Rhizosphere Carbon Fluxes Under Drought and Hydraulic Redistribution Conditions
Authors
Richard Marinos1 (rmarinos@buffalo.edu), Fiona Ellsworth1*, Scott Mackay1, Angela Possinger2, Mitchell Hitchcock1
Institutions
1State University of New York–Buffalo, NY; 2Virginia Tech University, Blacksburg, VA
Abstract
Hydraulic redistribution (HR) is the passive movement of water from wet soil regions to dry soil regions (for example from deep soils at the water table to dry surface soils) using plant roots as conduits. It is well appreciated that HR plays an important role in plant growth and survival during periods of drought but less is known about how HR sustains microbial life in the soil. HR provides water to microbes in the rhizosphere, and it also may flush root exudates into the rhizosphere. The central hypotheses behind this research are (1) plants produce higher quantities of root exudates when undergoing HR; (2) the flow of water during HR carries these exudates farther than they would normally diffuse into the soil, expanding the rhizosphere, and; (3) HR-delivered exudates and water sustain microbial activity during drought with important implications for carbon cycling in soils.
The experimental work on this project has focused on developing and refining analytical methods for the analysis of root exudates under both HR and non-HR conditions and preparing specimens in the greenhouse for performing these experiments. Working with collaborators at Environmental Molecular Sciences Laboratory (EMSL), researchers have developed novel exudate collection and FT-ICR-MSI analysis methods that permit imaging of root exudation along the root network. Researchers have also developed an extensive LC-MS based metabolite library and analytical workflow for processing of exudate samples.
The modelling work on this project has coupled the Carbon, Organisms, Rhizosphere, and Protection in the Soil Environment (CORPSE) soil biogeochemical model to a 1-D advection-dispersion model to model exudate transport and transformations in the rhizosphere. This has been coupled in turn to the TREES ecohydrological model. This model has been tested against data from several FluxNet sites and will be used to model root-rhizosphere processes under the greenhouse conditions of the experiment.