Plant communities of the Yuzhno-Sakhalinsk mud volcano

The Yuzhno-Sakhalinsk mud volcano is one of three centers of mud volcanism in Sakhalin Island. Regular eruptions and high salinity of substrates (exceed 27 g/l, pH 11) form specific conditions for ecosystems. The Yuzhno-Sakhalinsk Mud Volcano is a protected natural area, but there is still no data on its vegetation cover in scientific literature. The study of composition, structure and dynamics of the mud volcano plant community is important for nature conservation and biodiversity protection. Vegetation cover on the mud volcano surface was explored in summer-autumn seasons 2012-2013, 105 sample plots were formed. We found 33 vascular plants species of community's on the mud surface, generated after the violent eruptions in 1959, 1979 and 2001. These plant communities are different stages of vegetation succession. Pioneer community formed on the recently erupted mud (1-4 years) is composed of one species Triglochin palustre and the total coverage is less than 0.01%. The next stage in the succession is Triglochin palustre-Phragmites australis community on the surface created by eruption in 2001. Average plants cover of this community is 20%, mean floristic richness (mean number of species at 1x1 m plot) is 1.81. Phragmites australis-Aster glehnii community develops on the surface which was generated after the eruption in 1979. Mean floristic richness is 3.89, plants coverage is about 70%. The next Phragmites australis-Salix caprea community formed on the mud field appeared during the violent eruption in 1959. In contradistinction to younger communities Phragmites australis-Salix caprea are composed of plants at the first ontogenetic stages of trees (Salix caprea, Salix udensis, Betula platyphylla, Picea ajanensis) and shrubs (Rosa acicularis, Sorbus commixta) species. The total plants coverage is about 90% and mean floristic richness is 6.92. Bryophytes and lichens do not play a significant role in the composition of vegetation cover. The study of vegetation on the slopes of an old, almost non active, mud volcano, which is located 200 meters south-west of the current volcano, suggests that the succession to the mud volcano substrate finish with formation of zonal quasi-climax forest-community dominated by Abies sachalinensis. In contrast to old-growth forests, the forest on the mud volcano sediments has a poor floristic diversity and abundance, simplified vertical (no shrubs canopy and liana species) and a horizontal structure. Dynamic changes of vegetation cover are associated with improved growing conditions and the disappearance of ecotopic stress by reducing salinity of the substrate, accumulation of nutrients and soil cover formation with increasing the mud surface age. Key words: mud volcano; vegetation cover; community; succession.

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