The object of this work is threefold. In the
first place it is intended as a general and descriptive
account of typical areas of semi -natural vegetation in
Great Britain. Secondly a study of the effect of biotic
factors which produce this type of vegetation is involved,
and special attention is given to a particular aspect of
the biotic factor.i.e. the mechanical aspect. This latter
influence has received little attention up to the present.
Thirdly the economic applications of the study are investigated.
It is very notable that almost all studies of
vegetation in this country and certainly all vegetation problem:
related to agriculture have been approached from the chemical
or edaphic standpoint. The explanation lies in the fact that
the earliest investigators were chemists, and their outlook
has been acquired by the student, the investigator and the
agriculturist. It is hoped to show in the following work
that the solution to many ecological problems, especially
those of semi -natural vegetation,is to be found by a consideration of some purely mechanical force ;and that the
edaphic factor does not always exert the influence attributed
The results of the investigations have been exploited
economically, in several directions. For example it is found
that on the poorest grassland (from the graziers' point of view).
that the footpaths traversing it, possess an entirely different
flora of species with a high feeding value. A complete
understanding of the factors producing this contrast enables
the same changes to be produced in the field as a whole.
Again in the sphere of weed cont, where mechanical agents
are responsible for the presence or the propagation of certain
weeds, a knowledge of these agents, and their mechanism, is
shown to solve the problem of prevention and control.
The influence of domesticated and wild animals upon
vegetation is also shown to be due frequently to a mechanical
rather than a chemical influence.