A recent study by researchers from the University of Helsinki together with Dr Katerina Machacova, a visiting scholar, researched the relationship between trees in the Northern Hemisphere's boreal forest, which consists of pine, spruce and birch, and the release or consumption of the greenhouse gas nitrous oxide. As a surprise to the scientists, they found that the trees can release nitrous oxide into the atmosphere through their stems and canopies, although evidence points to the original source as being microbes in the soil that are transported by the transpiration stream of trees from roots to stems. And since soil has been shown to release large quantities of nitrous oxide, the study found that the release of the greenhouse gas by trees was only a fraction of the total.

 

But good news also came from the study, which the researchers termed "the most important discovery:" that the release of nitrous oxide by pine, spruce and birch varies with the seasons and that in the winter, the trees can become consumers of the gas thereby reducing their annual release totals.

Overall, as reported in Science Daily, "the forest is efficient in recycling by breaking up organic matter found in the soil and releasing nitrogen in a form (needle and leaf litter) useable by plants, which trees then use for growing."
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