Genomic Science Program
U.S. Department of Energy | Office of Science | Biological and Environmental Research Program

Legacy Effects of Warming Alter Simple and Complex Soil Organic Matter Decomposition

Authors:

Tanner Hoffman1* (tsh00009@mix.wvu.edu), Ember M. Morrissey1, Jennifer L. Kane1, Jeffrey Propster2, Rebecca L. Mau2, Michaela Hayer2, Egbert Schwartz2,3, Steven Blazewicz5, Bram W. Stone4, Kirsten S. Hofmockel4, Benjamin J. Koch2,3, Jennifer Pett-Ridge5,6, Paul Dijkstra2,3, Javier A. Ceja Navarro2,3, Michelle Cailin Mack2,3, Kaitlin R. Rempfert5, Sheryl L. Bell4, Bruce A. Hungate2,3

Institutions:

1Division of Plant and Soil Sciences, West Virginia University; 2Center for Ecosystem Science and Society (Ecoss), Northern Arizona University; 3Department of Biological Sciences, Northern Arizona University; 4Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory; 5Physical and Life Science Directorate, Lawrence Livermore National Laboratory; 6Life and Environmental Sciences Department, University of California–Merced

Goals

Microorganisms are major engines of the land carbon cycle, responsible for influencing the composition and radiative properties of the atmosphere, and for both creating and consuming soil organic carbon, a resource that provides multiple ecosystem services, and, when lost, exacerbates climate change. The project investigates the interactions within microbial communities and between microbes and their environment that underpin these dual roles of microorganisms in creating and consuming soil carbon. An overarching objective is to develop and apply omics approaches to investigate microbial community processes involved in carbon and nutrient cycling; interrogating community and taxon-specific microbial controls over key biogeochemical processes in terrestrial environments and testing quantitative ecological and biogeochemical principles using omics data. This work aims to facilitate the scaling of taxon-specific microbial data to connect the ecology of microorganisms with ecosystem level rates of carbon and nutrient cycling.

Abstract

Many ecosystems are predicted to become warmer and drier as global change progresses. Since carbon cycling feedbacks influence climate, understanding how warmer and drier conditions affect microbial interactions that influence the cycling and storage of carbon in terrestrial ecosystems is critical. However, researchers currently lack a holistic understanding of how interactions within soil microbial communities are impacted by global change, limiting the ability to understand and predict soil carbon cycling. Here, researchers aimed to understand how antagonistic and mutualistic microbial interactions are impacted by long-term warming and related to changes in carbon cycling. To address this aim, researchers leveraged a long-term experiment that was established in the San Francisco peaks region near Flagstaff, Arizona in 2002. Collared soil peds from a mixed conifer forest were either transplanted to a lower elevation (ponderosa pine forest) or incubated in their home ecosystem. This relocation of soil served as a proxy for climate change as the ponderosa pine ecosystem is ~2°C warmer. To test how climate change impacts soil organic carbon cycling via microbial interactions, ambient and warmed soils were harvested after 21 years and incubated in the laboratory at a uniform temperature and moisture. Isotopically labeled (13C) organic matter substrates of varying chemical complexity were added to the soil to observe microbial processing of complex (plant litter) and simple (synthetic root exudates) organic carbon substrates. Preliminary results indicate that a legacy of warming causes soil microbes to mineralize simple carbon (synthetic root exudates) more rapidly but have a reduced ability to degrade complex leaf litter. As complex organic substrates are often decomposed by a consortium of microorganisms working in concert, reduced litter decomposition could result from a warming-induced weakening of mutualistic microbial interactions. Future work will investigate these community dynamics using molecular and biogeochemical techniques. Specifically, quantitative stable isotope probing (qSIP) will be used to identify the microbial taxa that shift their carbon assimilation under warming and paired with metagenomics, transcriptomics, and metabolomics to determine how microbial interactions govern ecosystem responses to global change. The overarching goal of this research is to understand how climate change alters soil biogeochemistry and carbon sequestration potential via changes in the microbial interactions that govern decomposition.

Funding Information

This research was supported by the DOE Office of Science, BER Program, grant no. DE-SC0016207. Work at LLNL was performed under the U.S. DOE Contract DE-AC52-07NA27344 and Award SCW1779.Work at PNNL was performed under the U.S. DOE Contract DE-AC05-76RLO 1830 and FWP 79962.