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Keywords:

  • decomposition;
  • methanol;
  • N fertilization;
  • nitrogen;
  • PTR-MS;
  • VOCs

Abstract

Nonmethane volatile organic compounds (VOCs) are reactive, low molecular weight gases that can have significant effects on soil and atmospheric processes. Research into biogenic VOC sources has primarily focused on plant emissions, with few studies on VOC emissions from decomposing plant litter, another potentially important source. Likewise, although there have been numerous studies examining how anthropogenic increases in nitrogen (N) availability can influence litter decomposition rates, we do not know how VOC emissions may be affected. In this study, we measured the relative contribution of VOCs to the total carbon (C) emitted from decomposing litter and how N amendments affected VOC emissions. We incubated decomposing litter from 12 plant species over 125 days, measuring both CO2 and VOC emissions throughout the incubation. We found that VOCs represented a large portion of C emissions from a number of the litter types with C emissions as VOCs ranging from 0% to 88% of C emissions as CO2. Methanol was the dominant VOC emitted, accounting for 28–99% of total VOC emissions over the incubation period. N additions increased CO2 production in 7 of the 12 litter types by 5–180%. In contrast, N additions decreased VOC emissions in 8 of the 12 litter types, reducing net VOC emissions to near zero. The decrease in VOC emissions was occasionally large enough to account for the increased CO2 emissions on a per unit C basis, suggesting that N additions may not necessarily accelerate C loss from decomposing litter but rather just switch the form of C emitted. Together these results suggest that, for certain litter types, failure to account for VOC emissions may lead to an underestimation of C losses from litter decomposition and an overestimation of the effects of N additions on rates of litter decomposition.