Title: Spatially tracking carbon through the root-rhizosphere-soil system using laser ablation-IRMS

Abstract

The intimate relationships between plant roots, rhizosphere, and soil are fostered by the release of organic compounds from the plant into soil through various forms of rhizodeposition and the simultaneous harvestingof inorganic nutrients from the soil to the plant. Here we present a method to spatially track and map the migration of plant-derived carbon (C) through roots into the rhizosphere and surrounding soil using laser ablation-isotope ratio mass spectrometry (LA-IRMS). Weused switchgrass microcosms containing soil from field plots at the Kellogg Biological Station (Hickory Corners, Michigan, USA), which have been cropped with switchgrass since 2008. We used a ¹³CO₂ tracerto isotopically label switchgrass plants for two diel cycles and tracked subsequent movement of labeled C using the spatially specific (<100 µm resolution) δ¹³C analysis enabled by LA-IRMS.This approach permitted assessment of variable C flow through different roots and enabled mapping of spatial variability of C allocation to the rhizosphere. Highly ¹³C-enriched C (consistent with production during the ¹³CO₂ application period) extended ~0.5 – 1 mm from the root into the soil, suggesting that the majority of recent plant-derived C was within this distance of the root after 48 hours. Tracking the physical extent of root exudation into the rhizosphere canmore » help evaluate the localization of plant-microbe interactions in highly variable subsurface environments,and the use of the isotopic label can differentiate freshly fixed C (presumably from root exudates) from other types of subsurface C (e.g., plant necromass and microbial turnover). The LA-IRMS technique mayalso serve as a valuable screening technique to identify areas of high activity for additional microbial or geochemicalassays.« less

Authors:

Denis, Elizabeth H.  ^[1];

• Search DOE PAGES for author "Denis, Elizabeth H."
• Search DOE PAGES for ORCID "0000-0002-4150-5043"

Ilhardt, Peter D. ^[1]; Tucker, Abigail E. ^[1]; Huggett, Nicholas L. ^[1]; Rosnow, Joshua J.  ^[1];

• Search DOE PAGES for author "Rosnow, Joshua J."
• Search DOE PAGES for ORCID "0000-0001-6365-8350"

Moran, James J.  ^[1]

• Search DOE PAGES for author "Moran, James J."
• Search DOE PAGES for ORCID "0000-0001-9081-9017"

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+ Show Author Affiliations

1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Publication Date:

Sat Jun 01 00:00:00 EDT 2019

Research Org.:

Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1567258

Alternate Identifier(s):

OSTI ID: 1499134; OSTI ID: 1503718

Report Number(s):

PNNL-SA-135618
Journal ID: ISSN 1522-2624

Grant/Contract Number:  

AC05-76RL01830

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Plant Nutrition and Soil Science (Online)

Additional Journal Information:

Journal Name: Journal of Plant Nutrition and Soil Science (Online); Journal Volume: 182; Journal Issue: 3; Journal ID: ISSN 1522-2624

Publisher:

Wiley

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; laser ablation isotope ratio mass spectrometry, soil, carbon isotope, spatial, rhizosphere, map; carbon isotope; laser ablation‐isotope ratio mass spectrometry (LA‐IRMS); rhizosphere; soil; spatial