Even the Smallest Habitat Patch Matters: on the Fauna of Peat Bogs
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Journal of Insect Conservation (2019) 23:699–705 https://doi.org/10.1007/s10841-019-00164-8 ORIGINAL PAPER Even the smallest habitat patch matters: on the fauna of peat bogs Róbert Gallé1,2 · Ferenc Samu3 · Andreea‑Rebeka Zsigmond4 · Nikolett Gallé‑Szpisjak1 · István Urák4 Received: 24 January 2019 / Accepted: 12 June 2019 / Published online: 11 July 2019 © The Author(s) 2019 Abstract Peat bogs are highly endangered and very sensitive habitats in Central Europe. Their high water table, acidity and character- istic climate determine their specialized fora and fauna with numerous rare species. Peat bogs are threatened by soil erosion and nutrient infltration due to forestry management or grazing. Several small, natural peat bogs exist in the Carpathians, mainly covered with birch and pine forests. Here we assessed the efect of geological location, peat bog size and tree species on the spider fauna. We collected spiders with pitfall traps in eight peat bogs in Eastern Transylvania. We identifed several species of high nature conservation value, regarded to be rare in the Central-European fauna. We found higher species rich- ness, abundance and diversity in birch forests than in pine forests. The open canopy of birch forests may allow open habitat specialists to occur in high densities in these forests. Species composition was afected by geological location, indicating that the regional fauna of peat bogs in diferent mountain ranges are isolated. However, we found no signifcant efect of habitat area on spider assemblages, the valuable tyrphophilic spider fauna was present even in the smallest peat bog. Peat bog spider fauna requires specifc habitat conditions, we suggest that preserving hydrological properties and water quality even in the smallest bogs would conserve the specialized fauna. Keywords Spiders · Species richness · Small habitat patch · Habitat island · Conservation · Araneae Introduction in particular, represent highly threatened wetland ecosys- tems (Spitzer and Danks 2006). Peat bogs are nutrient-poor Wetland ecosystems provide both unique biodiversity and (oligotrophic) habitats dominated by sphagnum moss, char- substantial ecosystem services, however they are globally acterized by a high water table and low pH (Spitzer and decreasing in their condition and diversity through habitat Danks 2006; Battes et al. 2014). In bogs the slowly and loss, climate change and pollution (Keddy 2010). Peat bogs incompletely decaying plant material builds up as peat. This naturally accumulated peat layer has an important role in carbon stocking worldwide (Urák et al. 2017). Peat bogs Electronic supplementary material The online version of this have postglacial origin. They were once typical landscape article (https ://doi.org/10.1007/s1084 1-019-00164 -8) contains elements in Central Europe, but today, especially as a result supplementary material, which is available to authorized users. of human infuences (forest management activities, peat * Róbert Gallé extraction, climate warming, secondary succession), the [email protected] degradation of these habitats became pronounced (Doyle 1990; Buchholz 2016; Urák et al. 2017). As a consequence, 1 MTA Centre for Ecological Research, Institute of Ecology nowadays peat bogs are highly endangered and very sen- and Botany, Lendület Landscape and Conservation Ecology, Alkotmány u. 2-4, Vácrátót 2163, Hungary sitive habitats in Central Europe (Charman 2002; Riecken et al. 2006). Their characteristic climate, hydrology, food 2 Department of Ecology, University of Szeged, Közép fasor 52, Szeged 6726, Hungary scarcity and high acidity are limiting factors which deter- mine their unique, specialized fora and fauna with rare and 3 Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, P.O. Box 102, threatened species. For these reasons peat bogs are listed Budapest 1525, Hungary in Annex I of the European Habitats Directive as a priority 4 Department of Environmental Sciences, Sapientia habitat type (Scott et al. 2006; Haase and Balkenhol 2014). Hungarian University of Transylvania, Calea Turzii 4, 400193 Cluj-Napoca, Romania Vol.:(0123456789)1 3 700 Journal of Insect Conservation (2019) 23:699–705 Peat bogs can be viewed as habitat islands, then study- In the present study we focused on eight forested bogs in ing their biota can show how these isolated habitat patches the Nemira and Harghita mountain ranges (Eastern Transyl- contribute to regional biodiversity, and how their size and vania, Romania). The main questions of our study were: (1) geographical distribution afects their nature conservation are forested peat bog spider assemblages basically the same value. Peat bogs are foremost islands of a very specifc habi- in the whole studied region or do the two diferent mountain tat and as such harbor a specialist arthropod fauna (Spitzer ranges harbor distinct spider assemblages? (2) Do the spider and Danks 2006). Species richness and composition of indi- assemblages of large bogs difer from that of the small bogs? vidual patches