Researchers from the University of Illinois at Urbana-Champaign have mapped out the changes in soil carbon that take place as grasslands are grown and watered in a changing climate.
They say the findings offer a more accurate picture of the effects of climate change on the world’s grasslands.
“It is one thing to measure soil carbon,” said co-author Dr. Robert C. Sargent, an associate professor in the UIC College of Agricultural, Food, and Environmental Sciences.
“It is quite another to understand how those carbon changes relate to the changing climate and how the climate is changing the soil carbon.
It has been a challenging task.”
Sargent is a co-director of the Global Grasslands Network, a collaboration of more than 60 research institutions around the world that is looking at the impact of climate and grassland management on grassland ecosystems.
They’ve been working on the problem for more than two decades, with a view to better understanding grasslands’ carbon uptake and carbon storage.
“What we are trying to do here is to map the changes of carbon in soils that take up carbon dioxide during a climate change,” Sargion said.
Sargion is also an associate editor for Grasslands Magazine.
He said the findings provide a good way to understand the carbon that takes place as a grassland grows, whether it’s in the soil or in the water.
“The carbon in the soils can be a key indicator of the carbon stocks that can be left in the environment,” he said.
“In this case, carbon in soil is a very good indicator of carbon storage.”
Sustaining grasslands requires that the soil be stable, so if the soil is stressed, grasses will need to take up the stress, Sargions research shows.
Soil carbon is a key factor in the carbon cycle, which helps determine carbon uptake by plants and soil organisms.
Carbon is also key to the health of soil ecosystems, and the researchers used data from the Global Carbon Cycle (GC) database to study how carbon in different soils and plant adaptations change in response to climate change.
Suffering climate change in the United States and AustraliaSargions team looked at the carbon uptake of soil in both the United Kingdom and Australia over a 10-year period.
They found that the carbon in grasslands grew faster during the warmer months of the year, which meant the carbon storage that occurs during this time was larger.
“That is one of the major reasons that in Australia, grasslands have been losing their carbon stock,” Sargeant said.
In the United, the team found that grasslands tended to be more carbon-rich in the cooler months of spring and summer, which is when soil carbon levels are at their highest.
“This may explain why we found higher carbon uptake in the spring and fall in the Great Lakes, but we don’t know why,” Saghion said, “because in the dry season, carbon is much lower.”
In the tropics, Sargeions team also found that carbon uptake was more rapid during summer, as the soil was more exposed to the sun.
“We are seeing more and more grasslands in the tropic, and so the CO2 in the air is going up,” Saggion said in an interview.
“So what that means is that as carbon is coming down from the sky, it’s going up in the grasslands, so that the grasses are getting more carbon.”
In other words, in the southern hemisphere, more carbon is being stored in grassland soils as it is being released from the ground during the hottest months of summer.
But this increase in carbon in tropical grasslands is more pronounced in the northern hemisphere.
Saggions team found there was no correlation between carbon levels in the south and the carbon levels at the equator, so carbon in southern grasslands was likely to be offset by carbon stored in the poles.
The team also looked at carbon storage in soil in a variety of places in the world, including Africa, Asia, the Middle East, the North Pacific, the Mediterranean Sea, and Europe.
“The data shows that the CO 2 levels in grass land are lower in Africa and Asia,” Sagion said by email.
“And in Asia, there is a higher CO 2 storage in grasses, which may be explained by the presence of tropical grassland plants.”
In contrast, in temperate grasslands like the United Arab Emirates, the data shows more carbon storage and more carbon being released during the cooler summer months.
“When we looked at these data, we saw that it was the opposite in temperates,” Sager said.
But he added that there are differences in the climate between the Middle and Northern parts of the globe.
In South America, Sagions team focused on the carbon stores of grasslands that were being grown in the Amazon and the Amazon