Ancillary data supply strategies for improvement of temperature-based ETo ANN models

The development of new and more precise models for reference evapotranspiration (ET_o) 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 ET_o estimations and their performance depends highly on the specific relationships temperature-ET_o of the studied continental context. This paper describes the performance improvement of temperature-based ANN models through the consideration of exogenous ET_o 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 ET_o 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.     

Reference evapotranspiration estimation without local climatic data

The Penman–Monteith equation for reference evapotranspiration (ET_o) 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 ET_o 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 ET_o records and local temperature measurements. The cross-station multiple linear regression procedure is recommended due to its higher simplicity.     

Functional properties of bioplastics made from wheat gliadins modified with cinnamaldehyde

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.     

Biochemical properties of bioplastics made from wheat gliadins cross-linked with cinnamaldehyde

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.     

Participative site-specific agriculture analysis for smallholders

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.     

Self-thinning in four pine species: an evaluation of potential climate impacts

Key message

Self-thinning lines are species- and climate-specific, and they should be used when assessing the capacity of different forest stands to increase biomass/carbon storage.

Context

The capacity of forests to store carbon can help to mitigate the effects of atmospheric CO₂ rise and climate change. The self-thinning relationship (average size measure ～ stand density) has been used to identify the potential capacity of biomass storage at a given density and to evaluate the effect of stand management on stored carbon. Here, a study that shows how the self-thinning line varies with species and climate is presented.

Aims

Our main objective is thus testing whether species identity and climate affect the self-thinning line and therefore the potential amount of carbon stored in living biomass.

Methods

The Ecological and Forest Inventory of Catalonia was used to calculate the self-thinning lines of four common coniferous species in Catalonia, NE Iberian Peninsula (Pinus halepensis, Pinus nigra, Pinus sylvestris and Pinus uncinata). Quadratic mean diameter at breast height was chosen as the average size measure. The self-thinning lines were used to predict the potential diameter at a given density and study the effect of environmental variability.

Results

Species-specific self-thinning lines were obtained. The self-thinning exponent was consistent with the predicted values of ?3/2 and ?4/3 for mass-based scaling for all species except P. sylvestris. Species identity and climatic variability within species affected self-thinning line parameters.

Conclusion

Self-thinning lines are species-specific and are affected by climatic conditions. These relationships can be used to refine predictions of the capacity of different forest stands to increase biomass/carbon storage.

     

Changes in sorption/bioavailability of imidacloprid metabolites in soil with incubation time

Changes in sorption/bioavailability of two metabolites, imidacloprid-urea {1-[(6-chloro-3-pyridinyl)methyl]-2-imidazolidinone} and imidacloprid-guanidine {1-[(6-chloro-3-pyridinyl)methyl]-4,5-dihydro-1H-imidazol-2-amine} of the insecticide imidacloprid {1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine} with aging in different soils were determined. Soil moisture was adjusted to -33 kPa and ¹⁴C- and analytical-grade imidacloprid-urea and imidacloprid-guanidine were added to the soil at a rate of 1.0 mg kg^-1. Spiked soils were incubated at 25°C for 8 weeks. Replicate soil samples were periodically extracted successively with 0.01 N CaCl₂, acetonitrile, and 1 N HCl. Imidacloprid-urea sorption, as indicated by sorption coefficient values, was highest in the soil with highest organic C content, and increased by an average factor of 2.6 in three soils during the 8-week incubation period. Imidacloprid-guanidine sorption increased by a factor of 2.3 in the same soils. The increase in sorption was the result of a decrease in the metabolite extractable with CaCl₂ (solution phase); the amount of metabolite extractable with acetonitrile and HCl (sorbed phase) did not significantly change with incubation time. It appears the increase in sorption was because the rate of degradation in solution and on labile sites was faster than the rate of desorption from the soil particles. It may have also been due to metabolite diffusion to less accessible or stronger binding sites with time. Regardless of the mechanism, these results are further evidence that increases in sorption during pesticide aging should be taken into account during characterization of the sorption process for mathematical models of pesticide degradation and transport.     

Lipid droplet distribution of immature canine oocytes in relation to their size and the reproductive stage

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.     

Sorption of aged dicamba residues in soil

The effect of aging (residence time in soil) on dicamba (3,6-dichloro-2-methoxybenzoic acid) and a major metabolite, 3,6-dichlorosalicylic acid (3,6-DCSA) sorption was determined in an unamended and a carbon-amended sandy loam and in a silt loam soil. During the incubation, sequential solvent extraction with 0.01 M calcium chloride solution and aqueous acetonitrile + hydrochloric acid was used to determine the solution and sorbed concentrations of dicamba and 3,6-DSCA, and sorption coefficients were calculated. Dicamba was weakly sorbed to soil (Kd < 0.7). In contrast to some other classes of pesticides, sorption of dicamba did not significantly increase with aging, at least not until < 15% of the applied dicamba remained. 3,6-DSCA was strongly sorbed to soil (Kd > 8) and the Kd-a value increased by a factor of 2-6 during a 28-day aging period. Addition of a carbon source to the soil had minimal effect on the strength of sorption of aged dicamba. However, it did appear to decrease 3,6-DSCA availability to soil micro-organisms; once formed 3,6-DSCA was not further mineralized. While it appears that sorption can be well characterized for weakly sorbed pesticides using the batch equilibration method with freshly treated soils, this procedure may not be adequate for more strongly sorbed pesticides and their degradates.