Climate: A Factor in the Origin of the Pole Blight Disease of Pinus Monticola Dougl

Measurements of cores or disc samples representing slightly more than 76,000 annual rings from 336 western white pine tree were compiled to obtain a set of deviations from normal growth of healthy trees that would express the response of these trees to variation in the environment during the last 280 years. Their growth was demonstrated to be a function of temperature and available moisture for the period of climatic record from 1912 to 1958. Extrapolating the relation of growth to weather to the long tree ring record of western white pine, we find that the period 1916—40 represents the most adverse growth conditions with regard to intensity and duration in the last 280 years. This drought, superimposed on sites having severe moisture—stress characteristics, triggered the chain of events which ultimately resulted in pole blight. If the unfavorable conditions for growth during 1916—40 do not represent a shift to a new climatic mean and if western white pine is regenerated only on sites with low moisture—stress characteristics, the probability is high that pole blight will not reoccur for many centuries in stands regenerated from this date on.