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Heather Trust Annual Report; 2004
Environmentally Sustainable and Economically Viable Moorland Grazing Systems
Dr Nigel Critchley of ADAS Redesdale provides an introduction to a grazing project that is still in its infancy but is already proving the benefits that livestock grazing can bring to moorland habitat management.
Heavy grazing of heather moorland by sheep has been the object of much recent concern in many parts of the UK. Agri-environment schemes have partly addressed the problem by encouraging farmers to reduce sheep stocking levels on degraded moorland. Although this might be successful in preventing further loss of dwarf shrub cover, restoration is not guaranteed because the increased biomass of moorland grasses such as purple moor-grass [Molinia caerulea] and mat grass [Nardus stricta] can inhibit regeneration of heather and other more desirable species. [including birds. Ed] Mixed grazing regimes involving both cattle and sheep might provide part of the solution to this problem.
To address these issues, a major multi-disciplinary project is being funded by DEFRA, English Nature and the Countryside Council for Wales. A consortium comprising ADAS, the Centre for Ecology and Hydrology, Institute of Grassland and Environmental Research, Newcastle University, the RSPB and Scottish Agricultural College is using a combination of field experiments, computer modelling and consultation with practitioners to develop environmentally sustainable and economically viable grazing systems for restoring and maintaining heather moorland. The project aims to cover moorland habitats targeted by the UK Biodiversity Action Plan, including wet and dry upland heaths and blanket bog and will examine livestock production and economics as well as impacts on biodiversity.
Following a scoping study, current practice at a selection of sites is being evaluated with respect to its impact on biodiversity and economic viability. Models are also being developed to provide insights on the processes driving change and to assess the potential outcomes of different management scenarios. A vegetation model is being used to assess changes in plant species composition following grazing by sheep and/or cattle, combined with other management techniques. This model is linked to others, which will allow the wider implications for moorland invertebrates, birds and livestock production to be assessed and evaluated against system scale studies. The focus of invertebrate work is initially on spiders because they are sensitive to vegetation structure. The bird models have been developed from surveys of several UK regions. For those bird species studied, preliminary analyses suggest that although their abundance can differ between regions for a given vegetation condition, the direction of the response to variation in vegetation condition is consistent.
The system scale studies are being carried out at ADAS Pwllpeiran and Redesdale to assess the impact of sheep and cattle grazing on moorland vegetation recovery, livestock production, birds and invertebrates. Results after only one year are of course provisional.
At Redesdale, Scottish Blackface sheep at 0.66 or 1.5 ewes/ha are being grazed on mixed wet heath alone or with Continental cross dry cows at 0.75 cows/ha for up to nine weeks in summer. Results following the first year of grazing studies at Redesdale were encouraging. Cattle grazed the purple moor-grass dominated areas of former heather moor selectively. In these areas, cover of purple moor-grass declined in both paddocks with cows, but continued to increase when sheep were grazed alone at the lower stocking level and remained the same at the higher stocking level with sheep alone. Cows gained 42-67 kg liveweight and body condition scores increased. The presence of cows had no impact on sheep performance or lamb growth rate up to weaning.
At Pwllpeiran, four grazing treatments with Welsh Mountain sheep (at 1.0 or 1.5 ewes/ha) and/or summer grazing by Welsh Black cattle (0.5 cows/ha in July and August) are being compared on mat grass dominated moorland. In the first year, livestock tended to graze bilberry Vaccinium myrtillus but not mat grass itself, but there were no consistent treatment effects on the vegetation. Cattle gained liveweight but not condition score and performed better in the presence of sheep (at 1.0 ewes/ha) than with no sheep. Ewes gained both liveweight and condition score but performed better at the higher stocking rate or with cattle than at 1.0 ewes/ha with no cattle. Although these were relatively minor effects, the cumulative response in subsequent years will be important to follow in these relatively resilient systems.
Restoration experiments are being carried out at both system study sites to investigate the effects of rotavation, trampling by stock and heather seeding on the recovery of heathland vegetation, with and without subsequent access by stock. In the first year, heather seedlings have established in many plots. The relative importance of different disturbance treatments will be assessed in the coming years.
Foraging behaviour of two breeds of sheep (Welsh Mountain and Scottish Blackface) and cattle (Welsh Black and Continental cross) is being studied in experimental plots at Pwllpeiran containing varying proportions of dwarf shrub and grasses. This, in combination with laboratory analyses of faecal outputs, will improve our understanding of differences in diet selection between species and breeds, and the implications for moorland management.
The different elements of the project are interlinked and will be used to produce new grazing management guidelines for moorland when the project finishes in 2007.
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