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This article in JEQ

  1. Vol. 38 No. 6, p. 2267-2272
     
    Received: Aug 25, 2008
    Published: Nov, 2009


    * Corresponding author(s): crowley@ucr.edu
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doi:10.2134/jeq2008.0387

Nitrogen Deposition Effects on Carbon Storage and Fungal:Bacterial Ratios in Coastal Sage Scrub Soils of Southern California

  1. Kun Liu and
  2. David Crowley *
  1. Dep. of Environmental Sciences, Univ. of California, Riverside, CA 92521

Abstract

The effects of nitrogen (N) across a deposition gradient on bacterial and fungal degradation pathways were studied in southern California coastal sage scrub soils to determine whether elevated N levels alter microbial community structure and organic matter accumulation. Three sites across an N deposition gradient having low, intermediate, and high levels of atmospheric N deposition were studied for 20 mo. Fungi:bacteria (F:B) biomass ratios were determined by phospholipid fatty acid analysis. Plots at each location included control plots receiving ambient N deposition and treatment plots that were fertilized with an additional 50 kg N ha−1 yr−1 of slow-release urea. Results showed that organic carbon (C) levels varied seasonally but that F:B ratios were relatively stable and similar across the three locations and over time. Total organic C decreased in response to N additions only at the low N deposition site. The results suggest that organic matter degradation pathways leading to C storage in soils that have been exposed to high levels of atmospheric N deposition are not responsive to additional increases in N and that N effects on organic C in semiarid soils may be significant only in areas with prior low exposure to N pollution.

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Copyright © 2009. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America