Low-Density Management of White Pine Crop Trees: A Primer and Early Research Results

Abstract

Abstract Growing white pines at low density after pruning appears to offer many advantages over more conventional silvicultural systems. This article describes how to design and implement a low-density thinning schedule using published relationships between crown architecture and stemwood growth; empirically, appropriate crown development can be maintained by keeping Wilson's spacing/height ratio between 0.4 (before thinning) and 0.5 (residual stand). Short-term results from a replicated thinning study in east central Maine show that diameter growth of heavily released crop trees was 2.8 times that of similar trees in the unthinned controls and 1.6 times that of similar trees in plots thinned to the B line on the pine stocking guide. Despite the important differences in tree development between thinning methods, total stemwood volume growth per acre of the low-density treatment was only 5% less (and not statistically different) than the B-line treatment. Gross stemwood growth was strongly and linearly related to four parameters of stand density; no evidence of an optimum density zone (the Langsaeter hypothesis) was found. The traditional B line on the white pine stocking guide is shown to have little relevance to either low-density or high-production thinning schedules and should be replaced by a more flexible, less prescriptive approach.