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bioRxiv · 10.1101/2024.12.10.627762

Experimental Warming Alters Nitrogen Cycle in a Humid Tropical Forest

Bartz, P. M.·Reed, S. C.·Grullon-Penkova, I. F.·Cavaleri, M. A.·Shahid, S.·Wood, T. E.·Bachelot, B.
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Abstract

O_LIHumid tropical forests typically contain high soil nitrogen (N), supporting rapid rates of primary productivity and recovery from disturbances. Nitrogen fixation is regulated by microbial communities, which can be free-living in the soil and leaf litter (asymbiotic) or in symbioses with plants. C_LIO_LITo investigate how warming affects asymbiotic and symbiotic components of the N cycle, we analyzed soil and leaf litter samples as well as annual seedling census data from an experimental warming field site in Puerto Rico. C_LIO_LI16S and nifH sequencing revealed that warming significantly altered bacterial composition. Asymbiotic N fixation rates were 55% greater in soil (0.004 nmol N2/g/hr) and 525% greater (0.217 nmol N2/g/hr) in leaf litter from warmed compared to ambient plots. This increase in fixation was associated with changes in the N-fixing bacterial community. Under warming, N fixers experienced a 4.4-fold increase in growth rate compared to non-fixers, yet competition with neighboring N fixers eventually reduced N fixer growth. Seedling growth, especially of N fixers, initially increased following hurricane disturbances before declining. C_LIO_LITogether, our findings suggest that warming increases the flux of N from the atmosphere into this tropical forest, driving changes in both microbial and tree dynamics. C_LI

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Bartz, P. M., Reed, S. C., Grullon-Penkova, I. F., Cavaleri, M. A., Shahid, S., Wood, T. E., Bachelot, B.. 2024-12-16. Experimental Warming Alters Nitrogen Cycle in a Humid Tropical Forest. https://doi.org/10.1101/2024.12.10.627762

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