Integrated Harvesting of Medium Rotation Hybrid Poplar Plantations: Systems Compared

Abstract

In this study, the authors provide a direct comparison made between whole tree-harvesting (WTH) and cut-to length (CTL) methods, which was conducted in two sites in the Slovak Republic and applied to poplar plantations. Both systems, WTH and CTL, have been employed at the highest mechanization level in two sites: “Nivky” and “Skalica”. Two different strategies, namely, “mass handling” and “small-scale mechanization”, have been used for WTH and CTL, respectively. The study results showed that the level of productivity (ODT SMH−1) in the felling operation was almost double for WTH than for the CTL method in Nivky (+84%) and more than double in Skalica (+113%). The extraction operation under WTH showed a productivity increase from one fifth (+20%) to more than double (104%) that of the CTL method in the Nivky and Skalica sites, respectively. Regarding cost-efficiency (EUR ODT−1), the WTH system offers a similar trend except with respect to extraction in Nivky (higher productivity site), in which the CTL extraction was 4.5% less expensive than the WTH extraction. The study results show that the mass-handling technique deployed in the WTH system offers very good performance in poorer plantations since the very small tree size and low-growing stock challenge the CTL system more than the WTH system. The total operation (felling, bucking, and extraction) costs (EUR ODT−1) recorded by the study in commercial conditions (as contractors perform for revenue purposes) were 32.50 and 45.80 EUR ODT−1 for CTL and 43.30 and 53.60 EUR ODT−1 for WTH for the higher-yield site (Nivky) and lower-yield site (Skalica), respectively. Regarding the WTH System, the researchers found that the drop in efficiency (and the consequent rise in the costs-per-ton of product) depends largely on the bucking phase conducted using the harvester at the landing of the stacked piles of interlocked trees. The main results of this study demonstrate the promising strategy of mass handling associated with the WTH system in medium rotation coppice (MRC) harvesting and shows that bucking is the weaker phase. Future efforts must be made to ensure feasibility of the “mass handling” strategy alongside the entire workflow by means of finding suitable mobile machinery that can delimb, debark, and crosscut tree bunches instead of single trees.

Comparison between Different Mechanization Systems: Economic Sustainability of Harvesting Poplar Plantations in Italy

“…This is a fast and productive cutting method [37,38] that involves the use of a harvester that fells and prepares the logs in lengths generally of 2 m or 4 m, and then these are transported to the forest landing, through a forwarder. The use of CTL technology offers several advantages, in particular, an accurate evaluation and measurement of individual trees directly on the felling field, which is reflected in a better quality of the timber in terms of reducing the contamination of the logs, quality of uprooting, and recovered value [27,39,40].…”

“…At the same time, however, the CTL is relatively expensive and designed for processing single trees, which does not fit well with the limits imposed by plantations of small trees [40]. An alternative method is the harvesting system of the whole tree (whole-tree harvesting-WTH) [41], which consists of: (i) felling of whole trees, (ii) dragged by a skidder grapple on the landing, and (iii) transformed into trunks [27,39,42].…”

“…From an economic point of view, the WTH system provides a 10% higher productivity than the CTL system and a cost reduction of around 15 EUR/t [39]. However, the two methods shown are poorly specialized harvesting systems for medium-shift-coppice crops [44][45][46].…”