Restoration thinning permits stems to capitalise on high-rainfall years in a regenerating endangered forest ecosystem

<p><span>1. Passively regenerating native vegetation presents a cost-effective opportunity to sequester carbon and reinstate habitat in heavily cleared agricultural landscapes.</span></p> <p><span>2. However, in some cases a few woody species recolonise in dense, low-diversity stands that are slow to self-thin.</span></p> <p><span>3. Restoration thinning of over-dominant species has been proposed to accelerate ecosystem recovery, but its longer-term efficacy remains uncertain, and is likely to depend strongly on rainfall.</span></p> <p><span>4. This study focuses on a restoration thinning experiment established in 2007 in dense brigalow (<i>Acacia harpophylla</i>) regrowth in Queensland, Australia. Using variation in rainfall between 2007 and 2017, we examined the interactive effects of neighbourhood density and moisture availability on the growth and survival of <i>A. harpophylla. </i></span></p> <p><span>5. We also compared the strength of <i>A. harpophylla</i> density effects on itself to its effects on a sparsely distributed co-occurring tree species (<i>Casuarina cristata</i>) that was codominant in the original forest.</span></p> <p><span>6. Our results provide clear evidence that thinning permits <i>A. harpophylla</i> to grow rapidly during periods of high rainfall, and that interspecific competition between A<i>. harpophylla</i> and <i>C. cristata</i> is relatively weak. As such, thinning of dense <i>A. harpophylla</i> could be combined with seeding or planting of co-occurring tree species with complementary niches to further accelerate forest recovery in this extensive regrowth ecosystem.</span></p>