Link: https://doi.org/10.1093/jofore/fvab063
Summary: The Black Rock thinning project is intended to demonstrate that silvicultural interventions – here, thinning and long rotations – can help restore dense, young timber plantations back into structurally complex older forests. The authors measured tree growth after thinning that began in 1958 at an average stand age of 50. They also completed a financial analysis that considered how thinning revenues could offset the opportunity costs of extended rotations.
Key excerpts:
- “Thinnings at several intensities at total stand age of roughly 50 years effectively reset stand growth patterns. With quadratic mean diameters in thinned plots up to 40% higher than those of unthinned controls, thinned plot mean annual increments (MAIs) and periodic annual increments continue to rise 55 years after thinning, with the peak in board foot and cubic foot MAI apparently still decades in the future.”
- “Financial analysis of the opportunity costs of extending rotations to 100 years indicates that some thinning treatments can reduce opportunity costs by up to half at a 6% discount rate.”
- Mid rotation thinning of dense young plantations is “compatible with growing trees with large diameter stems, large branches, and large crowns.”
- Such thinning also reduces fuel accumulation by “lowering mortality rates of stems less than 60 years old and slowing the rate of crown recession, branch mortality, and branch litterfall.”