Fig. 1 contrasts gap density and area in gaps of different sizes among undisturbed, light removal and heavy removal treatment units at the Date Creek silvicultural systems study. The majority of gaps in natural stands are < 150 m* with a few up to 600 m2. After light removal logging, in which individual trees or small groups of trees were removed, gap density has increased over the natural forest but the size distribution is still similar to that found in the natural forest; few gaps exceeded 600 m* in size (Fig. la). Gap density increased further after heavy