Age of grassy strips influences biodiversity of ground beetles in organic agro-ecosystems

Ulrich Irmler,Mazhar Ranjha

doi:10.4236/as.2013.45030

Abstract

The following investigations were conducted to evaluate grassy strips of different age for organic arable fields. From September 2009 to October 2010, adult ground beetles were sampled by pitfall traps in three grassy strips (2, 4, and 9 years old), their adjacent cropping areas, their field edges, and a control field (age 0) in Schleswig-Holstein, northern Germany. Carabid assemblages were similar among the fields, strips and edges. Grassy strips and edges had higher species richness and lower activity density than the control field. Activity density increased with increasing distance from the field edge in grassy strips and in the adjacent fields. In cropping areas, species richness andShannon’s H increased with increasing age of strips, whereas evenness and activity density decreased with increasing distance from the field edges. Compared to carnivorous and phytophagous carbides, omnivorous species were affected less by age of strips and distance from field margins. In the strips, species richness of the dominant species increased with age and decreased with distance, but the effect of strip age on species richness was still found in more than150 mfrom the margin. A positive effect of the age of grassy strips on species richness was found for cropping fields, grassy strips and field edges. Old grassy strips also exerted greater influence on the species richness and biodiversity of the adjacent arable fields than the younger strips.

Highlights

The following investigations were conducted to evaluate grassy strips of different age for organic arable fields
Species richness and Shannon’s H increased with increasing age of strips, whereas evenness and activity density decreased with increasing distance from the field edges
In the Detrended Correspondence Analysis (DCA), the traps of the cropping areas, strips, and field edges of each of the three fields and of the control field were combined into one sample

Summary

INTRODUCTION

The following investigations were conducted to evaluate grassy strips of different age for organic arable fields. Among the soil-dwelling predators, the ground beetles (Carabidae) are used as biological indicators because of their diversity, well-known ecology and taxonomy, sensitivity to biotic and abiotic factors, relevance at multiple spatial scales and their ample collection without difficulty for analysis [10] They consume weed seeds [11], prey on pests [12], and have an integral position in the food web [13]. 3) Do older grassy strips support biodiversity better than the younger ones and 4) can we predict the combined effects of age and distance on the species richness in grassy strips and adjacent fields? The following questions should be answered: 1) have grassy strips beneficial effects on carabids in organic farming? 2) Does biodiversity change with the distance from field edges? 3) Do older grassy strips support biodiversity better than the younger ones and 4) can we predict the combined effects of age and distance on the species richness in grassy strips and adjacent fields?

Design

Data Analysis

Faunal Composition and Assemblages

Effect of Distance and Age of Grassy

DISCUSSION