Plant species richness decreased in semi-natural grasslands in the Biosphere Reserve Wienerwald, Austria, over the past two decades, despite agri-environmental measures
Introduction
Semi-natural grasslands contribute considerably to the overall biodiversity of Europe (Poschlod and WallisDeVries, 2002, Pärtel et al., 2005, Veen et al., 2009, Habel et al., 2013). For vascular plant species richness, some of them even hold the world record, with up to 116 vascular plant species occurring on 25 m2 at spatial scales between 10 and 50 m2 (Dengler et al., 2012, Wilson et al., 2012, Roleček et al., 2014). The high number of grassland types listed in the Habitats Directive (HD) of the European Union (Directive 92/43/EEC, European Commission, 2007) highlights their importance for the conservation of biodiversity. However, the total area of species-rich grasslands has strongly declined during the last century all across Europe, mostly because low-productivity grasslands were either abandoned or intensified (van Dijk, 1991, Stoate et al., 2009, Veen et al., 2009, Dengler et al., 2014). These changes are likely to be accompanied by an overall reduction of plant diversity and particularly by a loss of threatened species (Kleijn et al., 2009), because the type of management is one of the key drivers of species richness in European grasslands Klimek et al., 2007, Marini et al., 2008).
The Convention on Biological Diversity (Convention on Biological Diversity, 2010, Secretariat of the Convention on Biological Diversity, 2010, Perrings et al., 2011) targets at a substantial reduction of biodiversity losses until 2010 (a revised and updated strategic plan for 2020 is presented in the Aichi targets: Convention on Biological Diversity, 2010) at the global, national and regional levels. It was committed by more than 180 member states and transnational authorities, including the EU and Austria. Protected areas like UNESCO Biosphere Reserves (UNESCO, 1996) and Natura 2000 sites (Directive 92/43/EEC) were mentioned as important tools to halt biodiversity losses. The concept of Biosphere Reserves is not to focused on conservation of natural habitats (like in national parks) but on sustainable land use (UNESCO, 1996), making them particularly important for biodiversity conservation in agricultural and managed habitats such as semi-natural grasslands. Agri-environmental schemes (AES), established at both EU and national level (Kampmann et al., 2012, Batáry et al., 2015) represent another important conservation strategy to protect biodiversity in agricultural landscapes within and outside protected areas. However, the effectiveness of these programs for biodiversity conservation is in question (Kleijn et al., 2006, Wilson et al., 2007, Batáry et al., 2015).
Our study region, the Biosphere Reserve Wienerwald (Vienna Woods) in eastern Austria, contains a broad range of semi-natural grassland types (Willner et al., 2013). In a mapping of nearly 500 grassland sites within the Biosphere Reserve, more than 700 vascular plant species have been found, 10% of them being threatened in Austria (Pfundner and Sauberer, 2009). Compared to other parts of Austria and Central Europe, theses grasslands are managed with moderate intensity as the climate is too dry for high-productivity meadows and pastures. For centuries, small-scale farms with mixed livestock prevailed in the Wienerwald area. With 12–14 ha, the average farm size is still quite small compared to other parts of Austria and the EU, and many of the grasslands are managed by part-time farmers (Suske et al., 2003). Within the last decades, many farmers have abandoned livestock husbandry and started to sell hay to riding stables in the region. These changes in agricultural practises are likely to affect the conservation value of grasslands (e.g. Zechmeister et al., 2003).
The Austrian AES (also known as ÖPUL) started in 1995, when Austria became part of the European Union, and has been applied in five year periods since then. The ÖPUL program is designed to promote environmentally sound management of agricultural areas in Austria, including the extensive and protective utilization of (semi)natural habitats. Several measures like “renouncement of silage making”, “delayed (first) haycut” and the “reduction/renouncement of nitrogen fertilizers and pesticides” are intended to foster types of grassland management that maintains “high natural value farmland” and promotes grassland biodiversity (for simplicity we refer to these grassland-specific as AES in the following). Between 2007 and 2013, Austria had the second largest per ha expenditures for AES in the EU (Batáry et al., 2015). In 2011, the year of our field survey, 76.8% of all Austrian farms participated in AES programs, receiving subsidies of about € 270 million for grassland based farming (BMLFUW, 2012). Regarding these expenditures, knowledge on the effectiveness of AES in counteracting biodiversity losses is crucial, but empirical evidence is rare particularly in protected areas.
Against the background of the global failure to achieve the 2010 target of the Convention on Biological Diversity (Butchart et al., 2010, Secretariat of the Convention on Biological Diversity, 2010, Perrings et al., 2011), we examined plant species richness in species-rich grasslands in the Biosphere Reserve Wienerwald. In 2011, we re-observed 95 sites with Arrhenatherion and Brometalia communities (52 of them were managed according to AES) two decades after a first survey (Ebenberger, 1993, Huspeka, 1993) to detect potential vegetation changes. We addressed the following questions: (1) Does current plant species richness differ from historic observations and is there a link to changes in abiotic site conditions? (2) Do these changes depend on grassland type and/or management regimes? In particular, do changes on sites without management restrictions differ from abandoned grasslands or those managed according to AES?
Section snippets
Study area and historic survey
The Biosphere Reserve Wienerwald (Vienna Woods) covers an area of 105 km2 and is located in the north-eastern foothills of the Alps (center location of study sites: 10,17° E, 48.30° N) at altitudes between ∼200 and ∼900 m a.s.l. Mean annual temperature ranges from 6 to 10 °C and mean annual precipitation ranges from 600 mm at the eastern slopes to 900 mm on the highest peaks. The Biosphere Reserve is part of four Natura 2000 sites (AT1303000, AT1302000, AT1211A00, AT1211000; //natura2000.eea.europa.eu/
Species richness
The overall number of species per site decreased on average from 43.4 ± 8.8 (mean ± SD) in 1990/92 to 31.0 ± 10.5 in 2011 (Wilcoxon: p < 0.001; Fig. 2). Similarly, the mean number of threatened species decreased from 11.5 ± 5.4 species to 6.8 ± 4.3 (Wilcoxon: p < 0.001). The general pattern of decreasing species richness was confirmed for both communities and under each management regime (Table 1, Fig. 3). Mean number of overall and threatened species decreased in Brometalia meadows by 15 ± 15 and 6 ± 7,
Strong species losses due to changed management regimes
Both overall species richness and the number of threatened species declined at semi-natural grasslands of the Biosphere Reserve Wienerwald within the last two decades (Fig. 2, Table 1). This is in line with most re-observation studies ascertaining changes in species richness at various types of nutrient-poor, temperate European grasslands (Dupré et al., 2010, Homburger and Hofer, 2012, Wesche et al., 2012, Gillet et al., 2016). Evidence from these studies suggests temporal patterns of species
Conflict of interest
The authors declare that they have no conflicts of interest
Acknowledgements
Our study was supported by the Austrian Academy of Sciences (Man and Biosphere program).
Glossary
- EIV
- Ellenberg indicator values
- AES
- Agri-environmental scheme
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Contributed equally to the manuscript.