Impact of fire on plant-species persistence in post-mine restored and natural shrubland communities in southwestern Australia

Abstract

In many parts of the world, it is inevitable that fire will return as a natural disturbance factor to vegetation restored on anthropogenically-disturbed lands. Therefore, assessment of the ultimate success of restoration programs should include the ways in which these ecosystems respond to such natural disturbances. We compared the response of vegetation to experimental fires on mature (⩾8 y) post-mine restored and nearby natural shrubland communities in a Mediterranean-climate region of Australia. Pre- and post-fire perennial plant species composition was assessed in 40 × 40 m plots at three shrubland sites restored after mineral sand-mining, and at five natural shrubland sites. Additional quadrats were monitored for seedling survival over the first summer after fire. Species richness fell by 22–41% after fire in restored sites, but increased by 4–29% in natural sites. Of the species present before fire, 44–60% persisted after fire is restored sites, and 88–96% in natural sites. Only 42–66% of resprouting species recovered in restored sites, whereas 96–100% recovered in natural sites. Nonsprouting species recruitment was also lower in restored (18–57%) than natural (67–85%) sites. Seedling mortality over the first summer after fire was higher in restored sites (59–86% death of individuals) than in natural sites (14–60%). PCoA ordination showed that fire altered the floristic composition of restored sites much more than that of natural sites, and their vegetation diverged further from the targeted properties of natural communities. Our study highlights the importance of including the ability of post-anthropogenically-altered lands to recover from natural disturbances in determining the success of restoration programs.