1. BRC Science Highlight
Hotspots of soil N2O emission enhanced by water absorption by plant residue particles
Objective To understand how factors known to influence overall N2O emissions (plant residue, soil moisture, and soil pore size) affect microscale N2O production and emissions.
Approach
Examined N2O emissions for 110 days in microcosms constructed from soil dominated by small (<10 mm) or large (>35 mm) pores.
Assigned microcosms to 2 plant residue treatments (high and low nitrogen content leaf leaf discs) and to a no-residue control, and incubated at low (30%) or high (45%) water-filled pore space.
Site-preference analysis (difference in the placement of N atoms in N2O) identified the alternative microbial pathways of N2O production (microbial production via bacterial vs. nitrification and fungal denitrification).
Figure 1. Differences in N2O emission rates between soil microcosms with plant residues and control soil during 1–14 days of incubation for large and small pores.
Result/Impacts
N2O hotspots (i.e., soil volumes where most of the microbial N2O production occurs) of very small (mm) size can be a disproportionately large source of substantial N2O emissions.
Two prerequisite conditions necessary for a highly potent hotspot are (1) a spatially aggregated source of organic material (bits of plant residue) and (2) large pores in the vicinity (Figure 1).
Identifying the source and cause of accelerated N2O will help to design cropping practices to avoid this trade-off, and provide the knowledge needed to more accurately represent N2O fluxes in quantitative models.
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Kravchenko, A.N., et al. (2017). “Hotspots of soil N2O emission enhanced through water absorption by plant residue.” Nature Geoscience 10: DOI: /ngeo2963
GLBRC August 2017