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21.
S. Claassens P. J. Jansen Van Rensburg L. Van Rensburg 《Water, air, and soil pollution》2006,174(1-4):355-366
Assessment of soil microbial diversity, in terms of the actively growing population, may be a sensitive indicator of ecological stress and restoration processes. During this study, the relationship between microbial community structure; vegetation cover; and physical and chemical characteristics of topsoil covers at seven coal discard rehabilitation sites in South Africa were evaluated. A positive association was observed between the microbial biomass, vegetation cover and the organic carbon, ammonium, nitrate and phosphorus contents. Although the seven coal discard sites had different rehabilitation ages (1–8 years), there was no statistically significant difference between these sites based on physical and chemical characteristics. The various rehabilitation sites could be differentiated based on the microbial community structure. The Hendrina site was characterised by the highest viable biomass, monounsaturated fatty acids, and high ground cover. Bethal and Ermelo sites were the youngest sites (1 and 3 years) in terms rehabilitation age. Both these sites were associated with higher abundances of fungi and Actinomycetes than the other sites. Ratios of trans- to cis-monoenoic fatty acids and cyclopropyl fatty acids to their monoenoic precursors indicated stress in all sites sampled. 相似文献
22.
Interactions with dissolved organic matter (DOM) are generally believed to play a crucial role in the translocation of Al and Fe in acid sandy soils. Binding of Al and Fe to DOM affects their mobility in soils by altering sorption equilibria of charged sites on solid soil material, inducing precipitation of organo‐metallic complexes and preventing the formation of inorganic Al and Fe phases. The relative importance of the different processes, especially with respect to the translocation of Al, Fe and organic matter in podzols, remains unresolved. We determined the effect of the presence of solid soil material from the eluvial (AhE and AE, respectively) horizons of a Fimic Anthrosol and a Haplic Podzol on the metal‐to‐organic carbon (M/C) ratio in solution and the formation of dissolved organic Al and Fe complexes. Furthermore, we assessed the resulting influence on the mobilization of Al, Fe and DOM. Even under considerable metal loading, the M/C ratios and ‘free’ metal fractions in solution remained low and relatively constant, due to an apparent buffering by the solid phase and the formation of organo‐metal complexes in solution. The M/C ratios remained so low that significant precipitation of organo‐metal complexes due to saturation with metals was not found. The apparent buffering by the solid phase can be explained by a strong release of organic matter from solid soil material and adsorption of non‐complexed Al and Fe on solid organic matter upon metal addition. Adsorption of organo‐metal complexes most likely played only a minor role. The observations confirm the expected mobilization of Al, Fe and DOM in eluvial horizons and seem to indicate that even under fluctuating input of Al, Fe and DOM the soil solution will have a constant composition with respect to M/C ratios and percentage of Al and Fe present in dissolved organo‐metal complexes. 相似文献
23.
Nonsurgical videolaparoscopy for determination of reproductive status of the Arctic charr. 总被引:2,自引:0,他引:2 下载免费PDF全文
A I Ortenburger M E Jansen S K Whyte 《The Canadian veterinary journal. La revue veterinaire canadienne》1996,37(2):96-100
The efficient commercial production of Arctic charr is hampered by the limited and subtle sexual dimorphism shown by this species. This project examined the feasibility of low-cost videoendoscopy through the genital pore to determine sex, stage of maturity, and safety for 80, randomly selected, anesthetized Arctic charr. The sensitivity and specificity for correct assignment of male sex were 90% and 100%, respectively, among 3 observers in a single-blind design. Sensitivity and specificity for relative sexual maturity in the same fish were 96% and 54%, respectively. The observed mortality rate of 7% at the end of 3 weeks was confounded by the presence of unrelated disease. We conclude that the technique holds promise for application by producers to improve production efficiency. 相似文献
24.
J Jansen 《The Veterinary quarterly》1987,9(2):97-102
The trichostrongylid and strongylid egg output in a group of ewes lambing in March, the middle of the usual lambing time in the Netherlands, was compared with counts in groups of older ewes and yearling ewes lambing in May-June and with counts in a group of barren ewes. The groups lambing in March showed only a rise related to parturition date as normally seen in the Netherlands. A few of the late lambing ewes showed a slight rise in spring, but all of them showed a peri-parturient rise related to parturition date. In the late lambing ewes and in the barren ewes egg counts due to reinfection were seen in summer. It is concluded that under the present circumstances a true spring rise, the calendar phenomenon, occurs very irregularly, while a peri-parturient rise related to the parturition date is a common phenomenon. The occurence of high egg counts in summer, excluding consideration on the barren ewes, in the late lambing ewes only, suggests that changing the traditional husbandry system may influence the epidemiological pattern of the trichostrongylid infections. 相似文献
25.
RW Mitten 《Australian veterinary journal》1992,69(6):139-139
ECG Interpretation in Dogs and Cats, Video produced by Provet for the Unit of Veterinary Continuing Education of the Royal Veterinary College 相似文献
26.
An infection with second-stage larvae of the warble-fly H. diana in a horse is described. The second-stage larvae were incapable of developing into the third stage, because horses are unsuitable hosts and because the infected horse was treated with an insecticide. Since the horse was used for dragging trees in the forests, the infection was likely contracted via contact with H. diana, a normal parasite of roe deer in the Netherlands. 相似文献
27.
Paulo MJ van der Voet H Jansen MJ ter Braak CJ van Klaveren JD 《Pest management science》2005,61(8):759-766
Risk assessment of pesticides can be a statistically difficult problem because pesticides occur only occasionally, but they may occur on multiple components in the diet. A Bayesian statistical model is presented which incorporates multivariate modelling of food consumption and modelling of pesticide measurements which are for a large part below a measurement threshold. It is shown that Bayesian modelling is feasible for a limited number of food components, and that in a data-rich situation the model compares well with an empirical Monte Carlo modelling. 相似文献
28.
Retained foetal membranes in dairy herds in the Huntly district 总被引:4,自引:0,他引:4
K Moller P E Newling H J Robson G J Jansen J A Meursinge M G Cooper 《New Zealand veterinary journal》1967,15(7):111-116
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