Fine-scale vascular plant species richness in different alpine vegetation types: relationships with biomass and cover

Vascular plant species richness was related to biomass and vegetation cover in nine different alpine vegetation types on the Hardangervidda mountain plateau, western Norway. Each vegetation type was sampled within an 8m x 6m area, and the species-richness pattern analysed. Evidence for a unimodal relationship between species richness and both biomass and cover was found at the within-vegetation type scale. Cover was a better predictor for species richness than biomass, suggesting that light may be an important factor influencing species richness at this scale in alpine vegetation. The possibility that the results are an artefact of small grain size is also discussed, and several arguments for an ecological explanation of the humpback relationship between species richness and cover are discussed.