Bryophyte colonisation in experimental microcosms:: the role of nutrients, defoliation and vascular vegetation

A three-year multi-factorial microcosm experiment simulating fertilisation, defoliation and the composition of vascular vegetation in a dry grassland succession was used to test four hypotheses concerning the establishment and survival of bryophytes in grassland vegetation. H-1: bryophyte cover may be used to predict bryophyte species richness. H-2: bryophyte richness is suppressed at high nutrient levels and promoted by defoliation of vascular plants. H-3: species richness of bryophytes is influenced by the species composition of the vascular vegetation. H-4: bryophyte species richness is negatively correlated with vascular plant biomass. The relationship between bryophyte richness and bryophyte cover was found to follow the classical species-area richness curve. Bryophyte species richness responded positively to defoliation and negatively to fertilisation. The species composition of vascular vegetation had no significant effect on bryophyte richness. Bryophyte species richness was lower at high vascular plant biomass and vascular plant dry weight above 400 g m(-2) appeared fatal to bryophytes. At high nutrient levels, defoliation increased bryophyte richness, but defoliation did not fully compensate for the negative effect of fertilisation. The study reinforces the concern for short lived shuttle bryophytes in the agricultural landscape.