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Patterns of invasion within a grassland community
Author(s) -
Kolb A.,
Alpert P.,
Enters D.,
Holzapfel C.
Publication year - 2002
Publication title -
journal of ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.452
H-Index - 181
eISSN - 1365-2745
pISSN - 0022-0477
DOI - 10.1046/j.1365-2745.2002.00719.x
Subject(s) - native plant , introduced species , grassland , perennial plant , biology , competition (biology) , invasive species , ecology , plant community , agronomy , ecological succession
Summary1 Relatively 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. 2 To 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. 3 Cover 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. 4 To 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.