Thirty-year study shows thinning and clear-cutting boost mountain ash growth and carbon storage

A revisit to a 1987 Victorian forest experiment found that both large clear-cut areas and heavily thinned stands of mountain ash have thrived, with thinned trees growing larger and storing as much carbon as untouched forest.

In the mid-1980s the Victorian government invested the equivalent of A$26 million in the Silvicultural Systems Project to compare forest-management approaches in mountain ash ecosystems, establishing clear-cut, small-patch clear-cut, heavy-thinning and control plots at Tanjil Bren in the Central Highlands and Cabbage Tree Creek in East Gippsland. Early findings showed that large clear-cut areas produced the most vigorous ash regeneration, while smaller cuts favored understory species such as acacia.

A 2014 field visit by University of Melbourne researchers confirmed those patterns and revealed that trees left after heavy thinning grew to diameters over a metre, about 20 % larger than those in unharvested stands, and stored comparable or greater carbon. Camera traps detected Leadbeater’s possums in every silvicultural treatment plot but not in the untouched benchmarks, indicating important habitat benefits. The authors conclude that long-term experiments are irreplaceable, that thinning does not compromise carbon sequestration, and that no single silvicultural method solves forest management challenges.