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41.
Marcel Riedo Dimitrios Gyalistras † reas Fischlin‡ JürG. Fuhrer 《Global Change Biology》1999,5(2):213-223
Local effects of climate change (CC) and elevated CO2 (2 × CO2, 660 μmol mol–1) on managed temperate grasslands were assessed by forcing a dynamic ecosystem model with weather scenarios. The aims of the study were to compare the relative importance of individual and combined effects of CC, 2 × CO2, and photosynthetic acclimation, and to assess the importance of local site conditions. The model was driven by hourly means for temperature (T), precipitation (P), global radiation (G), vapour pressure (VP), and wind speed (U). Local climate scenarios were derived by statistical downscaling techniques from a 2 × CO2 simulation with the General Circulation Model of the Canadian Climate Centre (CCC-GCMII). Simulations over 14 growing seasons to account for year-to-year variability of climate were carried out for a low, relatively dry site, and a high, more humid site. At both sites, shoot dry matter responded positively to 2 × CO2 with the site at low elevation being more sensitive than the higher site. The effect of assumed changes in climate was negative at the lower, but positive at the higher site. Shoot dry matter was more sensitive to the effects of 2 × CO2 than to CC. Both effects combined increased shoot dry matter by up to 20%. This was attributed to direct effects of 2 × CO2 and increased T, and indirect stimulation via increased soil N availability. Biomass partitioning to roots increased with 2 × CO2 but decreased with CC, while an intermediate response resulted from the combination. Leaf area index (LAI) increased under 2 × CO2, but not enough to compensate fully for a decrease in leaf conductance. Under the 2 × CO2 scenario evapotranspiration (ET) decreased, but increased under CC. Photosynthetic acclimation reduced the effect of 2 × CO2 on shoot growth, but had little effect on ET. The seasonal water use efficiency (WUE) was improved under 2 × CO2, and reduced under CC. With the combination of both factors, the change was small but still positive, especially at the high elevation site with more favourable soil water conditions. This reflects the stronger positive yield response in combination with a smaller increase in ET under cooler, more humid conditions. The results for the combination of factors suggest that except for shoot growth, effects of 2 × CO2 and CC tend to offset each other. While CC determines the sign of the ET response, the sign of the biomass response is determined by 2 × CO2. The results highlight the importance of a site-specific analysis of ecosystem responses by using a flexible approach based on a combination of state-of-the-art downscaling, spatially resolved data sets, and a mechanistic model to obtain quantitative and reproducible assessments of climate change impacts at the ecosystem level. 相似文献
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K.-Peter Stahmann Herbert N. Arst Jr Henning Althöfer José Luis Revuelta Nicole Monschau Christina Schlüpen Cornelia Gätgens reas Wiesenburg Thomas Schlösser 《Environmental microbiology》2001,3(9):545-550
Riboflavin (vitamin B2 ), essential in tiny amounts as a precursor for oxidoreductase coenzymes, is a yellow pigment. Although it causes cytotoxicity via photoinduced damage of macromolecules, several microorganisms are striking overproducers. A question, unanswered for decades, is whether riboflavin overproducers can benefit from this property. Here, we report an ultraviolet (UV) protective effect of riboflavin. The spores of Ashbya gossypii , a riboflavin-overproducing fungus, are more sensitive to UV than those of Aspergillus nidulans . The addition of riboflavin to suspensions improves the UV resistance of both spore types. Interestingly, we show that regulation of sporulation and riboflavin overproduction in A. gossypii are linked. In batch culture, both were elevated when growth ceased. At constant growth rates, obtained in a chemostat culture, neither was elevated. Supplementation of cultures by cAMP, a known stress signal, negatively affected sporulation as well as riboflavin overproduction, establishing a second, independent argument for the linkage. 相似文献
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Local and regional assessments of the impacts of plant invaders on vegetation structure and soil properties of Mediterranean islands 总被引:7,自引:0,他引:7
