Humus forms in terrestrial ecosystems: a framework to biodiversity

Humus forms are the seat of most biological transformations taking place in terrestrial ecosystems, being at the interface between plants, animals and microbes. The diversity of terrestrial humus forms (mor, moder and mull) can be attributed to the existence of different patterns (strategies) for the capture and use of resources by ecosystems, in ascending order of biodiversity and bioavailability. Arguments are found in the parallel development of humus forms and terrestrial ecosystems, in exclusion mechanisms between organisms living in different humus forms, and in palaeontological studies. The diversification of terrestrial life forms in the course of Earth history, concomitant with an improvement in resource availability due to the development of sedimentary layers at the surface of continents, may explain the successive appearance of more active humus forms enabling the co-existence of an increasing number of organisms. Contradictory reports about the relationships between biodiversity and stability of ecosystems can be explained by the existence of different belowground pathways making ecosystems more stable.     

Sublethal effects of imidacloprid on the burrowing behaviour of two earthworm species: Modifications of the 3D burrow systems in artificial cores and consequences on gas diffusion in soil

Earthworms have been termed ‘ecosystem engineers’ (sensu [Jones, C.G., Lawton, J.H., Shachak, M., 1994. Organisms as ecosysem engineers. Oikos 69, 373-386.]) because of the important roles they play in the soil. As a consequence, it is assumed that if earthworms change their behaviour following exposure to pesticides or pollutants this could have a drastic impact on soil functioning. To test this assumption under laboratory conditions, we studied the burrow systems made by two earthworm species (the anecic Aporrectodea nocturna and the endogeic Allolobophora icterica) in artificial soil cores containing imidacloprid, a widely used neonicotinoid insecticide. After 1-month incubation period, the macropores created in the soil core were analyzed by tomography. In order to further characterize transfer properties associated with burrow systems gas diffusion measurements were also carried out. The burrow systems made by the two earthworm species were very different: A. nocturna made more continuous, less branched, more vertical and wider burrows than A. icterica. Some changes to A. nocturna burrow systems were observed after exposure to imidacloprid (they made a smaller burrow system and burrows were more narrow), but only at the highest concentration of imidacloprid used (0.5 mg kg⁻¹). A. icterica worms were more sensitive to imidacloprid and many differences in their burrow systems (length, sinuosity, branching rate and number of burrows) were observed at both concentrations tested (0.1 and 0. 5 mg kg⁻¹). As a consequence, the continuity of the burrow systems made by both species was altered following imidacloprid treatment. Gas diffusion through the A. nocturna soil cores was reduced but no difference in gas diffusion was observed in the A. icterica soil cores.     

Simultaneous differential pulse polarographic determination of cadmium, lead, and copper in milk and dairy products

The contents of potentially toxic elements lead and cadmium and the essential element copper in various milk and dairy products consumed in Turkey were determined by differential pulse polarography (DPP), primarily to assess whether the intakes comply with recommended desired concentrations for essential and permissible levels for toxic elements. A simple and rapid DPP method has been developed for the simultaneous determination of cadmium, lead, and copper in samples. Using the differential pulse mode, half-wave peak potentials as E(1/2) were -0.58, -0.40, and -0.07 V for cadmium (Cd), lead (Pb), and copper (Cu), respectively. Marketed formulations of dairy products have been analyzed by calibration and standard addition methods. Recovery experiments were found to be quantitative. The linear domain ranges were 0.00-674.28 microg/L for Cd (R2 = 0.9999), 0.19-2.94 mg/L (p < 0.01) for Pb (R2 = 0.9997), and 0.41-133.46 microg/L for Cu (p < 0.01) (R2 = 0.9999). The studies have shown that the method is a rapid, reproducible, and accurate determination of these elements in milk and dairy products and can be used in the analysis of marketed formulations in the milk and dairy industry.     

Novel protein from Labramia bojeri A. DC. seeds homologue to Kunitz-type trypsin inhibitor with lectin-like properties

This study starts by isolating and characterizing the first protein from Labramia bojeri seeds, which belong to the Sapotaceae family. The purified lectin analyzed by SDS-PAGE with and without beta-mercaptoethanol shows two protein bands (M(r) = 19 and 20 kDa), which cannot be resolved. Protein bands have shown similar characteristics as molecular masses, determined by gel filtration and native gel; N-terminal sequences presented a difference in their isoelectric points. We have suggested that those protein bands might be variants of the protein named Labramin. The sequence database search has shown that the N-terminal sequence of Labramin presented a high degree of homology to Kunitz-type trypsin inhibitor (82-52%) despite no trypsin inhibition activity detection. The lectin-like form from Labramin was better inhibited by glycoproteins and has also presented growth inhibition of the fungus Colletotrichum lindemuthianum and the yeast Saccharomyces cerevisiae, but it has not presented an apparent effect on Fusarium oxysporum.     

