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GUIDELINES for . . .
Spacer graphic Developing Stand Density Management Regimes

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Biological Concepts of Timber Production

      The biological concepts underlying the growth and yield of trees and stands are fundamental to an understanding of the relationships between density management and timber production. Consideration of other resources, such as water and wildlife, is also important in density management decisions, but are discussed only briefly here.

      Stand density changes from establishment to maturity in response to natural processes and management interventions such as plantation espacement, pre-commercial thinning (juvenile spacing) and commercial thinning. These and all other silviculture treatments which affect tree spacing will influence the subsequent growth of the stand and the harvest yield.

Stand production potential

      The production potential of a particular population of trees growing on a given site is a function of site and tree resources. The productivity of the site resource, for example, is determined by the inherent characteristics of the soil and climate. These characteristics are essentially fixed, although the effects of external factors (e.g., poor soil management, adverse climatic change, industrial pollutants) may temporarily or permanently impair site productivity. On the other hand, intensive forestry practices such as cultivation, irrigation, drainage and fertilization may increase the production potential. Large productivity gains are rarely practical, however, because production-limiting factors are costly to manipulate.

      The productive capacity of a particular species or species mixture is governed by its ability to utilize the site resource. This is a function of the ecophysiological characteristics of the species, and is largely fixed. There are, however, notable exceptions:

      • Selection for tree vigour during silviculture treatments can either increase or decrease the efficiency of production because of the wide variation in the productive potential of individual trees.
      • Inadvertent use of unsuitable provenances in reforestation can lower species productivity.
      • Genetic selection and use of improved growing stock in future managed stands can increase natural productivity through genetic gain.
      • Repression, a biological phenomenon important in lodgepole pine, can substantially reduce the height growth and productivity of all trees in stands established at high densities, particularly on sites of average or low productivity.

      Apart from these site and species exceptions, it is reasonable to assume that stand productivity potential is fixed.


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Copyright 1999 Province of British Columbia
Forest Practices Branch
BC Ministry of Forests
This page was last updated January 1999

Comments to: Tim Ebata <Tim.Ebata@gems8.gov.bc.ca>