Spatial isolation slows down directional plant functional group assembly in restored semi-natural grasslands
Article first published online: 25 JAN 2013
© 2013 The Authors. Journal of Applied Ecology © 2013 British Ecological Society
Journal of Applied Ecology
Volume 50, Issue 2, pages 404–413, April 2013
How to Cite
Helsen, K., Hermy, M., Honnay, O. (2013), Spatial isolation slows down directional plant functional group assembly in restored semi-natural grasslands. Journal of Applied Ecology, 50: 404–413. doi: 10.1111/1365-2664.12037
- Issue published online: 19 MAR 2013
- Article first published online: 25 JAN 2013
- Manuscript Accepted: 29 NOV 2012
- Manuscript Received: 5 APR 2012
- calcareous grassland;
- chalk grassland;
- community assembly;
- emergent groups;
- functional traits;
- generalist species;
- specialist species
- Ecological restoration schemes often assume that after reinstating appropriate abiotic conditions, plant communities will assemble following a single predictable pathway towards a fixed target state. This idea has recently been challenged, with increasing evidence that plant community assembly can only be considered deterministic at the plant trait level, rather than at the species level, and that the assembly outcome is largely influenced by the spatial context of the restoration site.
- We surveyed 147 vegetation plots across a chronosequence of 22 restored semi-natural grassland patches to quantify the effects of spatial isolation on both plant species and plant trait assembly. Trait level assembly was analysed using an emergent group approach, based on 28 functional plant traits. Additionally, we examined the effects of several dispersal-related plant traits on species recolonization capacities.
- Whereas total plant species richness of the restoration patches did not change through space or through time, progressing assembly was found to consist of a sequential replacement of generalist species with specialist species, which was reflected by a directional assembly at the plant trait level. Grassland isolation was found to slow down community assembly at both the species and the trait level without changing the general direction of assembly. This slowdown became less pronounced with increasing time since restoration.
- Spatial isolation of the restoration patches was found to act as a trait filter, independent of assembly age. We found a proportionally higher occurrence of species with light seeds and a high seed attachment potential in more isolated restoration patches, suggesting that colonization is more limited in isolated grasslands.
- Synthesis and applications. We demonstrate that the assembly process, at both the species and the trait level, is influenced by the position of the restoration patch in the landscape. Monitoring schemes following ecological restoration should therefore include the spatial context of the system while using both a trait-based and a species-based plant community analysis. Successful restoration requires physically interconnecting grassland fragments and probably the introduction of seeds or seedlings of species with low dispersability.