Peter Ľuptáčik, Peter Čuchta, Patrícia Jakšová, Dana Miklisová, Ľubomír Kováč, Juha M. Alatalo

1. Cushion plants can have positive impacts on plant richness in severe environments and possibly across trophic levels on arthropods, an under-studied topic.
2. This study examined whether soil communities under cushions of Silene acaulis and Diapensia lapponica have higher richness and abundance of soil microarthropods (Acari, Collembola) than adjacent non-cushion vegetation; and whether differences in collembolan and mite abundance and species richness between S. acaulis cushions and adjacent vegetation increase with elevation.
3. In total, 5199 individuals of Collembola (n=1392) and mites (n=3807) were identified to order/species level in samples along an elevation transect (1000, 1100, 1200, 1300, and 1400 m a.s.l.), and an exposed ridge above the treeline (1000 m a.s.l.) in northern Sweden. Paired soil samples were taken within cushions of Silene acaulis (along the elevation gradient) and Diapensia lapponica (on the exposed ridge) and adjacent non-cushion plant vegetation.
4. Silene acaulis had a positive effect on species richness and abundance of Collembola, with richness effects from 1100 m a.s.l. upwards. Oribatid mite abundance and richness were also higher in S. acaulis compared with adjacent vegetation.
5. Species richness of Collembola and Oribatida declined with increasing elevation from 1200 m a.s.l. Collembola abundance peaked at mid-elevation (1200 m a.s.l.) in both S. acaulis and adjacent vegetation, while oribatid mite abundance peaked at 1300 m a.s.l. in both vegetation types.
6. Cushions of D. lapponica on the exposed ridge had a significant positive effect on species richness, abundance and diversity of Collembola, and abundance of Oribatida.
7. Alpine cushion plants play an important role in supporting biodiversity of soil fauna in severe alpine environments, with the positive effect of cushion plants increasing with environment severity.