This thesis is a literature study. It focuses on the theory that a climax vegetation of closed forest systems covered the lowlands of Central and Western Europe in prehistoric times before man intervened and that it would still be there had this intervention not taken place. The theory also states that man's intervention, notably the introduction of livestock, has led to the disappearence of this climax vegetation in a process known as retrogressive succession. By the grazing of livestock the forest was degraded to thorny scrub and ultimately to grassland. According to the theory, it will revert to its natural vegetation of closed forest systems once the grazing of livestock is stopped.
The problem central to this study is that literature shows that pedunculate oak ( Quercus robur ) , sessile oak ( Q. petraea ) and hazel ( Coryllus avellana ) do not regenerate and cannot survive in closed forest systems while pollen analyses show that these species were present continuously in Central and Western Europe for 10,000 years since the end of the ice age. On the other hand these species do regenerate in park-like landscapes in the presence of grazing by cattle and horses, domesticated descendants of wild progenitors, and deer in so called wood-pastures.
The null hypothesis formulated in this thesis is that pedunculate oak, sessile oak and hazel have survived in the closed forest systems in the lowlands of Central and Western Europe and that the grazing of the indigenous large herbivores, such as aurochs ( Bos primigenius ), tarpan or European wild horse ( Equus przewalski gmelini ), European bison ( Bison bonasus ), Elk ( Alces alces ), red deer ( Cervus elaphus ), and roe deer ( Capreolus capreolus ), that inhabited these regions did not affect the composition of species or the succession of the forest in prehistoric times. The alternative hypothesis is that, in prehistoric times, the natural vegetation in the lowlands of Central and Western Europe was a park-like landscape, consisting of a mosaic of grasslands, scrub and solitary trees and groves surrounded by margins of scrub and forb fringe communities. The structure, composition of species and succession of this vegetation was largely determined by the large herbivores that inhabited the landscape.
The null hypothesis has been tested against succession theories, pollen investigations, historical texts, research into spontaneous succession in forest reserves and the ecology of the tree species that formed the climax vegetation in prehistoric times according to the theory being in force. A synthesis of the findings led to the conclusion that the primeval vegetation in the lowlands of Central and Western Europe was not a closed forest but a park-like landscape. In this landscape the vegetation followed a cyclical process, in which large herbivores played an essential role. The process was that in grazed grassland stands of thorny scrub evolved in which trees grew up being protected from damage by grazing. Eventually the trees developed into a forest which again slowly degenerated to grassland under the influence of large herbivores and "catastrophes" such as drought and storms, after which the cycle began anew. The result was that various biotopes varying from grassland, scrub to forest were permanently present but not always in the same place. This is called the theory of cyclical vegetation turnover. On the basis of the conclusion and this theory, the null hypothesis is rejected in favour of the alternative hypothesis. The importance of these findings for nature conservation in Central and Western Europe, with respect to the reference frames used by nature conservationists, is explained in an epilogue.
|Qualification||Doctor of Philosophy|
|Award date||23 Sep 1997|
|Place of Publication||Wijk bij Duurstede|
|Publication status||Published - 1997|
- nature conservation
- plant succession
- historical ecology