Fungal colonization of phyllosphere and litter of<Emphasis Type="Italic"> Quercus rotundifolia</Emphasis> Lam. in a holm oak forest (High Atlas,Morocco)

The microfungal flora of holm oak living, senesced and litter leaves was studied at five different stages of decomposition using three different isolation methods. Holm oak leaves are first colonized on the tree by a variety of primary saprophytes such as Trichothecium, Aureobasidium, Cladosporium, Epicoccum and Alternaria. After leaf fall there is an intensive development of the fungal flora, including both species already present in the phyllosphere and new colonizers from the litter layer. With increasing decomposition initial colonizers gradually disappear, being replaced by other forms. When all isolation methods were pooled, maximum biodiversity (species richness) of the fungus flora was observed during the first three stages of leaf litter decomposition, but strong variation occurred according to the isolation method. Sterilization of the leaf material revealed that a number of fungal strains were present inside the holm oak leaves before abscission, increasing from living to senescent stages, and that a strong decrease in the internal colonization of leaf litter was observed at late decomposition stages.     

Simulation of solution chemistry in an acidic forest soil

The computer simulation model SOILEQ was used to estimate soil solution chemistry over a 7 week period from October 3 to November 14, 1988 in the soils of a sugar maple forest located near St. Hippolyte, Quebec, Canada. Model parameters for pH-dependent CEC and exchangeable cations were calculated from laboratory measurements while soil solution chemistry, including Al solubility, at the start of the simulation was taken from values obtained from lysimeter samples. Model predictions were compared with values obtained from 12 sets of soil solution collectors over the same time period. Predicted values of Ca, Mg and K in the mineral soil horizons at 25-, 75- and 125-cm depths generally fall within the 95% confidence interval of the median for the measured values. Simulated values of pH and inorganic Al are not as close to the measured values. Some error due to drift is apparent, most notably for base cations in solutions leaving the organic surface horizons, and may be attributable to decomposition of organic matter, not included in the simulation model. The results indicate that other mechanisms that release H* (nitrification, for example) and base cations (mineral weathering or mineralization of organic matter) need to be considered.     

Sweet basil (Ocimum basilicum L.) and potassium fertilization

The objective of the present study was to examine the effect of potassium (K) fertilization and soil texture on total yield (1st and 2nd cuttings) and yield components of sweet basil (Ocimum basilicum L.) A greenhouse pot experiment was conducted in a completely randomized statistical design. Basil growth was examined in two different textured soils under three different doses of K fertilization. Generally, for the basil grown under clay soil conditions, moderate amounts of K fertilization is proposed to be sufficient if higher linalool contents are wanted. However, if the growing conditions are sandy loam in texture, it is suggested that higher doses of K be used. Results also highlighted the contribution of second cut as an important cultural practice in the cultivation of an annual basil.     

Application of solid/liquid extraction for the gravimetric determination of lipids in royal jelly

Gravimetric lipid determination is a major parameter for the characterization and the authentication of royal jelly quality. A solid/liquid extraction was compared to the reference method, which is based on liquid/liquid extraction. The amount of royal jelly and the time of the extraction were optimized in comparison to the reference method. Boiling/rinsing ratio and spread of royal jelly onto the extraction thimble were identified as critical parameters, resulting in good accuracy and precision for the alternative method. Comparison of reproducibility and repeatability of both methods associated with gas chromatographic analysis of the composition of the extracted lipids showed no differences between the two methods. As the intra-laboratory validation tests were comparable to the reference method, while offering rapidity and a decrease in amount of solvent used, it was concluded that the proposed method should be used with no modification of quality criteria and norms established for royal jelly characterization.     

Influence of soil properties on the adsorption-desorption of sulcotrione and its hydrolysis metabolites on various soils

The retention process of sulcotrione and its two hydrolysis products, 1,3-cyclohexanedione (CHD) and 2-chloro-4-methylsulfonylbenzoic acid (CMBA), were studied in four different soils (Belgium, Landes, Perpignan, and Martinique) under laboratory conditions. Adsorption isotherms were well fitted by a Freundlich relationship. The values of K(fa) ranged from 0.4 to 27.0, and the most adsorbed compound was CHD regardless the soil type. Sulcotrione and CMBA exhibited similar retention behaviors. According to adsorption and desorption results, sulcotrione presents a moderate affinity with soil components; however, its leaching capacity needs to be carefully assessed. Clay content seemed to be the most important factor influencing the adsorption capacity of each compound, whereas organic matter and pH had little influence. The soils were classified according to their adsorption capacity in the following decreasing order: Martinique, Belgium, Landes, Perpignan.     

1H nuclear magnetic resonance relaxometry study of water state in milk protein mixtures

1H NMR signal was used to characterize highly hydrated milk protein dispersions (3-20% dry matter) with various micellar casein concentrations (3-15%), whey protein concentrations (0-3%), lactose concentrations (0-7.5%), CaCl(2) concentrations (0-2 mM), and pH (6.2-6.6). The results showed the predominant effect of micellar casein concentration on water state and were consistent with the three-site relaxation model in the absence of lactose. The relaxation rates observed for these dispersions were explained by the free water relaxation rate, the hydration water relaxation rate, and the exchangeable proton relaxation rate. Hydration water was found to be mainly influenced by casein micelle concentration and structure. The variations in hydration with pH were consistent with those observed for classical measurement of voluminosity observed at this range of pH. The effects of lactose and whey protein content are discussed.