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Response of Western redcedar to release and fertilization in a mixed-species standAuthor(s): Leslie C. Brodie; Constance A. Harrington
Source: In: Harrington, Constance A., tech. coord. 2010. A tale of two cedars: International symposium on Western redcedar and yellow-cedar. Gen. Tech. Rep. PNW-GTR-828. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 139-144.
Publication Series: General Technical Report (GTR)
Station: Pacific Northwest Research Station
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DescriptionWestern redcedar (Thuja plicata Donn ex. D. Don) is of high commercial value, is considered highly shade tolerant and occurs more commonly in mixed-species, uneven-aged stands than in pure stands. Successful maintenance of redcedar as a component of mixed-species stands to enhance diversity or to overcome the difficulties of establishing redcedar regeneration is dependent on its response to release and other silvicultural treatments. To assess the response of western redcedar to release and fertilization in a mixed-species stand, 74 western redcedar trees were selected to represent a wide distribution of diameter and crown classes in a stand in which the overstory had been recently removed in Capitol State Forest near Olympia, WA. Three types of competition indices were calculated for each study tree in order to quantify the extent of the release treatment as well as to characterize the current growing conditions. Pre-treatment values for the competition indices were calculated retrospectively using the number and size of stumps present. Half of the study trees were fertilized with urea at the rate of 200 kg of N/ha. Percent DBH growth increased significantly in response to fertilization every year for 3 years following fertilization with the greatest effect the first growing season after application. Percent height growth was more affected by the presence of overtopping trees following the release treatment than by fertilization. Of the competition indices modeled, the percent overlap of influence areas (based on tree size) was the most consistently effective at predicting percent diameter and height growth at all years when measurements were taken up to year 15. Western redcedar responded positively to removal of overtopping trees; thus, this type of release should be considered a viable management option. Response to fertilization was positive but short lived.
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CitationBrodie, Leslie C.; Harrington, Constance A. 2010. Response of Western redcedar to release and fertilization in a mixed-species stand. In: Harrington, Constance A., tech. coord. 2010. A tale of two cedars: International symposium on Western redcedar and yellow-cedar. Gen. Tech. Rep. PNW-GTR-828. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 139-144.
KeywordsRedcedar, release, fertilization, management, height growth, diameter growth.
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