ALBERT

Description:    The impact of different land-use types on species is traditionally estimated by correlating landscape proportions recorded in buffer areas around focal points with species data observed at these sites. If a high proportion of a specific land-use type exists within a small radius, it will be accumulated in larger buffers and may confound the interpretation at larger scales. We sampled freshwater invertebrates in ten streams using cages with artificial substrate and compared the effects of arable land proportions calculated in disc-shaped buffers of increasing radius versus areas calculated from non-overlapping rings of increasing radius. We hypothesize that (1) the accumulative disc-based approach leads to confounding effects across increasing buffer size and that (2) the use of ring-based methods facilitates the identification of relevant scales for conservation measures. The abundance of crustaceans showed a positive relationship with arable land proportions, but Plecoptera abundance and the taxonomic richness of Ephemeroptera and Plecoptera decreased with increasing arable land proportions in the surrounding landscape. Our results further support the presence of confounding effects in disc-based analyses, as correlations between arable land proportions and Crustacea, or Plecoptera, respectively, were affected by the accumulation of small-scale area proportions. The distance at which arable land proportions significantly affected benthic fauna in freshwater streams was consistently shorter if calculated from rings rather than from discs. Although an a priori definition of ring width introduces new challenges, a combined use of disc- and ring-based techniques for the estimation of land-use effects may substantially improve the realization of conservation and protection measures in terrestrial and aquatic systems. Content Type Journal Article Pages 1-6 DOI 10.1007/s10452-011-9358-8 Authors Christine Schneider, Department of Animal Ecology, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany Klemens Ekschmitt, Department of Animal Ecology, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany Volkmar Wolters, Department of Animal Ecology, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany Klaus Birkhofer, Department of Animal Ecology, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany Journal Aquatic Ecology Online ISSN 1573-5125 Print ISSN 1386-2588