Sphagnum niche diversification in two oligotrophic mires in the southern Alps of Italy

Niche breadth and niche overlap values for water table depth, pH, conductivity, and base cation concentrations in mire water were calculated for nine Sphagnum species at two nutrient-poor mires in the southern Alps of Italy. Water table depth is more important than chemical status in controlling the distribution of Sphagnum species. The chemical status of mire water is best indicated by water pH. The Sphagnum species occupying the extremes of the water table gradient exhibit narrow niche breadth and a low niche overlap values. For these reasons they are best regarded as specialists. This is particularly evident for hollow species. The sharp segregation of hallow Sphagna along both the water table depth and the chemical gradient is thought to be determined by higher degree of competition taking place in hollow habitats. On the other hand, hummock species appear to be segregated by physiological tolerance rather than competition. The Sphagnum species occupying the middle of the moisture ...