The 100-Year Experiment

BiodiversiTree project turns farmland into forest

John Parker inspects one of 18,000 seedlings with intern Emily DuBois.

An Irish-Canadian farmer once told his son that the true meaning of life was to plant trees whose shade he did not expect to sit under. It’s a proverb many altruists and humanitarians have taken to heart, though ecologists like John Parker tend to take it more literally.

In March 2013, SERC ecologist John Parker began planting an entire forest. That forest will be the longest-running field experiment in SERC’s history—an experiment he most likely will not live to see completed.

The full experiment will take two years to plant, even with more than 80 volunteers shouldering the load. Whitney Hoot, the project coordinator, shows volunteers how it’s done. Holes need to be completely filled with soil so infant trees don’t drown in a well of rainwater. Occasionally they trim what Hoot calls “suicidal” trees, whose roots curve upward into a J. “It will grow along the surface instead of growing down, and it just can’t get enough water,” she says. “And so rather than killing the tree immediately, it will take a couple of years.”

Then, once they’re in the ground, there’s the matter of watering all 18,000 seedlings. “In a perfect world, it would rain every day for forty-five minutes and get sunny again, but that ain’t gonna happen,” Parker says. But the labor pains of birthing the forest will pass. When they do, Parker and the ecologists after him will have something priceless: the chance to watch it evolve over a century or longer.

Project BiodiversiTree

The name BiodiversiTree comes from the key question Parker wants to answer: Is a diverse forest a better forest? Are trees more likely to survive surrounded by other species? Will it shelter more animals? And will it do more for people, filtering out our pollutants and absorbing our carbon?

There’s reason to think it will. Different tree species have different root systems. Grouping them together minimizes competition for water and nutrients—and increases the odds of them stopping harmful chemicals before they reach Chesapeake Bay. Tasty plants stand a greater chance of survival if they hide among less palatable ones. And a forest with more plants that survive, period, will do a much better job soaking up CO2.

The project is one of just a handful in the world like it, and the largest in North America. The Smithsonian has two experimental forests in Panama. By comparing them, ecologists can find out if diversity matters as much in the temperate zone as it does in the tropics, where researchers have roughly 400 tree species to work with. Perhaps it matters more.

“If you have four hundred species, you’ve got a lot of species that might be functioning relatively similarly, and so one can take up the slack if you lose another to disease or pests,” Parker says. “Here, you’ve only got thirty, thirty-five species. But if you look at the distribution of species, it’s dominated by just three or four.” If one species falls by the wayside—like the tulip poplar—it could drastically alter the ecosystem.

Susan Cook-Patton checks a sycamore seedling Whitney Hoot plants the final tree, an ironwood

To test that, the team needs to design the forest carefully. They have divided the farmland into 35-by-35-meter plots. Each plot holds 255 trees, and they have 16 species to choose from. Each day Susan Cook-Patton, Parker’s postdoc, puts out colored flags denoting which trees go where. Some contain only oak, or beech, or elm. Others contain mixtures of four or 12 species. By the time it’s finished, a mosaic of 120 forest plots will cover the landscape.

Parker has done similar projects on a smaller scale, with 1 meter-squared plots. His findings back up the pros of diversity. Survival rates for saplings in mixed communities were only slightly higher than in segregated ones (3 percent), but those that lived grew 17 percent larger in a mix. A grasslands project at the University of Minnesota found the same thing: Plants grow better in mixed company than by themselves.

Forests Past and Future

When complete, the saplings will cover 70 acres of former cropland. There will be trees with special goo on their roots to help them absorb water. There will be trees with cages to protect them from deer. Some trees will get a “bloodmeal” spray of pig blood, to see if the scent of a kill does a better job scaring deer off. All the while ecologists will track how the 120 mini-forests handle climate change, water pollution and animal communities.

Scientists aren’t the only ones with a stake in the forest. In Anne Arundel County, developers who cut trees in critical areas—land within 1,000 feet of shoreline—have to plant new trees inside the critical area or face a hefty fine. Or, they can buy forest mitigation credits. Since BiodiversiTree falls within critical area, it has those credits to sell. It also can sell forest interior dwelling species (FIDS) credits for animals.

But that is only the first half of the project. Nearby, another 70 acres of forest remains untouched. As Parker and his successors watch the new forest grow, they will face another question: What legacy does three decades of farming leave in its wake? Other ecologists like Tom Jordan will observe the nearby stream, to see if the new forest does a better job protecting Chesapeake Bay from pollution than the previous landscape.

“It’s very stressful. I’ve never had a project this big,” Parker says. Still, most academics leave their legacies in scientific journals. Parker relishes the thought of leaving something more. “When do you ever get a chance to start an experiment that could easily run itself for the next hundred years?”

After they finish planting, Parker hopes to leave one more thing. There’s a small open space in front of a barn overlooking the watershed, too small for an entire plot. He plans to use it as a demonstration area for visitors. Inside will be two concentric rings of 8 trees, one for each species in the experiment. “I’m going to call it Treehenge.”

To volunteer with BiodiversiTree, contact SERC Citizen Science Coordinator Alison Cawood.