Agriculture, Ecosystems and Environment 79 2000 159–174
Development of vegetation on set-aside land for up to nine years from a national perspective
C.N.R. Critchley
∗
, J.A. Fowbert
ADAS Newcastle, Kenton Bar, Newcastle upon Tyne NE1 2YA, UK Received 28 June 1999; received in revised form 25 November 1999; accepted 25 November 1999
Abstract
Set-aside provides an opportunity to counteract recent declines in arable farmland biodiversity in the UK. Its recent widespread adoption has allowed its vegetation to be assessed from a national perspective. A botanical survey of 97 sites in
England, stratified by intensive arable and mixed agriculture geographical regions, was carried out. Set-aside vegetation was established by natural regeneration or sown cover, and aged up to 9 years. Vegetation was recorded at each site from 30 quadrats
located on transects running from the field boundary towards the field centre. Overall, cover was dominated by perennials and monocotyledons, with a large number of other species occurring at only a few sites. Species functional types and individual
species frequencies differed between region, establishment method natural regeneration or sown cover, and site age. The mixed agriculture region had vegetation with characteristics more similar to grassland, whereas in the arable region succession
remained at an earlier stage for longer. Sown species accounted for differences between establishment methods. Succession continued after 5 years, with increasing species richness, perennials and species characteristic of non-arable habitats. Species
richness within sites declined with increasing distance from the field boundary. Variation between sites in plant community composition was not accounted for by generalised soil and site management data. Although overall botanical diversity was low,
the development of permanent grassland habitats on non-rotational long-term set-aside is a realistic objective. This needs to be balanced against known benefits of rotational short-term set-aside. Variation between regions suggests that benefits to
biodiversity will accrue at differing rates in arable and mixed farming landscapes. At a national scale, regional differences should be taken into account when implementing policy objectives to optimise biodiversity benefits from set-aside. © 2000
Elsevier Science B.V. All rights reserved.
Keywords: Set-aside; Biodiversity; Vegetation succession; Arable plant communities; Vegetation survey; Functional types; UK
1. Introduction
Biodiversity on arable farmland has undergone severe declines in recent decades in those parts of Eu-
rope where intensification of agricultural production
∗
Corresponding author. Tel.: +44-191-214-1704; fax: +44-191-271-6763.
E-mail address: nigel.critchleyadas.co.uk C.N.R. Critchley
has occurred. In the UK, this has been well docu- mented and comprehensively reviewed e.g. Anon.,
1995; Kirkwood, 1997; Sotherton, 1998. One of the most important recent changes in management
of arable land in the UK has been the introduction of set-aside as a means of supply control, by tem-
porary cessation of arable production on a defined percentage of the total arable area. With up to 6.4 mil-
lion ha set-aside in Europe at its peak in 1993–1994
0167-880900 – see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 8 8 0 9 9 9 0 0 1 5 5 - 3
160 C.N.R. Critchley, J.A. Fowbert Agriculture, Ecosystems and Environment 79 2000 159–174
Sotherton, 1998, this was potentially significant for biodiversity on arable farmland.
The establishment of vegetation on abandoned arable land, and its early successional changes have
been comprehensively described from old-field sys- tems e.g. Bazzaz, 1975; Pickett, 1982; Lepš, 1987.
Similar processes in set-aside vegetation have been observed in studies of single sites and surveys within
restricted geographical areas Fisher et al., 1992; Wilson, 1992; Turley et al., 1994. The common se-
quence in naturally regenerated set-aside vegetation is the initial establishment of annual species along
with self-sown crops from the previous season’s shed seed volunteers, which decline rapidly in abundance
during the first 2–3 years, to be largely replaced by perennial grasses by the fifth year. Where vegetation
cover is sown, the sown species tend to dominate the vegetation during this early phase, suppressing other
species, and particularly the annuals that are other- wise characteristic of the first 2 years. Spatial pat-
terns of species richness within fields tend to reflect those observed for arable weeds and their seedbanks
within arable crops, with greatest concentrations be- ing within a few metres of the field edge Marshall,
1989; Rew et al., 1992; Wilson and Aebischer, 1995. Corbet 1995 noted that empirical studies of set-aside
have been short-term and influenced by site-specific factors. More recently, the effects of management
on set-aside vegetation have been reported from a 10-year experiment Hansson and Fogelfors, 1998.
Assessments of the value to biodiversity of set-aside vegetation have highlighted the need for appropriate
management if positive benefits are to be realised Firbank et al., 1993; Sotherton, 1998.
The first set-aside in the UK was introduced as a voluntary scheme in July 1988 Anon., 1988, and was
followed by a second voluntary scheme for 1 year in August 1991 Anon., 1991a. In May 1992, set-aside
became part of the Arable Areas Payment Scheme AAPS under the reform of the Common Agricul-
tural Policy of the European Union Anon., 1992. The original 1988 scheme in the UK required a minimum
of 20 of eligible land on a holding to be taken out of production in return for annual compensation pay-
ments, but this was subsequently reduced under the AAPS to 5 by 1996–1997. With these administra-
tive changes, also came modifications to the rules for set-aside management, but, in general, land entered
into set-aside could either be rotated annually around the holding rotational set-aside, or be kept in the
same place non-rotational set-aside. Set-aside land could either be in blocks usually whole fields or as
20 m wide strips that were usually sited along field boundaries. Vegetation on set-aside fallow had to be
established either by natural regeneration or by sown cover grasses and, in some cases, legumes. This veg-
etation had to be cut periodically at least once a year and cultivation was only allowed to control weeds or
before establishing new plant cover. Pesticides and fer- tilisers were prohibited except under certain exemp-
tions. From October 1991, some set-aside land could be grazed with livestock Anon., 1991b.
With some fallow set-aside sites now in existence since 1988, and set-aside widely adopted from 1992,
there was an opportunity to re-assess the development of its vegetation to include later years of succession,
and its variation at a national scale. The success of wildlife habitat recreation on arable land in the longer
term is largely dependent on the development of suit- able vegetation. The timescale over which this is likely
to occur, and its consistency in different geographical regions will have important implications for the future
management of set-aside land for biodiversity.
The aim of this study is to describe the variation in fallow set-aside vegetation from a national perspec-
tive, including the full age range of sites currently in existence. This was achieved by field survey of a sam-
ple of sites from England, UK.
2. Methods
