Executive Summary
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INSTITUTE OF TERRESTRIAL ECOLOGY (NATURAL ENVIRONMENTAL RESEARCH COUNCIL) Project T02059o1 MAFF / NERC Contract BD0303 FINAL REPORT REVIEW OF CALCAREOUS GRASSLAND AND HEATHLAND MANAGEMENT R.F. PYWELL, J.M. BULLOCK, R.J. PAKEMAN, J.O. MOUNTFORD, E.A. WARMAN, T.C.E. WELLS & K. WALKER Institute of Terrestrial Ecology Monks Wood, Abbots Ripton, Huntingdon Cambridgeshire PE17 2LS December 1995 Executive summary EXECUTIVE SUMMARY 1. Both lowland heaths and calcareous grasslands are products of centuries of utilisation by man. Past management practices have included livestock grazing, burning and cutting; 2. These practices have produced habitats and landscapes of great structural and biological diversity which are greatly valued for nature conservation and their aesthetic qualities; 3. Cessation of these practices will lead to the development of woodland and scrub and an associated loss of the characteristic assemblages of plants and animals associated with these habitats. Intensification or alteration of management practices may lead to the dominance of a few species and a similar loss of biodiversity. 4. In this review we differentiate between conservation or 'maintenance management' and those, more drastic management practices, required to restore the ecosystem structure and function when these changes have taken place ('restoration management'); 5. The objectives of conservation management include preservation of the original structure and function of the ecosystem, prevention of unwanted successional changes and the provision of an economic return; 6.This review aims to identify and evaluate practical, cost-effective management procedures for achieving these objectives. This was achieved from the study of : (a) long term management experiments: fully randomised, replicated experiments incorporating different management treatments; (b) sites of known management history, where it was possible to relate past and present vegetation types to given management regimes. 7. Grazing by cattle or sheep was found to be the traditional and preferred management of calcareous grassland, producing the greatest floristic and structural diversity. 8. Livestock grazing has three important ecological impacts on the calcareous grassland ecosystem: selective defoliation, trampling to create gaps, and nutrient addition and removal. The nature of these impacts will vary considerably depending upon the type, breed and age of the livestock. Lowland breeds may provide an economic return from extensive grazing systems, but are considered unsuitable for coarse vegetation. Hardy breeds are able to eat unpalatable species and utilise herbage of poor nutritional quality. However, they are more difficult to obtain and handle, and provide a lower agronomic return. 9. It is difficult to derive precise rules for grazing management because of local variation in soil fertility, climate, ii Executive summary productivity and palatability. These grasslands are of lower productivity and produce less digestible herbage than improved grasslands. Extensive beef and sheep grazing systems are likely to be the preferred agronomic management option. Grazing should aim to remove most of each year's herbage, either during the summer growth period or during the winter. Flexibility in approach is required to allow for between-year variations in productivity. Timing of grazing should be carefully controlled to avoid harming sensitive plant and invertebrate species. Rotational management regimes are likely to be the most advantageous for nature conservation management. Moderate stocking densities (e.g. 0.6 - 1.4 LU ha-1 for longer periods (e.g. 16 - 20 weeks) are likely to be the most beneficial. However, high stocking rates for short periods have been effective in controlling unpalatable species. Frequent measurement of sward structure and height is likely to be the best means of regulating grazing rather than target stocking rates as recommended in the current ESA guidelines. 10. In some situations it is neither economic nor practical to maintain grazing animals outside the farming system. This is particularly the case where predominantly arable farms have only small and relatively inaccessible grazing areas, or are on the urban fringe. In such cases, cutting may be the only management option. Cutting has markedly different effects from grazing on the ecology of grassland. Mowing causes an immediate and uniformly drastic alteration in the structure of the sward. It is non-selective and does not create the valuable mosaic of gaps in the sward associated with livestock trampling. Removal of hay also causes a gradual depletion of nutrients and loss of productivity. Finally, the timing of cutting will strongly influence the eventual composition of the sward as some species are prevented from setting seed. 11. Considerably less is known about the management of lowland heaths. This reflects their marginal use in the agricultural system. 