Draft requirements to fell junipers

Abstract

An inexpensive method of tree felling is needed to precondition dense stands of mature junipers (Juniperus spp.) for the effective use of prescribed burning. The purpose of this research was to determine draft requirements to fell individual juniper trees at different striking heights. These baseline data are necessary to design an elevated chaining technique. Sites in Oklahoma with single-stemmed Ashe juniper (Juniperus ashei Buchholz) (N=40) and Texas with multi-stemmed redberry juniper (Juniperus pinchotii Sudw.) (N=45) were selected for evaluation. A horizontal breaking bar was cabled to an instrumented tractor drawbar for draft force determinations. Data from the drawbar loadcell were stored in a laptop computer data acquisition system. Maximum force to fell junipers was determined at striking heights of 0, 0.6, 0.9, and 1.2 m in Oklahoma and striking heights of 0, 0.6, and 0.9 m in Texas. Force to fell Ashe juniper trees at striking heights of 0, 0.6, 0.9, and 1.2 m averaged 149, 78, 50, and 38 kN, respectively. Striking trees at 0.9 m compared to 0 m (ground level) reduced the felling force by 67% and still uprooted 50% and severed 50% at ground level. With redberry junipers, felling force at striking heights of 0, 0.6, and 0.9 m averaged 81, 14, and 12 kN, respectively. At the striking height of 0.6 m, required draft was reduced by 84% compared to ground level striking, and 67% of the trees were severed at ground level and the remainder were uprooted. To predict force to fell a given size tree, draft was regressed on basal stem diameter in Ashe juniper or total basal stem area in redberry juniper. Based on these data, we concluded an anchor chain modified for elevated striking heights could substantially reduce the tractor drawbar draft for preconditioning of dense stands of juniper by chaining.