The effect of prolonged drought and recovery on soil VOC fluxes in an experimental rainforest

Abstract Drought can affect the capacity of soils to emit and consume biogenic volatile organic compounds (VOCs). Here we show the impact of prolonged drought followed by rain and recovery on soil VOC fluxes from an experimental rainforest. Under wet conditions the rainforest soil acted as a net VOCs sink, in particular for isoprenoids, carbonyls and alcohols. The sink capacity decreased progressively during drought, and at soil moistures below ~19% the soil became a source of several VOCs. Position specific 13C-pyruvate labelling experiments revealed that soil microbes were responsible for the emissions and that energetic investment in VOC production increased during drought. Soil rewetting induced an emission pulse of carbonyls and dimethyl sulfide due to water-induced mobilization of carbon and sulfur pools of soil organic matter. Results show that, the extended drought periods predicted for tropical rainforest regions will strongly affect soil VOC fluxes thereby impacting atmospheric chemistry and climate.