Researchers study rare forest remnant to uncover ecological history of ivory-billed woodpecker habitat in eastern Arkansas

FAYETTEVILLE, Ark. — The sighting of an ivory-billed woodpecker may be disputed, but University of Arkansas researchers studied the trees at the site and say the forest itself represents a critically endangered habitat — one that may provide historic blueprints for its own present-day management.

When visitors hear a woodpecker knocking in Bayou de View, it may be tapping on a giant, ancient bald cypress tree. Last fall, graduate students Mark Spond and Daniel Griffin and Distinguished Professor David Stahle of the Tree Ring Laboratory in the J. William Fulbright College of Arts and Sciences slogged through hip-deep mud and water and strapped themselves to trees to develop tree-ring chronologies that depict historic precipitation patterns in the forest.

They report their findings, together with UA researchers Malcolm Cleaveland, Falko Fye and Brian Culpepper and David Patton of the Ancient Cross Timbers Consortium in Oklahoma, in the journal Eos, Transactions of the American Geophysical Union.

What they found was a remnant forest of bald cypress and tupelo, a type of ecosystem that has all but disappeared from the landscape. Researchers estimate that while nearly 17 million hectares once covered the South, less than 5,000 hectares, or 0.003 percent of the original forest cover, remains today.

Bayou de View turns out to be part of that tiny remnant.

“We’re talking about an extremely endangered forest habitat,” Spond said.

As they explored the forest, they found three different types of habitat — areas that have been thoroughly logged, areas that have been selectively logged for tupelo and areas that show no evidence of logging.

The researchers mapped out a quarter-hectare plot of unlogged forest and took tree-ring cores — pencil-thin slices that show ring growth — from each tree and log in the plot for a total of about 320 trees. They found many trees in the 300- to 500-year range, some in the 600-year range and a handful over 1,000 years old.

“Bald cypress is the longest-lived tree in eastern North America,” Spond said, “And it’s a tree that has a dramatic response to drought.”

In the Eos article, the researchers combined the tree-ring precipitation correlation data with data from the Black Swamp and Mayberry Slough in Arkansas to form a reconstruction of drought and precipitation that dates back about 850 years. They found that severe droughts lasting at least 10 years occurred during the 14^th, 15^th and 16^th centuries. Because bald cypress seedlings require somewhat dry conditions to germinate, the researchers speculate that the droughts would have killed many of the mature trees while spawning others. This massive tree die-off also may have increased the ivory-billed woodpecker numbers, because the birds feed mainly on wood-boring larvae that live in dying and recently dead trees.

Knowing how the trees respond to different types of conditions can help modern-day forest managers better understand the current dynamics of the trees in a given ecosystem.

A few bald cypress remnant forests with non-commercial timber exist, and only three sites with the columnar, commercial-grade timber still exist in North America. Arkansas is the site of one of each — a commercial-grade ancient forest and the non-commercial grade ancient forest at Bayou de View. Without the existence of this forest remnant, there would be no debate over the ivory-billed woodpecker, as the habitat where it lives would have vanished.

Stahle also examined documentation by an early 20^th-century forest observer who recorded the age structure typically found in cypress swamps, which offers a predictive model for where old-growth bald cypress-tupelo remnant forests have been and may still be found.

“This is an introductory article to let people know about this forest habitat,” Spond said. “But the interest in this forest is going to continue.”