Mellon Foundation Grant Boosts Forest Research

Mellon Foundation Grant Boosts Forest Research

BY LIA UNRAU
Rice News Staff

Research aimed at understanding forest dynamics—how forests change over time—will get a boost with a three-year grant from the Andrew W. Mellon Foundation.

The $164,000 grant will fund a program led by Paul Harcombe, Rice professor of ecology and evolutionary biology, who has been studying forest dynamics for more than 30 years.

Harcombe collects data on tree populations in the Big Thicket area in East Texas, noting which trees die and which survive each year. He is comparing dry, moist and wet forests consisting of hardwoods and pines.

The Mellon grant is allowing Harcombe to summarize 20 years of data to identify long-term trends in forest growth and decline.

Harcombe is working first to create a clear record of how a forest population changes, then to interpret that record to learn about the interaction of natural and human forces in causing the change.

“It is partly a consequence of what happened in the past and also knowing year-to-year changes,” Harcombe says.

“In the Big Thicket, some populations, especially American beech and ironwood, decreased more than I expected,” Harcombe says.

The ironwood decline was caused by a prolonged flood, but it still is not known why the beech trees suddenly started to die.

Many researchers would like to know how important big storms are in creating space that allows new trees to come in.

While some scientists have postulated big changes in tree populations due to storms, Harcombe says that when a hurricane hit one of the East Texas forest strands in 1986, damage from wind was minimal.

Flooding can play a role as well, Harcombe says. A 1989 flood in one study area had a bigger effect than he would have expected, causing the loss of nearly 10 percent of the trees.

Harcombe warns to take care in interpreting the findings, however, because 20 years is a relatively short period of time in the life of a forest.

It is possible that this type of research could have implications for the forestry industry.
“If the forestry industry could somehow mimic the natural process, that would be good,” Harcombe says.

“What I see is that the natural disturbance regime is not as intense as was thought,” he says. “The disturbance patches are not as big.”

Says Harcombe, “If we do want to manage forests in a different way, this information will help us understand that we’re doing it for valid reasons.”

He has found that the rate of change is more tree-by-tree replacements rather than through devastating storms.

“This may be a little bit surprising to many people,” he says. “We tend to be influenced by major events, such as hurricanes and tornadoes, and we tend to extrapolate from them. The natural tendency is to overemphasize the importance of these events.

“We have to remind ourselves that in most forests, most of the time those extreme events are not a major factor,” Harcombe says.

Harcombe expects to complete additional field work this summer and then he hopes to publish several research papers describing his findings.