Effects of Grazing on Orthopteran Assemblages of Central-European Sand Grasslands
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Research Article Z. KENYERESJournal of Orthoptera Research 2018, 27(1): 23-3323 Effects of grazing on orthopteran assemblages of Central-European sand grasslands ZOLTÁN KENYERES1 1 Acrida Conservational Research L.P., Tapolca 8300, Hungary. Corresponding author: Zoltán Kenyeres ([email protected]) Academic editor: Corinna S. Bazelet | Received 12 June 2017 | Accepted 14 January 2018 | Published 12 June 2018 http://zoobank.org/931577F0-49AA-4CA9-965A-E2A5FB862ECC Citation: Kenyeres Z (2018) Effects of grazing on orthopteran assemblages of Central-European sand grasslands. Journal of Orthoptera Research 27(1): 23–33. https://doi.org/10.3897/jor.27.15033 Abstract of the habitat-structure (Metera et al. 2010). Nutrient-poor habi- tats seem to be the most sensitive to grazing intensity (Kruess and The effect of grazing on Orthoptera assemblages has long been the Tscharntke 2002). When the grazing pressure decreases or is aban- focus of research worldwide due to the high sensitivity of orthopterans doned in the grasslands of a temperate climate zone, the coverage to changes in vegetation structure. According to previous studies, grazing of the dominant, narrow-leaved perennial monocotyledons of the has individual, spatially-different effects on orthopteran assemblages. The associated plants increases (Critchley et al. 2008), while the cover- current case study was carried out between 2012 and 2016 in a subarea age of annual plant species becomes reduced (Matus et al. 2003). 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 In addition to the favorable changes for the vegetation-dependent of 2014, the overgrazing pressure was overall reduced, for the most part, insect communities, the abandonment of grazing can also cause in the examined grassland patches. The study aimed to answer how the the invasion of weeds in the grasslands (Sedláková and Fiala 2001). complete abandonment of grazing and moderate grazing influences the This usually greatly decreases the presence of rare and threatened species richness, diversity and density of the orthopteran assemblages. In- Orthoptera (Fonderflick et al. 2014). Therefore, in the habitats vestigations in Central European sand steppes confirmed that both intense grazed traditionally, the maintenance of extensive grazing is a pre- grazing and the abandonment of grazing have a detrimental effect on the requisite for preserving biodiversity (Dolek and Geyer 2002) and structure of orthopteran assemblages: (a) the Shannon diversity index was seems to be far more suitable than mowing (Weiss et al. 2013). higher on moderately grazed sites than on grazed and ungrazed ones; (b) The high sensitivity of orthopterans to a change in vegeta- the number of habitat specialists of sandy grasslands was higher on mod- tion structure is well known (Báldi and Kisbenedek 1997, Sam- erately grazed patches than in grazed habitats; and (c) the frequency of geophilic species was higher on grazed patches than on moderately grazed ways 1997, Gardiner et al. 2002, Bazelet and Samways 2011, Weiss and grazing-abandoned ones. et al. 2013). Based on this, the effect of grazing on orthopteran assemblages has been the focus of research worldwide and for a Key words long time (e.g. White 1975, Jepson-Innes and Bock 1989, Prendi- ni et al. 1996, Kruess and Tscharntke 2002, Jauregui et al. 2008, density, diversity, Hungary, land use intensity, sheep, vegetation structure Gardiner and Haines 2008, Zhu et al. 2015). Grazing results in individual, spatially different effects on the orthopterans. Some studies, for example, revealed lower orthopteran density in grazed Introduction grasslands than in ungrazed ones (Welch et al. 1991, Onsager 2000), while in other cases the opposite was found (Wingerden The structure of habitats and their insect communities exposed et al. 1991). These differences are likely to be due to not only the to direct and indirect human impact usually can be considered a habitat-dependent effects of the grazing, but also to species-specif- transient state (Pickett et al. 1992). This phenomenon can be well ic responses (O’Neill et al. 2003, Jauregui et al. 2008) of orthopter- observed in grazed grasslands where current vegetation structure, ans to intensity (Kruess and Tscharntke 2002, Cease et al. 2012), as a background factor to the insect communities, is highly influ- timing (Fonderflick et al. 2014) and livestock type (Dolek and enced by the intensity, spatial and temporal characteristics and Geyer 2002) of grazing. Most of the results of the assessment of abandonment of grazing (Carboni et al. 2015, Török et al. 2016). the impact of grazing suggest that, according to the intermediate- Both the vertical and horizontal structure of vegetation, through disturbance hypothesis of Connell (1978), orthopteran assem- the removal of the biomass and through