Soil seed bank development of smoke-responsive plant species in a 23-year restoration chronosequence and implications for resilience to fire

Aims: Responses of ecological restoration projects to disturbances are rarely explored, yet their capacity to withstand and recover from disturbance (resilience) is a critical measure of restoration success. In many plant communities, the soil seed bank (SSB) provides an important source of propagules for species persistence and community resilience to disturbance. Understanding how SSBs develop with time can inform restoration of resilient ecosystems. Here, in fire-prone Banksia woodland restoration following sand mining, we ask: (a) how does the smoke-responsive (dormancy broken by smoke) SSB develop over time; (b) what plant-trait and climate factors influence its development; and (c) what do the data suggest for the resilience of these restored woodlands to fire?Location: Ellenbrook, Swan Coastal Plain, Western Australia (latitude -31.76, longitude 115.95).Methods: We used smoke, a key germination cue associated with fire disturbance, to trigger germination of the SSB in Banksia woodland restoration. Using a chronosequence of nine ages between 3 and 26 years since initiation of restoration, we tested how the SSB develops using counts and richness of germinating native and invasive annuals, and native perennial obligate seeding and resprouting species. To understand the contribution of above-ground restored vegetation to SSB development, we compared Sorensen's similarity of the smoke germinable SSB (smoked SSB) and untreated germinable SSB (control SSB) with above-ground vegetation.Results: Smoked SSB germinant density decreased with restoration age for both native and invasive annuals, but was stable for native perennials. Similarity between smoked SSB and above-ground vegetation was higher for perennial obligate seeders than for resprouters and peaked for perennials at 23 years.Conclusions: Post-fire regeneration potential of the SSB was evident across the chronosequence, with restoration age influencing the density of native annuals and overall composition of the SSB. The findings for perennial species suggest an increase in resilience to fire with restoration age.