A Seven-Year Study of Cone Production as Related to Xylem Layers and Temperature in Pinus ponderosa

Abstract

In 1955 the writer published the results of a study of the thickness of xylem layers in Pinus ponderosa and three other tree taxa, all of which were sampled near their upper and lower limits of altitudinal distribution in eastern Washington and northern Idaho. No correlation with either-temperature or precipitation, or their combined influence on the environmental water balance, could be found at either distributional extreme. One possible explanation is that whereas temperature and/or moisture might well set altitudinal limits through their control over seedling success, climate would not necessarily exert a critical control over xylem production. That is, the prevailing wetness of the soils at the start of summer might carry the plants along until the time of endogenous cessation of cambial activity in midsummer (Daubenmire, 1946; Daubenmire and Deters, 1947), but seedlings become increasingly vulnerable to drought throughout summer. Another possibility is that variations in fruiting habits of the trees might make periodically heavy demands on metabolites which could obscure weather influences in large measure. This paper presents the results of a study aimed primarily at determining what influence, if any, variations in cone production may have on the annual xylem increments of Pinus ponderosa in the same region as the first study mentioned. LITERATURE REVIEW