SEASONAL SHRINKAGE OF MONTEREY PINE AND REDWOOD TREES

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Abstract
Detailed analysis of dendro-graphic records indicates that the fall or winter swelling which has been observed by MacDougal in Monterey pine trees is preceded by a progressive contraction during the dry season of the summer and fall. It appears, furthermore, that such shrinkage may occur during an unusually dry spring. In either case, with the advent of rain[long dash]or sometimes in foggy weather[long dash]such changes in diam. may be checked or reversed. The fall or winter swelling is accordingly to be ascribed to rehydration of the desiccated stem, and probably is not connected with cell division. Redwood trees also exhibit these seasonal variations, which are very closely related to MacDougal''s previously described diurnal fluctuations. Chief among the conditions affecting shrinkage and rehydration are the evaporating power of the air (dependent upon atmospheric humidity, temp., and wind movement) and the amount of soil moisture available, the latter apparently being the more significant from the standpoint of seasonal fluctuations. A tree may be shrinking in one part while swelling in another.