Palynology on lake sediments from the Pyrenees

A multi-proxy palaeoecological investigation including pollen, plant macrofossil, radiocarbon and sedimentological analyses, was performed on a small mountain lake in the Eastern Pyrenees. This has allowed the reconstruction of: (1) the vegetation history of the area based on five pollen diagrams and eight AMS14C dates and (2) the past lake-level changes, based on plant macrofossil, lithological and pollen analysis of two stratigraphical transects correlated by pollen analysis. The palaeolake may have appeared before the Younger Dryas; the lake-level was low and the vegetation dominated by cold steppic grasslands. The lake-level rose to its highest level during the Holocene in the Middle Atlantic (at ca. 5060±45 b.p.). Postglacial forests (Quercetum mixtum and Abieto-Fagetum) developed progressively in the lower part of the valley, while dense Pinus uncinata forests rapidly invaded the surroundings of the mire and remained the dominant local vegetation until present. The observed lowering of the lake levels during the Late Atlantic and the Subboreal (from 5060 ± B.P. to 3590±40 b.p.) was related to the overgrowth of the mire. The first obvious indications of anthropogenic disturbances of the vegetation are recorded at the Atlantic/Subboreal boundary as a reduction in the forest component, which has accelerated during the last two millennia.

Pollen profile from Schonen, Sweden

Two new Standard pollen diagrams from the raised bog Ageröds mosse in central Scania are presented and discussed. They have been made giving extensive consideration to the NAP and spores also. The new diagrams comprise in the main only the Post-glacial and can easily be compared with the earlier published Standard diagram from the bog (T. NILSSON 1935). The development of the Post-glacial Vegetation in the surroundings is also discussed and compared with the conditions in the southernmost part of the province (Bjärsjöholmssjön, T. Nilsson 1961). One of the new diagrams has been prepared in connection with the study of a core brought up by means of a special borer in order to bring about C14 datings. The core was almost ömlong and had a diameter of 6 cm. It was divided into pieces of 2-6 cm, which were preserved. After the preparation of the pollen diagram, suitable samples were selected for C14 dating. In all 33 samples, comprising the whole Post-glacial inclusive of the youngest part of the Late-glacial, were C14-dated. With the aid of the C14 dates the growth conditions of the bog are discussed. After very slow Sedimentation of predominantly minerogenous deposits in the last part of the Late-glacial, and still slow Sedimentation of gyttjas in the oldest part of the Post-glacial, the rate of growth (primarily of the gyttja) distinctly increased in the first part of the Late Boreal. A temporary retardation of the growth of the sphagnum peat at the end of the Sub-boreal is probably entirely local. The average rate of growth of the really highly humified parts of the old sphagnum peat amounts to 42 mm per Century, that of the slightly humified young sphagnum peat 81 mm per Century or somewhat more. Based on the C14-determinations, the pollen zone boundaries have been given the following approximate dates: boundary Late-glacial/Post-glacial (DR/PB) 8300 B.C., boundary Pre-boreal/Boreal (PB/BO) 7900 B.C., boundary Early Boreal/Late Boreal (BO 1/2) 6800 B.C., boundary Boreal/Atlantic (BO/AT) 6200 B.C., boundary Early Atlantic/Late Atlantic (AT 1/2) 4600 B.C. (?), boundary Atlantic/Sub-boreal (AT/SB) 3300 B.C., boundary Early Sub-boreal/Late Sub-boreal (SB 1/2) 1700-1800 B.C., boundary Sub-boreal/Sub-atlantic (SB/ SA) 300 B.C., boundary Early Sub-atlantic/Late Sub-atlantic (SA 1/2) 650 A.D.

Pollen and non-pollen palynomorphs counting data from Borsteler Moor (Germany)

In order to reconstruct regional vegetation changes and local conditions during the fen-bog transition in the Borsteler Moor (northwestern Germany), a sediment core covering the period between 7.1 and 4.5 cal kyrs BP was palynologically in vestigated. The pollen diagram demonstrates the dominance of oak forests and a gradual replacement of trees by raised bog vegetation with the wetter conditions in the Late Atlantic. At ~ 6 cal kyrs BP, the non-pollen palynomorphs (NPP) demonstrate the succession from mesotrophic conditions, clearly indicated by a number of fungal spore types, to oligotrophic conditions, indicated by Sphagnum spores, Bryophytomyces sphagni, and testate amoebae Amphitrema, Assulina and Arcella, etc. Four relatively dry phases during the transition from fen to bog are clearly indicated by the dominance of Calluna and associated fungi as well as by the increase of microcharcoal. Several new NPP types are described and known NPP types are identified. All NPP are discussed in the context of their palaeoecological indicator values.