Field evidence of smoke-stimulated seedling emergence and establishment in Mediterranean Basin flora

Question In many plant species from fire-prone ecosystems germination is promoted by smoke. Mediterranean Basin (MB) flora is no exception. However, most information regarding germination response to smoke in the MB comes from a few experiments performed in laboratory conditions. This approach does not consider factors that occur in the field, such as species interactions, density-dependent processes or the fact that seeds spent time in the soil seed bank. In addition, species selection has been biased (e.g. there is a lack of information about annual species). Hence the importance of smoke relative to other fire cues is not clear, and we have a biased knowledge of post-fire community assembly in the MB. In this framework, we tested the following hypotheses: (1) smoke enhances seedling emergence and establishment from the soil seed bank of MB species, and (2) annual species are an important component of this smoke-stimulated flora. Location Mediterranean fire-prone shrublands in eastern Spain. Western Mediterranean Basin. Methods We performed a field experiment in which we applied a liquid smoke treatment and tracked seedling emergence and seedling establishment during 1yr. Differences between smoke and control subplots with respect to seedling emergence and seedling establishment were analysed at different scales: community, growth form (annual or perennial), family and species level. Results At the community level, smoke played a clear role in seedling recruitment, increasing seedling emergence and seedling establishment. In addition, for most plots, families and species, establishment was higher in smoke subplots compared to the control. Annual species establishment was clearly stimulated by smoke but no effect was detected for perennials. Conclusions Smoke derived from wildfires has a key effect on plant recruitment and hence on community assembly in the MB vegetation.