Since its development in the 1980s, the NVC has become the
standard classification used for describing vegetation in Britain.
Whereas many other classifications are restricted to particular
types of vegetation (e.g. the Stand Type classification which
describes only woodland (Peterken 1981), the NVC aims to describe
all the vegetation of Great Britain. This means that it is possible
to analyse, and map, a complex site, composed of several habitat
types (e.g. woodland, scrub, heathland and bog) using the same
classification system. Successional or treatment related changes in
the vegetation, for example between open glades, shaded rides and
the vegetation of clear-fells can e more easily described than is
possible using other classifications.
The NVC is a 'phytosociological' classification, classifying
vegetation solely on the basis of the plant species of which it is
composed. The resulting communities can usually be correlated to
other factors, especially geology and soils, age and management;
but the plant species alone are used to assign the vegetation to a
community.
The NVC breaks down each broad vegetation type (e.g. woodland,
calcareous grassland, mires) into communities, designated by a
number and name (e.g. W8 Fraxinus excelsior – Acer campestre –
Mercutialis perennis woodland, CG1 Festuca ovina – Carlina
vulgaris grassland, M10 Carex dioica – Pingnuicula
vulgaris mire). Many (but not all) of these communities
contain several sub-communities, designated by a letter (e.g. W8a
Fraxinus excelsior – Acer campestre – Mercurialis
perennis woodland Primula vulgaris – Glechhoma
hederacea sub-community). Sub-communities may be further
divided into variants (e.g. M10bi and ii) but this has not been
adopted within the woodland section of the classification.
Woodland section of the NVC
The NVC woodland classification is based on 2,648 samples from
ancient and recent woods throughout Britain (Rodwell 1991). This is
the biggest data set yet analysed for the production of a woodland
classification in Britain (the Stand Type system, for example, was
based on about 800 samples (Peterken 1981)). Apart from the sheet
numbers of samples, the geographic and ecological spread of
sampling makes it the classification most representative of the
range of British woodland. The relationships between the NVC and
other woodland classifications are shown in Appendix 1.
There are 18 main woodland types and seven scrubs or
underscrubs, most of which are divided further to give a total of
73 sub-communities.
Factors other than plant composition are also important in
nature conservation terms. Two woods may be of same vegetation
type, but if one is regularly coppiced and the other is high forest
the bird and invertebrate life will be very different. Ancient
examples of a type are likely to contain more of the species
typical of ancient woodlands (e.g. oxlip Primula elatior,
herb-Paris Paris quadrifolia) than recent examples of the
same type. The NVC should not therefore seen as the only way of
describing woodland, but rather as one element in such
descriptions.
Subsequent to the publication of British Plant Communities,
various gaps in coverage of the NVC have been identified at
community and sub-community level, including several woodland and
scrub types (Rodwell et al. 2003; Goldberg 2003). No
attempt has been made to incorporate these into the present guide,
pending further analysis and formal description (Strachan &
Jackson 2003).
A seminar was held in 2001 by JNCC and the British Ecological
Society to review ten years experience of using the NVC
classification for woodlands (Goldberg 2003). Topics covered
included the wide range of uses, as well as limitations, of the
current classification, consideration of possible future
developments, and a European perspective on British woodlands. A
phytosociological conspectus in Volume 5 of British Plant
Communities (Rodwell 2000) also places all NVC communities
within a hierarchical framework of European vegetation and gives
helpful insight into the floristic relationships of NVC woodland
and scrub types.