EGU21-15077, updated on 30 Aug 2023
https://doi.org/10.5194/egusphere-egu21-15077
EGU General Assembly 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Effects of drought conditions on VOC soil fluxes within the rainforest mesocosm of Biosphere 2

Giovanni Pugliese1,2, Johannes Ingrisch3, Thomas Klüpfel2, Kathiravan Meeran3, Gemma Purser4, Juliana Gil Loaiza5, Joost van Haren5,6, Jürgen Kreuzwieser1, Nemiah Ladd1, Laura Meredith5,6, Christiane Werner1, and Jonathan Williams2
Giovanni Pugliese et al.
  • 1Ecosystem Physiology, Faculty of Environment and Natural Resources, University of Freiburg, 79110 Freiburg, Germany
  • 2Max Planck Institute for Chemistry, Atmospheric Chemistry Department, 55128 Mainz, Germany
  • 3Institute of Ecology, University of Innsbruck, 6020 Innsbruck, Austria
  • 4School of Earth Sciences, The University of Edinburgh, Edinburgh EH9 3FE, U.K.
  • 5School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, 85721, USA
  • 6Biosphere 2, University of Arizona, Oracle, AZ, 85623, USA

Volatile organic compounds (VOC) play an important role in determining atmospheric processes that control air quality and climate. Although atmospheric VOC concentrations are mostly affected by plants, soils are significant contributors as they are simultaneously a source, a sink and a storage of atmospheric VOCs. The aim of the present study was to assess the effects of a prolonged drought condition on VOC soil fluxes in the tropical rainforest mesocosm of Biosphere 2 (B2; Tucson, Arizona, USA). The absence of atmospheric chemistry due to UV light filtering by the glass and the possibility to control and manipulate the conditions of the ecosystem make the B2 an ideal set-up to study the rainforest VOC dynamics.

The experiments were conducted over the 4 months B2WALD campaign during which the rainforest was subjected to a controlled drought period of about 10 weeks followed by a rewetting period. Soil VOCs fluxes were measured continuously by means of a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) that was connected to 12 automated soil chambers (LI 8100-104 Long-Term Chambers, Licor Inc.) placed in 4 different locations within the B2 rainforest.

The B2 rainforest soil acted as a strong sink for all isoprenoid species. The isoprene sink steadily weakened during drought period, but increased sharply back to the pre-drought levels after the rain rewet. In contrast, the monoterpene soil sink became slightly stronger during the mild drought period (up to 5 weeks after the last rainfall) but weakened during the severe drought period (up to 10 weeks after rainfall). A huge increase in monoterpene uptake was observed after the rain rewet. The oxidation products of isoprene (methacrolein, methyl vinyl ketone and isoprene peroxides) showed a similar trend to the monoterpenes, even in absence of atmospheric chemistry. The species with molecular formula C5H8O was taken up by the soil during predrought, which was reduced during mild drought period but increased again during the severe drought period.Sulfur-containing compounds including DMS and methanethiol all showed a significant emission peak immediately after the rain rewet.Oxygenated VOCs such as methanol and acetone were taken up by the soil in wet conditions. The uptake of both compounds strongly decreased with the drought and in severe drought conditions they were even emitted by the soil.

In summary, soil VOC fluxes changed markedly with the onset and development drought stages (pre, mild and severe drought) of the B2 rainforest, mirroring atmospheric VOC concentrations and soil microbial activity changes related to overall ecosystem response to drought and recovery.

How to cite: Pugliese, G., Ingrisch, J., Klüpfel, T., Meeran, K., Purser, G., Gil Loaiza, J., van Haren, J., Kreuzwieser, J., Ladd, N., Meredith, L., Werner, C., and Williams, J.: Effects of drought conditions on VOC soil fluxes within the rainforest mesocosm of Biosphere 2, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15077, https://doi.org/10.5194/egusphere-egu21-15077, 2021.