Spatial distribution of Coleoptera species on exposed riverine sediments (ERS) along the small river Mjöån with suggestions for management practices to increase biodiversity

Abstract

From the sandy shores of Mjöå river in Southern Sweden beetles were collected from eight sites during one season, using both pitfall traps and splashing combined with hand picking. Altogether 508 individuals from 53 species were registered. Soil samples were taken from each spot to analyse organic content, distribution of grain size fractions and density of mineral soil. The eight spots differed concerning soil properties. Among a selection of twelve species, compared by using data from collection by splashing method, both PCA and cluster analysis revealed differences in beetle assemblages. The most obvious pattern was a discrepancy between digging and non-digging species. The differences are believed to at least partly be caused by differences in proportion of the smallest grain fraction (< 0,125 mm) with a negative correlation between number of individuals of Dyschirius thoracicus and the proportion of fraction < 0,125 mm grains. The results show that the species have different abiotic preferences. Since the total area of available shores are rather small, and added to that a differentiation in microhabitats, the favourable conditions for each species is even smaller. To possibly extend the area for ERS species, enhancing erosion of the brinks by cattle grazing and/or removal of root systems from trees growing along the river
could be tried.