Pacific Northwest Research Station

Title: Belowground competition influences growth of natural regeneration in thinned Douglas-fir stands

Author: Devine, Warren D.; Harrington, Timothy B.

Date: 2008

Source: Canadian Journal of Forest Research

Description: 

Using a factorial combination of understory removal and trenching treatments, we examined the influences of belowground competition from understory and overstory vegetation on growth of naturally established Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) saplings in thinned stands of Douglas-fir on moderately productive, glacially derived soils near Tacoma, Washington. Under limited light (26% ± 16% of full sun), sapling height and diameter growth were significantly reduced by belowground competition from overstory trees. Regardless of presence or absence of belowground competition from trees, understory vegetation did not have a detectable effect on sapling growth. Belowground competition from overstory trees had a greater negative effect on growing season soil water content than did understory vegetation. Under the conditions of restricted light availability in this study, limitations in soil water content from competition had a strong growth-limiting effect on Douglas-fir regeneration. As potential canopy trees in a future uneven-aged stand, this sapling cohort would benefit from root gaps created during harvests.

Keywords: Douglas-fir, regeneration, nitrogen, soil water, competition, understory

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Citation

Devine, Warren D.; Harrington, Timothy B.  2008.  Belowground competition influences growth of natural regeneration in thinned Douglas-fir stands.   Canadian Journal of Forest Research.