Silviculture to encourage regeneration of a new
cohort
Oliver's (1981; Oliver and Larson, 1996) stages of
stand development provide a useful model of the gradual ``transformation'' of ``natural'' even-aged stands to more complex structures. Of particular importance is the transition from stem exclusion to the understory reinitiating stage. The former stage is characterized by an even-aged stand occupying all the available growing space. The latter stage Ð understory reinitiating - is characterized by the regeneration of new cohorts and development of new structural variability. Whereas one structure generally lacks variability the other is defined on the basis of having variability in the form of a new age class or canopy stratum. The cause of this change is the inability of the original age class or cohort to occupy the growing space fully and to exclude new cohorts. In these stands originating from natural regeneration, this may be caused by tree mortality, crown abrasion, or many other causes.