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Monday, June 23, 2014

Resurrecting the chestnut tree requires patience, effort, wisdom and the right amount of ignorance

David Brooks

Like any good researcher, Eric Berry embraces appropriate ignorance.

“I’ve enjoyed not knowing which is which,” said the St. Anselm College biology professor said last Wednesday, looking around at the roughly 350 chestnut trees planted in a study plot at Beaver Brook Association in Hollis. ...

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Like any good researcher, Eric Berry embraces appropriate ignorance.

“I’ve enjoyed not knowing which is which,” said the St. Anselm College biology professor said last Wednesday, looking around at the roughly 350 chestnut trees planted in a study plot at Beaver Brook Association in Hollis.

The plot is designed to help return the glorious American chestnut to our forests, after fungal blight wiped them out a century ago. Part of a national program by the American Chestnut Foundation, it contains a few pure American chestnut trees that aren’t yet old enough to be killed by the blight, a few pure blight-resistant Chinese chestnut trees, and a whole bunch of mixtures.

There are no labels and no obvious visual clues to differentiate them and Berry says that’s good.

“I don’t like to know; it will bias my data collection,” Berry said.

Avoiding bias is the whole idea behind double-blind studies, a cornerstone to scientific research.

If Berry knew which trees were so-called F3B3 hybrids – the 5th-generation cross between American chestnuts and the blight-resistant cousin, Chinese chestnut, that seems to be the species’ best hope – this knowledge might unconsciously color his measurements of height, girth or timing of bud development. It’s better to be “blind,” just in case.

Berry, clipboard in hand and statistical analysis at the ready, is one of many people volunteering at the Beaver Brook site, which was created in 2012 when other volunteers planted almost 400 chestnut seeds, born of trees carefully tended for years by the American Chestnut Foundation.

The decades-long attempt to restore the chestnut, which once made up 25 percent of the hardwood trees on the Eastern seaboard, is mostly a volunteer effort.

The Telegraph has written frequently about local programs that hand-collect pollen from the few chestnut trees which remain in our woods, undiscovered by blight, so they can help create cross-bred hybrids in an attempt to develop the best resistant stock for New England.

This isn’t the only effort to return the chestnut tree, by the way. A State University of New York program has genetically modified American chestnuts, in which a gene taken from wheat is inserted into the trees’ DNA, shows promise – although it’s not easy to measure resistance to a disease that doesn’t show up for many years.

And the chestnut tree isn’t the only target to cross-breeding restoration efforts.

Two programs, one based in Keene, are trying to do the same thing with the American elm, virtually wiped out by Dutch Elm Disease. I have a couple of the Liberty Elm Trees hybrids growing at my home; one died of the disease, but the others are more than a decade old and doing well.

We need these efforts because our ash trees are almost certainly doomed by the invasive emerald ash borer, our hemlocks are under attack by the wooly adelgid beetle, and climate change may drive sugar maples further north. Forest diversity needs human help.

The Beaver Brook plot, right across Ridge Road from the Maple Hill Farm that is association headquarters, isn’t very impressive looking except for a huge deer-proof fence that would be the envy of any southern New Hampshire gardener. At three years old, the biggest chestnut tree is barely at eye level, while many are much smaller and some of the PVC tubes which protected young seedlings are empty because the planting died. None comes close to a glorious black walnut tree, decades or maybe centuries old, that towers overhead.

The plot is one of 11 overseen by the New Hampshire/Vermont chapter of American Chestnut Foundation. Only it and a plot in Vermont have so-called progeny trees, the F3B3 strain produced by years of so-called backcross breeding – in which the children of American-Chinese crosses are bred back with pure American chestnuts, over and over. The foundation thinks this strain, which is 15/16th American, is most likely to resist the fungal blight while still looking like the American chestnut.

Even if true, Berry’s expertise will come in handy when the time comes to analyze the results to maximize effectiveness, since such analysis is part of his research specialty.

Different strains were located randomly around the plot, to spread out the possible effects that can happen even within less than one acre.

“The quadrant will get more shade than that one out there,” Berry said, gesturing around the plot, while plants near the black walnut have to cope with that species’ ability to release a chemical that inhibits the growth of competing trees.

Teasing out these different effects will take statistical analysis of the sort that field biologists regularly do, and will help guide practices once the time comes to plant some chestnuts out in the wild. Should nuts be planted on shady hillsides, or along river bottoms, or in fields cleared by logging, or somewhere else?

Those will be hard decisions to make, but important ones. No ignorance needed.

GraniteGeek appears Mondays in The Telegraph. David Brooks can be reached at 594-6531 or dbrooks@nashuatelegraph.com. Also, follow Brooks on Twitter (@granitegeek).