Evaluating the role soil nutrients play in regulating soil greenhouse gas fluxes from the pristine tropical forests: evidence from a nutrient manipulation experiment in Uganda
- 1University of Augsburg, Institute of Geography, Augsburg, Germany (tamjos95@gmail.com)
- 2Environmental Control Department, Nordwestdeutsche Fortlische Versuchanstalt, Göttingen, 37079, Germany
- 3Soil Resources, Department of Environmental Systems Science, ETH, Zurich, 8092, Switzerland
- 4Sustainable Agroecosystems, Department of Environmental Systems Science, ETH, Zurich, 8092, Switzerland
- 5Ngetta Zonal Agricultural Research and Development Institute (NGEZARDI), P.O.Box 52, Lira, Uganda
- 6Soil Science of Tropical and Subtropical Ecosystems, Büsgen-Institute, University of Göttingen, Göttingen, 37077, Germany
The exchange of the climate-relevant greenhouse gases (GHGs) at the soil-atmospheric interface is regulated by both abiotic and biotic controls. However, evidence on nutrient limitations of soil GHG fluxes from African tropical forest ecosystems is still rare. Therefore, an ecosystem-scale nutrient manipulation experiment (NME) consisting of nitrogen (N), phosphorus (P), N + P, and control treatments was set up in a tropical forest in northwestern Uganda. Soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes were measured monthly using static vented chambers for 14 months. A root trenching treatment was also done in all the experimental plots in order to disentangle the contribution of root and microbial respiration to total soil CO2 effluxes. In parallel to soil GHG flux measurements, soil temperature, soil moisture, and mineral N were determined. Lifting the N limitation on the soil nitrifiers and denitrifiers through N fertilization significantly increased N2O fluxes in N, and N + P addition plots in the transitory phase (0-28 days after N fertilization, p < 0.01). However, sustained N fertilization did not significantly affect background (measured more than 28 days after fertilization) N2O fluxes. Alleviation of the P limitation on soil methanotrophs through P fertilization marginally and significantly increased CH4 consumption in the transitory (p = 0.052) and background (p = 0.010) phases, respectively. Simultaneous addition of N and P (N + P) significantly affected transitory soil CO2 effluxes (p = 0.010), suggesting a possible co-limitation of N and P on soil respiration. Microbial CO2 effluxes were significantly larger than root CO2 effluxes (p < 0.001) across all treatment plots so was the contribution of microbial respiration to the total soil CO2 effluxes (about 70 %, p < 0.001). Despite the fact that soil respiration was affected through N + P fertilization, neither heterotrophic nor autotrophic respiration significantly differed in either the N + P or the other treatments. Overall, the study findings suggest that the contribution of tropical forests to the global soil GHG budget could be altered by changes in N and P availability in these biomes.
Key words: Soil greenhouse gas fluxes, nutrient manipulation experiment, soil nutrient limitation, and Ugandan tropical pristine forest.
How to cite: Tamale, J., Hüppi, R., Griepentrog, M., Turyagyenda, L. F., Barthel, M., Doetterl, S., Fiener, P., and van Straaten, O.: Evaluating the role soil nutrients play in regulating soil greenhouse gas fluxes from the pristine tropical forests: evidence from a nutrient manipulation experiment in Uganda, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1415, https://doi.org/10.5194/egusphere-egu21-1415, 2021.
