FEATURE ARTICLE
Cliffs as Natural Refuges
Rocky precipices around the world provide a surprisingly sheltered environment for plants and animals
Douglas W. Larson, Uta Matthes, Peter Kelly
Happy Trails
Like many scientific advances, the key to our understanding took form while we were applying ourselves to a different (and very practical) problem. We were trying to establish whether people hiking along the trails at the edge of the Niagara Escarpment were harming the adjacent vegetation. We began by carefully examining the trees situated near these well-trod paths. To gauge whether the recent visitors had done any damage, we needed to know the productivity of the trees in the years before the trails were established. Fortunately, it is not difficult to gain such historical records about a tree, which chronicles its life with a series of annual growth rings.
Measuring the width of tree rings without chopping through a trunk requires an instrument called an increment corer, essentially a slim metal tube with an auger at the tip. Although this device leaves a small hole, it does little harm to the tree being sampled. During the first day of field work, we extracted cores from some dozen trees, including a specimen the size of a small Christmas tree that was perched on a tiny ledge near the top of the vertical face. Normally, annual growth rings are plainly visible on a newly extracted core, but this slim plug of wood appeared to lack the usual light and dark banding. Only after polishing it with fine-grained sandpaper and placing it under a microscope could we see the rings. To our astonishment, we were able to count nearly 400 annual increments, some thinner than a human hair. Hurriedly we processed a few other samples from similar trees and realized that this 400-year-old Christmas tree was not a freak.
Such sluggish growth is unusual, but it is well within the range of the ancient Bristlecone Pines of the American West, which were made famous during the 1950s by University of Arizona botanist Edmund Schulman. Only at this point did we realize that the cliffs where we had been working for nearly three years constituted a thin strip of old-growth forest, a vestige of pre-Columbian North America that had survived in the heart of industrial Canada, not 60 kilometers from the nation's largest city.
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