Studying How Warming Affects Ecosystem Carbon Uptake

May 8, 2019

Curiosity about carbon and nitrogen cycles in plants and microbes took a Texas Tech assistant professor of biology to the bottom of the world to gather data. Natasja van Gestel spent four months in Antarctica to try to understand how warming affects ecosystem carbon uptake.

She wanted to know if carbon uptake will lessen with warming, or perhaps increase with warming.

“Plants and microbes are key to these cycles, they make the cycle go. So, microbes decompose carbon and liberate nitrogen. Some microbes can actually photosynthesize just like plants do. It’s really nice,” she says. “There’s a lot of interactions between plants and some microbes and my interest is primarily in how does environmental change affect how they process these elements. It’s really important because one of my main worries is rising carbon dioxide in the air.”

  Over the course of their stay at Palmer Station, a research outpost operated by the U.S. Antarctic Program and funded by the National Science Foundation, van Gestel and graduate assistant Kelly McMillen collected almost 400 data files regarding fluxes of CO2. 

Van Gestel says getting data from both plants and soil microbes was essential to understanding how warming is going to affect each of them.

“If you have more warming, you know that plants are really good at photosynthesis. You take some of the CO2 from the atmosphere and some of that gets transferred to the soil, which we want, but then there’s the microbes that are important also, they generate nutrients but they also in the process release carbon dioxide. So the flux of carbon is the opposite from the microbial perspective. Some of the energy that they are releasing, some of it build biomass, but some of it is going back into the atmosphere. So, you have this cycle that’s occurring, so there’s some carbon going from the atmosphere to the soil, and then from the soil back into the atmosphere. There’s these two opposing fluxes.”

  The two women set up 40 plots, 10 each at four sites within a gradient of plant productivity. Half of the plots at each site were for control purposes and half were warmed using a cone-shaped plastic fiber sheet which surrounded the plot.  

  Carbon fluxes are sensitive to warming: photosynthesis and respiration rates increase in response to warming. What they don’t yet know is how the net carbon flux – the difference in photosynthesis and respiration – will change in response to warming.

“We have this warming chamber right next to the control plots and we look to see what are the changes and what are the differences between fluxes in the warm plots relative to the control plots,” she explains.

  Van Gestel went to Antarctica for her research because there are fewer confounding variables.

“If you were to do a similar experiment elsewhere, there’s just so many species…it’s far less complex in Antarctica. So if you want to see how microbes are responding it’s good that we don’t have all of those insects in the soil maybe messing up the results, or we don’t have a high species diversity and then also the abundance of microbes is low and so is the diversity, which makes it a little simpler to study. Antarctica, I’m using that as a model system,” Van Gestel says.

Van Gestel’s research was funded by a $300,000 grant from the National Science Foundation. She says her results provide details about what was happening to the ecosystem while she and McMillen were there and help inform climate models about warming effects on carbon fluxes.

“What if next year is going to be a drier year, or it’s going to be warmer, we don’t know. And how is this going to affect the results. That’s why I would like to go back because there is so many hypotheses that I would like to test,” she says.

Van Gestel, who is a quantitative ecologist, says she and McMillen hope to have data from their research fully analyzed by the end of summer.