Symbiotic N<Subscript>2</Subscript> fixation and nitrate utilisation in irrigated lucerne (<Emphasis Type="Italic">Medicago sativa</Emphasis>) systems     

Huimin Yang  Murray Unkovich  Ann McNeill  Xianzhi Wang 《Biology and Fertility of Soils》2011,47(4):377-385

Symbiotic N₂ fixation by lucerne (Medicago sativa) has capacity to provide significant inputs of N to agro-ecosystems, and the species has also been shown to scavenge soil mineral N and thus act as a sink for excess reactive N. The balance between these two N cycle processes was investigated in an extensive irrigated lucerne growing region where nitrate contamination of groundwater has been reported. We sampled 18 permanent pure lucerne stands under irrigation for standing dry matter, total shoot N, and N₂ fixation using ¹⁵N natural abundance along with activity of the inducible enzyme nitrate reductase as indicators of use of soil NO₃⁻ by lucerne. On average 65% of lucerne N was obtained from symbiotic N₂ fixation. Converting standing dry matter estimates to annual N₂ fixation amounts we calculated average N₂ fixation of 311 kg N/ha, including N in roots and nodules. Uptake of N from soil by lucerne was calculated to be 181 kg N/ha/year. We were not able to identify the source of this soil mineral N, although nitrate reductase activity of lucerne was higher than that of non-N₂ fixing species examined.  相似文献   

Food resources and cyprinid diet in permanent and temporary Mediterranean rivers with natural and regulated flow          下载免费PDF全文

Carlos M. Alexandre  Sabrina Sales  Maria Teresa Ferreira  Pedro R. Almeida 《Ecology of Freshwater Fish》2015,24(4):629-645

This study addresses the differences in food availability, diet and feeding activity of the Iberian barbel, between permanent and temporary nonregulated rivers, and the effect of flow regulation on feeding parameters. A total of 267 adult barbels were seasonally collected in four nonregulated and regulated rivers from permanent and temporary basins, and their gut content was analysed. Locally available food sources were evaluated across sites and seasons. Barbels from the permanent nonregulated river exhibit a more variable and diversified diet in which invertebrates assumed a large importance, especially during high flows. Barbels from the temporary nonregulated river presented a more uniform diet composed of plant material and detritus, particularly in drought seasons. Flow regulation affected different flow components in both systems, but the effects on food resources and barbels' diet were similar, resulting in an intra‐annual stabilisation of resource availability and fish diet, with a higher consumption of plants and detritus. Changes in fish diet and feeding activity in both nonregulated and regulated rivers were strongly associated with the seasonal variability of streamflow components, particularly between low‐ and high‐flow periods, and with the reduction in flow variability in the case of dam regulation. Results from this study can be used to improve guidelines for flow requirement implementation.  相似文献   

Digestive system development and study of acid and alkaline protease digestive capacities using biochemical and molecular approaches in totoaba (Totoaba macdonaldi) larvae     

Mario A. Galaviz  Lus M. López  Alejandra García Gasca  Carlos Alfonso Álvarez González  Conal D. True  Enric Gisbert 《Fish physiology and biochemistry》2015,41(5):1117-1130

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E. Melanie DuPuis: Nature’s perfect food: how milk became America’s drink     

Evan Perrault 《Agriculture and Human Values》2011,28(4):583-584

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Books received     

Carol J. Pierce Colfer 《Agriculture and Human Values》2011,28(4):589-590

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Performance evaluation of forest co-management: a case study of Chunati Wildlife Sanctuary,Bangladesh     

Umma Tamima 《林业研究》2016,27(4):853-861

The objective was to evaluate the performance of the co-management of Nishorgo Support Project at Chunati Wildlife Sanctuary in Bangladesh. I adopted the Focus Groups Discussion method for opinion survey and applied the SWOTAHP technique for data analysis. Local people did not participate in the decision-making process of forest management and they perceived co-management as a threat to their livelihoods. Moreover, mistrust and misunderstanding among different stakeholders, political and ethical conflicts, lack of property rights of tribal communities, and lack of accountability and transparency were identified as the drawbacks of co-management.  相似文献   

Molecular cytogenetic identification and phenotypic description of a new synthetic amphiploid,Triticum timococcum (AtAtGGAmAm)     

Péter Mikó  Mária Megyeri  András Farkas  István Molnár  Márta Molnár-Láng 《Genetic Resources and Crop Evolution》2015,62(1):55-66

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Jody Emel and Harvey Neo: Political ecologies of meat     

Heide K. Bruckner 《Agriculture and Human Values》2016,33(3):739-740

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Brian K. Obach: Organic struggle: the movement for sustainable agriculture in the United States     

Kelly Yearick 《Agriculture and Human Values》2017,34(2):505-506

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A.D. McIntyre (ed): Life in the world’s oceans—diversity,distribution and abundance     

Malcolm Jobling 《Aquaculture International》2011,19(3):597-598

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