Repeat burning affects species composition in degraded Cumberland Plain Woodland

Abstract

Cleared areas in Scheyville National Park, New South Wales, that formerly supported Cumberland Plain Woodland (CPW) now have a long unburnt mixed native and exotic grassland. To test whether re-introducing fire to these sites would benefit native species composition, and drive it towards that of neighbouring remnant woodland, an experiment was established in three grassy areas (grassy blocks) with prior agricultural land use, and one block in a remnant woodland. Replicate plots were established within blocks, and assigned to a repeat fire treatment, or unburnt controls. Plots in the fire treatment were burnt on all blocks in 2001, and in the grassy blocks only in 2005. Although the two fires did not result in recruitment of new native species on the grassy blocks, the successive fires had other beneficial effects. More native species were apparent in the above-ground vegetation on burnt than unburnt plots after both fires, and more summer-growing native grasses were apparent above ground and increased in abundance after the second fire. The large flush of exotic forbs that appeared after the first fire was not repeated after the second fire; many of these forbs had an obligate seeder fire response, and the short inter-fire interval may not have allowed replenishment of their seed bank. Burning did not result in recruitment of new native species in the grassy areas, and did not make the grassy areas more similar to the woodland in species composition. In the woodland, the first fire did not significantly affect species composition. Re-instating fire to degraded grassy sites will not by itself return the site to good quality CPW in the short term, but may contribute positively in the longer term through beneficial effects on natives and adverse effects on exotics.