The Relation of Precipitation and Annual Tree-Ring Growth of Douglas-Fir in Stands of Different Ages in the Western Oregon Cascade Range

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Title: The Relation of Precipitation and Annual Tree-Ring Growth of Douglas-Fir in Stands of Different Ages in the Western Oregon Cascade Range
Author: Argo, Kathryn L., 1985-
Abstract: The extent to which precipitation has an impact on annual ring-growth of Douglas-fir trees and how that impact differs between stands of different age classes has been a little-studied topic, particularly in the Pacific Northwest. Three stands of different ages (young, mature, and old-growth) containing Douglas-fir located in the western Oregon Cascade Range near Blue River, Oregon were cored and measured. Tree-ring width records within each stand were crossdated, and standardized ring-width chronologies for each stand were created using standard tree-ring methods. Significant correlations between precipitation and recent growth histories of each stand were determined using DendroClim2002. Precipitation data were obtained from a meteorological station located in the young stand within HJ Andrews Experimental Forest. Significant correlations differed between stands of different ages. Positive significant correlations occurred between ring-widths in the mature and old-growth stands with June and October monthly precipitation values. The young stand showed significant negative correlations with precipitation in October and November of the previous year and February precipitation of the current calendar year. When precipitation data were modified by altering outliers, correlations changed idiosyncratically by month suggesting the modification was not extensive enough or irrelevant. When a long growth history from the old-growth stand was correlated with precipitation data, the most significant correlations were with monthly precipitation in April and June of the current year and July of the previous year. These correlations suggested that precipitation in the form of rain, particularly around the months on either end of the growing season, have significant relation to tree-ring growth. In addition it was discovered that ring growth in young stands react negatively to precipitation whereas mature and old-growth stands have positive correlations between ring growth and precipitation.
Description: 33 p. A THESIS Presented to the Department of Environmental Studies of the University of Oregon in partial fulfillment of the requirements for the degree of Bachelor of Science with Honors in Environmental Science, Spring 2007.
Date: 2007-06-07

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