科研之友
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摘要
Small streams and rivulets in agricultural landscapes are among the most threatened habitats throughout Europe. Many species occurring primarily within these habitats are listed in the EC Habitats and Species Directive. One example is the damselfly Coenagrion ornatum, which was rediscovered during the last decade in the Elbe Valley (Czech Republic) after more than 40years. The occurrence of this species, however, was observed only at highly altered sites. Several management attempts, unfortunately, had led to the local extinction instead of strengthening of existing populations, precisely because they ignored the habitat preferences of the target species. This study analysed the effects of several physiochemical and environmental characteristics of 30 ditch segments in relation to the presence and abundance of C. ornatum. The occurrence of C. ornatum was found to be positively correlated with the diversity of macrophyte vegetation and negatively with shading. Populations of C. ornatum occurred mostly in smaller, well-warmed sections of channel, while the species clearly avoided those sections with gravel or concrete substrates. The results indicate that under certain circumstances, the ongoing utilisation of channels particularly for drainage accords with the objectives of protecting this species and could substitute for routine conservation management activities. Supplementary effective management should focus on removing overgrowing vegetation, eliminating such negative interventions to the channel as strengthening the stream bed, and encouraging the development of rich vegetation along the watercourses (e.g. by establishing buffers or overflows).
- 出版日期2015-3
