Minnesota Science
Vol. 47, No. 3
Aid Available to Forestry Professionals
by Larry Etkin
Many factors affect tree growth, and forestry professionals can often suggest ways for forest owners to improve tree growth on their land. Unfortunately, environmental factors such as climate and soil type can't be altered.
A "site index" helps in choosing tree species and management practices to encourage fast, productive tree growth. An index expresses the relationship between a tree's age and height. A 50 foot tall, 50 year old tree has an index of 50. "Any element in the environment that affects height growth will likewise affect site index," says forest soil scientist Donald Prettyman.
"A site index reflects both genetic factors and an integrated response of trees to an environment," says Prettyman. A site index is often used to estimate the quality of a site with respect to timber production. The indexes for different tree species can vary substantially on any given site.
Besides genetic variations within species, tree growth on any site can be affected by a species' individual responses to soil type, availability of nutrients to roots at various depths, local geographically influenced climate affects, etc.
Indexes and the value of "indicator species" – using a known species to predict growth performance of another with similar requirements – are discussed by Prettyman in a new publication, "Forest Soils-Climate-Site Index Relationships for Minnesota." He recommends the publication to owners and managers of forest within Minnesota, and to forestry management professionals and educators.
The publication is available for $1.50 by mail from the Distribution Center,
20 Coffey Hall, University of Minnesota, 1420 Eckles Ave., St. Paul, MN 55108-6064
(Minnesota residents add $.10 sales tax per copy ordered). Request publication
AD-MR-6062-D. Make checks payable to the University of Minnesota.