Monitoring of microbial activity in soil using biological oxygen demand measurement and indirect impedancemetry

This paper describes a technique that allows one to monitor simultaneously oxygen consumption and carbon dioxide production in order to better characterize microbial activity in soil. The experimental methodology is based on biodegradation tests in biometric flasks filled with soil and equipped with a CO₂ trap (KOH solution) and OxiTop^® measuring heads (used for Biological Oxygen Demand [BOD] determination). CO₂ was measured using both indirect impedancemetry and acid/base titration. First, results showed that the concentration of the KOH solution concentration is a key design parameter for the sensitivity of the method. Second, respiratory quotient was calculated during the biodegradation tests in microcosms. Biomass evolution was also monitored to study the possible correlation between the respiratory quotient and biodegradation phases. As a conclusion, it is stated that on-line monitoring of the respiratory quotient can provide relevant information concerning in situ soil microbial activity.     

Spatial population structure of the Cabrera vole in Mediterranean farmland: The relative role of patch and matrix effects

There is mounting evidence that both patch networks and the intervening matrix influence species persistence in fragmented landscapes, though the relative importance of each of these factors in determining spatial population structure remains poorly understood. This study examined this issue using a three-year data set on the distribution of Cabrera voles (Microtus cabrerae) in Mediterranean farmland. The spatial pattern appeared consistent with a metapopulation structure, as voles occupied discrete tall herb patches scattered across the agricultural landscape, where local extinctions and colonizations induced temporal changes in occupancy patterns. Patch dynamics determined deviations from classical metapopulation assumptions, with over half the extinctions resulting from agricultural disturbance or vegetation succession, and recolonizations often occurring after the recovery of suitable habitat conditions sometime after disturbance. Occupancy in undisturbed patches was more stable, with vole occurrence in one year strongly reflecting that in the previous year. Overall, occupancy increased with both patch size and connectivity, but the unique contribution of patch variables to explain variation in vole occurrence was far smaller than that of matrix attributes. Voles occurred more often in patches surrounded by natural pastures, while prevalence declined with increasing cover by shrubland, pine plantations, improved pastures and grazed cropland. It is hypothesised that unfavourable land uses may increase the effective isolation of habitat patches through increased predation risk of dispersing voles. Conservation of the Cabrera vole in Mediterranean farmland should thus strive to maintain lightly grazed fields surrounding well-connected networks of suitable habitat patches.     

Predicting on-farm soybean yields in the pampas using CROPGRO-soybean

Soybean is the main rainfed crop in a wide range of latitudes and sowing dates of the Argentine Pampas. It is sown alone or as a second crop after other winter and summer crops. Modelling approaches have proved to be helpful in the decision making process. The on-farm evaluation of CROPGRO is rather difficult since input data are scarce and frequently of worse quality than those from experimental works. Moreover, CROPGRO simulation of water dynamic processes and their relation with biomass production has not been comprehensively evaluated in soybean crops. The aims of this study were (i) to evaluate the CROPGRO-soybean performance, with emphasis on water demand and supply and biomass production under water limited conditions, (ii) to generate a revised CROPGRO model improving those aspects, and (iii) to compare simulations outputs using the original and the revised CROPGRO models, with on-farm crop data set. In the revised model, we multiplied potential evapotranspiration by 1–1.22 when LAI increased from 0 to ≥4.0. We set a root extension rate of 4.0 cm/thermal day and a maximum rooting depth of 2.5 m. Finally, we included a nonlinear equation to simulate the relationship between relative transpiration and relative gross photosynthesis. The ability of the revised CROPGRO-soybean to simulate water content depletion and biomass production was tested against several experiments with an imposed drought period. We also calibrated cultivar parameters using “ad hoc” tests in a range of environments (combinations of sowing dates and locations). The models were evaluated with data from 155 commercial farms. V (%) (root mean square error as percentage of the observed mean) for the total cycle length, vegetative period, and reproductive phase simulations were 7, 13 and 15%, respectively. The revised CROPGRO was more accurate in simulating crop yield, biomass, harvest index and yield numeric components. V (%) values ranged from 11 to 17% (revised version) and from 13 to 22% (original version). Besides, V (%) values for yield were 16% with the revised model versus 32% with the original one, considering only paddocks with higher water stress level. The robust prediction of phenology, biomass and yield components obtained with the revised model across different environmental conditions, support its use in the decision making process of the soybean crop at the farm scale.     

Assessing landscape functional connectivity in a forest carnivore using path selection functions

Context

Understanding connectivity patterns in relation to habitat fragmentation is essential to landscape management. However, connectivity is often judged from expert opinion or species occurrence patterns, with very few studies considering the actual movements of individuals. Path selection functions provide a promising tool to infer functional connectivity from animal movement data, but its practical application remains scanty.

Objectives

We aimed to describe functional connectivity patterns in a forest carnivore using path-level analysis, and to explore how connectivity is affected by land cover patterns and road networks.

