S 0.60
 0.50
 S0.40
 0.30
 0.20
 0.10
 0.00
 0.5 2 5 6 8 10 10 12 14 15 16 17 18 19
 Site Designated by Age




 Figure 7.24. Relative Frequency of Canopy Tree Species in Constructed Forested
 Wetlands. The Graph Includes Only Those Species Found in Natural
 and Constructed Wetlands.


 The results of this study support the existence of a hierarchical pattern of tree size
 class distribution in constructed forested wetlands, and this distribution appears to change
 with time. When all tree species are lumped together, the system as a whole exhibits this
 hierarchical pattern. This hierarchical distribution can be explained by recruitment into
 the smallest size class and differential growth and survival rates, which result in only a
 portion of the individuals within a size class entering the next larger size class with time.
 SP6 and Morrow Swamp are the only sites that deviate from this distribution. A fire
 occurring in SP6 may have killed a sizable number of trees in each of the larger size
 classes. The large number of trees in the small size class results from recruitment after
 the fire and/or supplemental planting. Morrow Swamp also shows a unique size class
 distribution reflecting the presence of only one species, which exhibits the distribution of
 an even age stand.

 Size class distributions of individual species show a variety of patterns. Acer sp.
has a hierarchical distribution in many sites where it occurs, regardless of age. This
suggests that the recruitment of Acer sp. is an ongoing occurrence and that stochastic
events or environmental conditions that inhibit recruitment have not occurred. In two
sites, Acer sp. occurs in only the smallest size class. This could result from relatively
recent recruitment or site conditions that are not suitable for growth and survival.
Taxodium sp., on the other hand, does not demonstrate a hierarchical distribution, but
rather resembles a cohort of trees established at one time moving up through the size


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