Conspecific versus heterospecific litter effects on seedling establishment

Plant litter is an important determinant of seed germination and seedling establishment. Positive effects of litter have received considerable attention, but few studies have explicitly tested whether seedlings are more facilitated by conspecific litter compared to heterospecific litter. In order to contrast conspecific and heterospecific facilitative effects on seedling establishment, we used Anthriscus sylvestris, Angelica sylvestris, Pimpinella saxifraga and different combinations of their seeds and litter seedbeds as a model system. Although litter had a significant species-specific effect on seedling emergence, we found no evidence of strictly conspecific facilitation. Anthriscus sylvestris displayed a positive response to all types of litter. In contrast, there was a clear negative effect of conspecific litter in Pimpinella saxifraga. Activated carbon did not modify the negative effect, indicating that chemical compounds were not the cause. Our study suggests a high level of idiosyncrasy in response to litter at the species level.