Effects of grazing on orthopteran assemblages of Central-European sand grasslands

Zoltan Kenyeres

doi:10.3897/jor.27.15033

Abstract

The effect of grazing on Orthoptera assemblages has long been the focus of research worldwide due to the high sensitivity of orthopterans to changes in vegetation structure. According to previous studies, grazing has individual, spatially-different effects on orthopteran assemblages. The current case study was carried out between 2012 and 2016 in a subarea dominated by open sandy grasslands in the Carpathian Basin. The ~70 ha study area was grazed by 250–300 sheep in 2012. In the beginning of 2014, the overgrazing pressure was overall reduced, for the most part, in the examined grassland patches. The study aimed to answer how the complete abandonment of grazing and moderate grazing influences the species richness, diversity and density of the orthopteran assemblages. Investigations in Central European sand steppes confirmed that both intense grazing and the abandonment of grazing have a detrimental effect on the structure of orthopteran assemblages: (a) the Shannon diversity index was higher on moderately grazed sites than on grazed and ungrazed ones; (b) the number of habitat specialists of sandy grasslands was higher on moderately grazed patches than in grazed habitats; and (c) the frequency of geophilic species was higher on grazed patches than on moderately grazed and grazing-abandoned ones.

Highlights

The structure of habitats and their insect communities exposed to direct and indirect human impact usually can be considered a transient state (Pickett et al 1992)
The most prevalent species was Calliptamus barbarus with 580 individuals (24%), followed by Acrida ungarica with 514 individuals (19%), Euchorthippus declivus (Brisout de Barneville) with 302 individuals (11%), Oedaleus decorus with 279 individuals (10%), Oedipoda caerulescens (Linnaeus) with 210 individuals (8%), Myrmeleotettix maculatus with 185 individuals (7%), Dociostaurus brevicollis with 117 individuals (4%), Euchorthippus pulvinatus with 54 individuals (2%) and Omocestus petraeus (Brisout de Barneville) with 52 individuals (2%)
Grazing intensity or abandonment of grazing has a detrimental effect on the structure of orthopteran assemblages (Kruess and Tscharntke 2002, WallisDeVries et al 2007, Eschen et al 2012)

Summary

Introduction

The structure of habitats and their insect communities exposed to direct and indirect human impact usually can be considered a transient state (Pickett et al 1992) This phenomenon can be well observed in grazed grasslands where current vegetation structure, as a background factor to the insect communities, is highly influenced by the intensity, spatial and temporal characteristics and abandonment of grazing (Carboni et al 2015, Török et al 2016). In addition to the favorable changes for the vegetation-dependent insect communities, the abandonment of grazing can cause the invasion of weeds in the grasslands (Sedláková and Fiala 2001) This usually greatly decreases the presence of rare and threatened Orthoptera (Fonderflick et al 2014). In the habitats grazed traditionally, the maintenance of extensive grazing is a prerequisite for preserving biodiversity (Dolek and Geyer 2002) and seems to be far more suitable than mowing (Weiss et al 2013)

Methods

Results

Conclusion