Poliakova, Anastasia (2011) Reconstruction of the Vegetation of Podporozhsky District (Leningrad Oblast, Russia) during the Holocene according to Pollen Analysis. (Master thesis), State University of St. Petersburg, Russia ; University of Hamburg, St. Petersburg, Russia ; Hamburg, 66 pp.

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Abstract

Sediment sequences retrieved from two coring sites at the Lake Novoe (Point N1 (60° 48.984´ N; 34° 57.718´W, depth – 2.7 m.); point N2 (60° 49.265´ N; 34° 57.451´ W, depth – 3.07 m), North-Eastern part of Podporozhsky district, Leningrad region, northwestern Russia, were analyzed for pollen analysis. Studied community passed through 5 stages in its development. Age control was calibrated by comparison of our pollen data to ones described in literature related to the same region (Onega Lake surroundings). Pollen data from ten cores were taken for this purpose. Birch woodlands, probably thinly-planted were widespread in Preborial stage (10 200-9300 years ago), then distinct change towards to warmer and more humid climatic conditions took place, open Pinus–Betula forest around the lake were gradually replaced by boreal forest with Picea, Pinus, Betula, Alnus incana and Corylus. This type of communities continued to dominate till the end of Boreal period (8000 years ago). The Atlantic period (8000 - 4600 years ago) was marked by increased abundance of broad-leaved species and thermiphyllic herbs. Quercus, Ulmus, Tilia and Corylus appeared in the area simultaneously. At the end of the Atlantic period broad-leafed woods began being replaced by spruce and pine-tree communities. Later, during the Subboreal (4600-2500 years ago), these processes continued. Subatlantic period (started 2500 years ago) marked by development of Pine woods with birch and willow. Coasts of the lake probably were covered with grasslands formed by Poaceae, Cyperaceae, and Asteraceae. Modern stage of community was studied by means of phytosocialogical descriptions along 4 km transect. Besides, pollen traps were set every 200 m through this transect. Nowadays forests of Piceeta-Pineta formation prevail within 70% of territory, 30% of it are covered by secondary wood communities with Betula, Alnus and Salix. Specter of trapped pollen reflected composition of plant communities satisfactory, with a value of 4.9 for grasslands and 7.7 (maximal – 9.1) in forests and shown the mean value about 5.7±2.3 which is of satisfactory correction.

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