may depend on local factors, such as the size (3) Do forest tree species has an efect on the spider fauna? of the habitat patch and idiosyncratic diferences in local vegetation, but also on the regional species pool. Large habi- tat patches may not support more arthropod species than Materials and methods small patches due to a higher frequency of generalist species in smaller fragments (Gibb and Hochuli 2002). However, Study sites and spider sampling species composition may difer signifcantly, with the total number of specialist species being generally higher in larger Our study was conducted in eight peat bogs in Eastern patches (Bonte et al. 2002). Transylvania, Romania, all are situated in remote areas and Studying island biogeography of bogs is best done in majority of the sampled bogs are hardly accessible. All sam- regions where these habitat types occur in abundance and pling sites were situated in forest-bogs. Eastern Carpathian there is a considerable size variation among them. The spider peat bogs consist of two main forest habitat types (1) rela- fauna of Northern and Western European peat bogs is rela- tively open birch forest (Vaccinio-Betuletum pubescentis tively well known (e.g. Kupryjanowicz et al. 1997; Koponen Libbert 1933); (2) closed Scots pine forest (Vaccinio-Pine- 2002; Relys et al. 2002; Buchholz 2016). Their fauna consist tum sylvestris Kleist 1929 em. Matuszkiewicz 1962). We of cold-adapted species with preferences for wet habitat, sev- established ten sampling sites, fve sites in Scots pine and eral species were identifed as tyrphobiontic (occur exclu- fve sites in birch forest, one at each bog and the two larg- sively in bogs) or tyrphophilic species (characteristic bog est bogs containing two sites, one site in pine forest and species but not restricted to them, Spitzer and Danks 2006). one in birch forest. The bogs were located in two mountain Scott et al. (2006) suggested that the spider indicator spe- ranges Nemira and Harghita Mountains, at an elevation of cies are a surrogate taxon for the conservation value of the 925–1040 and 1025–1080 m a.s.l., respectively (Fig. 1). All peat bog invertebrate fauna. We have much less information peat bogs are part of Natura 2000 ecological network. For on Central and Southern European peat bog spider faunas, exact position and detailed description of bogs please see but see Kurka (1990) for the Czech Republic, Stambuk and Online Resources 1 and 2. Erben (2002) for Croatia, Samu and Urák (2014), and refer- We applied pitfall traps consisting of plastic cups (250 ml) ences therein for Romania. By studying Transylvanian peat with approximately 120 ml of 50% ethylene–glycol solution bogs we can collect crucial missing information and also and some drops of detergent. Fifteen traps were arranged in answer ecological questions related to their isolated nature. each site in a 3 × 5 grid, keeping 10 m distance from each Peat bogs in Eastern Transylvania are located in the Car- other. The traps were open between mid-June to mid-July pathians between 400 and 1200 a.s.l. (Pop 1960). There are in 2013. Arthropods were sorted and conserved in 70% eth- more than 25 peat bogs in the region scattered along sev- anol-solution. Spiders were identifed under stereoscopic eral mountain ranges, ranging between 1 and 120 ha in size microscope, using standard keys (Nentwig et al. 2017). The (Samu and Urák 2014). The dominant forest vegetation types nomenclature follows the World Spider Catalog (Platnick of the bogs are scots pine and birch forests, with diferent 2018). The juvenile individuals were identifed up to family habitat structure and presumably diferent invertebrate fauna level but were not considered for statistical analyses. (Eggleton et al. 2005). The majority of the remaining peat bogs are small and Data analysis degraded by soil erosion and nutrient infltration due to intensive forestry management or grazing. Furthermore, Data of the pitfall traps in each sampling site were pooled the remaining peat bogs are situated in diferent mountain prior to the analyses. Using species richness and abundance ranges (e.g. Mts. Nemira, Mts. Harghita). The lowlands as response variables, respectively, we tested the efect of between the mountains may constitute a geographical bar- forest type, peat bog size and mountain range with mixed- rier resulting in disjunct distribution of mountain species efect general linear models (GLMM) with a Poisson error (Mráz et al. 2007). The remaining few natural peat bogs are term, and with a negative binomial error term if we detected strictly protected and/or situated in remote areas where forest overdispersion in the data (lme4 package: version 1.1.12, management is not feasible. glmer and glmer.nb functions, respectively). To incorporate 1 3 Journal of Insect Conservation (2019) 23:699–705 701 dissimilarity matrix with a maximum number of 100 random starts. To test whether habitat, size and mountain range had a signifcant efect on species composition, a permutational multivariate analysis of variance (ADONIS) was conducted using Bray–Curtis distance matrix and 5000 Monte-Carlo randomizations.