A global synthesis of fire effects on soil seed banks

Fire is a major disturbance affecting plant communities in terrestrial ecosystems. Understanding fire effects on soil seed banks is critical in the context of altered global fire regimes. Through a systematic and quantitative review of the literature, we provide the first global assessment of how soil seed banks respond to fire based on 539 paired comparisons. The overall effects of fire on soil seed bank richness (i.e., the species richness in soil seed bank) and abundance were negative and neutral, respectively. Wildfires and high-intensity fires led to greater decreases in the richness and abundance of the seed bank than prescribed burns and low-severity fires, respectively. As an important fire cue, the presence of simulated smoke increased seed bank richness and abundance, but simulated heat shock had no effect on both two metrics, in contrast to the findings of previous empirical studies. Strong, positive fire effects on soil seed bank abundance were found in Mediterranean ecosystems, but fire effects were negative for forest ecosystems, especially tropical forests. Both the richness and abundance of tree species in the seed bank decreased after fire. Burning only had a negative effect on the soil seed bank in habitats with no previous fire history or a short fire history. As time elapsed post-fire, the soil seed bank abundance also increased. Overall, fire tended to decrease soil seed bank richness globally, and this was especially the case for high-severity fires in non-fire-prone ecosystems. Our findings enhance our understanding of the spatiotemporal variability in fire effects on soil seed banks, and highlight the importance of monitoring post-fire seed bank composition across ecosystems, with crucial implications for vegetation regeneration and ecosystem recovery.