A Minnesota bog could shape climate change predictions
GRAND RAPIDS — Welcome to a warmer future.
The greeting is centered above the entrance to Plot 17. One of 10 greenhouse glass-encased pods in the Marcell Experimental Forest, Plot 17 is part of a 10-year, $50 million federal project involving 100 scientists and technicians from throughout the U.S. and Canada.
What happens in this bog 30 minutes north of Grand Rapids will inform climate change models around the world.
Bogs, those cold repositories of decaying plant material, make up only about 3 percent of the Earth’s land mass. But they hold about one-third of the planet’s carbon, accumulated over 10,000 years since the glaciers' last retreat.
Current projections don’t consider how bog ecosystems might respond — or contribute — to climate change.
Scientists want to know the tipping point at which that stored carbon would be released, whether it would be released as carbon dioxide or methane (the latter has 30 times the warming potential), and how it might change the ecosystem.
The largest experiment
Line 2 of the black-and-white government label affixed to Plot 17 reads: +9.0 C, Ambient CO2.
Over the next decade, SPRUCE — the Spruce and Peatland Responses Under Climate and Environmental Change Experiment — will study the effect of warming with and without increased carbon dioxide levels, from the black spruce to the microbes underground.
“It’s the largest climate manipulation experiment ever attempted,” said Stephen Sebestyen, research hydrologist with the U.S. Department of Agriculture Forest Service in Grand Rapids.
The project is funded by the Department of Energy’s Biological and Environmental Research Program and run by the DOE’s Oak Ridge National Laboratory and the Forest Service with collaborating universities. Part of Oak Ridge’s mission is understanding the carbon cycle — including whether energy production causes changes to the climate.
Construction of the $10.5 million infrastructure started in 2009.
The experiment began in August when researchers turned the heat on. The heat bill will be the largest of the annual expenses, estimated at $5 million.
Two pods are kept at each of five incremental temperatures, from ambient to 9 degrees Celsius (16 degrees Fahrenheit). In June, carbon dioxide levels will be increased by as much as 900 parts per million — the high end of 100-year predictions — in half of the pods.
Inside Plot 17, eight fans blow warm air into the open-topped octagonal chamber rimmed by inward-slanting, heat-retaining panels.
This is the first time the earth itself has been warmed as part of a climate change experiment. About 3 meters underground, a system works like the coils of a radiator to heat the peat. Researchers flipped that switch in June 2014.
“The primary goal here is to look at the fate of the stored carbon in the system, which is mostly a below-ground phenomenon. What happens to that peat if you warm it up? In addition, look at what happens to the plants, and microbial diversity and function underground,” said Paul J. Hanson of Oak Ridge, SPRUCE lead and coordinating investigator.
Packing in the research
Each identical experimental space, 12 meters in diameter, looks a bit like a green pincushion.
“Every inch of that footprint is pretty much occupied and spoken for,” said Randy Kolka, supervisor of the Marcell Experimental Forest’s Northern Research Station.
Colonies of capped tubes stick out of the ground. One contains a robotic camera that captures a weekly, 1-meter-deep, 360-degree view of root growth and organisms, sending about 40,000 images to Oak Ridge National Laboratory in Tennessee. A Grand Rapids area naturalist checks other clear tubes for the same thing by hand. Data are meant to show carbon delivery via root growth and death.
The trees are heavily tagged. Every 30 minutes, dendrometers record black spruce trunks’ diameter, a measure of transpiration. Farther up the trunk, lichen hangs suspended from a clear line, part of an Oregon State University study.
On the surface, sphagnum moss and leatherleaf surround tagged lengths of trunk about 5 inches long and 3 inches in diameter. With buried mesh bags full of organic matter, they’re part of a decomposition study.
Soil and water tests center on nitrogen, phosphorous, carbon, mercury and sulfur cycles.
Demand for soil cores is so great that the sampling has been restricted to two cores a year divided 30 ways.
A tower in the center of the 8-meter-tall enclosure holds monitors that record temperature, wind direction and speed, relative humidity, carbon dioxide and solar radiation.
Within a ring about the size of a fire pit grow small shrubs, grasses and mosses — plants of the bog, intact. To record gas emissions minus the effect of trees, researchers cap it with a dome for a couple of minutes and then measure the concentration of carbon dioxide, methane and water vapor.
“The scales of these things in the past have been more the size of that ring, because it takes money, time and planning to to it — and big teams of people to do it,” Sebestyen said during a late-October tour of the 20-acre site.
“This is big science. We’re hoping for big outcomes.”
The 1,000-year view
SPRUCE will help predict the effect of climate change 100, 500 or 1,000 years from now.
Those predictions might include which plants survive, which do not.
“Have you changed the balance so that if primary production — if plant growth — was ever so slightly outweighing decomposition in the past, is that shifting so that you may be getting an equaling out or is decomposition actually outweighing production?” Sebestyen said.
Whether droughts are longer, floods more frequent — that sort of information could inform foresters, farmers and insurance companies. Knowing what species are most likely to survive could inform fisheries and wildlife managers.
The Forest Service’s role is to present the information. How it’s used will be up to individuals and governments. Sebestyen makes that point carefully and repeatedly.
“We don’t expect that 11 meters of peat to be gone in, say 100 years or 500 years or 1,000 years. It’s how much of it is gone. How much of it goes into the atmosphere,” Sebestyen said. “But there are also other mechanisms.”
Carbon can be released up, down or sideways. For example, the bodies of plant-eating critters that sink to the bottom of the bog add more carbon. Peat bogs could release dissolved organic matter, a form of carbon, into lakes or oceans.
“The bottom line of SPRUCE is what really matters. If we measure the growth rate of the moss or the tree, one of them’s going to be a bigger part of the ecosystem. One of them is going to have a growth rate that allows it to stabilize more carbon. So we want to know: Are they both important? Is one vastly more important? The methanogen, the genesis of methane? Or the methanotroph, the eater of methane?” Sebestyen said.
Knowing how an ecosystem might function will help manage that ecosystem.
“We’re not going to solve everything here, Sebestyen said, speaking above the constant hum of the fans. “We can’t do everything. But we’re taking bits and pieces here and there and trying to come up with solid information that can feed back into basic knowledge and ecosystem models.”
Follow Ann Wessel on Twitter @AnnWessel.