Prior disturbance legacy effects on plant recovery post‐high‐severity wildfire

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AbstractLarge, high‐severity wildfires are an important component of disturbance regimes around the world and can influence the structure and function of forest ecosystems. Climatic changes and anthropogenic disturbances have altered global disturbance patterns and increased the frequency of high‐severity wildfires worldwide. While the recovery of plant communities at different successional stages after fire is well known, the influence of prior disturbances and stand age is poorly understood. Despite this, high‐intensity wildfires can produce long‐lasting legacy effects, which can influence the resistance and resilience of ecosystems. Here, we quantified the influence of prior stand age and disturbance history on the recovery of plant communities in the Mountain Ash and Alpine Ash forests of south‐eastern Australia after high‐severity wildfire. Specifically, controlling for stand age, we compared the abundance (percent cover) of different plant life forms and reproductive strategies in forests that were, at the time of high‐severity wildfire in 2009, “young” (28–35 yr old and previously logged), “mixed” age (26, 70–83, >150 yr old), “mature” (70–83 yr old), and “old‐growth” (>150 yr old). We uncovered evidence that the legacy of prior disturbance and stand age at the time of high‐severity wildfire can influence the recovery of plant communities in early successional forests. Specifically, we found that “young” forests burnt in 2009 had a higher abundance of ruderal and graminoid species, but had a lower abundance of persistent, onsite seeders, including Acacia and eucalypt species, relative to “old‐growth” forests burnt in 2009. “Mature” aged forests burnt in 2009 also had a lower abundance of Acacia, eucalypt, and shrub species, relative to “old‐growth forests” burnt in 2009. Our findings provide evidence of advanced recovery in forests that were older when burnt by high‐severity wildfire, relative to younger forests burnt by the same wildfire. Further, we also demonstrate the influence of different environmental conditions on plant communities. In a period of rapid, global, environmental change, our study provides insights into the recovery of plant communities post‐wildfire with implications for forest management. Further, our findings suggest that predicted increases in the frequency of high‐severity wildfires may have consequences for forest regeneration.