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This article in SSSAJ

  1. Vol. 75 No. 1, p. 56-68
     
    Received: Mar 12, 2010
    Published: Jan, 2011


    * Corresponding author(s): mlhaddix@nrel.colostate.edu
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doi:10.2136/sssaj2010.0118

The Role of Soil Characteristics on Temperature Sensitivity of Soil Organic Matter

  1. Michelle L. Haddix *a,
  2. Alain F. Planteb,
  3. Richard T. Conanta,
  4. Johan Sixc,
  5. J. Megan Steinwegd,
  6. Kim Magrini-Baire,
  7. Rhae A. Drijberf,
  8. Sherri J. Morrisg and
  9. Eldor A. Paulh
  1. a Natural Resource Ecology Laboratory, 200 West Lake Street, Colorado State University, Fort Collins, CO 80523-1499
    b Dep. of Earth & Environmental Science, 240 South 33rd Street, University of Pennsylvania, Philadelphia, PA 19104-6316
    c Dep. of Plant Sciences, University of California, One Shields Avenue, Davis, CA 95616
    d Natural Resource Ecology Laboratory, Graduate Degree Program in Ecology, 200 West Lake Street, Colorado State University, Fort Collins, CO 80523-1499
    e National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401
    f Dep. of Agronomy and Horticulture, 377P Plant Science, University of Nebraska, Lincoln, NE 68583-0915
    g Biology Department, Bradley University, 1501 W. Bradley Ave., Peoria, IL 61625
    h Natural Resource Ecology Laboratory, Dep. of Soil and Crop Sciences, 200 West Lake Street, Colorado State University, Fort Collins, CO 80523-1499

Abstract

The uncertainty associated with how projected climate change will affect global C cycling could have a large impact on predictions of soil C stocks. The purpose of our study was to determine how various soil decomposition and chemistry characteristics relate to soil organic matter (SOM) temperature sensitivity. We accomplished this objective using long-term soil incubations at three temperatures (15, 25, and 35°C) and pyrolysis molecular beam mass spectrometry (py-MBMS) on 12 soils from 6 sites along a mean annual temperature (MAT) gradient (2–25.6°C). The Q10 values calculated from the CO2 respired during a long-term incubation using the Q10-q method showed decomposition of the more resistant fraction to be more temperature sensitive with a Q10-q of 1.95 ± 0.08 for the labile fraction and a Q10-q of 3.33 ± 0.04 for the more resistant fraction. We compared the fit of soil respiration data using a two-pool model (active and slow) with first-order kinetics with a three-pool model and found that the two and three-pool models statistically fit the data equally well. The three-pool model changed the size and rate constant for the more resistant pool. The size of the active pool in these soils, calculated using the two-pool model, increased with incubation temperature and ranged from 0.1 to 14.0% of initial soil organic C. Sites with an intermediate MAT and lowest C/N ratio had the largest active pool. Pyrolysis molecular beam mass spectrometry showed declines in carbohydrates with conversion from grassland to wheat cultivation and a greater amount of protected carbohydrates in allophanic soils which may have lead to differences found between the total amount of CO2 respired, the size of the active pool, and the Q10-q values of the soils.

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Copyright © 2011. Soil Science SocietySoil Science Society of America

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