Gross Influences on Heartwood Formation in Black Walnut and Black Cherry Trees.
Forest Service research paper,
FOREST PRODUCTS LAB MADISON WIS
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Heartwood formation in black walnut Juglans nigra L. and black cherry Prunus serotina Ehrh. was studied in relation to tree age, size, and growth rate, vertical position in tree, morphological characteristics of heartwood-sapwood transition zones, between-tree and between-stand variation, and the broad-organizations of physiological control over the process. Heartwood formation near ground level commences at 3-8 years tree age in walnut, 3-9 years in cherry. In walnut, both between-stand and between-tree variation contribute significantly to total variation in sapwood ring number. In cherry, of these two sources of variation, only between-tree variation is important. Walnut shows little correlation between number of sapwood rings and recent rates of radial growth, while cherry exhibits a compensation for fast radial growth through a reduction in the number of sapwood rings. Results indicate that sapwood will be excessively wide in walnut grown under intensive culture in the absence of genetic or silvicultural control of heartwood formation, and that such control is biologically feasible.