Canadian Forest Service Publications

Foliage and stand growth responses of semimature lodgepole pine to thinning and fertilization. 1998. Yang, R.C. Canadian Journal of Forest Research 28(12): 1794-1804.

Year: 1998

Available from: Northern Forestry Centre

Catalog ID: 18799

Language: English

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Abstract

The aim of this study was to quantify the interactive response of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) to thinning and nitrogen (N) fertilization in midrotation stands by assessing foliar and stand growth response relationships and determining the optimum fertilizer regime. The experiment design was a factorial arrangement of treatments with two thinning intensities (thinned and unthinned control) and four N levels (0, 180, 360, and 540 kg·ha-1). Foliage was sampled annually from trees in buffers for 4 years following treatment and plot trees measured at a 5-year interval. Results indicated that the effect of fertilization on fascicle length and needle dry mass disappeared 2 years after N treatment, while thinning effects on foliage emerged 3 years after fertilization. Both first year fascicle length and dry mass were reliable predictors (r2=0.87 and 0.82, respectively) of subsequent stand volume growth. Applications of N at 360 kg·ha-1 to thinned and unthinned plots, respectively, improved 10-year periodic height increment by 20 and 19%, diameter at breast height by 29 and 34%, basal area by 21 and 36%, and total volume by 25 and 28%. Fertilization of N at this level appears to be optimal based on foliar and mensurational responses. High N loadings increased tree mortality and accelerated stand development and so it could be advantageously used as a tool for managing overstocked stands.

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