ECOFACT Volume 1 Introduction and Approach - Centre for Ecology ...

aggregate classes are well represented, indicating the inherent variability of this landscape. The
upland landscape is dominated by AC VII and AC VIII.
• Plot types
Percentage frequency of the six plot types, (ie main, habitat, boundary, hedge, streamside and
roadside).
Distribution maps, areas and lengths
The average area (for main plots) and length (for linear plots) per land class were entered into a
Geographical Information System (GIS) together with the land class of each 1 km2 in Great
Britain, in order to produce the predictive distribution maps. For main plots, this figure was
weighted according to the relative area of vegetated land in the sample 1 km squares. A statistical
procedure was used to estimate the area of the CVS classes and their associated standard errors.
A similar procedure was followed for the relative lengths of the four linear features, except that
the weightings were by length rather than area. Estimates of lengths of the CVS classes along
roadsides, streamsides, hedges and boundaries are also provided. Where a class is not
represented by a plot type, the map for that plot type is blank or has negligible area or length.
Floristic characteristics
• Species number
A figure is given for the total number of species recorded in all the plots found within the
vegetation class.
• Number of species groups
The species recorded from the plots were classified into 37 species groups (Table 1), according to
their ecological demands (Bunce 1977; Prieto & Sanchez 1992). Each species occurs in only one
group and all the species in any given group have similar habitat requirements. The vegetation
classes vary in their species complexity. Management associated with crop production creates a
narrow, uniform range of ecological conditions suitable for only a few species of a restricted
ecological range, so that only crop and weeds are present, eg species group 1. In contrast, the
woodland plots often contain mixtures of species tolerant of a variety of ecological conditions,
such as grassland, eg species group 27, or dense woodland, and plots on the edge of woodlands
may contain species from grassland, scrub and tall woodland, eg species group 25. The number of
species groups provides a useful measure of the diversity of the vegetation.
Both the vegetation classes and species groups were simultaneously arranged (ordered) according
to the principal gradient described by DECORANA (ie Axis 1 in Figure 1), so that they were ranked
in the same way in the listings, and so that users would know that adjacent numbers had more in
common that those further apart.
Table 1. Brief descriptions of the 37 species groups (defined by applying Ward’s minimum
variance clustering of DECORANA scores). Three examples of the list of species belonging to each
group are given in order to provide an overall picture of the composition; the groups are ordered
according to their average DECORANA scores.
Species
group Species group name Characteristic species
1 Crop or crop edge plants on fertile soils Bromus sterilis, Convolvulus arvensis,
Lamium album
2 Crops, crop edge or grassland on eutrophic Elymus repens, Rumex crispus, Sonchus