Improved guidelines for any-aged forestry

Abstract

Any-aged forest management (AAF) is a means to reduce clear-felling without compromising profitability or timber production. The concept of AAF is to choose between clear-felling or thinning one harvest at a time based on what is better at that time in terms of the management objectives for the forest. No permanent choice is made between rotation forest management (RFM) and continuous cover forestry (CCF). Optimized AAF is never less profitable than RFM or CCF because all cutting types of both RMF and CCF are also allowed in AAF. This study developed a new set of guidelines for managing boreal forest stands under AAF when the forest landowner maximizes economic profitability. The first part of the guidelines indicates whether the stand should be cut or left to grow. This advice is based on stand basal area, mean tree diameter, minimum allowable post-thinning basal area, site productivity, and discount rate. If the optimal decision is harvesting, the second instruction determines whether the harvest should be clear-felling or thinning. In the case of thinning, the remaining two steps determine the optimal harvest rate in different diameter classes. The guidelines were developed using two different modeling approaches, regression analysis, and optimization, and applied to two Finnish forest holdings, one representing the southern boreal zone and the other the northern parts of the boreal zone. The results show that AAF improves profitability compared to current Finnish management instructions for RFM. The use of clear-felling also decreased the lower the minimum acceptable post-thinning basal area of the stand.

Individual-tree-selection in uneven-sized Norway spruce stands in southern Sweden: Developments of tools for simulation and optimization

“…When future price variation was assumed to 5%, dbh decreased to 31 cm (eastern Finland). The figures presented in Pukkala (2022) suggest that the target diameter in southern Finland roughly corresponds to the stand basal area weighted mean diameter (discount rate = 3%, basal area = 30 m 2 ha -1 ).…”

“…Tools which enable formulation of tree-level guidelines for ITS of Norway spruce in Fennoscandia have been presented in some recently published papers. The most comprehensive example is a model framework for calculation of optimal thinning rates per diameter class developed by Pukkala (2018Pukkala ( , 2022. Another study by Lohmander (2019b), presented an optimization methodology that can be used for calculating target diameter guidelines adaptive to butt log quality class, market price and local competition.…”

“…Instead, cutting type is optimized per management intervention together with timing and some sort of thinning intensity distribution between diameter classes (Pukkala et al 2014a). This form of optimization has been developed by Pukkala (2014aPukkala ( , 2015Pukkala ( , 2018Pukkala ( , 2022. Decision criteria are optimized at stand level and are presented as a stepwise support system to decide a) if the stand is to be treated or left without treatment, b) if the stand is to be clear-cut or thinned, c) thinning type (indicating how intensity is distributed between diameter classes), and d) dbh where thinning intensity is 50%.…”

“…The function created by Pukkala (2022) for thinning intensity per diameter class can, in practice, be used as a target diameter model. The predictors of the model indicate which stand-level variables that are influential for the size of the target diameter, a) mean diameter, b) stand basal area, d) temperature sum, e) discount rate and f) site index.…”

“…expectations about market price variation (Lohmander 2007, Vauhkonen andPukkala 2016). Nevertheless, the probability that USM is the optimal choice increases with a higher share of pulpwood-sized tree classes (Pukkala 2018, Pukkala 2022, lower stand density (Pukkala 2018), lower latitudes (Pukkala 2022), lower mean diameter (Pukkala 2018, Pukkala 2022, higher regeneration costs Rämö 2016, Pukkala 2018), and larger roundwood market price variation (Tahvonen 2009, Pukkala andKellomäki 2012). An average Norway spruce stand which is not too dense or overstocked with large trees is, therefore, likely to be most profitable to manage with USM directly through continuous selective cuttings (Tahvonen et al 2010, Pukkala 2022.…”