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The main aim of the study was to test the cladoceran planktonic:littoral (P/L) method in Holocene lake-level studies with three cores from a small lake (Iso Lehmälampi, 60°219N, 24°369E), in southern Finland. The cores were analysed for pollen, diatoms and Cladocera, which provided marker horizons, such as appearance level and maxima of species, for correlation with the fluctuations in P/L ratio in the cores. P/L fluctuations appeared to be corresponding and contemporaneous in all three cores and suggested that there were changes of lake level during the Holocene. Water level was high c. 9000–8000 14 C yr BP and low c. 7000 BP. The time from c. 4000 BP to modern times is characterized by several short-term fluctuations in water level. The P/L record appeared to be most informative in cores taken outside the shallow littoral area where redeposition may ‘smooth’ the curves. The chydorid species composition was rather uniform in the three cores and showed that analysis from only one core can give a reliable picture of species succession. Although the same P/L fluctuations could be found in all cores, there were large differences in the amplitude of fluctuations in the curves; this suggested that it is not possible to reconstruct the magnitude of lake-level change with this method. [ABSTRACT FROM AUTHOR]

Forest fires produced charcoal throughout the Holocene and charcoal was preserved in lake sediments. This study compares differences in sedimentary charcoal between southern and northern Finland. Yearly influx of the total surface area of the charcoal particles ( mm 2 cm -2 yr -1 ) was estimated at different latitudes: two lakes from southern Finland (60° 219N, 60° 599N), two from the Kuusamo area (66° 219N), NE Finland and one lake from NW Finnish Lapland (68° 409N). The results show that the mean amount of charcoal deposited in southern Finland was about 10 times higher than that from Kuusamo and 100 times higher than that from NW Finnish Lapland. These differences existed for the whole Holocene and were accompanied by changes in temperature and humidity, as well as drastic changes in forest type. It is suggested that the climatically induced difference in forest biomass at different latitudes accounts for the differences in charcoal influx. Since high-resolution charcoal analyses are not available, it is not clear if the fires were also less frequent in the Kuusamo area; however, there is evidence from Lapland of very long intervals between fires. [ABSTRACT FROM AUTHOR]