On a recent spring afternoon, John Parker stood in his lab: a giant parcel of land covered with trees of varying heights. Some of the plants came up to his knees and resembled shrubs; others were tall enough to climb. A hawk flew overhead, unaware of the important research taking place below.

“This is a big experimental forest,” said Parker, who was dressed more like a hiker than the senior scientist he is. “We have 20,000 trees.”

Parker is one of about 100 researchers who conduct experiments at the Smithsonian Environmental Research Center (SERC) in Edgewater, Maryland, on the Chesapeake Bay. For more than 55 years, the center has attracted scientists interested in learning about the environment generally and forests, estuaries, wetlands and agriculture specifically. SERC has several indoor labs, but a lot of the work takes place outside on its 2,650-acre property, a size equal to more than 2,000 football fields.

“We are really trying to couple the land and the sea,” said Pat Megonigal, associate director of research. “We like to see the whole ecosystem.”

During the drive to Parker’s study site, Megonigal stopped in a dense forest and pointed out an identification tag dangling from a trunk like a silver earring. The tulip poplar is part of a global study about tree growth. Poking above the treetops, a 203-foot-tall metal structure called the NEON (National Ecological Observatory Network) tower was measuring the amount of carbon dioxide the trees were inhaling during the day and exhaling at night.

“The whole point is to understand the birth, life and death of trees,” Megonigal said.

Parker’s project, BiodiversiTREE, involves planting one, four or 12 species in different plots to see whether the trees grow better in mixed company or alone.

Some results from the experiment, which is designed to last 100 years, are already in: The sycamore trees grouped with their own kind are sprouting up faster than the ones sharing space with other species. Those sycamores are expanding horizontally, creating a canopy over the stubbier plants.

“You get different strategies depending on your neighbors,” said Parker, who braves ticks, sharp branches and poison ivy when out in the field.

At the Global Change Research Wetland, on the Rhode River, the scientists are exposing the salt marsh plants to threats, such as invasive species (plants or animals not native to the area) and hotter conditions.

In one section of the wetlands, heaters warmed the grasses by 3, 6 and 9 degrees above the air temperature. “A little bit of warming helps a lot,” Megonigal said. “A lot of warming helps less.”

The researchers move through the wetlands on narrow fiberglass boardwalks. They wear rubber boots because their feet are sometimes submerged in water.

Megonigal followed a long walkway lined with reeds to an experiment that involved placing plants on a ladder in a tidal creek so they will flood with water. The goal is to see how they would respond to a rise in sea level. Nearby an alligator head floated on the water’s surface. The fake reptile isn’t part of a study, but it’s evidence that the Smithsonian researchers have a sense of humor.

This story is part of a series about lesser-known aspects of the Smithsonian Institution, which celebrates its 175th anniversary in 2021.

If you go

What: Explore the trails of the Smithsonian Environmental Research Center.

Where: 647 Contees Wharf Road, Edgewater, Maryland.

When: Mondays through Saturdays, 8:30 a.m. to 4:30 p.m. Closed federal holidays.

For information: Visit the website serc.si.edu for directions, trail map and pre-visit health self-check questions.