EGU21-886
https://doi.org/10.5194/egusphere-egu21-886
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Gross rates of soil N2O emission and uptake and denitrification gene abundance in temperate cropland agroforestry and monoculture systems

Jie Luo1, Lukas Beule2, Guodong Shao1, Edzo Veldkamp1, and Marife D. Corre1
Jie Luo et al.
  • 1The University of Göttingen, Faculty of Forest Sciences and Forest Ecology, Soil Science of Tropical and Subtropical Ecosystems, Göttingen, Germany
  • 2The University of Göttingen, Faculty of Agricultural Sciences, Molecular Phytopathology and Mycotoxin Research, Göttingen, Germany

Monoculture croplands are considered as major sources of the greenhouse gas, nitrous oxide (N2O). The conversion of monoculture croplands to agroforestry systems, e.g., integrating trees within croplands, is an essential climate-smart management system through extra C sequestration and can potentially mitigate N2O emissions. So far, no study has systematically compared gross rates of N2O emission and uptake between cropland agroforestry and monoculture. In this study, we used an in-situ 15N2O pool dilution technique to simultaneously measure gross N2O emission and uptake over two consecutive growing seasons (2018 - 2019) at three sites in Germany: two sites were on Phaeozem and Cambisol soils with each site having a pair of cropland agroforestry and monoculture systems, and an additional site with only monoculture on an Arenosol soil prone to high nitrate leaching. Our results showed that cropland agroforestry had lower gross N2O emissions and higher gross N2O uptake than in monoculture at the site with Phaeozem soil (P ≤ 0.018 – 0.025) and did not differ in gross N2O emissions and uptake with cropland monoculture at the site with Cambisol soil (P ≥ 0.36). Gross N2O emissions were positively correlated with soil mineral N and heterotrophic respiration which, in turn, were correlated with soil temperature, and with water-filled pore space (WFPS) (r = 0.24 ‒ 0.54, P < 0.01). Gross N2O emissions were also negatively correlated with nosZ clade I gene abundance (involved in N2O-to-N2 reduction, r = -0.20, P < 0.05). These findings showed that across sites and management systems changes in gross N2O emissions were driven by changes in substrate availability and aeration condition (i.e., soil mineral N, C availability, and WFPS), which also influenced denitrification gene abundance. The strong regression values between gross N2O emissions and net N2O emissions (R2 ≥ 0.96, P < 0.001) indicated that gross N2O emissions largely drove net soil N2O emissions. Across sites and management systems, annual soil gross N2O emissions and uptake were controlled by clay contents which, in turn, correlated with indices of soil fertility (i.e., effective cation exchange capacity, total N, and C/N ratio) (Spearman rank’s rho = -0.76 – 0.86, P ≤ 0.05). The lower gross N2O emissions from the agroforestry tree rows at two sites indicated the potential of agroforestry in reducing soil N2O emissions, supporting the need for temperate cropland agroforestry to be considered in greenhouse gas mitigation policies.

How to cite: Luo, J., Beule, L., Shao, G., Veldkamp, E., and Corre, M. D.: Gross rates of soil N2O emission and uptake and denitrification gene abundance in temperate cropland agroforestry and monoculture systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-886, https://doi.org/10.5194/egusphere-egu21-886, 2021.

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