It could be called lending a helping branch.
Scientists from The Nature Conservancy are using small branches from large survivor American elms in a handful of locations throughout New England to try to develop new Dutch elm disease-resistant strains of the stately tree that, decades ago, was among the most prominent in city parks and streets throughout much of the United States.
In coming days, aided by Chesterfield arborist Jim McSweeney, Conservancy ecologist Christian Marks will visit several Western Massachusetts sites to take sample branches for large elms that survived the onslaught of Dutch elm disease that ravaged the American elm population in the Northeast from from the 1950s through the 1970s and continues into the present. Samples also are being taken from sites in Connecticut and Eastern New York.
“The disease has had a profound impact on trees that were treasured by so many people in city parks and streets,” Marks said. “It also had a dramatic impact on floodplain forests along New England’s rivers.”
Before Dutch elm disease, American elms, among New England’s largest trees, would grow to dominate the forest canopy, creating a unique ecological niche that combined flood tolerance with shade tolerance
The elm still is the second most abundant tree species in the floodplain forests of the Connecticut River watershed; however, today’s elms are typically much smaller than those that preceded the disease, and the unique niche the larger trees created has been mostly lost. Restoring it would benefit these crucial floodplains.
“An array of bird species and other plant life rely on these floodplains, but they also have important benefits for people,” Marks said. “Among other things, they absorb flood waters and blunt the impact of ice-buildup, protecting communities from potentially expensive and dangerous flooding.”
Marks and others have been scouting New England for exceptionally large American elms that are growing near smaller elms displaying the disease. These large healthy individuals are likely to have been exposed repeatedly to the disease and may have genetic resistance.
Scientists are crossing samples from the most promising trees among these large elms with American elm selections developed by the U.S. Forest Service that are already proven to be highly tolerant to Dutch elm disease. The offspring from these controlled crosses will be planted at floodplain forest restoration sites. Once the elms reach sufficient size, the trees will be tested for disease resistance.
“We’ll make the most resistant American elm varieties among them available to the public, as well as planting them in our own floodplain forest restoration projects on the Connecticut River,” Marks said. “One day, maybe, these incredible giants once again will lend their beauty to our parks and streets and their strength to our floodplains.”
This is the third year of this elm restoration project. So far, cuttings from nine elms in Connecticut, Massachusetts, New Hampshire and Vermont have been collected, and 20 crosses have been completed. This March, cuttings will be collected from at least 16 more elms.
The Nature Conservancy is the leading conservation organization working around the world to conserve the lands and waters on which all life depends. The Conservancy and its more than 1 million members have protected nearly 120 million acres worldwide. Visit The Nature Conservancy on the Web at www.nature.org/mass