Diatoms, Cladocera, and chironomids preserved in the sediments of Lake Dalgoto were studied to reconstruct the history of the lake ecosystem in the context of the vegetation history as represented by the pollen stratigraphy. Younger Dryas silty sediments at the base of the core are characterized by low diversity of aquatic organisms. The transition to the Holocene is indicated by a sharp change from silt to clay-gyttja. The migration and expansion of trees at lower elevations between 10200 and 8500 14C-yr BP, along with higher diversities and concentrations of aquatic organisms and the decreased proportion of north-alpine diatoms, point to rapidly rising summer temperatures. After 6500 14C-yr BP the expansion of Pinus mugo in the catchment coincides with signs of natural eutrophication as recorded by an increase of planktonic diatoms. In the late Holocene (4000-0 14C-yr BP) Pinus peuce and Abies are reduced and Picea expands. Cereal grains and disturbance indicators suggest late-Holocene human modification of the vegetation.
Bibliographical noteFunding Information:
We appreciate the cooperation of the staff of Regional Office of National Park Pirin for arranging the field work. The core was obtained with the aid of H. E. Wright, E. Bozilova, A. Velchev, D. Dimitrov, E. Kozuharova, D. Uzunov, S. Tonkov and R. Kol-chakov. We thank W.O. van der Knaap for help with numerical analysis and H. E. Wright and H.J.B. Birks for discussions and improvement of the manuscript. The study was supported by the Swiss National Science Foundation (Grant No. 7BUPJ041258) and the National Science Fund in Sofia, Bulgaria (B-625/ 96).
- Late Quaternary environment
- Southwestern Bulgaria