Woodland Education Centre
Ecological Surveys 1996 - 1998The Effects of Management
The dominant plant species on the project site were grasses. Initially, Bents (Agrostis spp.) were dominant, but by 1998, Yorkshire Fog (Holcus lanatus) had become the most dominant grass species on the site. This seemed to be related to brushcutting. This relationship was indicated by the fact that the only areas where Yorkshire Fog was not dominant, were those which were not cut.
Brushcutting is non-selective and reduces all vegetation to ground level at regular intervals. This eliminates competition from species which would grow taller than the grass, given time (Gorse, Heather, tree seedlings). If these were allowed to grow up, they would outcompete the Yorkshire Fog and Bents and prevent them from becoming dominant. (However, they would also in time shade out the underlying developing heath vegetation.)
The main effect of brushcutting to date seems to have been to encourage the spread of Yorkshire Fog.
The vegetation of the project site has always been dominated by grasses, mainly species of Bent (Agrostis spp.) which are characteristic of acid soils and Yorkshire Fog. Initially, the Bents were dominant over the site, but by 1998, Yorkshire Fog had taken over as the most dominant species (Table). The percentage cover of Yorkshire Fog more than doubled from 1997 - 1998.
Changes in distribution and abundance of Yorkshire Fog from 1996b -1998 are illustrated in Figures A - C below. Corresponding with the increase in % cover of Yorkshire Fog, the % cover of the Bent species had generally declined (Figures D-J).
Distribution of the major grass species on the project site.
The kite diagrams above are a visual representation of the distribution of Yorkshire Fog (Holcus lanatus) and Agrostis spp. across the sections 1 - 9 of the project site.
The distribution patterns shown are derived from mean % cover data from the belt transect surveys. The scale is shown below diagram A. Each row represents the change in distribution of the named species with time (1996-1998).
Dominance by Yorkshire Fog and Common Bent is undesirable on the project site because it leads to an unbroken sward which does not allow for the establishment of other species. In the summer months, the grass reaches heights in excess of 1m, shading out other smaller competing species.
In contrast, species such as Bristle Bent, characteristic of heathlands, form individual tussocks which still allow for the establishment of other heath species in between plants.
A relationship between the increasing dominance of Yorkshire Fog and cutting was indicated by the fact that the only areas in which Yorkshire Fog was not dominant were those which were not cut (sections 5 and 9), together with section 7, where grasses were initially controlled by the use of Kerb granules.
Brushcutting is non-selective and reduces all vegetation to ground level at regular intervals. This eliminates competition from species which would grow taller than the grass given time, such as Gorse, Heather and tree seedlings. If these are allowed to grow up, as in sections 5 and 9, they outcompete the Yorkshire Fog and Bents and prevent them from becoming dominant. Thus the dominant species in sections 5 and 9 included Gorse, Heather and Silver Birch (Table).
While this would seem to indicate that brush cutting is unfavourable by promoting the spread of grasses, it must be remembered that in time, the tallest vegetation would also shade out underlying heath species. Brush cutting is therefore necessary for long-term considerations.
Continue to the effects of brushcutting on tree seedlings
Ecological Surveys 96 - 98