Multi-tree cut-to-length harvesting of short-rotation poplar plantations

Natascia Magagnotti,Kalle Kärhä,Piotr S Mederski,Raffaele Spinelli

doi:10.1007/s10342-020-01335-y

Abstract

Small tree size represents the main challenge when designing a cost-effective harvesting system for European short-rotation plantations. This challenge is further complicated by the need to obtain 4-m logs for high-end products, which rules out the possibility of deploying whole-tree chipping. Both challenges can be met through mass or multi-tree handling (MTH), which must begin at the time of felling and continue uninterrupted along the whole supply chain. The objective was to: (1) gauge the productivity and the cost of CTL harvesting applied to these plantations; (2) assess log yield and capacity to match dimensional specifications; (3) determine if MTH applied to CTL technology offers a real benefit compared with conventional single-tree handling. The authors conducted a time study using a block design with a two-machine cut-to-length harvesting system (i.e. harvester and forwarder) in single- and multi-tree handling operations on the clear cutting of a hybrid poplar plantation in Poland, as well as we manually measured the produced volumes of the study. Higher productivity (+ 8%) was achieved under the multi-stem handling mode. The MTH system proved capable of containing harvesting costs below € 15 per green ton, while fulfilling set timber quality requirements in terms of value recovery and log quality specifications. A new, software-based, MTH system is recommended to be used in short-rotation poplar plantation for logs and biomass harvesting. When the coppicing season is over, the system can be deployed for the conventional thinning operations.

Highlights

Economy of scale favors concentrated production in very large plants, and that is true for all sectors—including the wood industry
Mean gross log yield varied between 37 and 42% of the total harvest between two treatments used: between 11 and 17% of all logs did not match the set quality specifications, because their small-end diameter was smaller than 7 cm or their length diverged more than 15 cm from the 4 m target (Table 2)
When the productive machine hour (PMH) productivity is converted into the scheduled machine hour (SMH) productivity applying a 20% delay factor according to Spinelli and Visser (2008), the corresponding productivity figures are 6.5 and 7.3 m3 log volume SMH−1, respectively, which are almost exactly what is reported in this paper

Summary

Introduction

Economy of scale favors concentrated production in very large plants, and that is true for all sectors—including the wood industry. It is crucial to find solutions that can guarantee a steady wood supply in large volumes, which is especially critical at a time when the wood market is unsettled by deep structural changes (Hetemäki and Hurmekoski 2016). In such a predicament, wood industries can benefit from building a strategic feedstock reserve that they can control directly, and use to balance the eventual fluctuations in supply volume and price (Stanton et al 2002).

Methods

Results

Discussion

Conclusion