Elevated Nitrogen Slows Carbon Decay in Forest Soils

New clues emerge about microbial decomposition mechanisms.

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Increased nitrogen in forest soils decreases the diversity and expression of genes involved in carbon deconstruction by bacteria and fungi, including this species in the order Auriculariales.

The Science

Global production of agricultural fertilizers has vastly increased the amount of nitrogen compounds entering natural terrestrial ecosystems. Although increased nitrogen availability clearly boosts primary productivity (i.e., growth of plants) in ecosystems, the impacts of this nitrogen influx on the decomposition of dead plant material by soil microbes remain poorly understood.

The Impact

Findings from a forest soil study shed new light on poorly understood processes occurring in these soils and improve the ability to predict ecosystem responses to changing environmental variables.


A collaborative team of Department of Energy (DOE) researchers at the Universities of Michigan and Oklahoma examined carbon decomposition by soil fungi and bacteria at experimental forest sites in Michigan. GeoChip 4.0, a DNA microarray containing probes for thousands of functional genes, was used to measure expression of genes involved in degradation of complex carbon compounds in soil samples from sites exposed to elevated nitrogen input for the past 18 years. Compared to nearby control plots, sites with elevated nitrogen showed significant decreases in the diversity and overall expression levels of fungal and actinobacterial genes involved in deconstruction of cellulose, lignin, and other plant compounds. This finding correlates with a long-term observation of decreased carbon decomposition rates in soils at the nitrogen-elevated sites and points toward the specific mechanism underlying this shift.


Sarah D. Eisenlord
School of Natural Resources and Environment, University of Michigan
Ann Arbor, Michigan


This research was supported by the National Science Foundation’s Long-Term Research in Environmental Biology program and DOE’s Office of Science Biological and Environmental Research program


Eisenlord, S.D., et al. “Microbial mechanisms mediating increased soil C storage under elevated atmospheric N deposition.” Appl. Environ. Microbiol. 79, 1191–1199 (2013). [DOI: 10.1128/AEM.03156-12].

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Last modified: 1/3/2016 12:03:40 PM