Prescribed burning to increase the richness of long-unburned and fragmented mallee communities

Abstract

Fire regimes have been altered by human activity in fire-prone landscapes around the world. In eastern Kangaroo Island in South Australia, the frequency of fire has decreased and the richness of fragmented remnant plant communities is declining. Land managers in this area are considering reintroducing fire through prescribed burning to increase native plant species richness, but the effects of such an intervention are difficult to accurately predict. This thesis explores solutions to this problem by experimentally testing the effect of prescribed burning on the richness of long-unburned and fragmented native plant communities.

A total of 35 prescribed burns were conducted by a large number of local fire-fighters and land managers and in spring and autumn in 2009 and 2010. Post-fire surveys revealed that prescribed burning increased native plant species richness. However, unexpectedly, this result was not influenced by burn season or pre-fire modification of vegetation structure and fuels. The effects of prescribed burning on post-fire native plant species richness also varied considerably between experimental sites. Subsequent analysis revealed that high post-fire native plant species richness was associated with high pre-fire native soil seedbank richness, low introduced soil seedbank richness, low post-fire canopy cover, low soil heating during fire events, the exclusion of native herbivores and the amount of native vegetation within 500 m.

This thesis provides land managers with the knowledge to adapt site selection and prescribed burn methods to maximise post-fire native plant species richness in fragmented plant communities in eastern Kangaroo Island. The findings are also likely to be applicable to other long-unburned and fragmented fire-prone ecosystems that support substantial soil-seedbanks.