Methods

We radiotracked 22 common genets in a mixed forest-agricultural landscape of southern Portugal. We developed path selection functions discriminating between observed and random paths in relation to landscape variables. These functions were used together with land cover information to map conductance surfaces.

Results

Genets moved preferentially within forest patches and close to riparian habitats. Functional connectivity declined with increasing road density, but increased with the proximity of culverts, viaducts and bridges. Functional connectivity was favoured by large forest patches, and by the presence of riparian areas providing corridors within open agricultural land. Roads reduced connectivity by dissecting forest patches, but had less effect on riparian corridors due to the presence of crossing structures.

Conclusions

Genet movements were jointly affected by the spatial distribution of suitable habitats, and the presence of a road network dissecting such habitats and creating obstacles in areas otherwise permeable to animal movement. Overall, the study showed the value of path-level analysis to assess functional connectivity patterns in human-modified landscapes.

     

Clinical, haematological, biochemical and economic impacts of Trichinella spiralis infection in pigs

The purpose of this work was to assess the clinical, haematological and biochemical responses of pigs experimentally inoculated with Trichinella spiralis. Groups of three pigs were inoculated per os with 100, 500 and 5000 T. spiralis muscle larvae, two pigs were used as control. Clinical evaluation of disease in pigs included daily examination, rectal temperature measurements and cardiac and respiration rates. Haematological studies included: hematocrit (%), hemoglobin (g/dl), and white cell, neutrophil, lymphocyte and eosinophil counts. Blood biochemistry included: bun (mg/dl), creatinine (mg/dl), AST (UI/l), ALT (UI/l), CPK (UI/l) and ALP (UI/l). No significant differences were observed in rectal temperature and in cardiac and respiration rates between inoculated animals and the control group (p> or =0.05). Significant differences were detected (p< or =0.05) in the values of % hemoglobin, and eosinophils, as well as in the values of CK, ALP, AST and ALT. The variations observed in some cases were related to the number of T. spiralis larvae inoculated and varied with the number of days post-infection. Inoculated pigs showed significant differences (p< or =0.05) in weight gain when compared with uninoculated controls. This study has clinical, haematological, and enzyme alterations in Trichinella infected pigs provides a better understanding of acute and chronic trichinellosis in pigs.     

Application of distributed SVM architectures in classifying forest data cover types

In many ‘real-world’ applications, a classification of large data sets, which are often also imbalanced, is difficult due to the small, but usually more interesting classes. In this study, a large data set, forest cover type classes, which is actually multi-class classification defined with seven imbalanced classes and used as a resource inventory information was analyzed and evaluated. The data set was transformed into seven new data sets and a support vector machine (SVM) was employed to solve a binary classification problem of balanced and imbalanced data sets with various sizes. In the two approaches considered, the use of distributed SVM architectures, which basically reduces the complexity of the quadratic optimization problem of very large data sets, and the use of two sampling approaches for classification of imbalanced data sets were combined and results presented. The experimental results of distributed SVM architectures show the improvement of the accuracy for larger data sets in comparison to a single SVM classifier and their ability to improve the correct classification of the minority class.     

Effect of Surfactant Structure on the Pasting Properties of Wheat Flour and Starch Suspensions

Systematic studies were performed on the effect of the surfactant alkyl chain length (10–16 carbon atoms) and the head group charge/structure (anionic, cationic, nonionic) on the pasting properties of wheat flour and starch aqueous suspensions by means of a Rapid Visco Analyser (RVA). An excellent agreement was observed between the effect of surfactants on the onset temperature of the pasting process (PT) and the time to reach peak viscosity (t_peak) of wheat flour and wheat starch suspensions. Moreover, a correlation was found between the effect of different surfactants on these two parameters. With the exception of the cationic surfactants (alkyl trimethyl ammonium bromides), the effect of surfactants (alkyl sulfates, maltosides, monoglycerides, and sucrose esters) was found to be strongly dependent on the surfactant chain length. Shorter chain surfactants (C10–C12) induced an earlier pasting, while longer chain surfactants (C14–C16) had the opposite effect. The effect of surfactants on PT and t_peak of flour suspensions was enlarged when the surfactant concentration was increased from ≈1% to 15% (w/w) on a dry starch basis.     

Molecular diagnosis of avian nephritis: preliminary report

Kidney samples from chickens diagnosed with acute nephritis and gout were subjected to histological and electron microscopic examination. The investigations revealed cytoplasmic inclusion bodies in the tubular epithelial cells containing round virions of about 30 nm in diameter. Since avian nephritis virus (ANV) is known as a potential causative agent of the so-called baby chick nephropathy, an RT-PCR assay was developed for the molecular detection of ANV-specific nucleic acid in the specimen. The specificity of the assay was confirmed by direct sequencing of the amplicon obtained in the reaction. The nucleotide sequence of the PCR product showed 92% identity with the reference ANV sequence deposited in the GenBank database. After having been validated on some other suspicious cases of avian nephritis, the PCR method described in this study can be a potential tool for routine diagnostic examination of samples submitted from cases of gout and nephropathy in chickens.