Alteration of nitrous oxide emissions from floodplain soils by aggregate size, litter accumulation and plant-soil interactions

Ley, M. and Lehmann, M. F. and Niklaus, P. A. and Luster, J.. (2018) Alteration of nitrous oxide emissions from floodplain soils by aggregate size, litter accumulation and plant-soil interactions. Biogeosciences, 15 (22). pp. 7043-7057.

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Official URL: https://edoc.unibas.ch/68503/

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Semi-terrestrial soils such as floodplain soils are considered potential hot spots of nitrous oxide (N 2 O) emis- sions. Microhabitats in the soil - such as within and out- side of aggregates, in the detritusphere, and/or in the rhizo- sphere - are considered to promote and preserve specific re- dox conditions. Yet our understanding of the relative effects of such microhabitats and their interactions on N 2 O produc- tion and consumption in soils is still incomplete. Therefore, we assessed the effect of aggregate size, buried leaf litter, and plant-soil interactions on the occurrence of enhanced N 2 O emissions under simulated flooding/drying conditions in a mesocosm experiment. We used two model soils with equivalent structure and texture, comprising macroaggre- gates (4000-250 μm) or microaggregates ( < 250 μm) from a N-rich floodplain soil. These model soils were planted with basket willow ( Salix viminalis L.), mixed with leaf litter or left unamended. After 48 h of flooding, a period of enhanced N 2 O emissions occurred in all treatments. The unamended model soils with macroaggregates emitted significantly more N 2 O during this period than those with microaggregates. Lit- ter addition modulated the temporal pattern of the N 2 O emis- sion, leading to short-term peaks of high N 2 O fluxes at the beginning of the period of enhanced N 2 O emission. The pres- ence of S. viminalis strongly suppressed the N 2 O emission from the macroaggregate model soil, masking any aggregate- size effect. Integration of the flux data with data on soil bulk density, moisture, redox potential and soil solution composi- tion suggest that macroaggregates provided more favourable conditions for spatially coupled nitrification-denitrification, which are particularly conducive to net N 2 O production. The local increase in organic carbon in the detritusphere appears to first stimulate N 2 O emissions; but ultimately, respiration of the surplus organic matter shifts the system towards redox conditions where N 2 O reduction to N 2 dominates. Similarly, the low emission rates in the planted soils can be best ex- plained by root exudation of low-molecular-weight organic substances supporting complete denitrification in the anoxic zones, but also by the inhibition of denitrification in the zone, where rhizosphere aeration takes place. Together, our exper- iments highlight the importance of microhabitat formation in regulating oxygen (O 2 ) content and the completeness of den- itrification in soils during drying after saturation. Moreover, they will help to better predict the conditions under which hot spots, and "hot moments", of enhanced N 2 O emissions are most likely to occur in hydrologically dynamic soil sys- tems like floodplain soils.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Geowissenschaften > Aquatic and Isotope Biogeochemistry (Lehmann)
UniBasel Contributors:Lehmann, Moritz F
Item Type:Article, refereed
Article Subtype:Research Article
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:27 Apr 2020 13:26
Deposited On:10 Apr 2020 17:15

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