Forest canopies help determine natural fertilization rates
In this week’s issue of Science, a team of researchers from the United States and Sweden report on a newly identified factor that controls the natural input of new nitrogen into boreal forest ecosystems. Nitrogen is the primary nutrient that dictates productivity (and thus carbon consumption) in boreal forests. In pristine boreal ecosystems, most new nitrogen enters the forest through cyanobacteria living on the shoots of feather mosses, which grows in dense cushions on the forest floor. These bacteria convert nitrogen from the atmosphere to a form that can be used by other living organisms, a process referred to as “nitrogen-fixation.” The researchers showed that this natural fertilization process appears to be partially controlled by trees and shrubs that sit above the feather mosses.