based models, which only consider local data. The local performance of the model presents 0.084 of average absolute relative error (AARE). The external performance of the model presents 0.1072 of AARE. 相似文献
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Balaguer MP Gómez-Estaca J Gavara R Hernandez-Munoz P 《Journal of agricultural and food chemistry》2011,59(12):6689-6695
Cinnamaldehyde is a naturally occurring α,β-unsaturated aldehyde. Its potential as a natural cross-linker to improve the physical performance of cast wheat gliadin films was evaluated. The cross-linking reaction was found to be dependent on the pH of the reaction medium, with pH 2 as the optimum. The water resistance (weight loss after immersion), mechanical properties (Young's modulus, tensile strength and elongation at break), thermal properties (T(g) and decomposition behavior), optical properties and morphology of films were evaluated. Cross-linked films showed high transparency, maintained their integrity after immersion, and displayed significant improvements in tensile strength and Young's modulus without impairment of their elongation properties. These effects, which were proportional to the amount of cinnamaldehyde added, highlight the possible formation of intermolecular covalent bonds between "monomeric" gliadins, leading to a polymerized network. Thus, this treatment could provide a new alternative to the toxic cross-linkers commonly employed and so extend the use of gliadin films. 相似文献
8.
Lipid droplet distribution of immature canine oocytes in relation to their size and the reproductive stage
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Federica Ariu Alessandro Strina Ombretta Murrone Laura Falchi Daniela Bebbere Sergio Ledda Maria Teresa Zedda Salvatore Pau Luisa Bogliolo 《Animal Science Journal》2016,87(1):147-150
This study investigated the distribution of lipid droplets (LD) in immature canine oocytes in relation to their size and the reproductive stage. Oocytes were collected from the ovaries of bitches at different estrous stages, divided according to their size (110‐120 µm; >120 µm), and stained with Nile Red to detect lipid droplet distribution. At the follicular phase most of the oocytes displayed a diffuse pattern of LD distribution, whereas at anestrus and luteal phase oocytes showed LD mainly in a peripheral/ perinuclear LD distribution. A significantly higher intensity of LD has been recorded in the oocytes > 120 µm compared to those of smaller size (110 ‐ 120 µm) at all stages of the estrous cycle. At follicular phase, oocytes > 120 µm displayed LD intensity similar to that of oocytes > 120 µm at luteal phase and higher compared to the oocytes of the other groups. 相似文献
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The relationship between tree growth and competition may depend on some subjective choices that are commonly left to the researcher. Among these are the neighborhood radius, the number of years of growth that are integrated, and tree age. We have evaluated the importance of these factors when relating growth and competition in a forest stand with contrasted densities of the dominant tree species (Pinus nigra) and understory shrub species (Adenocarpus decorticans). Previous to this evaluation we performed a randomization test to assess the relationship between tree growth and neighbors. By using Daniels index of competition we found that the use of a fixed neighborhood radius underestimated the importance of tree competition. The coefficient of determination (r2) of the relationship between tree growth and Daniels index increased asymptotically with the number of years considered. Five years of growth gave high r2 independently of the density of trees and shrubs. The intensity of competition was weakly affected by the characteristics of the plot (tree and shrub densities), and did not change with time. In contrast, the potential growth at equal competition – as represented by constant a in the allometric model – changed with time suggesting a gradual decrease in potential tree growth in the plots with higher tree density, and a gradual increase in those plots with high density of shrubs. These results may reflect tree canopy closure and the senescence of Adenocarpus decorticans. A method is suggested to select optimum neighborhood radius and growing period for the calculation of competition indices. By applying this method we were able to explain as much as 79–84% of the variability in tree growth of this stand. 相似文献
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Pau Brunet-Navarro Frank J. Sterck Jordi Vayreda Jordi Martinez-Vilalta Godefridus M.J. Mohren 《Annals of Forest Science》2016,73(4):1025-1034