Distribution and spatial autocorrelation of carabid species in differently-treated post-agricultural areas

<p>The distribution of carabid beetles in a landscape composed of forests and differently treated post-agricultural open fields was studied over the four years period from 2004 to 2007. The area was investigated using a net of pitfall traps with a distance of 100 m between the traps in east-west direction and about 50 m in north-south direction. Five species, which were collected with more than 1000 individuals (Calathus erratus, Calathus fuscipes, Harpalus rubripes, Harpalus tardus, Poecilus versicolor), were selected for further research. Preliminary analyses of the data have shown that the species react sensitively on the different treatments of the ground. However, data were pooled over the four years of study and the spatial pattern based on the single sampling plots has not been analysed yet.</p><p>In the present paper I analyse the spatial distribution patterns of the selected species for the single study years as well as for the pooled data collected over the four years. Geary&#x2019;s C indem of spatial autocorrelation was used to assess the degree of aggregation of the species in defined parts of the study area. As expected due to the preliminary studies, Calathus erratus and Poecilus versicolor showed generally strong spatial autocorrelations and Harpalus tardus showed weak spatial autocorrelations. Calathus fuscipes showed also strong spatial autocorrelations for the single years, but for the pooled data it was slightly below the expectations, suggesting variation in spatial aggregation between the years. An unexpected strong spatial autocorrelation was calculated for Harpalus rubripes when analysing the pooled data. However, this species showed high fluctuations in spatial autocorrelation between the sampling years, with a particular strong spatial autocorrelation calculated for 2006. Since the highest number of individuals of Harpalus rubripes was recorded in this year, this result may have influenced the calculated spatial autocorrelation for the pooled data. The results lead to the conclusion that the connection of individual species to specific habitat types may be differently pronounced between different years. This might be useful with respect to work out indicatory values of species for environmental monitoring.</p>