Our Top 20 reasons for why trees enhance our cities continues this month as we examine the scale of time that is instantly created when we view massive, spreading trees. They silently tell of ages long passed and we wonder what they could impart to us, if only they had human speech! Trees however, do have their own language, and if we are willing to interpret the signs, we would be humbled by their stories!
In our oceans, we are in awe of the majestic size of large whales and their ability to survive at great depths, travelling vast distances. On the land, we experience similar grandeur with trees that have great size, and which live in some of the most extreme climates, questioning how they live such extraordinarily long lives - in the same piece of ground! Although trees do not travel, they do in fact move - through the soil, extending and exploring with their root systems when they have a healthy mycorrhizal partnership. In her 2016 and 2017 TED talks, Susan Simard of the University of British Columbia, showed how there is a symbiotic relationship between different trees and their entwined root systems. This relationship enables trees to connect with and, most importantly, share information and nutrients. They create a mutuality and so they are able to quickly respond to changes in climate, water availability, and browsing by animals.
In Ontario, one example of this amazing relationship is that of the Eastern White Cedar trees living on the edge of the Niagara escarpment which are approximately 1,200 years old; normally the same tree in its normal forest conditions lives to about 200 years. They have reached this venerable age because they adjusted to grow within the limits of where their roots can explore each year. A 1,200-year lifetime has seen a lot of climatic changes!
In cities, trees generally encounter difficult conditions for their roots thrive, but when they do adapt, they can live very long lives and grow to the height of a 4, 5 or sometimes 6 storied building. The introductory pictures to this blog are of an Elm on Alice street in Guelph; what we don’t see is the tree's root system. Less than 10 years ago the nearby road was rebuilt and during the excavations no major roots were found. That is because the roots went down into the soil as the tree had no interest in growing laterally into hard-packed road base which had neither water nor nutrients. This tree would have grown from a seed which sent deep roots instead of lateral root growth which would have met the site’s limitations of the road and the nearby house foundation. In other words, the tree avoided growing roots into unproductive soil. This tree is healthy, having survived human interference and diseases; its root system is healthy and has not been compromised.