Root-microbe interactions control soil C stabilization
Creators: name: University Of California Office Of The President
Publisher: name: University of California Office of the President
publisherIdentifier: https://ror.org/00dmfq477
publisherIdentifierScheme: ROR
Year: 2024

description: Our UC Berkeley – LLNL team proposes to explore the mechanisms through which plant roots impact microbial organic matter decomposition and stabilization in soil. The research proposed will address: 1) the effects of living roots on soil organic matter decomposition rates and the microbial communities mediating these decomposition processes and 2) the role of soil microbes in sorption of root-derived carbon to mineral surfaces. We hypothesize that root-microbe interactions influence C stabilization in the following ways: H1: Decomposition rates and microbial decomposer communities are spatially differentiated along live roots: 1) vertically with root maturity and 2) radially with distance from root surface; H2: Stabilization of root carbon over time involves a multi-step process: consumption of root C by microbes, colonization of mineral surfaces by microbes, sorption of cell debris to surfaces Our research goals will be accomplished using a marriage of two powerful techniques that are unique to the UC Berkeley and LLNL teams, and will involve close collaboration among a LLNL staff scientist, UC Berkeley graduate student, post-doctoral researcher, and faculty member. Direct identification of microbial activity through the incorporation of stable isotopes into microbial communities is called stable isotope probing (SIP). SIP can be accomplished through the physical separation of isotopically-labeled DNA or RNA (Density-gradient SIP; as done at UC Berkeley) or through isotopic analysis of single cells (NanoSIMS: nanometer-scale secondary ion mass spectrometry; as done at LLNL). NanoSIMS is a destructive sputtering and imaging technique that allows one to create an isotope or elemental ratio map of the sample surface with 50-nanometer resolution. We propose to utilize a unique combination of these two approaches, in which soil microbial communities utilizing specific organic carbon compounds will be identified through Density-gradient SIP and subsequently visualized with a newly developed technique “EL-FISH” that couples in-situ 16S probe hybridization to stable isotope uptake visualized by NanoSIMMS. These methods are currently recognized as among the most powerful techniques in microbial ecology, and their combination will provide unparalleled insight into the structure, function, and biogeography of soil microbial community members and their roles in mediating carbon sorption to mineral surfaces in soil. Research addressing Carbon Management and Climate Change is presented as a major program in the area of Energy and Environment under the Lawrence Livermore National Laboratory Mission Statement. “Advancing the understanding of… the carbon cycle, and carbon management and especially to advance understanding of the interrelationships between the fate and effects of carbon in the biosphere…” is stated as a key mission for the lab. The research we propose addresses a primary controller (if not the primary controller) of partitioning of plant root carbon to CO2 vs stabilized, long-lived soil organic matter. Understanding the mechanisms through which roots impact the microbial processing of plant debris and the ultimate fate of plant debris in soil is central to understanding and ultimately managing the terrestrial carbon cycle