Silviculturists designing treatments to encourage
development of new age classes of trees should be cognizant of the need to also provide adequate growing space for the post-regeneration growth and development of the regenerating cohort or lower canopy classes. The relative growth rates of the understory and overstory of a two-strata stand have been described as a tradeoff between production of these two stand components: by shifting growing space occupancy from one stratum to the other, increment is also shifted (O'Hara, 1998). Furthermore, the relationships between understory and overstory production probably vary with species because of differences in shade tolerance. Intolerant species will require larger gaps or greater amounts of light energy than tolerant species. However, any assessment of the relative tradeoff in growth should recognize that understory growth rates do not have to equal or even approach those of comparable open-grown trees. Understory trees need only to advance in stature to eventually replace older cohorts without excessive mortality or deterioration in stem form.