Montserrat Vilà Marc Tessier Carey M. Suehs Giuseppe Brundu Luisa Carta Alexandros Galanidis Philip Lambdon Manuela Manca Frédéric Médail Eva Moragues Anna Traveset reas Y. Troumbis Philip E. Hulme 《Journal of Biogeography》2006,33(5):853-861
Aims Although biological invasions occur throughout the world, and some invaders are widespread in many habitats, few studies on the ecological impact of invaders have examined multiple sites. We tested how the impact of three widespread plant invaders changed depending on the identity of the species and the invaded island. We also tested whether relative species loss was lower in species‐rich communities than in species‐poor ones. Location We conducted floristic surveys and soil analyses in eight Mediterranean Basin islands: Crete and Lesbos (Greece), Sardinia (Italy), Corsica, Bagaud and Porquerolles (France), and Mallorca and Menorca (Spain). Methods We compared native species richness and diversity, proportion of life forms, soil percentage nitrogen, percentage organic carbon, C/N, and soil pH in nearby paired plots of 2 × 2 m: one control and one invaded by either the deciduous tree Ailanthus altissima, the succulent subshrubs Carpobrotus spp. or the annual geophyte Oxalis pes‐caprae, across eight Mediterranean Basin islands. Results On average, the presence of invaders reduced species diversity, Carpobrotus spp. exhibiting the largest impact and Oxalis the least. However, the relative impact was island‐dependent, and was positively but weakly associated with the species richness of the recipient community. Therophytes were the life form that experienced the largest decrease across islands. The effects of invasion on soil properties were very variable. Total N changed (increased) only in plots invaded by Ailanthus, significantly decreasing the C/N ratio. The presence of this tree increased soil pH, whereas the opposite was found in plots invaded by the other two species. Organic C increased in plots invaded by Ailanthus and Carpobrotus species. Main conclusions By conducting an analysis at multiple sites, we found that the three plant invaders had an impact on plant community structure not entirely concordant with changes in soil properties. The impacts depended on the identity of the species and of the invaded island, suggesting that impact of invaders is context‐specific. The impact in terms of species loss was not lower in species‐rich than in species‐poor communities. 相似文献
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Altered protein expression pattern in colon tissue of mice upon supplementation with distinct selenium compounds
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Jette Rahn Claudia Lennicke Anna P. Kipp Andreas S. Müller Ludger A. Wessjohann Rudolf Lichtenfels Barbara Seliger 《Proteomics》2017,17(11)
The essential trace element selenium (Se) is controversially discussed concerning its role in health and disease. Its various physiological functions are largely mediated by Se incorporation in the catalytic center of selenoproteins. In order to gain insights into the impact of Se deficiency and of supplementation with different Se compounds (selenite, selenate, selenomethionine) at defined concentrations (recommended, 150 μg/kg diet; excessive, 750 μg/kg diet) in murine colon tissues, a 20‐week feeding experiment was performed followed by analysis of the protein expression pattern of colon tissue specimens by 2D‐DIGE and MALDI‐TOF MS. Using this approach, 24 protein spots were identified to be significantly regulated by the different Se compounds. These included the antioxidant enzyme peroxiredoxin‐5 (PRDX5), proteins with binding capabilities, such as cofilin‐1 (COF1), calmodulin, and annexin A2 (ANXA2), and proteins involved in catalytic processes, such as 6‐phosphogluconate dehydrogenase (6PGD). Furthermore, the Se compounds demonstrated a differential impact on the expression of the identified proteins. Selected target structures were validated by qPCR and Western blot which mainly confirmed the proteomic profiling data. Thus, novel Se‐regulated proteins in colon tissues have been identified, which expand our understanding of the physiologic role of Se in colon tissue. 相似文献
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Eduardo N Taboada Joanne M MacKinnon Christian C Luebbert Victor PJ Gannon John HE Nash Kris Rahn 《BMC evolutionary biology》2008,8(1):229