Experimental assessment of dispersal and habitat limitation in an oligotrophic wet meadow

The ability of a non-resident species to establish a viable population when sown or transplanted into a target community is often considered as indirect evidence that its absence in the community is caused by dispersal limitation. We evaluated the importance of dispersal and habitat limitation in an oligotrophic wet meadow community by a sowing experiment where seeds of three resident and three non-resident dicotyledonous species were added to the target community, into disturbed (litter and moss removal by raking) and undisturbed plots. The sowing experiment was supplemented with a transplant experiment, to overcome possible seedling failure in early life stages. Recruitment and survival of seedlings and transplants were monitored for 5 years. Disturbance increased recruitment, but decreased survival, in both resident and non-resident species. Recruitment was slightly better in the non-resident species, while survival was slightly better in the resident species. Three species reached the reproductive stage at the end of the experiment, one resident and two non-resident. The two non-resident species would probably be able to establish viable populations and consequently their absence can be caused by dispersal limitation. On the contrary, one of the non-resident species was not able to overcome the seedling state, and this inability can cause its absence. Two of resident species failed to establish themselves; this failure to establish is probably related to the prevailing vegetative propagation of these species. This shows that the failure to establish is not sufficient evidence that a species is habitat limited.