Conservation of vascular plants in single large and several small mires: species richness, rarity and taxonomic diversity.
A study was conducted during 1994-95 in Finland within a 1600 ha area containing patchy boreal spruce (Picea abies) and pine (Pinus sylvestris) mire habitats. Vascular plant species were assessed in relation to (i) whether single large or several small (SLOSS) reserves contain more species and (ii) whether patch shape should be as nearly circular as possible. SLOSS and patch shape were tested using comparisons of species richness, taxonomic diversity and rarity of species. The number of species was unrelated to the size of spruce mire, but increased with size of pine mire. In contrast, the rarity score increased in relation to the area of spruce mires, but it was unrelated to the area of pine mires. Taxonomic diversity was unrelated to size in the case of spruce mires, but increased with size in pine mires. The SLOSS comparison indicated that several small mires contained more vascular plant species compared to a large one of equal size. Several small mires also exhibited higher rarity scores and taxonomic diversity than a single large mire. The number of species, rarity score and taxonomic diversity increased in relation to the number of small mires in a group for both pine and spruce. Species richness, species rarity and taxonomic diversity were unrelated to mire shape.