Dr. Michael Weintraub is spending his summer in one of the colder places in the world.Weintraub, a University of Toledo assistant professor of environmental sciences, is leading a research team studying soil in the Arctic tundra to gain clues to how climate change will affect the area.
For thousands of years, Arctic plants have been growing faster than they can decompose in the cold tundra soil and there is a risk that as climate change occurs, the warming will significantly accelerate decomposition. If that were to happen, a large amount of carbon dioxide would be released into the air, exacerbating the problem because there is roughly twice as much carbon in soil as in the atmosphere, Weintraub said.
“But it’s too simple a viewpoint that warmer weather will mean more decomposition,” Weintraub said. “We have to think of the seasonality plant growth and soil nutrient availability as well.”
That’s what Weintraub’s team is doing. He is the lead investigator for “The Changing Seasonality of Tundra Plant-Soil Interactions” project in northern Alaska funded with a $1.6 million grant from the National Science Foundation.
Weintraub is leading a team of 11 people from six different universities who are gathering data on how the timing of plant growth impacts soil nitrogen availability in the tundra, how this timing would be impacted by a warmer climate, and what the implications might be.
Out of their 10 100-square-meter, square research plots in the Alaskan tundra, five briefly had a black cloth placed over the snow in early May to absorb heat and melt the snow about a week earlier than it would otherwise, and the other half had no manipulation. In areas of all 10 plots, there are clear, open-top chambers that act like mini greenhouses to warm the soil.
In these plots, the team installed sensors to constantly monitor plant growth by measuring greenness and is using a specialized camera lowered into clear tubes in the ground to collect data on root growth.
The team also uses microlysimeters — small porous tubes installed in the ground — to collect soil water and measure its nitrogen content, which is a less invasive way than taking soil samples.
“If we push around the timing of plant growth, do we see plant nutrient uptake from the soil move around in the same way?” Weintraub asked. “Knowing that will help us develop a better understanding of plant-soil interactions, and we can better develop forecasts to predict what will happen in the future.”
Specifically, the team is measuring nitrogen availability in the soil. There is limited availability of this nutrient because most of it is tied up in plants that do not decompose, leaving it inaccessible.
During the growing season, the nitrogen is sucked out of the soil by plant roots, with a pronounced crash in nitrogen availability when roots start to grow, which could occur sooner and prolong the nitrogen-limited time if there is an earlier snowmelt and higher temperatures. The lack of nitrogen could prevent decomposition by inhibiting decomposer microbes in the soil despite the warmer climate, Weintraub said, creating a seasonal interaction between the timing of plant growth and decomposition.
Dr. Anthony Darrouzet-Nardi, a postdoctoral research associate at UT, is part of the team helping to coordinate the fieldwork. He said he is fascinated by soil nutrients and how they interact with microbes and plant roots, which is really only partially understood.
“I hope that this research improves our understanding of soil nutrient cycling in Arctic ecosystems and provides some useful ideas for the ongoing efforts to predict the effects of global change,” he said.
Weintraub, Darrouzet-Nardi and the rest of the team are spending most of this summer and the next in the Arctic, gathering data and analyzing soil nitrogen during the growing seasons. Next year they will accelerate snowmelt in the same plots again. In the final year of the three-year, grant-funded project, they will test their theories along a latitudinal transect to see if the process is similar throughout Arctic ecosystems.
“This is a great opportunity to work on research that people are paying attention to as they try to understand how warming is impacting the Arctic,” Weintraub said. “We are studying change as it happens and hopefully gaining a better understanding to predict future changes.”