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  • Author or Editor: W. Zalewski x
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When evaluating the effects of yeast culture (Saccharomyces cerevisiae1026) supplied with or without a vitamin premix and mineral bioplexes on some intermediates and end-products involved in the synthesis of milk constituents in 30 early-lactation Black and White Lowland cows, no significant differences were found in the glucose level, mineral contents and enzyme activities of the blood serum. The effect of yeast culture on the availability of minerals for milk synthesis depended upon the dynamics of degradation of mineral bioplexes in the rumen and the cows' mineral status. The insignificant increase found in blood total protein content and the simultaneous small differences in blood urea nitrogen (BUN) and milk urea nitrogen (MUN) values in cows supplied with the yeast culture were probably associated with a high ammonia incorporation into microbial protein in the rumen, which increased protein supply for milk protein synthesis and decreased the nitrogen loss.

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The question whether and to what degree urbanization causes a decrease in diversity of animal and plant species and changes in community structure is still a matter of debate. While many studies used ground beetles, vertebrates, and butterflies as assumed model taxa, little work has been done with other, particularly insect, taxa. Here we report on rural and urban diversities of communities of carcass visiting destruent and predatory beetles (Coleoptera). From 8 rural and 2 city sites, we sampled 15323 destruent beetles representing 58 species and 1871 predators from 43 species. We observed a reduced diversity and changes in community structure of both beetle guilds towards the city. However, these changes were guild specific and our study gives no evidence that there are simple rules that govern rural and urban patterns of diversity. Species abundance distributions did not significantly differ between the study sites. There is also no evidence that the intermediate disturbance hypothesis might apply. Lastly, we found only little support for a homogenizing effect of urban environments on carrion visiting beetles.

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The impact of disturbance on animal and plant assemblages has been described mainly in terms of aggregate community properties like species richness, abundance, or productivity. However, the question how disturbance acts on species interactions, particularly on patterns of co-occurrence, has received much less attention. Here we use a large pitfall trap sample of spiders from two complexes of lake islands in Northern Poland to show how disturbance by tourist visits affects species richness, composition and co-occurrence. On the pristine and protected islands of Lake Wigry, species co-occurrence was significantly segregated. Further, island species richness and abundances could be predicted from environmental correlates, particularly from island area, soil fertility and humidity. In turn, on the lake islands that are frequently visited by tourists, species co-occurrences were random and environmental correlates other than island area failed to predict species richness and abundances. However, species composition, α-, β-, and γ-diversities, as well as average local spider abundances did not significantly differ between both island complexes. Our results show that disturbance disassembles the structure of spider communities prior to visible richness and abundance effects. This result has implications for biological conservation. The detection of community disassembly might be an early sign for factors that act negatively on ecosystem functioning.

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