Stem breakage of Pinus radiata during mechanical felling in Kinleith Forest, Central North Island, New Zealand
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
This report examines stem breakage of Pinus radiata as a result of mechanical felling in Kinleith forest. Four machines were studied, two Bell TF120 feller-bunchers and two Timbco T445 hydro-bunchers. The machines broke between 84% and 100% of the trees felled. Most causes of breakage could not be determined. Of that which could, falling trees striking stumps and previously felled logs accounted for the majority of the breakage. The machine operators and the machine types studied were deemed to be significantly different and thus separate breakage functions were derived for each operator and machine type. The breakage function currently used by Carter Holt Harvey Forests Kinleith, produced from manual felling data, was compared with the newly developed mechanical functions and found to be different. For this reason a mechanical breakage function was created. Nested analysis showed that most of the variation in relative break heights was due to differences in individual trees, not differences in machines or differences in operators. Two sets of statistically significant equations between height and machine type and the breakpoint variables diameter at the break point and relative break height were identified. Although the models account for some of the breakage, none of the relationships developed completely explain how the variables influence stem breakage. Further research is required into operator and the landing environment variables and how these affect felling breakage.