Decline of rare and specialist species across multiple taxonomic groups after grassland intensification and abandonment Andreas Hilpold1,*,§, Julia Seeber1,2,§, Veronika Fontana1, Georg Niedrist1, Alexander Rief2, Michael Steinwandter1, Erich Tasser1, Ulrike Tappeiner1,2 1 Institute for Alpine Environment, Eurac Research, Drususallee 1, 39100 Bolzano/Bozen, Italy 2 Department of Ecology, University of Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria § these authors contributed equally as first authors * corresponding author: [email protected], Institute for Alpine Environment, Eurac Research, Drususallee 1, 39100 Bolzano/Bozen, Italy Abstract Traditionally managed mountain grasslands are declining as a result of abandonment or intensification of management. Based on a common chronosequence approach we investigated species compositions of 16 taxonomic groups on traditionally managed dry pastures, fertilized and irrigated hay meadows, and abandoned grasslands (larch forests). We included faunal above- and below-ground biodiversity as well as species traits (mainly rarity and habitat specificity) in our analyses. The larch forests showed the highest species number (345 species), with slightly less species in pastures (290 species) and much less in hay meadows (163 species). The proportion of rare species was highest in the pastures and lowest in hay meadows. Similar patterns were found for specialist species, i.e. species with a high habitat specificity. After abandonment, larch forests harbor a higher number of pasture species than hay meadows. These overall trends were mainly supported by spiders and vascular plants. Lichens, bryophytes and carabid beetles showed partly contrasting trends. These findings stress the importance to include a wide range of taxonomic groups in conservation studies. All in all, both abandonment and intensification had similar negative impacts on biodiversity in our study, underlining the high conservation value of Inner-Alpine dry pastures. Keywords (5-8): biodiversity survey, land-use change, multi-taxon study, trait-based approach, biodiversity conservation 1 Introduction The agricultural landscapes in Central Europe are currently in a state of change. This is especially pronounced for mountain areas, where frameworks for agriculture are, due to steepness, elevation and remoteness, frequently harsher than in lowlands, often leading to the abandonment of farms (Lasanta et al. 2017). Also regions where agriculture has been maintained (e.g. easily accessible locations on hillsides) show strong changes in agricultural practice via intensification of grassland management (fertilization and irrigation), specialization on a single land-use form (e.g. livestock farming), or the establishment of permanent crops (orchards and vineyards) (Mottet et al. 2006, Graf et al. 2014, Egarter Vigl et al. 2016). Less favoured grasslands such as steep alpine pastures and meadows are continuously abandoned (Niedrist et al. 2009). In the continental valleys of the Central Alps pastures on south-exposed slopes are usually covered by typical dry grassland vegetation which resemble that of the driest parts of Eastern Europe. Most prominent are the dry grasslands in the valleys of Aosta (Italy), Valais (Switzerland) and Vinschgau/Val Venosta (Italy). The European Union gave high priority to their conservation by including them in the Habitat Directive “Sub-Pannonian steppic grasslands” (code 6240*, Lasen and Wilhalm 2004, European Commission 2013). These types of grassland are especially affected by recent land use changes, since their fodder value is even lower than that of other pastoral habitats (Graf et al. 2014). They are, however, rich in floristic and faunistic elements which are extremely rare in Central and Western Europe (e.g., Canthophorus melanopterus, Tamanini 1982; Omocestus petraeus and Stenobothrus nigromaculatus, Nadig 1991; Astragalus exscapus, Wilhalm 2018) and are in the focus of several Agri-Environmental Measures of the EU. Numerous studies emphasize the outstanding value of dry grasslands for European biodiversity (e.g. Swaay and Warren (2006) for butterflies, Lacasella et al. (2015) for spiders). Dry calcareous grasslands exhibit among the highest alpha diversity of vascular plants on a small scale worldwide (Wilson et al. 2012). These “hotspots of biodiversity” (Cremene et al. 2005) are under constant threat due to land-use changes and ensuing habitat fragmentation (Zulka et al. 2014, Braschler and Baur 2016, Lengyel et al. 2016). Virtually all Alpine pastures below the treeline will be substituted by forests on the long term, if the grazing impact were reduced (Ellenberg and Leuschner 2010), or changed into more productive land use forms, such as hay meadows, vineyards or crop