ON THE MAXIMUM EXTENT OF TREE ROOTS

Based on literature reports, personal communications and our own observations, maximum vertical and radial root extents were tabulated for various woody species, primarily forest trees and shrubs, and horticultural trees. Data were summarized for 49 families, 96 genera and 211 species, as well as for forest stands composed of mixtures of species. These data demonstrate the inherent capability of many species to develop deep or far-reaching roots in the absence of restrictive soil or substrate characteristics. These data also suggest that extensive roots may play a more important role in uptake of water and nutrients than indicated by their density alone, and that actual, rather than assumed, root extent must be evaluated on a site-specific basis to provide realistic estimates of ecosystem properties and processes.