Corvallis, Ore.-A study has found that nitrogen from agriculture and other sources in small amounts actually helps forests by increasing the growth of trees and boosting the amount of carbon dioxide they absorb and store. But there’s a limit, according to Beverly Law, a professor of forest science at Oregon State University and one of the researchers, who warned that too much nitrogen can lead to other nutrient and acidity problems. “People expect that if a little is good, a lot is better – but that’s not the case,” remarked Law. “We’re trying to figure out how much carbon these forests are taking up now to offset greenhouse gases and how much they will take up in the future.” Law stressed that the level of nitrogen that can be beneficial amounts to about 10 percent, or 10 kg per hectare. The researchers measured how much carbon was being absorbed and sequestered, or taken out of the atmosphere and locked up, in the growing plants in forests in North America and Europe. They also monitored how much nitrogen was being deposited in those forests by automobile engines, factories, and intensive agriculture. One of ways nitrogen benefits is as a plant fertilizer, and it appears to have this effect in forests in this study. Higher nitrogen deposition rates were found to cause loss of other nutrients like calcium on the West Coast and increase acid content in soils in the eastern U.S. The study findings have been published in the journal Nature.
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