Ladd, S. N. | Search bioRxiv

bioRxiv2026

Soil viral response to drought disturbance and ecosystem recovery in an artificial rainforest

Anthropogenic climate change is driving increased temperature and altered precipitation patterns in tropical rainforests, yet the impact of severe drought on soil viral communities and their recovery capacity remains poorly understood. Soil viruses can exert strong controls on bacterial populations impacting microbially-mediated soil processes such as carbon cycling. At the same time, viruses are very sensitive to changes in the soil environment. We leverage meta-omics data from soils collected during a two-month drought and one-month recovery experiment carried in the Biosphere 2 Tropical Rainforest artificial biome. Our results indicate that soil viral community structure responds to small scale soil habitat heterogeneity more strongly than on overall changes in moisture. Additionally, the abundance of soil viruses was associated with a higher diversity of metabolites in the soil, suggesting viruses play a key role in soil biogeochemical processes. Altogether, our study suggests that soil viruses are an active part of tropical rainforest soil microbial communities and that is necessary to understand their response to drought.

microbiology↗

bioRxiv2022

Leaf-level metabolic changes in response to drought affect daytime CO2 emission and isoprenoid synthesis

In the near future, climate change will cause enhanced frequency and/or severity in terrestrial ecosystems, including tropical forests. Drought responses by tropical trees may affect their carbon use, including production of volatile organic compounds (VOCs), with unpredictable implications for carbon cycling and atmospheric chemistry. It remains unclear how metabolic adjustments by mature tropical trees in response to drought will affect their carbon fluxes associated with daytime CO2 production and VOC emission. To address this gap, we used position-specific 13C-pyruvate labeling to investigate leaf CO2 and VOC fluxes from four tropical species before and during a controlled drought in the enclosed rainforest of Biosphere 2. Overall, plants that were more sensitive to drought had greater reductions in daytime CO2 production. Although daytime CO2 production was always dominated by non-mitochondrial processes, the relative contribution of CO2 from the tricarboxylic acid cycle tended to increase under drought. A notable exception was the legume tree Clitoria fairchildiana, which had less anabolic CO2 production than the other species even under pre-drought conditions, perhaps due to more efficient refixation of CO2 and anaplerotic use for amino acid synthesis. C. fairchildiana was also the only species to allocate detectable amounts of 13C label to VOCs, and was a major source of VOCs in the Biosphere 2 forest. In C. fairchildiana leaves, our data indicate that intermediates from the mevalonic acid pathway are used to produce the volatile monoterpene trans-{beta}-ocimene, but not isoprene. This apparent crosstalk between the mevalonic acid and methylerythritol phosphate pathways for monoterpene synthesis declined with drought. Finally, although trans-{beta}-ocimene emissions increased under drought, it was increasingly sourced from stored intermediates and not de novo synthesis. Unique metabolic responses of legumes may play a disproportionate role in the overall changes in daytime CO2 and VOC fluxes in tropical forests experiencing drought.

plant biology↗