How to decrease the negative effects of medium intensity disturbances on arthropod communities

G Györffy,L Körmöczi

doi:10.5194/we-2-14-2001

Abstract

Abstract. One of the major goals in nature conservation practice is to optimise the timing or the method of treatments or both. We studied the response of the Auchenorrhyncha (Insecta: Homoptera) assemblage to annual mowing in three different locations along an elevation gradient of a mesic grassland. Several weeks after mowing, the total number of imagoes and larvae decreased considerably, and the relative abundance differences between populations at different elevations also decreased, reflecting the density dependent effect of this treatment. The rate of changes in species composition was greatest in the microhabitats with more comfortable microclimates, in the opposite direction of the alteration of abundance, perhaps interfering with the migration. By the next spring the fauna of the wettest habitat proved to be the most sensitive to mowing and the most different from the others. The overall similarity of the insect communities increased, i.e. the community-level biodiversity decreased due to homogenising effect of mowing. In a heteromorphous habitat, the variability of spatio-temporal dynamics of the populations makes it impossible to find either single optimal time or optimal rotation plan for treatment based on the habitat types. For this reason, we suggest mowing in stripes parallel to the elevation gradient, which would mean synchronous treatment of each microhabitat instead of randomly chosen patches, where the execution is problematic. It is easier to keep the ratio of treated to untreated areas at 50%. Stripes should be narrow enough to provide the possibility of migration to favourable habitat patches, and should not hinder mechanical mowing. Suggested width of stripes is 10–15 m for Auchenorrhyncha.

Highlights

One of the major goals in nature conservation practice is to optimise the timing or the method of treatments or both
Nature conservation is dominated by concepts that originated from agriculture or other unsuitable sources (Morris and Plant 1983), instead of those which consider the ecological demands of many different plant and animal species (Morris 1982)
We analysed the 1990 samples to learn how the chosen insect group is connected to the habitat variability, what its spatio-temporal dynamics are, and whether there is a period where mowing has less of a negative effect

Summary

Introduction

One of the major goals in nature conservation practice is to optimise the timing or the method of treatments or both. The variability of spatio-temporal dynamics of the populations makes it impossible to find either single optimal time or optimal rotation plan for treatment based on the habitat types For this reason, we suggest mowing in stripes parallel to the elevation gradient, which would mean synchronous treatment of each microhabitat instead of randomly chosen patches, where the execution is problematic. Different kinds of treatments (e.g. mowing) for nature conservation are often applied to prevent the undesirable successional changes (e.g. forestation of a grassland) of certain communities. It is necessary to optimise the timing of treatments so that the members of certain ecological communities suffer the smallest negative effect possible, while still fulfilling the original goals. Our aims were to determine the effects of annual mowing on insect communities and, according to the results, to give recommendations for the optimal method of treatment

Objectives

Methods

Results

Conclusion