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キーワード:
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要旨:
Droughts are occurring with increased frequency and duration in tropical rainforests due to climate change, significantly impacting soil carbon (C) dynamics through both dry-down and rewet events. The role of microbes as drivers of changing C cycling in soils, including emissions and uptake of volatile organic compound (VOC), remains largely unknown. Here, we aimed to characterize microbial responses to drought, rewet, and recovery using an integrative, multiple 'omics approach. We hypothesized that microbial communities would adapt to drought by altering their C allocation and cycling strategies, which would then abruptly change with rapid influx of water during rain rewet. To study this, we conducted an ecosystem-wide 66-day drought experiment in the tropical rainforest biome at Biosphere 2 (Oracle, AZ). To track carbon allocation by microbes during pre-drought and drought, we injected position-specific 13C-pyruvate solution into a soil chamber and measured C isotope ratios of VOC and CO2 fluxes. Additionally, we collected soil samples at various time points before and during drought and rain rewet for multi-omics analysis to assess C dynamics and microbial activity. Our results revealed that during drought, 13C-VOCs efflux (acetate and acetone) increased, driven by increased production and buildup of intermediate metabolites as interconnectivity between central carbon metabolism pathways decreased, and 13C-CO2 efflux decreased, driven by an overall decrease in microbial activity. This change in microbial carbon allocation was associated with an increase in recalcitrant (i.e. lignins and tannins) and a decrease in bioavailable (i.e. proteins and carbohydrates) compounds during drought. However, immediately following rewet, there was a pulse of bioavailable compounds that increased in abundance, corresponding to the emission pulses of several VOCs, which then both decreased again by 24 hr post rewet. Our results demonstrate an active role of microbes in shifting soil C pools and impacts on atmosphere through VOC emissions and will help us to better understand the impacts of increased droughts at the ecosystem-to-global scale.
