Present address and correspondence: Department of Ecology and Evolutionary Biology, University of Bremen, FB2, Leobener Str., D-28359 Bremen, Germany (e-mail email@example.com). Contribution no. 2165 from the Bodega Marine Laboratory, University of California at Davis.
Patterns of invasion within a grassland community
Article first published online: 27 SEP 2002
Journal of Ecology
Volume 90, Issue 5, pages 871–881, October 2002
How to Cite
Kolb, A., Alpert, P., Enters, D. and Holzapfel, C. (2002), Patterns of invasion within a grassland community. Journal of Ecology, 90: 871–881. doi: 10.1046/j.1365-2745.2002.00719.x
- Issue published online: 27 SEP 2002
- Article first published online: 27 SEP 2002
- Received 9 February 2002 revisionaccepted 15 July 2002
- invasive plant species;
- northern California coast;
- plant competition;
- soil characteristics;
- water and nitrogen availability
- 1Relatively few studies have looked for patterns of invasion by non-native species within communities. We tested the hypotheses that: (i) some types of microhabitats within a community are more invasible than others; (ii) microhabitat types that differ in invasion also differ in resource availability; and (iii) invasibility is mediated by effects of these resources on competition between native and non-native species.
- 2To test the first two hypotheses, we measured plant cover and soils in a coastal grassland in northern California. Consistent with these hypotheses, cover of non-native plants was consistently high where nitrogen-fixing shrubs had recently grown, in the bottoms and sides of gullies and on deep soils, and these microhabitats tended to have relatively high nitrogen or water availability.
- 3Cover and number of native species tended to be lower where cover of non-native species was higher, indicating that non-native species as a group negatively affected native species. However, the number of non-native species also tended to be lower where the total cover of non-natives was higher. This suggests that a few non-native species excluded natives and other non-natives alike.
- 4To test the third hypothesis, we grew a common non-native, the annual grass Lolium multiflorum, and a common native, the perennial grass Hordeum brachyantherum, at different levels of water and nitrogen. The relative competitive ability of the native was higher at lower nitrogen availability but not at lower water availability. When 10-week-old native plants were grown with non-native seedlings and nitrogen was relatively low, the native out-competed the non-native. However, the non-native out-competed the native at all resource levels when species were both grown as seedlings. Competition between native and non-native grasses in this system may thus help prevent invasion by non-natives in microhabitats where nitrogen availability is low, but invasion may be relatively irreversible.