Ecological Indicators 20 (2012) 337–344 Contents lists available at SciVerse ScienceDirect Ecological Indicators jo urnal homepage: www.elsevier.com/locate/ecolind Orthoptera as ecological indicators for succession in steppe grassland ∗ Thomas Fartmann , Benjamin Krämer, Friederike Stelzner, Dominik Poniatowski Department of Ecology, Institute of Landscape Ecology, University of Münster, Robert-Koch-Straße 28, 48149 Münster, Germany a r t i c l e i n f o a b s t r a c t Article history: Understanding the effects of land-use on threatened ecosystems is of special relevance for nature con- Received 9 January 2012 servation. The aim of our study was to use Orthoptera as ecological indicators for succession in Central Received in revised form 23 February 2012 European steppe grasslands. Accepted 1 March 2012 Orthoptera showed a clear response to succession. Each successional stage harboured a unique assem- blage. Species richness of habitat specialists was highest in the earliest seral stages. In contrast, density Keywords: of all species peaked at the intermediate successional stage. Early successional stages are mostly likely Abandonment to be preferred by specialized Orthoptera because they provide warm suitable oviposition sites (bare Global change Grasshopper ground) and microclimatic conditions. The density peak in the mid-successional stage probably reflects a Grazing trade-off between favourable ambient temperatures for optimal development, sufficient food and shelter Habitat management against predators. Species richness Although all successional stages of steppe grassland are relevant for conservation, early and mid- successional stages are the most important. Consequently, conservation management should aim at re- introduction of a traditional, low-intensive land use for abandoned steppe grasslands. As an optimal land use, we recommend traditional rough grazing with sheep and goats, which creates a heterogeneous habitat structure with bare ground, and avoids the accumulation of litter, favouring Orthoptera. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Orthoptera appear to be suitable model organisms to monitor the effects of global-change on steppe ecosystems (cf. Poniatowski Grasslands are among the dominant habitat types throughout and Fartmann, 2008): (i) they are highly sensitive to environ- Europe, accounting for almost a quarter of the total EU-25 land mental changes such as grazing and abandonment (Kruess and surface (EEA, 2005). Semi-natural grasslands in particular harbour Tscharntke, 2002a; Marini et al., 2009, 2010; Schirmel et al., 2010b); high numbers of plant and animal species and are therefore of and (ii) orthopterans are key organisms in grassland ecosystems, high nature conservation value (Veen et al., 2009). However, area as they are the main arthropod consumers (Curry, 1994) and food and biodiversity of these grasslands have considerably decreased source for vertebrates (e.g. birds or lizards) (Belovsky and Slade, across Europe during recent decades (Stoate et al., 2009; Watt et al., 1993). 2007). Land-use changes are assumed to be the major driver of this Habitat selection in Orthoptera depends on a complex combi- development (Chapin et al., 2000; Sala et al., 2000). Agricultural nation of different and often interrelated environmental factors intensification and abandonment have especially been identified as (see review in Ingrisch and Köhler, 1998). The main determi- the main reasons for the strong decline of species-rich grasslands nants are vegetation structure (Gardiner et al., 2002; Poniatowski since the 1950s (Stoate et al., 2009; Van Dijk, 1991). and Fartmann, 2008) and microclimate (Gardiner and Dover, Among semi-natural grasslands, steppes belong to the most 2008; Willott and Hassall, 1998). Predation and food availabil- species-rich habitat types (Cremene et al., 2005). At their north- ity are partly interrelated with the aforementioned parameters, western range limit in Central Europe, steppes are restricted to and may also be important, particularly in sparsely vege- extraordinarily dry areas (<500 mm annual precipitation) with tated habitat types (Belovsky and Slade, 1993; Wünsch et al., warm summers (Hensen, 1995; Fig. 1). Due to their role as bio- 2012). diversity hotspots, and the great threats they face, they are priority The impact of land use on Orthoptera species richness in Central habitats of the EU Habitats Directive (Ssymank et al., 1998). European grasslands is widely known (e.g. Gardiner, 2009; Kruess and Tscharntke, 2002a; Marini et al., 2008). However, there is a gap in our knowledge about the community level. By considering communities or species groups for certain successional stages, we ∗ expect to provide distinctly deeper insights into the response of Corresponding author. Tel.: +49 251 8331967; fax: +49 251 8338338. E-mail address: [email protected] (T. Fartmann). orthopterans to land-use change. 