13
10 91-100% cover
9 75-90%
8 51-74%
7 34-50%
6 26-33%
5 11-25%
4 4-10%
3 many individuals
2 less than 4% several individuals
1 few individuals
Both measures are necessary because many species which are frequent in a community
have characteristically low covers, and many infrequent species can have high abundance
when they do occur.
The NVC classifies vegetation types by its constant species, and the abundance and
frquency of each species is tabulated. Sub-communities of the main type community are
identified by the presence of species which are differentials (when confined absolutely to
one sub-community) or preferentials (when they are not so strictly confined).
A final list of associate species is shown, which are not constant throughout but which
occur at low frequencies showing no particular affiliation to any of the sub-communities.
On the day of the Hales Wood survey, the party was unfortunately not armed with the
rather expensive "British Plant Communities - Woodlands" volume or the NVC key, but
the survey method was used; selecting a homogeneous stand of vegetation; laying out
five quadrats of 4m x 4m; and recording frequency and abundance of all species. A brief
summary of the frequencies recorded is quite interesting:
Oxlip Primula elatior 100%
Willowherb Epilobium (Chamaenerion) angustifolium 100%
Violets Viola spp. 80%
Meadowsweet Filipendula ulmaria 100%
Creeping thistle Cirsium arvense 60%
Marsh thistle Cirsium palustre 80%
Wood averts Geum urbanum 60%
Sanicle Sanicula europaea 40%
Celandine Ranunculus ficaria 80%
St. John's wort Hypericum sp. 80%
Enchanters' nightshade Circaea lutetiana 80%
Burdock Arctium minus 80%
Lords and Ladies Arum maculatum 40%
Wood anemone Anemone nemorosa 20%
Barren strawberry Potentilla sterilis 40%