Does soil seed bank diversity limit post-fire regeneration in fragmented native vegetation?

Background/Question/Methods

Prescribed burning is a management tool used both for limiting the accumulation of fuel in order to reduce the risk of wildfires, and for stimulating the regeneration of fire-adapted native vegetation. Here we examine the role of the soil seed bank in the regeneration of Eucalyptus cneorifolia dominated mallee vegetation following prescribed burns on Kangaroo Island in South Australia.

Results/Conclusions

Thirty-eight small (<5ha) highly-senescent remnants have been partially burnt, all of which had not previously been burnt for 20-80 years. We sampled soil from each of these sites prior to burning, and subjected the soil samples ex situ to both smoke aerosol and heat treatments to simulate burning. One hundred and thirteen indigenous plant species and fifty exotic species germinated. Of these, fifty-four indigenous species were absent in the above-ground herbage, including ten rare or threatened species, and three new records for Kangaroo Island. Eighteen indigenous species and six exotic species germinated in heat/smoke treated soil but not in untreated control trays from the same sites, indicating the importance of fire in regenerating these areas. However, burning was also found to increase the frequency of a number of weed species indicating that weed competition  may be a problem when regenerating small remnants. However, results indicated that this is more likely to be problem in previously grazed sites. While indigenous soil seed banks were found to be significantly more diverse than the aboveground herbage in ungrazed sites, this was not the case in previously grazed sites.