Simulation of geometric thinning systems and their time requirements for young forests

Abstract

In Fennoscandia, large areas that have not been subjected to pre-commercial thinning (PCT), and thus support dense stands, are becoming suitable for harvesting biomass. However, efficient systems for harvesting biomass from young stands have not yet been developed. In order to optimise biomass harvesting it is here hypothesized that the handling unit should not be a single tree but a corridor area, i.e., all trees in a specific area should be harvested in the same crane movement cycle. Three types of corridor harvesting approaches (using accumulating felling heads for geometric harvesting in two different patterns) were compared in terms of time required to fell a corridor of standardised size. Corridors are defined as strips of harvested areas between conventional strip-roads. Harvests were simulated in two types of stands, first thinning (FT) and delayed PCT stands, in which the spatial positions of the trees had been mapped. The differences in simulated time consumption per corridor were minor when the only variable changed was the corridor pattern. However, there were ca. 2-fold and 3-fold differences in simulated time consumption per corridor between the harvesting approaches for the FT stand and the PCT-stand, respectively. Furthermore, area handling (felling head accumulating all trees corridor-wise, with no restrictions on the accumulated number of trees except for a certain load limit) was found to give up to 2.4-fold increases in productivity compared to a single-tree (reference) approach for the FT stand.In conclusion, the simulation results clearly show the benefits of applying area-harvesting systems in young, dense stands.

Simulation of harvester productivity in selective and boom-corridor thinning of young forests

“…Santesson & Sjunnesson, 1972;Wang et al, 2005), felling operations in environments similar to those considered in this study (e.g. Bergström et al, 2007;Iwarsson Wide & Belbo, 2009) and harvester and forwarder working patterns (e.g. Gullberg, 1997;Ovaskainen et al, 2004;Ovaskainen et al, 2006;Ovaskainen, 2008).…”

“…Johansson & Gullberg, 2002). Towards this end, Bergström et al (2007) have compared the productivity potential of conventional and future (hypothetical) harvesting systems for forest fuel thinning (full trees) in young dense forests. They found that combining geometrical thinning systems (boomcorridor thinning) with customized techniques could increase productivity up to 2.4-fold.…”

“…However, the scope of simulations presented by Bergström et al (2007) was limited in terms of both the types of stands considered and repetitions, so more extensive analyses are required to assess the generality of the apparent potential productivity gains, and further quantify them.…”

Systems Analysis of Ten Supply Chains for Whole Tree Chips

“…Research and development specifically focusing on this are geometric thinning patterns [11,12], shown to have considerable potential, especially when used in combination with continuous cutting devices [13], multi-stem handling and pre-bunching in the stand for further processing [14][15][16]. Options for extraction including by forwarder [17,18], chipping in-field and extraction [19], and bundling of whole trees in-field [20,21] are methods with varying efficiencies in small trees.…”

Application of a primarily deductive framework describing time consumption for hauling of logs to road-side

“…Consequently, there has been an increase in the amount of research and development aimed at identifying more efficient and cost-effective techniques and systems for energy wood extraction, involving new and improved approaches to extracting logging residues, stumps and whole trees from young stands (e.g. Bergström et al 2007). In other parts of the world forest haulage is most often done as skidding; partly carrying and partly dragging the logs, stems or trees.…”