Experimental warming and drying increase older carbon contributions to soil respiration in lowland tropical forests.

Lee H Dietterich, Daniela F Cusack, Karis J McFarlane, Alexandra L Hedgpeth, Kari M Finstad, Andrew T Nottingham

Journal: Nature communications 2024;15(1):7084

PMID: 39154003

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Abstract

Tropical forests account for over 50% of the global terrestrial carbon sink, but climate change threatens to alter the carbon balance of these ecosystems. We show that warming and drying of tropical forest soils may increase soil carbon vulnerability, by increasing degradation of older carbon. In situ whole-profile heating by 4 °C and 50% throughfall exclusion each increased the average radiocarbon age of soil CO efflux by ~2-3 years, but the mechanisms underlying this shift differed. Warming accelerated decomposition of older carbon as increased CO emissions depleted newer carbon. Drying suppressed decomposition of newer carbon inputs and decreased soil CO emissions, thereby increasing contributions of older carbon to CO efflux. These findings imply that both warming and drying, by accelerating the loss of older soil carbon or reducing the incorporation of fresh carbon inputs, will exacerbate soil carbon losses and negatively impact carbon storage in tropical forests under climate change.

Address: Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, USA. [email protected].; Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, CO, USA.; Department of Geography, University of California - Los Angeles, Los Angeles, CA, USA.; Smithsonian Tropical Research Institute, Panama City, Panama, Republic of Panama.; Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, CO, USA.; Department of Biology, Haverford College, Philadelphia, PA, USA.; Environmental Laboratory, U.S. Army Engineer Research and Development Center, Vicksburg, MS, USA.; Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, USA.; Department of Geography, University of California - Los Angeles, Los Angeles, CA, USA.; Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, USA.; Smithsonian Tropical Research Institute, Panama City, Panama, Republic of Panama.; School of Geography, University of Leeds, Leeds, UK.

DOI: 10.1038/s41467-024-51422-6

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MeSH Terms: Forests, Tropical Climate, Hot Temperature, Carbon, Panama, Carbon Dioxide, Soil, Water, Seasons, Rain, Altitude