Vegetation and site conditions of a Sphagnum percolation bog in the Kolkheti Lowlands (Georgia, Transcaucasia)
This paper characterizes vegetation, site conditions, and human impact in the Ispani II percolation bog on the eastern Black Sea coast of Georgia. The TWINSPAN analysis distinguished 13 vegetation groups which were summarized to six vegetation (sub)types: the Juncus effusus-Sphagnum palustre type, the Sphagnum austinii-Polytrichum strictum-Rhododendron ponticum type divided into three subtypes, and the Carex lasiocarpa-Campylopus pyriformis-Potentilla erecta type divided into two subtypes. The PCA ordination showed the importance of bog edge distance, ash content, C/N ratio and slope for separating the vegetation types. Grazing is an important differentiating factor in the bog margin and burning in the southeastern bog part. Both interventions lead to increased relief differences and the formation of anthropogenic hummock-hollow-structures. Since the 1920s the bog is influenced by eutrophication by wind-blow material from agricultural fields, which probably caused the marked decline of Sphagnum austinii since the 1930s. The central northwest part of Ispani 2 bog probably hold the last remnants of the (near) original (and extremely species-poor) vegetation that characterized the Kolkheti Lowlands bogs before the beginning of intensive land reclamation in the first decades of the 20th century. The most important treats beside drainage are fires and cow grazing.