Management of spontaneously regenerated mixed stands of birch and Norway spruce in Sweden

Abstract

Timber production and profitability were evaluated for spontaneously-regenerated mixtures on two formerly clearcut areas. The abandoned areas developed into birch-dominated ( Roth and Ehrh.) stands with successional ingrowth of Norway spruce ( (L.) H. Karst.). An experiment with randomized treatments within blocks was established, using three management strategies and one unthinned control, resulting in variation in optimal rotation age, merchantable volume and species composition. The management strategies were evaluated based on total production (volume) by using measured growth data 42 years after clearcutting and the modelled future stand development. The long-term effects of spontaneous regeneration and management strategies were evaluated based on land expectation value (LEV) and compared with a fifth management strategy using artificial regeneration and intense thinnings. 12 years after treatment, at a stand age of 42 years, the unthinned control had produced the highest total stem volume. At interest rates of 2% or higher, the unmanaged forest was an economically viable strategy, even compared to an intensive management strategy with a preferred merchantable timber species. Interest rates clearly impacted the profitability of the different management strategies. This study shows that when spontaneous regeneration is successful and dense, the first competition release can have a high impact on the development of future crop trees and on the species mixture.Betula pendulaBetula pubescensPicea abies

The Value of Hybrid Aspen Coppice Investment under Different Discount Rate, Price and Management Scenarios: A Case Study of Estonia

“…In the case of the low discount rate, energy wood coppicing in repeated 5-year cycles turned out to be an undesirable investment. A similar tendency was observed with natural birch stands in Sweden, where unmanaged stands (large proportion of biofuel) provided lower LEVs than thinned stands with a discount rate of 1% [25]. Although with the highest possible prices, energy wood coppicing also offered high LEVs, the minimum prices resulted in negative LEVs and with the 2nd quartile prices the LEVs were notably lower compared to in other management scenarios.…”

“…All the other management scenarios (with longer rotations) provided negative LEVs, no matter which price scenario was considered. The price of energy wood can have a great impact on the final LEV value in unmanaged deciduous stands [25], but in our case, the price of energy wood remain consistent over the observed period.…”

“…The single-tree method involves only one intermediate cutting, and most of the revenues come from final felling, which in the case of high discount rates much of its net present value is lost and results in negative LEVs. A study in Sweden found that unmanaged forests become an economically viable strategy in comparison with thinned stands in natural birch forests with discount rates over 2% [25].…”

“…Systematic corridor thinning (synonym: strip thinning; in a broader sense: geometric thinning) has been proposed as a cost-efficient method for young and dense stands to optimise early management cost [22,23] and provide additional biomass for energy [20,21]. Although single-tree selection in a dense forest stand has higher cost than corridor methods [24], it might offer more revenues in later harvest stages from greater volumes of valuable wood assortments [25]. Therefore, the selection of an optimal management plan for hybrid aspen coppice stand providing the maximum land expectation value (LEV) is a challenging task where various aspects such as the costs of management activities, wood price volatility and discount rate scenarios need to be considered.…”

“…In Northern Europe, the economic feasibility has been proven for birch stands managed with relatively short cycles (23-26-years) for biomass production when considering discount rates up to 5% [30]. At the same time, thinning does not always provide higher profitability over unmanaged birch stand [25]. Hybrid aspen has been shown to be profitable on former agricultural soils in the first-generation planted stands providing IRR of 4.4-7.3% and positive LEVs with 1-5% discount rates [16], but the profitability of coppicing followed by different thinning treatments has not been comprehensively evaluated.…”