Microbial diversity declines in warmed tropical soil and respiration rise exceed predictions as communities adapt

Authors: NOTTINGHAM, ANDREW - University Of Leeds; SCOTT, JARROD - Smithsonian Tropical Research; SALTONSTALL, KRISTIN - Smithsonian Tropical Research; Broders, Kirk; MONTERO-SANCHEZ, MARIA - Smithsonian Tropical Research; PUSPOK, JOHANN - Smithsonian Tropical Research; BAATH, ERLAND - Lund University; MEIR, PATRICK - University Of Edinburgh

Submitted to: Nature Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2022
Publication Date: 9/5/2022
Citation: Nottingham, A.T., Scott, J.J., Saltonstall, K., Broders, K., Montero-Sanchez, M., Puspok, J., Baath, E., Meir, P. 2022. Microbial diversity declines in warmed tropical soil and respiration rise exceed predictions as communities adapt. Nature Microbiology. 7:650–1660. https://doi.org/10.1038/s41564-022-01200-1.
DOI: https://doi.org/10.1038/s41564-022-01200-1

Interpretive Summary: Soil microbes form some of the most biologically diverse communities on earth and play an important role in the global carbon cycle. Nowhere is this more critical than in tropical forests where high biological diversity is responsible for vast stores of soil organic carbon. But increases in global temperatures could cause major changes in these microbial communities. ARS Researchers at Peoria, Illinois, and at the Smithsonian Tropical Research Institute in Panama, studied how experimental warming of the soil in a tropical forest would impact microbial diversity. They found a large decline in microbial diversity, and also observed 'warm-adaptation' in specific microbial groups including pathogens and species that decompose organic matter. The measured CO2 emissions also substantially exceeded predictions, likely as a result of temperature adaption, activity of microbes, and abiotic enzyme activity in the soil. This work is significant in that the results are counter to observations in temperate forests and demonstrate far greater CO2 emissions from tropical forest soils than previously assumed.

Technical Abstract: Perturbation of soil microbial communities by rising temperatures could have important consequences for biodiversity and future climate, particularly in tropical forests where high biological diversity coincides with a vast store of soil carbon. We carried out a 2-year in situ soil warming experiment in a tropical forest in Panama and found large changes in the soil microbial community and its growth sensitivity, which did not fully explain observed large increases in CO2 emission. Microbial diversity, especially of bacteria, declined markedly with 3 to 8'°C warming, demonstrating a breakdown in the positive temperature-diversity relationship observed elsewhere. The microbial community composition shifted with warming, with many taxa no longer detected and others enriched, including thermophilic taxa. This community shift resulted in community adaptation of growth to warmer temperatures, which we used to predict changes in soil CO2 emissions. However, the in situ CO2 emissions exceeded our model predictions threefold, potentially driven by abiotic acceleration of enzymatic activity. Our results suggest that warming of tropical forests will have rapid, detrimental consequences both for soil microbial biodiversity and future climate.