Nearby mature forest accelerates plant succession following timber harvesting

Timber harvesting can disadvantage plants that rely on living mature forest as a recolonisation seed source rather than the soil seed bank. Nearby mature forest can supply seeds and shaded microclimates, accelerating post-harvest ecological succession through edge effects (‘mature forest influence’). We tested whether time since harvesting and proximity to mature forest affected plant species composition in wet eucalypt forest. Surveys were conducted in regenerating clearcut sites of three age classes (∼7, ∼27, and ∼45 years post-harvest), using transects extending across the mature forest–clearcut boundary. Plant composition differed among age classes, with older forests supporting more mature forest indicator species and fewer young forest indicator species, consistent with expected successional trajectories. Richness of mature forest indicator species increased with proximity to mature forest edges, providing evidence of mature forest influence. Richness of young forest indicator species showed no change across the edge distance gradient. Community composition varied with distance from mature forest, with the edge influence extending approximately 17 m in ∼7-year-old sites, 25 m in ∼27-year-old sites, and 27 m in ∼45-year-old sites. Similar depths of influence in ∼27 and ∼45 year old age classes likely reflect seed dispersal limits, suggesting reproductive maturity may be needed for deeper recolonisation of mature forest plants. Although mature forest influence was important, it had less impact on community composition than other factors like soil chemistry and topography. Our findings suggest that variable retention forestry that retains mature forest near to harvest areas should accelerate succession through increased seed availability and shading.