Short and long-term effects of prescribed fires in autumn and spring on surface-active arthropods in dry sclerophyll eucalypt forests of Victoria

The effects of two prescribed low-intensity fires in spring and autumn varying from means of 229–303 kW m−1 within the period 1985–1999 on epigeal invertebrates were assessed. The approximately 14 year study was based on 76,375 arthropod specimens, representing 31 ordinal or lower level taxa contained in 3160 pitfall trap samples from a spring and autumn sites burnt twice and an unburnt reference site within a 46.3 ha area. The study indicates that while there appears nil effect by prescribed fires on the surface-active fauna in the short and long term on spring burnt sites and in the short term on autumn burnt sites, in the longer term (over 13 years) on autumn burnt sites, significant increases in total taxa activity in the 1997/99 period, primarily as a result of increases in activity of the groups total non-insects, Acarina, and Formicidae were observed. Conversely, during the same period, a decrease in activity of the Dermaptera was recorded while the situation for the Collembola and Diptera is less certain as changes in activity occurred on both the autumn burnt and unburnt reference sites. However, as no significant change in activity was observed in the short term (i.e. before and immediately after the first fire) for any of the aforementioned taxa, it cannot be stated for certain that the changes in activity following the second fire are due to fire or non-fire effects. This may apply for the Formicidae, especially following the second fire in 1997/99 when both the average soil temperature and soil dryness index (SDI) were substantially higher than that normally experienced thus possibly stimulating increased ant activity. Also, as the study was conducted to ordinal and sub-ordinal level only, it is uncertain whether the above changes in activity are spread over a range or confined to individual species within ordinal groups. Further study should address this issue.