Single tree harvest systems: an application to radiata pine in New Zealand

Abstract

The study was intended to establish whether single-tree harvest system is a viable alternative to the usual system of clearfell harvesting for radiata pine in New Zealand. In clearfell systems all trees are felled at the same time based on the financial maturity of the stand. Although the clearfell system is easy to administer, it may produce smaller sized and lower quality wood, and a lower net present value, than a system where individual trees are allowed to continue to grow to financial maturity that can produce higher quality log volumes and values. Hence it was expected that a higher net present value could be obtained from a single-tree harvest system. In single-tree harvest systems, two targets or decision rules were used to harvest single trees. One decision rule was based on a target diameter and the other was based on financial maturity. The computer programme MARVL was used to simulate individual tree value and Gro-MARVL was used to grow trees over time so that changes in value can be estimated. The results shown that generally, a single-tree harvest system produced more volumes and revenues of higher grade logs than a clearfell system. But in terms of NPV, effectively there was no big difference between single-tree harvest systems and a clearfelling system. Single-tree harvest system with either target diameter or financial maturity, were also effectively the same in economic terms. However, the target diameter option was simpler in operation compared to the financial maturity option and would be preferred for this reasons. It has also been shown that the choice of preferred harvesting option can be changed in a change of discount rates.