Enhancing diversity of species-poor grasslands: an experimental assessment of multiple constraints
Article first published online: 12 DEC 2006
Journal of Applied Ecology
Volume 44, Issue 1, pages 81–94, February 2007
How to Cite
PYWELL, R. F., BULLOCK, J. M., TALLOWIN, J. B., WALKER, K. J., WARMAN, E. A. and MASTERS, G. (2007), Enhancing diversity of species-poor grasslands: an experimental assessment of multiple constraints. Journal of Applied Ecology, 44: 81–94. doi: 10.1111/j.1365-2664.2006.01260.x
- Issue published online: 12 DEC 2006
- Article first published online: 12 DEC 2006
- Received 4 January 2006; final copy received 9 October 2006 Editor: Rob Freckleton
- livestock grazing;
- 1Many 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.
- 2The 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.
- 3Severe 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.
- 4Low-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.
- 5Different grazing management regimes had little impact on diversity. This may reflect the constraining effect of the July hay cut on species dispersal and colonization.
- 6Synthesis 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 range of more specialist species to establish. However, further research is required to determine the long-term effectiveness of these approaches.