Paleoecological studies in the Klokkeweel bog near hoogkarspel (prov. of Noord-Holland)

Abstract

The course of filling-in and subsequent bog development of a brackish eutrophic lake is analyzed by means of investigations of pollen, spores, algae, fungal remains, diatoms and plant macrofossils. Some unknown and/or not generally known micro- and macro-fossils are described and illustrated. 14C datings and ignition residue determinations have been made. The analysis was expected to provide information about both regional and local vegetational developments, but the picture presented by the micro- and macrofossils is mainly local. In the lake sediment, deposited on a subsoil of marine clay, and the overlying peat the following phases in the vegetational succession have been defined: (a) initial phase with small elodeids, dominated by Myriophyllum spicatum; (b) littoral phase, characterized by vegetation types of Callitricho-Batrachion; (c) floating mat phase: Cicuto-Caricetum pseudocyperi, followed by a Caricetum paniculatae; (d) willow scrub with undergrowth of Dryopteris; and (e) birch carr. Salinity, alkalinity and trophic degree decrease with the advancing succession. The vegetation shows traces of human influence, but apparently the local succession is not strongly affected. The phase with birch carr shows two periods of wetter conditions, dated ca. 750 B.C. and ca. 600 B.C., respectively. The final period may explain the widespread abandonment of prehistoric settlements in West Friesland. The pollen diagram shows a mysterious maximum of Pinus from ca. 750 to ca. 650 B.C.