The intermittent character of tree growth is reviewed. Different parts of trees grow at varying rates and at different times. Shoot growth of many Temperate Zone trees occupies a relatively short part of the frost-free season. Marked apical dominance in conifers is emphasized, with the amount of annual shoot elongation decreasing down the main axis and inward on branches of the main stem. Growth intermittency also is indicated by the production of lammas and proleptic shoots. There is considerable evidence that shoot growth of many species depends on stored foods rather than products of current photosynthesis. Often there is much better correlation of shoot growth with environment of the season of bud formation than with the season of bud expansion into a shoot. Cambial growth, which lasts longer than apical growth, also is basically intermittent. It varies with environmental change, at different stem heights, and around the tree bole. Intermittency in cambial growth is related to live crown ratios and degree of suppression. In suppressed trees cambial growth in the lower bole may be negligible. Much of the observed variation in radial change in stems reflects hydration changes which are superimposed on cambial growth. Cambial growth initiation may be readily confused with rehydration of stems prior to beginning of cambial growth in the spring.
Document Type: Journal Article
Professor of Forestry, University of Wisconsin, Madison
Publication date: September 1, 1963
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