Enhancing diversity of species-poor grasslands: an experimental assessment of multiple constraints

• Published in: The Journal of applied ecology 2007-02, Vol.44 (1), p.81-94
• Main Authors: PYWELL, RICHARD F, BULLOCK, JAMES M, TALLOWIN, JERRY B, WALKER, KEVIN J, WARMAN, ELIZABETH A, MASTERS, GREG
• Format: Article
• Language: English
• Subjects: agricultural land; Animal, plant and microbial ecology; Applied ecology; Biodiversity; Biological and medical sciences; competition; Conservation, protection and management of environment and wildlife; disturbance; ecological restoration; Ecosystem studies; Ecosystems; Environmental degradation: ecosystems survey and restoration; Forbs; Fundamental and applied biological sciences. Psychology; General aspects; Grasses; Grassland management; Grassland soils; Grasslands; grazing; herbivory; livestock grazing; Mollusca; pastures; pest control; plant communities; Plants; PLFA; range management; restoration; Rhinanthus; Soil ecology; soil fertility; Soil inoculation; Soil microorganisms; Species; species diversity; Vegetation Management and Restoration
• ISSN: 0021-8901; 1365-2664
• DOI: 10.1111/j.1365-2664.2006.01260.x

1. Many grasslands in north-west Europe are productive but species-poor communities resulting from intensive agriculture. Reducing the intensity of management under agri-environment schemes has often failed to increase botanical diversity. We investigated biotic and abiotic constraints on diversification by manipulating seed and microsite availability, soil fertility, resource competition, herbivory and deficiencies in the soil microbial community. 2. The effectiveness of 13 restoration treatments was investigated over 4 years in a randomized block experiment established in two productive grasslands in central-east and south-west England. 3. Severe disturbance involving turf removal followed by seed addition was the most effective and reliable means of increasing grassland diversity. Disturbance by multiple harrowing was moderately effective but was enhanced by molluscicide application to reduce seedling herbivory and by sowing the hemiparasite Rhinanthus to reduce competition from grasses. 4. Low-level disturbance by grazing or slot-seeding was ineffective in increasing diversity. Inoculation with soil microbial communities from species-rich grasslands had no effect on botanical diversity. Nitrogen and potassium fertilizer addition accelerated off-take of phosphorus in cut herbage but did not cause a reduction in soil phosphorus or increase botanical diversity. 5. Different grazing management regimes had little impact on diversity. This may reflect the constraining effect of the July hay cut on species dispersal and colonization. 6. Synthesis and applications. Three alternative approaches to grassland diversification, with different outcomes, are recommended. (i) High intervention deturfing, which would create patches with low competitive conditions for rapid and reliable establishment of the target community. For reasons of cost and practicality this can only be done over small areas but will form source populations for subsequent spread. (ii) Moderate intervention (harrowing or slot-seeding) over large areas, which would establish a limited number of desirable, generalist species that perform well in restoration. This method is low cost and rapid but the increases in biodiversity are less predictable. (iii) Phased restoration, which would complement the above approaches. Productivity and competition are reduced over 3-5 years using Rhinanthus or fertilizers to accelerate phosphorus off-take. After this time harrowing and seeding should allow a wide rang