Postglacial trends in palynological richness in the northern Fennoscandian tree-line area and their ecological interpretation

Abstract

The northern Fennoscandian tree-line area consists of fairly distinct vegetation zones. The pollen stratigraphies of two boreal sites and two tundra sites were studied and the palynological data analysed numerically. The main aim was to measure palynological richness, using rarefaction analysis, and to assess its value in reflecting patterns of past floristic richness. Rates of palynological change were measured using both chord distance and Euclidean distance as the dissimilarity coefficient. The results show low palynological richness during the Younger Dryas. The values increase rapidly at the transition to the Holocene. During the Holocene the values are in reversed order in relation to present vegetation density, the tundra sites having the highest palynological richness. This suggests that differences in the size of the pollen catchment may have an important role in palynological richness estimates and that no straight comparisons of palynological richness should be made between sites from different vegetation zones. Most pronounced changes in palynological richness take place in the Lake Rautuselka core, where high Pinus pollen influx is correlated with low palynological richness. At the boreal sites, high rates of change are associated with higher palynological richness whereas no similar relationship is observed at the tundra sites.

Late Weichselian (Valdaian) and Holocene vegetation and environmental history of the northern Timan Ridge, European Arctic Russia

“…7) indicates more open conditions ( [Birks and Line 1992]; [Odgaard 1994]). [Seppä 1998] also found a richness increase during the Holocene tree-line retreat in Fennoscandia. In paz 15-7, present-day tundra taxa (e.g.…”

“…6), and (3) decreasing palynological richness ( Fig. 7), lower than in the Lateglacial of SW Norway ( [Paus 1992]) and in the early Holocene of northern Fennoscandia ( [Seppä 1998]). Paz 25-3 is interpreted to reflect ameliorating conditions passing the level of intermediate disturbance ( [Grime 1973]) towards increased competition (cf.…”

“…As this caused an increased pollen source area, palynological richness increased (cf. [Birks and Line 1992]; [Seppä 1998]), long-distance representation (e.g. Pinus, Picea, Alnus) improved, and pollen influx decreased (cf.…”

“…Vaccinium-type and Melampyrum. A more open local vegetation is shown by rising palynological richness ( [Birks and Line 1992]; [Seppä 1998]), improved long-distance representation (e.g Pinus spp., Artemisia), and increased Poaceae values. The paz, closely ordinated with modern surface samples ( [Paus 2000]), reflects a tundra similar to the present.…”

Fifty years of Quaternary pollen analysis in Fennoscandia 1954–2004

“…McAndrews studied pollen stratigraphies from four small lakes along the major west-east prairiesavanna -deciduous forest -mixed coniferous forest vegetational gradient and associated annual precipitation climatic gradient. The same sampling design was adopted by Hyvä rinen (1975,1976) and subsequently by Seppä (1996Seppä ( , 1998 in their studies of Holocene forest history and tree-line dynamics in northern Finland and northern Norway. Transects of sites along climatic and vegetational gradients are particularly useful in reconstructing climatic and vegetational change as plant responses to climatic change are likely to be greatest at or near range margins such as occur along major climatic and vegetational gradients.…”