© 1978 by Institute of Chartered Foresters
Irregularity in British Forestry
Forestry Commission, Forest Research Station Wrecclesham, Famham, Surrey
The world's forests at present yield one cubic metre per hectare per annum. The very small area of plantations yield seven or eight times as much per hectare. To satisfy an increasing population it is inevitable that agriculture will encroach upon forest land and that plantations will become relatively more important as a source of wood.
Specialisation is leading to differing emphases in forest policy in different regions and the relevance of irregularity depends in fact upon the relative importance of the various policy objectives.
Irregularity means different things to different people but to the forester it implies mixed species, all-aged-crops or crops having a wide range of size classes.
The available evidence on the relationship between irregularity and production is not always unequivocal but, in general, even-aged and low-thinned crops produce a somewhat greater yield than all-aged or crown thinned stands. Mixtures can sometimes produce more volume than any of the constituent species alone but the production of the species having the highest yield class can probably not be increased by including slower growing species within the crop. There is little evidence one way or the other on the relationship between man-made irregularity and health.
Foresters feel that it is imprudent from the points of view of management and aesthetics to create large areas of uniform forest but socio/economic trends favour regular working. These conflicting considerations can be reconciled by creating variable forests composed of regular stands. In particular, a small wood planting grant designed to favour broadleaves might better be given for a mixture of small pure stands designed to give a predominantly hardwood appearance, than for a tree by tree mixture of broadleaves and conifers.