trampling, are changed blages show the largest diversity in moderately grazed grasslands by grazing (Asner et al. 2004). Intensive grazing (~overgrazing) in (Batáry et al. 2007, Fabriciusová et al. 2011, Jerrentrup et al. 2014). grasslands usually results in decreased plant diversity, the invasion My study area is situated between the Danube and the Tisza of some grazing-tolerant plant species, and the overall degradation rivers in the Carpathian Basin in the eastern half of Central-Europe, JOURNAL OF ORTHOPTERA RESEARCH 2018, 27(1) 24 Z. KENYERES where the dominant vegetation type is the Pannonian sand steppe content: 8.5%; humus content: 2.9%; pH-H2O: 7.2; percentages of occurring in Europe only in the Pannonian biogeographical region the soil fractions: rough: 0.2%; middle-class: 9.7%; small: 80.6%; (6260 Pannonian sand steppes, 2002/83/EC Habitat Directive). mud: 7.1%; loam: 2.3%. Due to the conditions of the almost humus-less bedrock (sand), the structure and species composition of the habitats could remain po- Land use.—Based on the first known detailed map of the study area, tentially unchanged even for centuries in the absence of any inter- in the 18th century the typical land use of the open sandy grasslands ventions. However, grazing has been present in the area since, most studied was grazing (http://mapire.eu/hu/map/firstsurvey). In the likely, the Neolithic (Molnár et al. 2008), so for several thousand 19th and 20th centuries some places in the area were afforested, years. Thus, large herbivores played a role in the development of but the main form of land use on the grasslands was still graz- the actual state of the grasslands (Máté 2014). In the 16–17th cen- ing (see http://mapire.eu/hu/map/secondsurvey; http://mapire.eu/ tury, extensive grazing was carried out on a large area of the region hu/map/hkf_25e; http://mapire.eu/hu/map/hungary1941). After – mainly with cattle and, to a lesser extent, with sheep (Frisnyák et World War II the area was used as a closed military base, but the al. 2015). After the beginning of the 18th century, afforestation was grazing of sheep continued. When military operations ceased in carried out for the purpose of impeding erosion and for utilizing 1990, the grazing of sheep became increasingly intense. The ~70 ha areas unsuitable for agricultural use (mainly Pinus sylvestris and Ro- study area was grazed by 250–300 sheep in 2012. The overgrazing binia pseudo-acacia were planted). As a result, the extent of areas cov- pressure was overall reduced in the majority of the study area in the ered by forests increased from 3.5% to 60% (Molnár 2003). How- beginning of 2014 in order to conserve nature. ever, some hills covered by open sandy grasslands remained, and until the middle of the 20th century they were grazed by the sheep Experimental design.—Six sampling sites were established, as 50×50 of small farmers (Kun 1998). In the past decades and even now, m sized quadrats. Data collection was carried out from 2012 to grazing, especially sheep-grazing, was concentrated in small areas. 2016. One site was on a place ungrazed during the study (Un- The dominance of sheep grazing affected, among other things, the grazed – U-G), three sites were located in places on which grazing Fabaceae plant species of the sandstone pastures and their associat- pressure was reduced to zero at the beginning of 2014 (Grazing ed animal species, resulting in the decline or extinction of a number Abandoned – G-A), two sites were located in places on which graz- of plant species at the beginning of the 19th century (Máté 2014). ing pressure was reduced to a moderate level (Moderately Grazed In addition to the above historical landscape characteristics, – M-G) (Fig. 1). Sites were considered to be “grazed” (Grazed – G) responses of the orthopteran assemblages associated with the typi- prior to 2014 and the reduction of grazing pressure. cal habitats of the Central European sand steppes were affected by several local and global factors. From a local point of view, it Vegetation and landscape structure.—Measurements of the vegeta- can be said that the orthopteran assemblages of Central European tion parameters were carried out on 3 plots in each sampling site habitats grazed with different intensity have not yet been suffi- of each orthopteran sampling. The following parameters were re- ciently investigated. Certainly, in regards to the long-term effects corded: total vegetation cover (%), average height of the vegetation of the various types of grazing, and the long-term effects of the (cm), and bare soil (%). Height of the vegetation was measured in abandonment of grazing, there are several questions to be an- cm with the use of a 30 cm wide and 100 cm high white card. Total swered. Several further questions remain to be answered both lo- cover of the vegetation was measured in a square meter quadrat cally and globally with regards to quality and intensity of grazing occurring around the spot.