September 11, 2009

Most people will take great enjoyment from the sweep of scarlet from red maples across the Kentucky landscape this fall, but a University of Kentucky forestry researcher finds it a matter of some concern.

Anecdotal evidence indicated an increase in red maples throughout Northeastern forests, but there was no hard evidence to back that up until Songlin Fei, assistant professor in the UK Department of Forestry, decided to delve into the matter. In two separate studies in collaboration with Penn State's Kim C. Steiner, he documented first the proliferation of the tree in what had been primarily oak and hickory forests and then investigated the cause for the increase.

"Red Maple (Acer Rubrum L.) has recently come to a level of abundance in some parts of eastern North America that appears to be unprecedented in history," Fei said in a published paper co-authored with Steiner.

This is important because the forest ecosystems in eastern North America, including Kentucky's forests, have developed in concert with oak trees, which the 2009 Forest Inventory and Analysis National Program said account for nearly 40 percent of wood products harvested in the region. A decline in oaks could have serious economic effects on wood industries in those areas.

"It's part of a system that has already been established. Wildlife totally rely on this species," Fei said, pointing out that more than 90 wildlife species depend on the oak for food including birds, squirrels and chipmunks, and deer who prefer to browse oaks over maples.

"And the consequence potentially could be even bigger," he said.

Fei and his researchers are currently working on a project that examines how the species composition change in eastern forests could affect carbon sequestration.

"Based on existing research, red maple sequesters less carbon than an oak would," he said. "The oak system could potentially store more carbon. If the species composition changes in a big area, you have less carbon stored in the forest ecosystem, which could have consequences on global warming."

There are a number of possible causes for the rise in red maple over the last century. Fire management policy may have contributed, since oaks benefit from a fire disturbance while maples do not. The spread of invasive species, such as the gypsy moth, also could be a contributing factor. But Fei believes more than any other factor, it is current forest logging practices that are creating an ideal environment for red maples.

Maples, typically an understory tree, have abundant seed production and vigorously resprout from stumps.

"Over 90 percent of the maples, if you do not do any management, are going to resprout right away and recapture all their growing space within seven years," he said.

In Fei's and Steiner's most recent study, published in the Canadian Journal of Forest Research, they show that 30 years after removal of the overstory in 90 stands, average red maple basal area increased from 10.4 percent to 35 percent, with oak numbers decreasing from 81 percent to 31 percent in the stands during the same period.

The answer, according to Fei, is better management of maples during logging, as well as creating the right conditions for oaks before the harvest.

"Different regions will have different methodologies that can set up the right conditions," he said. "Some people are creating gaps in the canopy that aid in oak regeneration. Some areas use soil scarification (loosening up the bare soil). There's not one single answer to the whole situation, but our conclusion is that, look, if you don't really do a good job managing and just log it, you could increase the red maple."