Spatial and structural uniformity of lowland agricultural grassland in England: a context for low biodiversity
The contention that agricultural grassland within the UK is spatially and structurally uniform across wide differences in livestock farming intensity is examined. Total nitrogen (N) input was used as a surrogate for management intensity. Farms with average annual N inputs of >200 kg ha−1 were categorized as highly intensive, those with N inputs of 50–200 kg N ha−1 as moderately intensive and those with inputs of <50 kg N ha−1 were categorized as extensive. Four farms within each management category were selected in two discrete regions: one in south-west England, typifying a landscape dominated by agricultural grassland, the other in south-east England with a more mixed-farming landscape. Specific N input and management data, and sward botanical composition and structure, were obtained on four fields per farm. The south-west region had a higher proportion of farms with dairy cattle than in the south-east England region. The average N input and stocking rates were higher within the intensive-management category farms in south-west England than in south-east England. Old permanent grasslands contained variable amounts of sown species, such as Lolium perenne, and were dominated by a few (generally <5) non-sown grass species. Grassland that received >75 kg N ha −1 year−1 contained <7 plant species and <3 forb species m−2. Grassland communities with >12 plant species and >5 forb species m−2 were only found in study fields that received <50 kg N ha−1 year−1. Grasslands with >10 forb species m−2 were found only in sites receiving <15 kg N ha−1. Of importance at a landscape scale was ubiquity of species-poor and similar grassland plant communities across the management intensity range within and between livestock farms. Grassland in the extensive management category was similar in structure in terms of sward height and/or sward density to more intensively managed grasslands. This study revealed, albeit in two lowland sample regions in the UK, the ubiquity of grass-dominated, species-poor and structurally uniform grasslands, irrespective of apparently broad differences in farming intensity. The consequences of this spatial uniformity on grassland biodiversity are likely to be profound.
Document Type: Research Article
Affiliations: 1: Institute of Grassland and Environmental Research, Devon, UK 2: †Department of Zoology, Ecology & Plant Science, University College Cork, Cork City, Ireland 3: ‡The British Trust for Ornithology, The Nunnery, Norfolk, UK
Publication date: 2005-09-01