SoilBiologyBiochemistry.PDF

Soil Biology Biochemistry 99 (2016) 54e65 Contents lists available at ScienceDirect Soil Biology Biochemistry journal homepage: /locate/soilbio Mechanisms driving the soil organic matter decomposition response to nitrogen enrichment in grassland soils * Charlotte E. Riggs , Sarah E. Hobbie Department of Ecology, Evolution, and Behavior, University of Minnesota, Saint Paul, MN 55108, USA a r t i c l e i n f o a b s t r a c t Article history: Empirical studies show that nitrogen (N) addition often reduces microbial decomposition of soil organic Received 18 September 2015 matter (SOM) and carbon dioxide (CO2) production via microbial respiration. Although predictions from Received in revised form theoretical models support these findings, the mechanisms that drive this response remain unclear. To 19 April 2016 address this uncertainty, we sampled soils of three grassland sites in the U.S. Central Great Plains that Accepted 30 April 2016 each have received seven years of continuous experimental nutrient addition in the field. Nitrogen Available online 8 May 2016 addition significantly decreased the decomposition rate of slowly cycling SOM and the cumulative carbon (C) respired per mass soil C. We evaluated whether this effect of N addition on microbial respiration Keywords: Carbon resulted from: 1) increased microbial carbon