Palynological richness and pollen sample evenness in relation to local floristic diversity in southern Estonia

Abstract

The relationship between palynological diversity and floristic diversity was studied on the basis of sediment surface sample pollen data from nine small lakes and vegetation data within a 250 m radius from the lake shore of each. The nine study areas are situated in the patchy cultural landscape of Southern Estonia and were chosen to represent landscape changes along a gradient from closed forest to open vegetation. Two diversity measures – richness and evenness – were used to compare the palynological and floristic data. A total of 307 plant species were recorded in the vegetation representing 127 pollen types. Only 52 pollen types were recorded in the sediment surface samples of which 43 had parent plants in the vegetation. Significantly lower floristic richness was found in closed surroundings than in more open surroundings. Study sites with open vegetation also had significantly higher palynological richness (number of pollen types recorded in surface sediments). The additional pollen types recorded in surface sediments from open vegetation were widespread types mostly of insect-pollinated taxa such as Ranunculus, Rubiaceae, Melampyrum, Filipendula, Potentilla or Vaccinium. The parent plants of these pollen types were frequent in the landscape. This suggests that the main mechanism governing palynological richness in this study was not floristic diversity but rather variance in pollen productivity. Since woodland has a higher pollen production than open areas (grassland and fields) per unit land surface, open areas tend to show a better representation of slightly rarer but widespread herb pollen types. No relationship was found between palynological and floristic diversity of wind-pollinated taxa and tree taxa partly because the pollen source area for these pollen types is much larger than 250 m.