Impact of forest disturbance on the pollen influx in lake sediments during the last century

Abstract

The pollen accumulation rates of four lakes in different regions of Estonia were estimated in order to study the relationship between pollen influx and the character and intensity of disturbances in the pollen catchment area. The pollen influx data obtained are in accordance with model calculations on the size of the pollen source areas. The influx of arboreal pollen and that of the dominant taxa (mainly Pinus) in the lakes investigated shows that, in the case of small lakes (area 3–6 ha) in a forested landscapes, the bulk of the pollen originates from an area within 100–200 m around the lake. The distribution patterns of influx from two lakes situated close to each other but at different distances from forest fires show that past disturbances can be reliably detected when the disturbance occurred in the immediate vicinity of the lake and at least 25% of the local pollen source area was involved. In the case of a large lake (137 ha) only fires embracing thousands of hectares can be detected in the pollen diagrams.