DESIGN SOLUTION

AGE DIVERSITY

• Age diversity of street trees is needed to keep the urban forest healthy.

• There is some suggestion that age diversification is a better method of protection against disease than species diversification (within an urban context).

  • (Arnold, Henry F. Trees in urban design. 2nd ed. New York: Van Nostrand Reinhold, 1993.)

TREE PLANTING PROGRAM

The design solution that we came up with was that of a rotational tree planting program.  This rotation is based upon a principle of planned thinning.
When the trees are initially planted, they are spaced close together.  This forces the canopy of the tree up higher allowing more trunk under which people can walk.  This also gives a greater shade cover for the initial decade of plant growth.
This is followed up in a few decades with the thinning process.  The trees that are removed can then be used for other purposes, such as fire wood or hobby materials.  (Check out what other places do with their urban trees - not all applicable to Calgary's climate, but you get the idea.)
In another few decades, younger trees can be placed in between the older trees to start the next phase of tree growth.

34 Street NW with the recommended typology

34 Street NW during the replenishing phase

CONCLUSION

The Tree Planting Program is not intended to be a complete urban forest solution.  The scope of the design solution was to deal with the street trees.  These trees are a part of the public realm, though they straddle public and private space.  Homeowners should still be free to plant different types of trees in their yards.  Elms create a strong canopy form along streets.  This is a powerful structure.  The elms do not provide much of a wildlife corridor however.  Trees that bear some sort of fruit are ideal for this purpose.  With a mixture of plant types within the community of Parkdale, a healthy urban forest and a viable small critter corridor can certainly be achieved.