Abstract
AbstractAim: Species‐rich Nardus grasslands are high nature‐value habitats. In Switzerland, many of these grasslands are degraded even though they have been under protection since the 1980s. Degradation shows two divergent trends: Nardus grasslands are either dominated by Nardus stricta or by eutrophic plants, both trends leading to the disappearance of typical Nardus grassland species. With this study, we aim to identify the factors that could be adjusted to conserve the integrity of this habitat.Location: Bernese Alps, Switzerland.Methods: In 2016, we investigated the underlying causes of this degradation process by assessing vegetation composition in 48 Nardus grasslands located in the Swiss northern Alps of canton Bern and linking it to soil, management and environmental variables. To explore the effect of the degradation on higher trophic levels, orthopteran species richness and densities were assessed.Results: Results show that Nardus meadows (mown) are rarely degraded compared to Nardus pastures (grazed). Within pastures, eutrophic plants are most abundant on small pastures with low soil carbon/nitrogen ratio, indicating high nutrient availability. Nardus stricta dominance is most problematic on north‐exposed slopes and in summer pastures. A plausible driver of both degradation trends is the grazing management regime: within small pastures at low elevation where the grazing periods are short but intense, soil carbon/nitrogen ratio is low because of high dung deposition, thus the eutrophic species become dominant. Contrastingly, on large summer pastures with low‐intensity and long‐term grazing, N. stricta becomes dominant due to selective grazing. Both degradation trends show a negative impact on the orthopteran density.Conclusion: Species‐rich Nardus grasslands are a precious alpine habitat for specialised plant species and orthopterans. With an extensive mowing regime or a more controlled grazing regime that homogenises intensity in time and space, species‐rich Nardus grasslands can be conserved in Switzerland.
Highlights
Species‐rich, ecologically important Nardus grasslands occur in almost all European countries and cover up to 20% of all Natura 2000 areas
In Nardus pastures, we recommend to differenti‐ ate conservation action according to the elevation: in low elevation pastures, it should focus on reducing the dominance of eutrophic plants, whereas in highly elevated pastures N. stricta cover should be constrained
We found that the vegetation composition differs according to the grazing management: on summer pastures, which are grazed once over the whole summer, we found more Nardus grassland indicator species (NGIS) than in spring and autumn pastures that are grazed twice a year
Summary
Species‐rich, ecologically important Nardus grasslands (the species‐ rich Nardion strictae habitat; Delarze, Gonseth, Eggenberg, & Vust, 2015) occur in almost all European countries and cover up to 20% of all Natura 2000 areas (habitat type 6230; Galvànek & Janàk, 2008). Threats are imposed by management intensification and on the other, by land abandonment (European Environment Agency, 2012; Galvànek & Janàk, 2008; Janssen et al, 2016). Both trends have se‐ vere negative impacts, leading to species‐poor or common eutro‐ phic vegetation communities (Galvànek & Janàk, 2008; Stevanovic, Peeters, Vrbnicanin, Sostaric, & Acic, 2008; Tasser & Tappeiner, 2002). They avoid N. stricta due to the high abrasiveness and the poor digestibility of the plant leaves
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