Economic assessment of an alternative silvicultural method (partial felling) to harvest a stand of Pinus radiata, Chaneys forest, Canterbury

Abstract

Exotic plantation forestry in New Zealand is a significant land use activity, and is increasingly being recognised as a resource that can provide multi-use values. However, the standard harvesting practice of clearfelling can create adverse effects on the environment. An alternative silvicultural practice (partial felling) is proposed for harvesting mature stands of Pinus radiata, based on a conceptual model that harvests individual trees when financially mature, or the age beyond which the tree is not increasing in value at a rate greater to the minimum acceptable rate of return (MAR). Therefore, this exploratory study compared the net present values of a range of scenarios involving clearfelling and partial felling from a 25 year-old stand of Pinus radiata, Chaneys Forest, Canterbury.

To model growth and value predictions, the programme MARVL, including GroMARVL, was utilised due to its ability to provide individual tree growth and yield information. Tree spacing and tree malformation were also selection criteria. Economic analysis involved deriving stumpage values from harvest revenues and costs and discounting back to a present value using the NZIF valuation standard.

Results highlighted a large variation in rate of value increase for trees within a stand. Partial felling 30 of percent basal area provided greater returns than 20 percent, and overall provided a net present value higher than the optimal clearfelling scenario (30 years) when all residual trees were removed at age 35 years. This is mainly due to a greater volume of larger, higher quality log types that produced a higher value.

There were limitations, particularly with the use of GroMARVL, as certain requirements of this study were outside the realms of what the MARVL software was initially designed for. These limitations need to be addressed before this alternative method would be utilised for forest planning.