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Impacts of root structure and chemical composition of exudates on soil carbon stabilization


EMSL Project ID
50409

Abstract

Root traits and the chemical composition of root exudates are critically important in regulating soil carbon(C) inputs and stabilization, but highly uncertain and poorly represented in global C cycling and modeling. The proposed research aims to assess how root structure and rhizosphere chemistry differ among cultivars of Panicum virgatum (switchgrass) and Andropogon gerardii (big bluestem), and how these differences contribute to variability in root-derived soil C accumulation in a long-term field experiment. The data collected with this project will support the experimental design of a larger project with which we will establish links between rhizosphere chemistry, microbial community structure, microbial residue formation and SOC stabilization.

Our group has collected a wealth of preliminary data on root traits and long-term soil C dynamics in a variety of switchgrass cultivars. We have found that specific root length (SRL) can predict root-C input across cultivars in the short-term, but departures from this relationship observed in the longer term suggest that other factors mediate SOC stabilization We have some preliminary data to suggest that there is variation among cultivars in soil chemistry, and we expect that this variation plays a role in the ability of different cultivars to sequester soil C. However, our preliminary data so far are limited to very few cultivars of switchgrass and big bluestem. Additional data collected with this proposed project, will provide stronger proof of principle that there are significant differences in soil chemistry among cultivars and species, and that this variation plays a significant role in regulating the processes of soil C stabilization.

We will leverage a long-term (10 years) field experiment to address our questions. The field site is located at the Sustainable Bioenergy Crop Research Facility in Batavia. The experimental site utilizes a C3-C4 vegetation change (before switchgrass establishment in 2008, the site supported a stand of perennial, cool-season Eurasian pasture grasses for 36 years) allowing for the quantification of root derived soil-C. We will collect soil samples from four switchgrass- and two big bluestem cultivars. We will quantify root biomass and SRL, and fractionate the soil to assess root-C associated with particulate organic matter, and silt and clay fractions. In addition, we will collect rhizosphere dissolved organic matter using sequential extractions with water and methanol to identify free metabolites and metabolites adsorbed to soil minerals. The proposed research will advance our understanding of how key plant root traits regulate soil C input and SOC stabilization.

Project Details

Project type
Limited Scope
Start Date
2019-02-21
End Date
2019-04-23
Status
Closed

Team

Principal Investigator

Marie-Anne de Graaff
Institution
Boise State University

Co-Investigator(s)

Julie Jastrow
Institution
Argonne National Laboratory