by Whit Gibbons

November 5, 2006

It was raining when Caleb Hickman, Tom Luhring, and I left the Savannah River Ecology Lab (SREL) last week on a field trip to a swamp along the river. We were on a mission: to find the biggest overcup oak tree in the state. Overcup oaks are so named because the cap of the acorn completely surrounds the nut itself. These are among the larger species of oaks, and two in the Congaree National Park, near Columbia, S.C., each about five and a half feet in diameter, currently share the national size record.

We had an hour's walk after we reached the floodplain of Upper Three Runs Creek (UTRC), which is a magnificent place. Walking through a southern floodplain forest during a slow autumn rain is inspirational, and the clear, sandy-bottomed stream is notable for having the highest known biodiversity of aquatic stream invertebrates in the world. The rich diversity exists in part because the stream is protected from agricultural, urban, and industrial impacts as it flows through the Department of Energy's Savannah River Site (SRS) to the Savannah River.

The irony of a former nuclear production reactor site having such excellent environmental credentials perplexes some people. University of Georgia scientists at SREL provide independent oversight on how DOE activities affect SRS habitats and the overall environment and on whether DOE is being a proper environmental steward. Even a well-meaning government agency benefits from a system of checks and balances of its activities.

The high biodiversity at UTRC and throughout the SRS has been noted nationally and internationally in scientific journals, magazines, and newspapers, but one barometer of environmental value has received little attention: The SRS is home to at least three South Carolina state champion trees--Carolina cherry, winged elm, and sand pine. For a tree to qualify as a champion of its species, three size criteria are taken into account--its girth, height, and crown cover. A tree's total points are determined by adding a point for each inch of the circumference, a point for each foot of height, and a point for every four feet of crown spread. For example, the largest flowering dogwood tree reported from Alabama was 96 inches in circumference (two and a half feet in diameter), 41 feet high, with a crown spread of 46 feet, for a total of 148 points.

A list of record size trees in the country, including measurements, location, and name of the person who nominated each one, can be found in the 2006-2007 register at www.americanforests.org/resources/bigtrees. Many common trees can grow larger than most of us are aware. Live oaks and bald cypress are big trees, but imagine the record live oak in Louisiana with a diameter of almost 12 feet, a height of 55 feet, and a crown spread of 132 feet. A cypress tree in Mississippi has a trunk 17 and a half feet in diameter. Or consider the biggest pecan tree, in Texas: diameter, seven feet; height, 136 feet; spread, 132 feet.

Each state has a Big Tree list as well. To find out where the champion trees are in your state, check out the state's Web site under State Registers. After checking the Champion Tree Database for South Carolina a few years ago, I was able to track down the record-size Carolina cherry on the SRS. I am not sure where the winged elm and sand pine are, but by using the same registry, I know who nominated them and can ask the nominator where to find the trees.

When we found the big overcup oak tree last week, we measured its girth with a tape measure we had brought with us. The diameter of the tree was about five feet three inches, slightly smaller than the two state champions. But we had not come prepared to measure the height and spread, and as these are incorporated into the formula for deriving the total points, the overcup oak on the SRS could actually qualify for the state record.

The SRS currently has three official state champion trees. Perhaps after SREL personnel return to the UTRC floodplain to measure the height and crown of the overcup oak, the SRS will be able to boast of a fourth champion.

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