Germination ecology of the endangered species Asterolasia buxifolia (Rutaceae): smoke response depends on season and light

Abstract

In fire-prone regions, many plant species rely on persistent seed banks for post-fire recovery. Understanding dormancy and germination cues is, therefore, important to predict population response. However, the germination ecology of species with physiologically dormant seeds in fire-prone regions is complex. We used the endangered species Asterolasia buxifolia, from riparian habitat in fire-prone south-eastern Australia, to investigate physiologically dormant seeds and their response to fire. We assessed whether fire cues alone promoted germination, or whether seasonal factors and light also played a role. Additionally, we tested the resilience of seeds to heat-shock temperatures produced in soil during fire, so as to identify potential factors that restrict such species to fire refugia. Seeds germinated only at winter seasonal temperatures, and had an obligate smoke and light requirement. Heat-shock treatments above 80°C slowed the germination rate. Smoke-related germination and the tolerance of A. buxifolia seeds to high fire-related temperatures demonstrated that recruitment dynamics can be driven by fire; however, germination is restricted to winter temperatures. This highlights the potential that changes to fire season may have on population persistence. The slow germination rate caused by heat, and a light requirement, may contribute to restricting this species to riparian habitat.