Cable thinning in young forests with average DBH of 5-8 inches : a case study

This paper describes the results of a time-study conducted\ud near Grand Ronde, Oregon, to determine the production\ud rates and total harvesting costs of a cable thinning in a\ud young stand. The stand had a species mix of 48 percent\ud western hemlock (Tsuga. heterophylla- (Raf.) Sarg.), 45 percent\ud Douglas-fir (Pseudotsuga meuziesil (Mirb.) Franco), and\ud 7 percent white fir (Abies concolor (Gord. & Fiend.) Lindi.).\ud The stand had an average age of 33 years, with a mean dbh\ud of the total stand (over 1.5 inches (3.8i cm) dbh) of 5.7\ud inches (14.48 cm). The mean dbh of the merchantable stems\ud (over 6 inches (15.84 cm) dbh) was 8.3 inches.\ud The yarder belonged to the small size class of yarders,\ud and was rigged with a live skyline system using a selfclamping,\ud manual slack-puliing carriage. Three hooking\ud techniques consisting of three chokers with sliders, presetting\ud three ring chokers andusing a toggle hook, and\ud flying six ring chokers per turn were compared on a production\ud basis.\ud Regression equations were developed for the individual\ud elements of the yarding cycles and for total cycle times\ud ftr each hooking technique. Results indicate that there is\ud no significant difference between the production rates of\ud three chokers and sliders compared with three preset\ud ring chokers and a toggle hook. There was a significant\ud difierence between the production rates when using the three\ud chokers and sliders compared with using six ring chokers\ud and a toggle hook. The six ring chokers and toggle hook\ud was about 13 percent faster per MBP.\ud The total harvesting cost was compared with the mill\ud value of the timber. The total harvesting cost included\ud felling, limbing, and bucking cost, equipment move-in and\ud move-out cost, yarding cost, loading cost, and hauling\ud cost. Not included in the harvesting cost was road costs,\ud engineering and layout costs, timber tax costs, or any\ud profit and risk costs. The total harvesting cost came to\ud $227.90 per MBP. The weighted average mill price for the\ud logs was $250.24 per MBP