National Science Foundation proved after a long study that nitrogen added to soil can make forests absorb more dioxide carbon. But even if nitrogen is one of the most abundant element in the atmosphere, it’s still a pollutant and can have a dramatic influence on the planet’s environment.
Scientists expect the level of nitrogen deposition to increase this century to two or tree times above current levels. The element is released from various sources like farm fertilizer, car exhaust, factory and power plant emission.
Kurt Pregitzer from the University of Nevada, Reno and other scientists have made their research on four experimental forests in northern Michigan. The discovery was quite astonishing as the forests grew very fast, storing and absorbing a lot of CO2. But the interesting facts showed on the forests floor. The decomposition of branches and leaves slowed down because microbes were unable anymore to decompose lignin.
Those microbes are “the gatekeepers of carbon transformation. What we didn’t anticipate was that storage of carbon in soil is directly altered by the addition of nitrogen. The really novel part, I think, is that the microbial community is actually altered.” said Pregitzer.
Because of the slow down of the microbe activity, more dead plant matter stays in the soil. This litter can entrap as much CO2 as can the trees, increasing the level of CO2 that the whole forest could absorb normally. Scientists are not yet able to understand why the decomposition slows down and how exactly the forests entrap carbon dioxide.
Nitrogen should not be seen as a climate savior, Pregitzer cautioned, because the effects can easily be seen: biodiversity loss, smog, acidification of forests, streams and lakes.
The experimental forests have all passed saturation, the point at which they can no longer absorb nitrogen, the element being released into groundwater. Future forests will be as well saturated leaching nitrogen into aquatic ecosystems. Leaching might not be a bad thing as the nitrogen excess could be taken by nearby plants. But people who drink the water with too much nitrogen could face blue baby syndrome, a potentially fatal blood disease that affects kids. Once in water, nitrogen goes to lakes and oceans, increasing the growth of phytoplankton, robbing water of oxygen and suffocating the aquatic creatures.
And like this wouldn’t be enough, saturating forests with nitrogen will lead to more nitrous oxide emission, a potent greenhouse gas. Nitrous oxide emissions in other areas, scientists say, could even offset the climate benefit of northern forests as carbon sinks.
Question everybody has in their mind is: “can nitrogen be considered good as it accelerates plant growth and slows decomposition or is it bad as it accelerates climate change through those emissions.”
[via sciam.com]