1470-160X/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.ecolind.2012.03.002 338 T. Fartmann et al. / Ecological Indicators 20 (2012) 337–344 Fig. 1. Range of Stipa capillata as a proxy for the distribution of steppe grassland (a) and the study area Lower Oder Valley (b) in Germany. Distribution data of Stipa capillata: R. May, pers. comm. (Federal Agency for Nature Conservation). The aim of this study was to use Orthoptera as ecological indi- diversity of vegetation types is high. Characteristic vegetation types cators for succession in Central European steppe grasslands. In within steppe grasslands are acidic grasslands (Corynephorion, particular we addressed the following research questions: Plantagini-Festucion), calcareous grasslands (Cirsio-Brachypodion, Festucion valesiacae, Koelerion glaucae) and fringe communities (Trifolio-Geranietea, different dominance stands) (Fartmann et al., (i) Does Orthoptera species richness or density differ among suc- 2001). cessional stages? (ii) Do all species, habitat generalists or habitat specialists show different diversity patterns? 2.2. Study design (iii) How should steppe grasslands be management to promote Orthoptera? In the Lower Oder Valley, 18 steppe grassland patches are known (I. Kämpf, pers. comm.). Of these, the eleven largest and most rep- 2. Material and methods resentative patches were selected for the study. The size of the ± ± patches ranged from 1.2 to 50.3 ha (mean SE = 16.8 5.0 ha). Four 2.1. Study area (36%) of them were grazed, especially by sheep. The remaining seven patches (64%) did not have any specific land use. However, at The study area (hereafter called Lower Oder Valley) of about three of these patches, grazing has been neglected during the last 2 285 km is located at the north-eastern edge of the German federal ten years (own observation). Each patch was divided into sections state of Brandenburg (NE Germany) near the border with Poland with homogenous vegetation structure according to Sänger (1977). ◦ ◦ ◦ ◦ (51 22 N/8 38 E and 51 38 N/9 25 E) (Fig. 1). The study area is con- Structural heterogeneity within the patches was the result of man- sistent with the Lower Oder Valley National Park and its buffer zone. agement activities and natural site conditions (soil type, aspect, The Lower Oder Valley is one of the most continental and driest slope; see ‘Study area’ [Section 2.1]). Within each homogenous sec- regions in Germany, having a mean annual precipitation of 532 mm. tion, a plot was randomly chosen (stratified random sampling). ◦ ◦ The mean temperature for January is −1.2 C and for August, 17.5 C Hence, the number of plots corresponded to the structural hetero- (weather station Angermünde, 1961–1990) (DWD, 1998). Within geneity of the patch (Poniatowski and Fartmann, 2010) and ranged the study area, steppe grasslands are restricted to the hilly region from two to 22 per patch. In total, 96 plots were studied. To avoid (10–60 m a.s.l.) west of the Oder floodplain. The area is formed by edge effects (Schirmel et al., 2010a) the size of each plot was at least 2 Pleistocene moraines consisting of marly till and sometimes sand 500 m and the Orthoptera densities were recorded in the centre (Scherf and Viehrig, 1995). of the plot. Due to the subcontinental climatic conditions, together with the Measurement of environmental parameters took place after occurrence of calcareous soils, the region is one of the hotspots quantitative sampling of Orthoptera in an undisturbed part of of steppe grasslands in Germany (Fartmann et al., 2001, Fig. 1). the plot. We recorded the following parameters of the horizontal Since soil type and aspect can greatly vary within steppe grasslands, structure (in 5% steps): total vegetation cover, cover of grass/herb, T. Fartmann et al. / Ecological Indicators 20 (2012) 337–344 339 Table 1 litter, moss, lichen and bare ground. Grasses, as the dominant Overview of metric variables used in non-metric multidimensional scaling (NMDS). plant growth form of steppe grassland, were further divided into tall-growing and low-growing grasses (mean height >50 cm Climate ◦ a Aspect ( ) (‘eastness’, ‘northness’) and <50 cm, respectively); moreover, low-growing grasses were ◦ * Inclination ( ) grouped into tussock and rhizomatous grasses (Fartmann, 1997). b Heat load In cases where cover was above 95% or below 5%, 2.5% steps were c Potential daily sunshine duration (h) used, according to Behrens and Fartmann (2004). The average turf Vegetation structure height was ascertained to an accuracy of 2.5 cm. Vegetation density Vegetation height (cm)