Dispersal and establishment limitation reduces the potential for successful restoration of semi-natural grassland communities on former arable fields

Oster, M; Ask, K; Cousins, SAO, et al. 2009. JOURNAL OF APPLIED ECOLOGY 46(6):1266-1274

Oster et al. compared species richness and individual species recruitment and persistence patterns in ex-arable Canadian grasslands of different ages, both observationally and in an experimental seeding trial. They found that species richness increased with time since abandonment in the observational plots, but that recruitment patterns did not vary between young and old fields in the seeded plots. This suggests that dispersal limitations may account for lower species richness in younger plots, and that the time scale for natural reassembly of communities may be long (>50 years). Recruitment was low in both unseeded plots and plots without herbicide, suggesting that restoration practitioners must address both dispersal and biotic (competition) filters to restore these lands.

Combining a space-for-time approach with experimental seeding allowed Oster et al. to make important statements about how dispersal and competition limit recruitment in this system. Their introduction hooked me, however, because it promised to relate these patterns to functional traits, and this analysis didn’t pan out at all. None of the traits they measured related to difference in species composition in any of the plots. This leaves me wondering whether they just measured the wrong traits, or if some stronger driver (climate variability, perhaps?) overwhelmed any pattern that was there.

Seeding of an old field restoration experiment in Western Australia. Credit: Lauren Hallett