Arctic permafrost typically functions as a vast freezer that preserves decaying plant matter for thousands of years, but rapidly warming climate is thawing permafrost and accelerating decomposition. Increased plant growth is needed to capture carbon that is released from decomposing organic matter, but plant growth depends on whether plants can extract critical nutrients from the soil. Supported by a $100,000 from the National Science Foundation, two of СƬƵ’s early career researchers are exploring nutrient dynamics in arctic and boreal ecosystems. Assistant Professors Elizabeth Herndon, Ph.D. (Geology) and Lauren Kinsman- Costello, Ph.D. (Biological Sciences) spent a week in Alaska in summer 2016 to study how soil properties influence whether plants and microorganisms can access the nutrient phosphate. This interdisciplinary, collaborative research effort has potential implications for understanding how highlatitude peatlands will respond to climate change.
“It’s this very cold, wet environment, but temperatures at high-latitudes are actually increasing at twice the rate they’re rising anywhere else on the planet,” Herndon said. “It’s thawing the permafrost, and driving shifts in vegetation and in hydrology. A lot of people are interested in how these environments will respond to the warming climate, because they currently store a lot of carbon that has the potential to be released into the atmosphere and accelerate climate change.”
The team, which also included one graduate and one undergraduate student, spent a week at the Alaska Peatland Experiment (APEX) Site just outside Fairbanks, AK, where a team of scientists have been using an adjusted water table in a wetland to monitor carbon dioxide and methane release. The scientists flooded one section of the wetland, while draining another. This experimental treatment provided an ideal setup for Herndon and Kinsman-Costello to study how soil moisture influences interactions between iron and phosphorus. Herndon brings her iron expertise while Kinsman-Costello is versed in phosphorus dynamics.
“We’re combining our knowledge bases to understand the interactions between the two,” Herndon said. “We want to know how soil moisture and iron cycling change the bioavailability of plant nutrients, specifically phosphate.”
Herndon said rising temperatures are drying out existing wetlands, causing iron that’s dissolved in the soil water to essentially rust out as iron oxide minerals in the soil. Phosphate binds to iron oxides, meaning that increased iron deposits could sequester phosphate, reducing the amount available to plants.
“Those plants are a sink for carbon dioxide,” she said, “so any nutrient limitation could also limit their ability to remove carbon dioxide from the air.”
Soils in high-latitude regions like Alaska contain high amounts of carbon because the vegetation decomposes slowly due to cold temperatures, leaving large amounts of peat.
“As the temperatures rise, that peat is going to start decomposing more quickly,” Herndon said. “If plant growth is limited, then plants can’t sequester the excess carbon dioxide released from peat decomposition.”
In addition to APEX, Herndon and Kinsman-Costello are investigating iron and phosphorus interactions in tundra and boreal soils from all across North America. Their research will provide better understanding of how these ecosystems will adapt to changing climate.