Vegetation of arable field margins in Breckland
In the Breckland Environmentally Sensitive Area (ESA), farmers are encouraged to
manage arable field margins to conserve arable plant communities using uncropped, cultivated
field boundary strips ("uncropped wildlife strips") (UWSs). This study aims to describe the
vegetation ofUWSs and to carry out an ecological assessment against the ESA objectives.
Data were collected from a sample ofUWS and normally cropped sites in three study
areas between 1989 and 1992. Species richness and non-crop biomass were greater in UWS
than cropped sites. Bromus sterilis became dominant in study area 1, and appeared to have a
competitive effect on other species. In study area 2 cultivations were done less frequently and
perennial Graminae spread and became abundant. In study area 3, Amsinckia micrantha
showed greatest increase but no effect on other species was apparent. Weed ingress into
adjacent crops was lower at UWS than normally cropped sites.
ESA objectives were translated into ecological criteria which could be directly
measured. Assessments by subjective expert opinion and using species autecological data
were compared. Subjective data were collected by a postal questionnaire of experts.
Indicator species for each criterion were identified by applying rule sets to a species-attribute
matrix. Site values for each criterion were calculated, and overall site values (foci) assigned
using a multiple criterion method. Subjective site assessments closely agreed with the site foci
and also with three of the five criteria. Over four years, half the sites were above the threshold
level which represented satisfying ofESA objectives.
Multivariate analysis of variation in the vegetation, from the main dataset and from a
second survey, showed sites with lower soil pH, K and total N were more successful. Those
with many overhanging or broadleaved trees, or previously cropped with sugar beet were less
Some amendments to management prescriptions are recommended.