Abstract
Accelerating the development of more heterogeneous forest structures is an important goal of many contemporary forest management regimes. However, long-term silvicultural experiments that compare different approaches to generating structural complexity are rare. We took advantage of a replicated silvicultural experiment that was established in mountain ash ( Eucalyptus regnans ) forests in southeastern Australia in the late 1980s. We evaluated multi-decadal forest development responses to seven different silvicultural treatments: clearfelling (clearcutting), seed tree, three gap sizes (0.25, 0.5, and 2 ha), and two levels of overstorey retention (30% and 50%), plus unharvested controls. We compared a range of stand structural and compositional attributes, non-timber values (e.g., sequestered carbon, total sapwood area [a proxy for stand water-use]), and habitat features in 53 study plots replicated across all of the silvicultural treatments. Thirty years after the experiment was initiated, three treatment groups were apparent: 1) the gap (0.25-2 ha) treatments were dominated by small-diameter mountain ash, a greater abundance of Acacia , and relatively low basal area; 2) the clearfell and seed tree treatments had moderate basal area of mountain ash and the most uniform size-class distributions; and 3) the overstorey retention treatments had the largest trees across all treatments, as well as the greatest basal area and size inequality. Our findings indicate that alternative silvicultural systems could be used to accelerate the development of large trees and complex forest structures and support a broader range of forest values than the standard clearfell, burn, and sow silviculture prescriptions historically applied in mountain ash forests.