Simulation of silvicultural scenarios and economic efficiency

C Alegria

doi:10.5424/fs/20112003-11070

Abstract

Seven silvicultural scenarios for pure and even aged maritime pine stands were simulated using a diameter class growth and yield model, for three levels of site index (low, medium and high). Total and merchantable yield along rotation and mean annual increment at rotation age were simulated. Revenue obtained from sale of standing timber (three commercial thinning and final harvest) was estimated. Costs paid for stand establishment (site preparation and plantation) and treatments (release, pre-commercial thinning and pruning) were also estimated. For each scenario, a cash-flow was simulated and economic efficiency was assessed using the net present value of an infinitive series of rotations (NPVIS) and the internal rate of return (IRR). The economic analysis results proved the selection of an intensive management stand prescription that is used as a guide for reforestation projects, using artificial regeneration by plantation, when the main goal is round wood yield. For areas of natural regeneration, a fully stocked stand prescription, pulp wood yield oriented, was selected. This prescription enables saving in site preparation and plantation costs, being at the moment the most suitable for the existing naturally regenerated maritime pine stands of Portuguese private forest areas.

Highlights

Stand growth and yield are strongly influenced by site quality and stand density (Loetsch et al, 1973; Husch et al, 1982; Avery and Burkhart, 1983; Clutter et al, 1983; Philip, 1994)
A crown competition factor (CCF) value of 100% indicates that the minimum density below which site is under stocked and values higher than 100% indicates that competition between stand trees increases (Husch et al, 1982; Clutter et al, 1983)
The stand density index used was fitted for the maritime pine stands in Portugal, using the data from the National Forest Inventory of 1985/87 (Luís et al, 1991) and defined as: c(SDI ) =

Summary

Introduction

Stand growth and yield are strongly influenced by site quality and stand density (Loetsch et al, 1973; Husch et al, 1982; Avery and Burkhart, 1983; Clutter et al, 1983; Philip, 1994). Stand density can describe the degree to which a site is being used and the intensity of tree competition. This parameter is the major factor that can be manipulated in order to influence stem quality, diameter growth, C. Unlike wide stand spacing which promotes individual tree diameter growth to a certain limit. This means that two completely different situations of stand density and composition of tree diameter may result in similar stocking level but leading to very distinct types of merchantable yield (Clutter et al, 1983; Davis and Johnson, 1987)

Methods

Results

Conclusion