Retrogressive forest development, as reflected in a mor pollen diagram from Mantingerbos, Drenthe, the Netherlands

Abstract

(pp. 47-48)

Like Draved, Mantingerbos is situated in a formerly rather isolated area (compare the maps in Waterbolk 1967). Human activity was low until about 1.000 years ago, when the first agriculture developed in the forest area, probably contemporaneous with the origin of the hamlet of Mantinge.

Fortunately the mor soil, which was a result of human activity, was never cut away as in almost all other areas in Northwestern Europe. The mor forms the basis for the pollen analysis in Mantingerbos. Until ca. 2800 B.P. the forest soil was a mull developed on brook sand, but as the mull was poor it only needed a small "push" to change into a more acid form. This "push" came from man who began to cut some trees, and the mull changed into amphimull, the transitional stage between mull and mor. This amphimull became slowly more and more mor-like and as man intensified tree cutting in early Medieval time the amphimull changed into a mor. The mor forest was rather stable until the whole forest was cleared probably only a few hundred years ago. When this clearing took place, Ilex was already a common tree or shrub in the forest, and because it was apparently not felled, it spread very quickly from suckers. Very soon a pure Ilex forest developed. At the same time the soil changed from a copromor into a mycomor and for that reason it is obvious, that Ilex must have been responsible for the soil change.

The pollen diagram from Mantingerbos demonstrates a strictly local vegetational development, and it is difficult to compare with other diagrams from Drenthe (van Zeist 1955, 1959), which are regional diagrams from more or less extensive Sphagnum bogs. Fossil mor has earlier not been found in the Netherlands, and so far no Postglacial diagrams prepared for small lakes in Drenthe have been published. Furthermore, the last one to two thousand years are not commonly represented in the pollen diagrams, because the upper part of the bogs has been destroyed by peat cutting and cultivation in recent centuries.

Iversen's purpose in Mantingerbos was, if possible, to obtain information on the behaviour of Ilex during Subboreal time. As the diagram includes only the last few hundred years of the Subboreal, no answer on that question can be given. However, it seems as if in Mantingerbos as well as in Draved, Ilex was to some extent favoured by human activities, and especially cattle grazing.

Through the work done in Draved and Mantingerbos,together with inspiration from P.E. Muller and others, it has been possible to put forward a theory for the soil development in areas with alluvial sand, sandy till or similar sediments. The theory explains, to some extent, the development of the soil from raw soil via protomull, amphimull, copromor to mycomor.