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Boreal Forest Plants Take Up Organic Nitrogen
Nasholm, T., Ekblad, A., Nordin, A., Giesler, R., Hogberg, M. and Hogberg, P.  1998.  Boreal forest plants take up organic nitrogen.  Nature 392: 914-916.

What was done
The authors injected radiolabelled glycine (organic nitrogen source) and ammonium (inorganic nitrogen source) into the soil of a boreal forest ecosystem located in northern Sweden to test whether uptake of organic nitrogen occurs in the field.  Sequential sampling of plants (Pinus sylvestris - pine tree, Picea abies - spruce tree, Vaccinium myrtillus - dwarf shrub, and Deschampsia flexuosa - grass) and soil was done six hours, one day and seven days after nitrogen source applications to determine the fate of the added nitrogen.

What was learned
The authors found that plants absorbed a significant amount of the organic nitrogen as intact glycine.  They conservatively estimated that the trees, grass and dwarf shrub took up 42%, 64% and 91% of the organic nitrogen, respectively, regardless of the types of root-fungi associations they possessed.

What it means
According to these data, plants in boreal forests do not have to wait for the mineralization of soil organic nitrogen to occur before they can acquire this essential element.  Instead, they can compete for and obtain it directly.  This phenomenon could have far reaching implications for plant nutrition in boreal forests, as the aerial fertilization effect resulting from increasing levels of atmospheric CO2 has been shown to be capable of enhancing biomass production in these ecosystems.  With increased biomass both above and below ground, greater amounts of organic material should accumulate at the forest floor; and some of the organic nitrogen in this litter should be directly accessible to plants in boreal forest ecosystems.  Consequently, with more nitrogen more readily available to them, boreal forest plants will likely be able to maintain the increased rates of photosynthesis and carbon sequestration that they typically exhibit in short-term atmospheric CO2 enrichment studies.

Reviewed 15 April 1999