| Summary: | An increased interest in continuous cover forestry (CCF) and a national policy change in Wales has generated a demand for knowledge of operational productivity in transformation relative to conventional working. This study took place within Coed Trallwm, a privately owned upland woodland in Mid Wales. The site is one of three study sites in Wales used by the UK Forestry Commission to study operational aspects of the transformation to CCF. A total of eight 0.5 ha buffered plots were installed in uniform areas of Sitka spruce (Pice a sitchensis). Treatments consisted of low thinning (paired plot), frame tree (paired plot), group system (paired plot), spatially-moderated creaming (single plot) and premature clearfelling (single plot). Harvesting removed 20% of the standing basal area in the transformation plots and 100% in the clearfell plot. Harvester and forwarder working was recorded through a time and work study in order to identify time differences in cyclical and non-cyclical operations and felling outputs between the different interventions. Relative brash mat production, rack usage and area coverage were also studied. Models for work phase time consumption and total productivity were developed for both machines. Harvester cyclic time consumption was found to be most related to tree size, spacing and morphology, and non-cyclic time consumption to the regularity of the racking system. Forwarder cyclic time consumption was most influenced by thinning type through its effect on assortment, and thinning intensity, through its effect on volume cut. Non-cyclic work was less strongly influenced by these factors. The productivity of both machines increased with mean felled tree diameter. Models for volume recovery, relative product assortments and volumes were also developed for intervention type. Volume recovery, proportion of log material and mean piece size all increased with mean felled tree diameter.
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