A Measure of the Effect of Soil and Atmospheric Moisture on the Growth of Ponderosa Pine

Author: Mace Arnett C.   Wagle Robert F.  

Publisher: Society of American Foresters

ISSN: 0015-749X

Source: Forest Science, Vol.10, Iss.4, 1964-12, pp. : 454-460

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Abstract

Simultaneous measurements of foliage moisture, diameter growth, precipitation, air temperature, and relative humidity were taken from June 22, 1961 to September 7, 1961 on 3 1/25-acre plots in second growth Pinus ponderosa Laws. stands located near McNary, Ariz. Plots 1 and 2 were artificially watered at rates of 1 and 2 inches of water per week with plot 3 utilized as a control plot. Artificially increasing soil moisture beyond levels resulting from natural precipitation significantly increased the diameter growth of the pine and a close relationship between diameter growth and amount of precipitation was established. Foliage moisture content was not significantly related to precipitation, nor did artificially increased soil moisture levels yield significant differences in foliage moisture content. A maximum daily temperature of approximately 70° F appeared to be optimum for diameter growth. Growth inhibition was associated with higher temperatures. Weekly fluctuations in growth and relative humidity followed similar patterns, leading to the conclusion that water tension in the plant, as influenced by temperature and/or relative humidity, is a primary factor in limiting growth.