The trees we must stand on guard for

Genotypes 1

Trees are like people. Even within the same species, each is slightly different. Each has a genetic makeup, a DNA structure, that is unique.

We’ve known about the genetics of trees for some time. But until recently, we never realized how finely tuned they are. Their genetics match trees perfectly to their immediate environment.

What we haven’t understood is that the match is so precise that a tree, or its seeds, won’t grow well even a short distance away. The least change in soil, climate, and length of daylight hours will result in a mismatch between the tree’s genetic expectation and its new location. Fifty kilometres can make the difference.

This means that if you are buying a tree, or a shrub, for your front yard, you should find out where its seeds originally came from. Not the nursery where it was planted, but where the parent tree, and its ancestors lived. The parent’s seeds will carry the genetic blueprint, developed over thousands of years of adapting to that one location.

If there is a mismatch between genetics and location, you may get a tree that will grow, but it will be weaker, and less well adapted to its new location. It may live only 30 to 60 years instead of three or four times as long. Its immune system won’t work as well, it will be more susceptible to damage and disease, and it probably won’t grow as large as the parent.

We live in Eastern Ontario where last winter’s ice storm ravaged the forests. It puzzled me why patches of red pine were the most severely hit, with ice bending 25-foot trees to the ground, while white pines survived pretty well intact.

Last week, I finally got around to asking Henry Kock why the red pine were so much more vulnerable. Kock is an interpretive horticulturalist at The Arboretum at Guelph University.

With eyes the colour of dark moss, a greying black beard that birds could nest in, and a tall angular body, he reminded me of the Green Man, the pagan god of woodlands.

For 18 years he has been gathering seeds from across Ontario, and bringing them to the Arboretum for research. He describes himself as a « fifth generation seedsman’’ — his father, who immigrated from Holland, and his ancestors going back another three generations made their livings growing seeds and running nurseries.

The Arboretum has a record of every seed collected — about 3,600 of them– that allows staff to locate, within 100 metres, where the parent grew. From those seeds thousands of trees have been grown for research on Arboretum grounds.

The red pines near our home were planted, in small pockets, by the Ontario Ministry of Natural Resources about 25 years ago. It’s Kock’s guess that they were especially vulnerable because the seedlings were genetically unsuited to our area. They grew tall and lush. But they turned out to be weak.

In some areas where the Ministry planted trees, whole forests died several years ago because no one at the time of planting appreciated the importance of tree genetics, Kock says.

The worst thing that can happen with malsuited trees is that they survive and continue seeding new, similarly defective trees, he says.

Only now, he says, are we beginning to understand how important it is to taintain genetic diversity. We need to protect the well adapted parent trees — the genotypes, he calls them — because they are the strongest, the most resilient. The most likely to be able to survive a global climate change.

« Genetic diversity is essential to the survival of our forests, and the forests are essential to biodiversity. And biodiversity,’’ he points out, « is essential to life on this earth.’’

When I look at the devastation among the red pines near us, whole sections folded down upon themselves like dominoes, his words take on a poignant and exceptionally powerful meaning. The ice storm was a preview of what global warming can be like.


NEXT WEEK: Climate change

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