Lifespan and dormancy type affect post-fire seed germination strategies: evidence from a multispecies experiment in a...

Fire is a major ecological force that shapes population dynamics and community structure in terrestrial ecosystems. Understanding seed germination responses to fire cues is crucial for predicting post-fire vegetation recovery. However, under the changing global fire regime, such responses in non-fire-prone ecosystems remain largely unknown. Here, we aimed to understand how fire influences population recruitment in non-fire-prone temperate grasslands and whether this influence is associated with key regenerative traits.

We conducted a seed germination experiment with 80 species originating from a non-fire-prone temperate grassland ecosystem, using Bayesian phylogenetic mixed-effects models to examine the effects of fire cues on seed germination.

We found that smoke and heat resulted in modest yet statistically significant increases in germination percentage. Germination of 24 species was significantly promoted by fire cues, among which 11 species responded significantly to heat shock and 13 species to smoke. However, these responses showed no significant phylogenetic signal. Furthermore, dormancy types were closely associated with the specific fire cues required to release dormancy, and annual and perennial species displayed markedly different germination responses to fire cues.

This study shows the critical role of fire cues in breaking seed dormancy in a non-fire-prone temperate grassland ecosystem. The differential germination responses among species are driven by dormancy type and lifespan. Although the overall increase in germination percentage was modest, the differential responses of seed germination to fire cues among species and functional groups reveal the potential importance of wildfires in reshaping community structure and composition. Our findings provide new insights into post-fire vegetation dynamics in temperate grasslands.