Carlyle, C.N. (Corresponding author, email@example.com) & Fraser, L.H. (firstname.lastname@example.org): Departments of Natural Resource Sciences, and Biology, Thompson Rivers University, 900 McGill Road, PO Box 3010, Kamloops, BC, V2C 5N3, Canada. Carlyle, C.N. & Turkington, R. (email@example.com): Department of Botany, and Biodiversity Research Centre, University of British Columbia, 6270 University Blvd., Vancouver, B.C., V6T 1Z4, Canada.
Using three pairs of competitive indices to test for changes in plant competition under different resource and disturbance levels
Article first published online: 27 JUL 2010
© 2010 International Association for Vegetation Science
Journal of Vegetation Science
Volume 21, Issue 6, pages 1025–1034, December 2010
How to Cite
Carlyle, C. N., Fraser, L. H. and Turkington, R. (2010), Using three pairs of competitive indices to test for changes in plant competition under different resource and disturbance levels. Journal of Vegetation Science, 21: 1025–1034. doi: 10.1111/j.1654-1103.2010.01207.x
Co-ordinating Editor: Dr. Hans Henrik Bruun.
- Issue published online: 26 OCT 2010
- Article first published online: 27 JUL 2010
- Received 4 May 2010;, Accepted 25 June 2010.
- Absolute and relative competition;
- Competitive effect and response;
- CSR strategy theory;
- Festuca campestris;
- Importance and intensity of competition;
- Nutrient availability;
- Pseudoroegneria spicata;
- R* theory
Questions: How do different resource and disturbance levels interact to affect competition? How do different indices of competition change the interpretation of how competition changes under different resource and disturbance conditions?
Location: Greenhouse, Thompson Rivers University, Kamloops, British Columbia, Canada.
Methods: Three pairs of indices that have been used to differentiate the predictions of Grime (CSR) and Tilman's (R*) theories were used to assess competition on two species of temperate bunchgrass, (Pseudorogeneria spicata and Festuca campestris) grown in a greenhouse on stress and disturbance gradients. Stress was created by manipulating the amount of water (high, low) and concentration of nutrient solution (high, low) added to pots, while disturbance was created by clipping (clipped, unclipped) in a fully factorial design. Plants were grown individually or with a single neighbour. The three pairs of indices were: (1) absolute and relative competition; (2) competitive effect and response; and, (3) competitive importance and intensity.
Results: Absolute competition and competitive importance were the only indices responsive to the resource gradient, which supports CSR theory, and also the only ones to record an effect of disturbance on the strength of competition – under high resource conditions. The other indices showed few responses along the gradients, which supports R* theory. Measures of competitive effect and response did not differentiate the two theories.
Conclusion: We show that some indices of competition show a decline with increased stress and disturbance, while other indices do not. Therefore, it is necessary to choose a competition index appropriate to the question being asked. Competitive importance and absolute competition were responsive to changes in stress and disturbance, while the other indices were not.