fields (Egarter Vigl et al. 2016). In South Tyrol, the analysis of the land-use change revealed two clear trends (Tasser et al. 2009): In the agriculturally favourable areas, grassland and arable land disappeared to a large extent (-59% of the area in 1860) and their place was taken by permanent crops such as apple orchards, vineyards or settlements. Until the 60’s, the south exposed slopes in the Vinschgau Valley were characterized by a mosaic of dry pastures and open wood grasslands. These land-use forms were later largely abandoned (-74%) and today, forests can be found in large parts of this area. Biodiversity studies on the impact of intensification and abandonment of low-input grasslands and dry pastures in particular are plentiful available. Both land-use changes may lead to the loss of characteristic species due to habitat simplification or degradation (as reviewed by Stoate et al. 2009). In most cases these studies are, however, related to plant diversity (Hector and Bagchi 2007, Hülber et al. 2017, Halada et al. 2017) or to the diversity of one or few animal groups, very often birds and butterflies (Lessard-Therrien et al. 2018, Zografou et al. 2017, Vermaat et al. 2017, Ernst et al. 2017). Yet, the study of multiple taxonomic groups is highly informative (Zulka et al. 2014), since patterns of single groups can be very different, partly due to high β-diversity in dry grasslands (Turtureanu et al. 2014). Furthermore, the utilization of species traits for evaluating community diversity patterns can provide more comprehensive insights than simple species numbers, since changes in environmental conditions due to land-use changes might result in the environmental filtering of species (Simons et al. 2016, Cadotte and Tucker 2017). In this study, we surveyed the species composition and traits of 16 taxonomic groups to study the effect of land-use changes on species diversity on formerly grazed dry grasslands in the Central Alps. We sampled a land-use transect from dry pastures to either intensively used grassland, i.e. hay meadows, or larch forests as successional stages after abandonment. Special emphasis was put on the conservation value of the three habitats, since although an impoverishment due to intensification and abandonment has been frequently reported for single organism groups, an overall assessment is still missing. To evaluate the conservation value we analyzed the proportion of rare and specialist species. We aimed to answer the following questions: (1) Does intensification or abandonment cause consistent patterns regarding species richness, specificity and rarity among different taxonomic groups? (2) Which taxonomic groups are especially affected by these land use changes? and (3) Does the share of rare and specialist species decline in the intensified or abandoned areas? 2 Material and Methods Compliance with ethical standards Eurac research has a general permit to conduct scientific research in the LT(S)ER area Matsch/Mazia. The study design was carefully planned to ensure that no populations were endangered. 2.1. Study area The Long-term socio-ecological research (LTSER) site Matsch/Mazia is located in the Central Eastern Alps, in the northernmost part of Italy (Province of South Tyrol, N 46.6840°, E 10.5860°, Fig. 1 aerial picture, Appendix A2 climate and site parameters). The climate at the study sites is subcontinental with 525 mm mean annual precipitation. The air temperatures range from a minimum of –15.29° to a maximum of +27.79°C with the coldest month average –2.67°C (January) and the warmest +15.93°C (July). We selected three habitat types with three replicates each: intensively used hay meadows, dry pastures, and larch forests. All nine sites were within a distance of 3 km and comparable regarding elevation (1500 m a.s.l.), inclination (5-15°) and aspect (southwest). The three hay meadows (H1, H2, H3) were already identified as hay meadows in old maps of the 19th century. Nevertheless, hay meadows in the investigated area underwent qualitative changes due to an installation of irrigation systems and an elevated fertilizing activity over the last fifty years (Pecher et al. 2017). Following Tomasi et al. (2016) they are not part of the Directive habitat 6520. They all belong to the class Molinio-Arrhenatheretea and therein to the alliance of Trisetion flavescentis. The dry pasture sites (P1, P2, P3) are part of the priority habitat Sub-Pannonian steppic grasslands (code 6240*) (Lasen and Wilhalm 2004) of the EU Habitats Directive. They belong to the alliance Stipo capillatae-Poion xerophilae (Br.-Bl. & Richard 1950) within the order Festucetalia valesiacae (Br.-Bl. & Tüxen ex Br.-Bl. 1950) (Mucina et al. 1993). All pastures were not subjected to substantial land-use-changes over