Thinning from above and below were compared using an
economic optimizing dynamic program, FORTE (Arthaud 1986).
Economically optimal (net present value maximizing) thinning
regime and rotation age were determined for benchmark economic
and model inputs. Sensitivity of net present value and
optimal management regime were tested for varying interest
rates (6 or 8%), site indexes (50, 60 and 70, base 25 years),
fixed and variable thinning costs, planting density (440, 680
and 910 trees per acre), stumpage prices and thinning type.
Given the same assumptions, thinning from below consistantly
provided the higher net present value for the optimal regime
than thinning from above. For the benchmark assumptions,
both thinning types had two thinnings in their optimal regimes.
Optimal rotation age and thinning timings occur later
when thinning from above. Both thinning types provided
higher net present values than not thinning under all conditions
except pulpwood management.