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Harvard Forest Symposium Abstract 2011

  • Title: Altered soil respiration in response to two decades of chronic N additions
  • Primary Author: Scott Ollinger (University of New Hampshire - Main Campus)
  • Additional Authors: Michelle Day (University of New Hampshire - Main Campus); Serita Frey (University of New Hampshire - Main Campus)
  • Abstract:

    Two decades of N amendments at the Harvard Forest chronic N addition experiment have resulted in increased soil carbon pools among a variety of other variables. To examine potential mechanisms responsible for this change, we measured soil respiration on treated and control hardwood and pine plots in 2009. Soil respiration was measured from mid April through October at 2-3 week intervals using a portable infrared gas analyzer. We tested differences among treatments in terms of the temperature response relationships, using interaction effect terms and by including the N fertilization level in the regressions. In hardwoods, temperature responses in the control, low and high N stands were significantly different from one another, with progressive declines in respiration at increasing N additions (Fig 1a). In Pines, the low and high differed from the control, but not from each other (Fig 1b). Temperature response Q10 values in the control plots were similar to those observed at the start of the experiment (1988-1990), whereas Q10 values for the treated plots had declined. These patterns represent a continuation of a trend observed in 2001 by Bowden et al. (2004).



    Table 1. Q10 soil respiration values in hardwood control (HWC), low N (HWL) and high N (HWH) plots for the periods of 1988-1990 (Bowden et al. 2004) and 2009.

    -------------------------------------

    1988-1990

    treatment Q10

    HWC 2.51

    HWL 3.20

    HWH 3.16



    2009

    treatment Q10

    HWC 2.46

    HWL 2.15

    HWH 1.90

    -------------------------------------



    Figure 1. Soil respiration in response to temperature at control and treated N addition plots in 2009.



    References:

    Bowden, R.D., E. Davidson, K. Savage, C. Arabia, and P. Steudler. 2004. Chronic nitrogen additions reduce total soil respiration and microbial respiration in temperate forest soils at the Harvard Forest. 2004. Forest Ecology and Management 196:43-56.

  • Research Category: Large Experiments and Permanent Plot Studies

  • Figures:
    • Soil Resp Chronic N.pdf