Magazine article American Forests

Building a Better Tree

Magazine article American Forests

Building a Better Tree

Article excerpt

When the goal is creating tougher trees for urban areas it means focusing on more than just parentage.

Are living things a product of their genetic make-up or of the environment? The answer is both. When it comes to making it in the world of trees, who you are is no more important than where you come from.

This is the second of a two-part series on trees and genetics. In the first part, Trees, Environment, and Genes (Summer 03), I discussed how and whether it's possible to recreate the "perfect tree." There's been much talk about whether it's possible to clone a tree and be assured that its offspring will grow up to be exactly like the "parent." Two identical clones will look diferent when grown on different sites. A tree is as much a product of where it grows as the genes from which it begins life.

Genetics plus environment equals phenotype is "one of the first things you learn in 'tree improvement 101,'" says Bert Cregg, a professor at Michigan State University. Put simply, two trees can be genetically identical but look very different because of the environmental conditions on the sites where they're growing. The concept of phenotype-the tree you see-provides a foundation for the initial and repeated research that must be conducted to confirm a scientific finding.

I was introduced to the concept of phenotype during a course in forest dendrology, the taxonomy of trees. It was there that I heard a fascinating story about the Scotch pine in America, relayed by the professor as a way to help us recognize the species. It also turned out to be a lesson in phenotype.

SCOTCH PINE IN AMERICA

The Scotch pine (Pinus sylvestrus) is widely grown for a variety of uses in the U.S. and is perhaps best known as a popular Christmas tree. The tree has unique, easily recognized orange bark on branches and bluish-green needles. It's a landscape specimen that's also grown for lumber production, much to the surprise to many forestry students in the U.S.

I remember rolling my eyes when the professor instructed us to include Scotch pine in the list of timber trees we needed to know. The trees I had seen in people's yards and in the parks of my hometown were far too crooked to be used for lumber. I learned a few weeks later, though, that Scotch pine is actually a well-established timber tree with a huge range that extends from Western Europe to parts of Asia.

What I didn't realize as I reluctantly prepared to add the tree to my timber list, was that I was about to learn a lesson about phenotype, that all-determining combination of genes and environment. The Scotch pine I had grown up around were crooked because of the seeds they grew from. Those seeds came from trees that grew in a specific mountainous area and were short, stunted, and crooked.

So just how exactly did this country get so many crooked Scotch pine when other countries are populated with gloriously straight ones? The answer dates back to the period just after World War I, when a widespread concern over shortages of forest products prompted a push for growing more timber resources.

It was a popular idea but ultimately unsuccessful because it focused on generating a lot of seed rather than a lot of good seed. People interested in making a few dollars energetically gathered bushels of pine cones, but it was easier to collect the cones that came from those short, crooked trees rather than from the tall ones. So people searched out the short, squatty ones for easy picking.

I saw my first tall, straight Scotch pine on a class trip to an experimental seed orchard. I remember the shock of seeing not just one but a whole plantation of these regal trees covering acres and acres.

Horticulturalist and author Donald Wyman, longtime curator of the Arnold Arboretum at Harvard University, describes the picturesque bluish-green Scotch pine in his book Trees for American Gardens. Although considered to be a valued timber tree in Europe, Pinus sylvestrus has not proved successful in the same capacity in the United States, despite being planted extensively here, Wyman says. …

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