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Gross nitrogen dynamics in the mycorrhizosphere of an organic forest soil

Title data

Holz, Maire ; Aurangojeb, Mohammad ; Kasimir, Åsa ; Boeckx, Pascal ; Kuzyakov, Yakov ; Klemedtsson, Leif ; Rütting, Tobias:
Gross nitrogen dynamics in the mycorrhizosphere of an organic forest soil.
In: Ecosystems. Vol. 19 (2015) Issue 2 . - pp. 284-295.
ISSN 1435-0629

Abstract in another language

The rhizosphere is a hot-spot for biogeochemical cycles, including production of greenhouse gases, as microbial activity is stimulated by rhizodeposits released by roots and mycorrhizae. The biogeochemical cycle of nitrogen (N) in soil is complex, consisting of many simultaneously occurring processes. In situ studies investigating the effects of roots and mycorrhizae on gross N turnover rates are scarce. We conducted a 15N tracer study under field conditions in a spruce forest on organic soil, which was subjected to exclusion of roots and roots plus ectomycorrhizae (ECM) for 6 years by trenching. The forest soil had, over the 6-year period, an average emission of nitrous oxide (N2O) of 5.9 ± 2.1 kg N2O ha−1 year−1. Exclusion of roots + ECM nearly tripled N2O emissions over all years, whereas root exclusion stimulated N2O emission only in the latest years and to a smaller extent. Gross mineralization–ammonium (NH4 +) immobilization turnover was enhanced by the presence of roots, probably due to high inputs of labile carbon, stimulating microbial activity. We found contrasting effects of roots and ECM on N2O emission and mineralization, as the former was decreased but the latter was stimulated by roots and ECM. The N2O emission was positively related to the ratio of gross NH4 + oxidation (that is, autotrophic nitrification) to NH4 + immobilization. Ammonium oxidation was only stimulated by the presence of ECM, but not by the presence of roots. Overall, we conclude that plants and their mycorrhizal symbionts actively control soil N cycling, thereby also affecting N2O emissions from forest soils. Consequently, adapted forest management with permanent tree cover avoiding clearcutting could be a means to reduce N2O emissions and potential N leaching; despite higher mineralization in the presence of roots and ECM, N2O emissions are decreased as the relative importance of NH4 + oxidation is decreased, mainly due to a stimulated microbial NH4 + immobilization in the mycorrhizosphere.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER142641
Keywords: Histosol; Mineralization–immobilization turnover; Nitrification; Nitrous oxide; emissions; Norway spruce; 15N tracer
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Chair Soil Physics
Research Institutions
Research Institutions > Research Centres
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 22 Jan 2018 14:16
Last Modified: 22 Jan 2018 14:16