Apparent Meteorological Requirements for Abundant Cone Crop in Douglas-Fir
Abstract:A 48-year record of Pseudotsuga menziesii cone crop abundance in western Oregon and Washington, expressed as "Abundant, Medium, Light, or Failure," was correlated with records of mean monthly temperature and total monthly precipitation at Salem, Oregon, a station centrally located in the region. The meteorological variables were converted to quartiles and, together with the cone crop rating, were assigned values on a 4-point linear scale. The statistic analyzed was the sum of 48 similar products, each product that of a year's cone crop value and the value of a meteorological variable a certain number of months prior to October of the crop year, up to 30 months. Knowledge of the joint sampling distributions permitted recognition of what are, under the null hypothesis, significant values of the statistic. The 48 years were then taken in pairs, assigned randomly to two subsamples, and the same analysis performed with each meteorological variable. A correlation was designated as biologically valid if it was statistically significant in all three analyses: one sum of 48 products and two of 24 products. Biologically valid correlations yield the conclusions that an abundant cone crop in a given October requires a warm January in the same year, a March-April with high precipitation 1 1/2 years before harvest, and a cool July two years before harvest. Possible physiological mechanisms for the correlations are suggested, but it is emphasized these results are only clues to the connection between weather and cone crop abundance, undoubtedly confounded with other factors such as nutrition and pressure of pest populations.
Document Type: Journal Article
Affiliations: Assistant Professor of Biometeorology, Oregon State University, Corvallis
Publication date: June 1, 1966
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