Introduced and native grass-derived smoke effects on Cymbopogon obtectus germination

Introduced grasses, such as buffel, alter the dynamics of grassy ecosystems by replacing native species and influencing recruitment. Several different smoke-derived chemicals are separately responsible for the promotion and inhibition of germination of various plant species. We tested whether smoke derived from the introduced buffel grass (Cenchrus ciliaris) produced the same density of germination as provided by smoke derived from a native spinifex grass (Triodia brizoides). Smoke from both spinifex and buffel grass significantly enhanced the germination of a native lemon grass (Cymbopogon obtectus) in comparison to untreated seed, reflecting the significant role of fire in woodlands across northern Australia. This is the first record of smoke-promoted germination in a species of Cymbopogon. However, smoke from the exotic buffel grass provided the same level of germination as that from the native spinifex, suggesting similarity in smoke chemicals involved. Further research is required to test the effect of buffel smoke on the germination of other species and whether exotics such as buffel grass provide the same temperature profile in the topsoil as does spinifex, and therefore equivalent germination cues to heat-shock responsive native plants.