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Impact of raised water levels on biodiversity & agricultural value of lowland wet grass (extension BD0213/4)(old BD0227) - BD1313

Within the context of agri-environment schemes, raised water-levels have been adopted as a means of enhancing the biodiversity of lowland wet grasslands. The central aim of the proposed research is to investigate the success of this technique in achieving its objectives, and to identify the concomitant effects on agricultural production and water-resource management. Implementation of raised water-levels has often resulted in rapid vegetation change, but there remains little evidence that the botanical objectives of ESA raised water-level tiers are being realised in the short term. The project will provide opportunities not only to investigate experimentally the impact of raised water-levels over a ecologically more realistic period, but also to test the predictions of eco-hydrological models. The project builds on three years of data gathered from an experiment at Tadham Moor in the Somerset Levels and Moors ESA (BD0213/4).

Agronomic results from Tadham Moor in 1997 showed a marked reduction in UME under Tier 3 water-levels, together with reduced mineral content in the hay, suggesting that their management for nature conservation purposes poses considerable constraints on commercial livestock farming. In is proposed to examine whether raised water-levels lead to reduced mineralization rates and overall availability of phosphorus and potassium. The proposed research will seek to test whether the early results are from Tadham Moor are representative of the likely agronomic impacts of raising water levels. The hydrological element of the research will take the opportunity to identify the major components of the water balance on raised water levels sites, so identifying the water resource requirements for the maintenance of such sites.

The project would provide rigorous underpinning for the management prescriptions employed in agri-environment schemes. The results would allow for the more effective targeting of such schemes, through demonstrating whether a) biodiversity goals are likely to be realised; b) the resultant constraints on agricultural output will make farming commercially no-viable; and c) the water-resources required to maintain such schemes have been realistically assessed.
1. To assess the scope for the manipulation and maintenance of prescribed water-levels at the field scale.

2. To establish the major components of the hydrological budget for the Tadham site.

3. To test the implications of 3-6 years of increased site-wetness (as defined by Tier 3 for the Broads and Somerset Levels and Moors ESAs) on the botanical diversity of lowland grassland in terms of:
-Plant community composition
-Populations of individual species of nature conservation importance and potential agricultural weeds
-Conservation or restoration of target plant communities.

4. To compare the field botanical results with the predictions made using eco-hydrological models.

5. To test the agronomic consequences of such management, and assess the representativeness of results for 1997, specifically in terms of:
-hay yield;
-hay quality;
-and output from grazing the hay aftermath.

6. To identify whether on peat soils Tier 3 raised water-levels have produced differences in soil nutrient conditions compared with Tier 1, through reducing mineralization rates and overall availability of phosphorus and potassium.

7. To refine present criteria for the identification of appropriate sites for the conservation or rehabilitation of lowland wet grasslands.
Project Documents
• Final Report : Impact of raised water levels on biodiversity & agricultural value of lowland wet grass.   (4714k)
Time-Scale and Cost
From: 1998

To: 2001

Cost: £266,512
Contractor / Funded Organisations
Natural Environment Research Council
Fields of Study
Environmental Stewardship