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Continued: Saving the ash tree, seed by seed

  • Article by: BILL MCAULIFFE , Star Tribune
  • Last update: November 4, 2009 - 11:42 PM

HOKAH, MINN. --  Walking the rails, roadsides and riverbanks of southeastern Minnesota, Andy David and his crew looked like they might have fallen off a boxcar. Two carried paper bags. One wore a white flannel Tyrolean hat and carried a sheaf of long yellow poles over his shoulder.

The four were actually on the front end of an effort -- part yard work and part science fiction -- to preserve one of the nation's most besieged natural species: the ash tree.

Poking into the branches of trees, stripping clumps of seed into bags and cataloging each sample, the group was one of dozens across the United States and Canada collecting ash seeds to restore the species after the emerald ash borer destroys much of the ash standing today. At risk in Minnesota are nearly 1 billion trees, roughly 6.4 percent of Minnesota's urban and wild forest.

"If we can store them for 20 years, we're basically buying time," David said. "Once the entomologists figure out a way to control emerald ash borer, we can then reintroduce that species into areas where we know it historically existed."

David is in his third season collecting ash seeds under the University of Minnesota's Rapid Agricultural Response Fund. Since 2002, when the ash borer was discovered to be the reason why ash were dying in Michigan, foresters have known that the insect would eventually make its way to Minnesota.

But the gathering has a new urgency this year. The bug was found in May in St. Paul, where its first 68 victim trees were quickly removed. Agriculture and forestry experts, and even private property owners, are now watching and waiting to see where else the bug might turn up next spring when the larvae burrow out of trees. They're trying to limit the destruction by removing infested trees, restricting the transport of ash brush and lumber, and injecting pesticides into particularly prized trees.

But it's widely assumed that the pest, which arrived in the United States in packing crates from China in the 1990s, will destroy hundreds of millions of the state's ash trees. It has killed 30 million trees in Michigan alone, and has been identified in 12 other states and two Canadian provinces.

One tree at a time

David was joined this year by Egon Humenberger, a native Austrian and assistant scientist in the University of Minnesota's Department of Forest Resources who handled the pruning tools; Julie Hendrickson, a forestry graduate student who's studying methods of ash seed sampling, and Val Green, a DNR forester who knew where the best trees were.

They set out Oct. 20 in Houston County, which has been under an ash quarantine since spring, when an infestation was discovered across the Mississippi River near Victory, Wis. One goal was to collect seeds from white ash, which isn't found elsewhere in Minnesota, then move west and north, collecting samples of the more common green ash, as well as of black ash, a swamp-loving species that make up 80 percent of Minnesota's ash.

David is primarily a plant breeder, working with conifers. But because he also focuses on genetics, the ash now represent a challenge.

"Oh, yeah!" he exclaimed as the group came upon a green ash tree, drooping with seeds, in a deep ravine between Hwy. 61 and some railroad tracks. David and Hendrickson used their fingernails to slice into the inch-and-a-half, paddle-shaped seed husks to get at the seeds. They snapped each in half to see whether their samples might have enough embryonic material to make them valuable.

"You want them white in the middle," he said. "If they're black, there's no material and they're no good." Most were black, which David thought might have been due to the extremely dry summer.

Seeds by the inch

But by collecting hundreds of seeds from each sample tree -- to a depth of about 2 inches in the bottom of a standard grocery bag -- the researchers said there should be enough to meet demand from nurseries and researchers who will want to plant and research ash over the next two decades.

"Every seed is like a little vault that holds the DNA," David said. "If we collect enough seeds, then we've got a pretty good representation of the genetic variation for that species."

By the end of the week, the group had collected seed from 62 trees across southern Minnesota. Individuals who are collecting seed on their own send it to David as well.

His most energetic contributors are members of the Leech Lake Band of Chippewa, who prize the ash for its flexibility in basket-making. Seeds they collect will be stored and returned to the tribe, whose reservation in northern Minnesota includes 22,000 acres of forest, about one-third of it ash.

"We want to keep our ash to replant -- if and when that time comes," said reservation forester Keith Karnes.

Into cold, dry storage

In the coming weeks, after he and Humenberger clean and sort collected seeds, David will send them to the National Plant Germplasm System (NPGS), a Department of Agriculture network of repositories established more than a century ago in which samples of seeds of all sorts of wild and domestic plant species from around the world are stored.

Some of Minnesota's seeds will go to a NPGS site at Ames, Iowa, where they will be housed in a repository holding 50,000 jars of seeds, including 20,000 varieties of corn, one of the largest collections of that seed on the planet.

He'll also send a small sample to the National Center for Genetic Resources Preservation in Fort Collins, Colo., the nation's backup spot for collected material from plants and animals.

Ash seeds at both places will have more than 90 percent of their moisture removed, then be X-rayed, wrapped in aluminum and stored in a flood- and tornado-proof vault at zero degrees, conditions thought to keep them viable for about 20 years.

Dave Ellis, plant curator at the national center in Colorado, hopes that, somewhere in the collection, there might be seed from a single tree with a gene that's resistant to the ash borer, as ash in China are. That would enable resistant ash to be bred and replanted sooner than it might take for the bug to eat its way through its North American food source.

Mark Weiderlechner, curator of woody and herbaceous ornamental plants at Ames, said the collection and preservation effort may allow science to help the ash tree in a way it could not help the American chestnut and American elm, which were nearly wiped out by non-native fungi. Disease-resistant elms are beginning to bring the tree back after about 40 years, but it has taken a century for disease-resistant chestnuts to get a hopeful start.

"Had it been possible to store the diversity of the American chestnut, or American elm, how much quicker we could have had chestnuts back in our forests and elms back in the streets," Weiderlechner said.

Bill McAuliffe • 612-673-7646

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