2.2. Silviculture to increase variability of
even-aged stands
There are cases where simply converting an even-
aged plantation to a multiaged stand may not be an option or other situations where variability needs to be integrated into even-aged management systems. There are many ways to enhance structural variability. For new plantations these might include planting to irregular spacing patterns or intentional species mixtures. Either technique will reduce uniformity. An often over-looked aspect of even-aged, mixed-species stands is their potential for stratification into complex canopy structures or distinct crown layers. Because of differential growth of different species, complex structures may develop that are relatively predictable given an understanding of stand dynamics. This is true for both broadleaf and conifer stands (Oliver and Larson,
1996). Northern red oak (Quercus rubra L.) stratifies
over its competitors in the northeast US (Oliver, 1975) and western larch (Larix occidentalis Nutt.) dominates in the mid-elevation forests of the inland northwest of the US (Cobb et al., 1993). These stratified mixtures have many of the features Ð such as variable canopy depths, wide variability in tree size, or even reverse-J diameter distributions Ð that are desired from uneven-aged stands.