Modellstudien zur Nitratauswaschung unter beweidetem Grünland     

Hark Ketelsen  Jens Hansen  Ernst-Walter Reiche 《植物养料与土壤学杂志》1999,162(6):685-696

Modeling nitrate leaching from grazed pasture A method for estimating nitrate concentrations in seepage water under pastures using the model WASMOD was developed. Urin-N and dung-N input by grazing cattle was calculated as a function of stocking rate, length of grazing, and amounts of urin-N and dung-N excreted (data from literature). Urin-N was modeled as NH₄⁺-fertilizer, dung-N as fresh organic matter (C/N ratio 18.6:1). The model was tested using average stocking rates on pastures and mowing pastures inside the waterworks ‘Föhr-West’ catchment area and a long-term climate scenario (35 yr). The modeled average nitrate concentration (55.5 mg l⁻¹) agreed well with the average nitrate concentration measured in the public wells (59.5 mg l⁻¹). Model studies indicate that the nitrate concentrations in seepage water can be reduced by 40% if the cattle graze only 9 hours per day and no longer than until mid of September.  相似文献   

The incorporation of environmentally derived 87Sr/86Sr and Sr/Ca in early otolith formation of Chinook salmon     

Paul Chittaro  Jens Hegg  Abby Fuhrman  Devin Robichaux  Rothboury Doung  Brian Beckman  Chris Fisher  Jeff Vervoort  Brian Kennedy 《Ecology of Freshwater Fish》2023,32(1):107-119

Effective species management often requires understanding patterns of movement and habitat use. A common approach in identifying where individuals reside relies upon chemical tracers from the environment that are incorporated into an individual's tissues. For fish, isotopes in their otoliths, specifically the portion of their otolith formed during their larval stage, have been used to identify the natal origin. Complicating this work, however, is the fact that during this life stage, there is a shift in the source of isotopes deposited onto the growing otolith from maternally to environmentally derived. The objective of this study was to identify the portion of the otolith representing this transition to environmentally derived isotopes so as to accurately investigate questions of natal origin for a threatened population of fall Chinook salmon (Oncorhynchus tshawytscha). We exposed developing larvae to four treatments that differed in terms of their water strontium isotope ratio (⁸⁷Sr/⁸⁶Sr) and used change-point analysis of otolith ⁸⁷Sr/⁸⁶Sr and strontium to calcium ratio (Sr/Ca) to identify the otolith radius corresponding to the transition to environmentally derived isotopes. Our results indicated this transition occurred, on average, at 132 μm (⁸⁷Sr/⁸⁶Sr; ±50 μm standard deviation) and 127 μm (Sr/Ca; ±29 μm) from the otolith core, which corresponded to the developmental time between hatching and exogenous feeding. A substantial proportion of our otoliths (i.e., 61%) did not show convergence between otolith and water ⁸⁷Sr/⁸⁶Sr by the end of the 113-day experiment, which was likely due to the dietary contribution of marine-based feed. Therefore, we were unable to recommend an otolith radius to target for the purposes of reconstructing natal origin apart from being beyond approximately 130 μm.  相似文献   

Characterization of Durum Wheat Semolina by Means of a Rapid Shear‐Based Method     

Alessandra Marti  Cristina Cecchini  Maria Grazia D'Egidio  Jens Dreisoerner  Maria Ambrogina Pagani 《Cereal Chemistry》2014,91(6):542-547

A rapid shear‐based test (the GlutoPeak test, recently proposed by Brabender) was used to investigate gluten aggregation properties of durum wheat semolina and to relate them to pasta cooking behavior. Thirty semolina samples were characterized by means of the conventional approaches used for pasta‐quality prediction (protein content, gluten index, and alveographic indices). All samples were also analyzed by the GlutoPeak test, obtaining three parameters: maximum peak torque, maximum peak time, and area under the peak. The GlutoPeak indices were significantly correlated with protein content, gluten index, and W alveographic parameter. The cooking quality of pasta obtained from the 30 semolina samples was evaluated by sensory analysis in terms of stickiness, bulkiness, firmness, and overall quality. The GlutoPeak indices were significantly correlated with the sensorial parameters. In comparison with the alveographic test, which is presently the most used rheological approach for semolina characterization, GlutoPeak analysis presents some advantages represented by a smaller amount of sample (9 g), a shorter time (less than 5 min), and the possibility that untrained analysts can carry it out. In addition, following testing with larger sample numbers, the GlutoPeak test has the potential to be used instead of the gluten index as a rapid and reliable approach for medium‐quality semolina characterization.  相似文献