Madrid, 1 (Europe Press)
Industrial manufacturing, agricultural practices, and most of all, vehicles burn fossil fuels that release nitrogen into the air. As a result, levels of nitrogen in Earth’s atmosphere have tripled since 1850. Researchers at UC Riverside wanted to see if this excess nitrogen affected the soil’s ability to hold carbon and prevent it from becoming carbon dioxide, a greenhouse gas. .
“Because nitrogen is used as a fertilizer for plants, we expected that supplemental nitrogen would encourage plant growth and microbial activity, thereby increasing carbon stored in the soil,” study co-author Peter Homiak, co-author of the study, explains in a statement by an assistant professor in the Department of Environmental Sciences at the University of Michigan. California.
In dryland soils, the type of soil that covers most of southern California, that wasn’t what they noticed.
Instead, the team found that, under certain conditions, the extra nitrogen causes dryland soils to become acidic and leach calcium. Calcium binds to carbon and both elements leave the soil together. This finding is detailed in the journal Global Change Biology.
To get their results, the research team took soil samples from environmental preserves near San Diego and Irvine that had been enriched with nitrogen in long-term experiments. This allowed them to accurately know the amount of nitrogen added and explain the observed effects.
In many cases, nitrogen can affect biological processes that, in turn, affect how carbon is stored in the soil. Among these processes is the growth of plants and the slowing down of microbes that help break down dead elements in the soil.
What the researchers did not expect was a significant effect on carbon storage through abiotic or non-biological means.
The pH scale measures the acidity or alkalinity — basic — of something. In general, soils resist drastic changes in pH, releasing elements such as calcium in exchange for acidity. As nitrogen led to soil acidification at some sites in this study, the soil attempted to counteract this acidity by releasing calcium. In doing so, some of the stable carbon was lost due to being bound to the calcium.
“This is a surprising result because the main effect appears to be abiotic,” says Johan Busbock, a graduate student in environmental sciences at UCLA and first author of the study. “This means that areas of bare soil with no vegetation cover and low microbial activity, which I always thought were areas where not much is happening, also seems to be affected by nitrogen pollution.”
Dryland soils have a limited capacity to hold moisture and low levels of organic matter, and cover approximately 45% of the planet’s land surface. It is responsible for storing a large amount of carbon in the world.
Future studies could shed more light on the extent to which dryland soils are affected by nitrogen pollution in the way that the study plots were. “We need more information about how widespread these acidification effects are and how they work under non-experimental conditions of nitrogen deposition,” says Püspök.
However, since there is no quick fix to this phenomenon and no clear way to reverse the process once it has begun, the researchers recommend reducing emissions as much as possible to help soils maintain their carbon stores.
Homyak explains, “Air pollution from fossil fuel combustion affects many things, including human health by causing asthma.” “It can also affect how much carbon these rain-fed systems can store for us. For many reasons, we have to control air pollution.”
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