12. Heathland management practices should aim to create a mosaic of different vegetation types at a variety of successional stages and spatial scales. This will provide habitat for a wide diversity of plant and animal species. 13. Degraded, degenerate or mature heathland may require an initial, one-off treatment to remove invasive species or excessive biomass before maintenance management can be initiated. This could take the form of winter burning or cutting to provide fresh growth for grazers. Additional control of invasive species (e.g. Bracken) with herbicides may also be required. It may be more cost-effective to initiate regeneration of some severely degraded heaths from relic seed banks. 14. Extensive grazing by cattle, ponies or sheep is the preferred and traditional management to maintain lowland heath. Hardy breeds are recommended. The stocking rate and grazing period should be based on local tradition, management objectives and the welfare of the animals. The intensity of grazing is important: overgrazing will cause the suppression of heath vegetation and cause a change to acid grassland; under-grazing will have little effect in halting succession. Summer grazing is more typical. iii Executive summary 15. It may be desirable to superimpose a rotational system of burning and cutting on this grazing system with the aim of producing a mosaic of different successional stages on a scale of > 0.5 - 1 ha. Burning and cutting alone are not an adequate substitute for grazing, especially in terms of diversity of plant species and vegetation structure. However, they will prevent succession to scrub. Burning should be carried out in the winter, following the MAFF code. It may be desirable to burn or mow only parts of the heath each year, to establish a mosaic of vegetation types. The frequency of burning or cutting will depend upon the rate of vegetation growth. Other management should also be considered, e.g turf-stripping to remove nutrients and rotovation to create bare ground. 16. If the conservation management of calcareous grassland and heathland is to be successful, it is important to first determine the objectives of management. This requires the evaluation of individual sites, together with knowledge of the plants and animals associated with the ecosystem. These objectives will need to consider local factors, such as access, topography, skills and tradition. This should produce a suite of viable and practical management options which will achieve the conservation objectives of management. It is citically important that the site is regularly monitored so that adjustments to the management regime can be made. This monitoring could take the form of simple sward measurements. iv Contents CONTENTS Page EXECUTIVE SUMMARY ii CONTENTS v LIST OF TABLES, BOXES, FIGURES & PLATES vii 1. INTRODUCTION 1 1.1 Aims 1 1.2 Background 1 2. INTRODUCTION TO LOWLAND CALCAREOUS GRASSLANDS 3 2.1 Definitions 3 2.2 History and development 3 2.3 The grassland environment 3 2.4 Calcareous grassland types 3 2.5 Nature conservation value of calcareous grasslands 6 2.6 Grassland management 7 3. CALCAREOUS GRASSLAND STUDY AREAS 10 3.1 Approach 10 3.2 Site recording 10 3.3 Analysis 11 4. EFFECTS OF MANAGEMENT ON THE STRUCTURE AND COMPOSITION OF CALCAREOUS GRASSLANDS 12 4.1 Livestock grazing 12 4.2 Cutting 45 4.3 Summary of other sites 59 5. RECOMMENDATIONS FOR THE MANAGEMENT OF CALCAREOUS GRASSLAND 60 5.1 Objectives of grassland management 60 5.2 Grazing management 60 5.3 Cutting management 65 v Contents 5.4 Existing ESA and Countryside Stewardship guidelines 66 5.5 Recommendations 67 6. INTRODUCTION TO LOWLAND HEATHS 68 6.1 Definitions 68 6.2 History and development 68 6.3 The heathland environment 69 6.4 Lowland heath types 69 6.5 The dynamics of heathland plant communities 71 6.6 Heathland management 72 6.7 Nature conservation value of lowland heath 74 7. LOWLAND HEATH STUDY AREAS 77 7.1 Site selection and recording 77 7.2 Site details and management 79 8. EFFECTS OF MANAGEMENT ON THE STRUCTURE AND FLORISTIC COMPOSITION OF LOWLAND HEATHS 93 8.1 Grazing 93 8.2 Cutting 99 8.3 Burning 101 8.4 Other management practices 103 9. RECOMMENDATIONS FOR THE MANAGEMENT OF LOWLAND HEATH 108 9.1 Summary of survey results 108 9.2 Existing ESA and Countryside Stewardship guidelines 109 9.3 Recommendations 111 10.CONCLUSIONS 113 10.1 Future research requirements 114 11. REFERENCES 116 12. ACKNOWLEDGEMENTS 118 13. APPENDIX I 119 vi Contents LIST OF TABLES, BOXES, FIGURES & PLATES List of Tables Table 2.1 Vascular plants of calcareous grassland which are classified as nationally rare (NR) or nationally scarce (NS). Red Data book species are further classified as endangered (e), vulnerable (v), or rare (r). Table 2.2 Traditional management of calcareous grassland communities defined by the NVC (Rodwell 1992) Table 3.1 The Domin cover-abundance scale. Table 4.1 Sample stocking rates and durations for plots S1-S6 during the period 1987-93. Table 4.2 Mean sward heights under different grazing regimes. Table 4.3 Mean root frequency of species recorded at Aston Rowant 1964 - 1993 (* = not recorded in that year). Table 4.4 Summary of changes observed in species during first five years of grazing experiment.