里海地区:环境的改变

人类活动严重地改变了里海地区的生态系统,最主要的影响是引起了生态系统中水流的改变和水质的恶化.地区环境的改变已经影响到了这一地区经济的发展,对鱼类资源的影响尤其明显.专家们利用GIwA计划中得出的一套方法,对这一地区共享水域中最重要的跨边界问题进行了评估.本报告关注促使这一地区环境改变的最重要的根本原因:生境和生物群落的改变.     

Risk factors associated with transcervical CVS losses

Factors found to be associated with pregnancy loss after transcervical CVS were race (higher for non-white), history of spontaneous abortion, unplanned pregnancy, history of spotting or bleeding during the pregnancy prior to CVS, and placental position (higher for fundal or lateral locations). Whether the increase in loss risk is due to the factor, per se, or the factor plus the CVS cannot be determined due to the lack of appropriate control data.     

Diversity of cereal aphid parasitoids in simple and complex landscapes

Structurally complex landscapes may enhance local species richness and interactions, which is possibly due to a higher species pool in complex landscapes. This hypothesis was tested using cereal aphid parasitoids (Hymenoptera, Aphidiidae) by comparing 12 winter wheat fields in structurally complex landscapes (>50% semi-natural habitats; n = 6) and structurally simple landscapes dominated by agricultural lands (>80% arable land; n = 6). Surprisingly, landscape structural complexity had no effect on aphid parasitoid species diversity. In complex landscapes 12 and in simple landscapes 11 species were found; 9 species occurred in both landscape types. Hence, arable fields in high-intensity agricultural landscapes with little non-crop area can support a similar diversity of cereal aphid parasitoids as structurally complex landscapes. This finding suggests that cereal aphid parasitoids may find necessary resources even in simple landscapes, making generalisations concerning the relationship between landscape composition and biodiversity in arable fields difficult.     

Reizgröße und Reizreaktion im Pflanzenreich

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