Impacts of Drying and Rewetting on the Radiocarbon Signature of Respired CO₂ and Implications for Incubating Archived Soils

authored by

Jeffrey Beem-Miller, Marion Schrumpf, Alison M. Hoyt, Georg Guggenberger, Susan Trumbore

Abstract

The radiocarbon signature of respired CO₂ (∆¹⁴C-CO₂) measured in laboratory soil incubations integrates contributions from soil carbon pools with a wide range of ages, making it a powerful model constraint. Incubating archived soils enriched by “bomb-C” from mid-20th century nuclear weapons testing would be even more powerful as it would enable us to trace this pulse over time. However, air-drying and subsequent rewetting of archived soils, as well as storage duration, may alter the relative contribution to respiration from soil carbon pools with different cycling rates. We designed three experiments to assess air-drying and rewetting effects on ∆¹⁴C-CO₂ with constant storage duration (Experiment 1), without storage (Experiment 2), and with variable storage duration (Experiment 3). We found that air-drying and rewetting led to small but significant (α < 0.05) shifts in ∆¹⁴C-CO₂ relative to undried controls in all experiments, with grassland soils responding more strongly than forest soils. Storage duration (4–14 y) did not have a substantial effect. Mean differences (95% CIs) for experiments 1, 2, and 3 were: 23.3‰ (±6.6), 19.6‰ (±10.3), and 29.3‰ (±29.1) for grassland soils, versus −11.6‰ (±4.1), 12.7‰ (±8.5), and −24.2‰ (±13.2) for forest soils. Our results indicate that air-drying and rewetting soils mobilizes a slightly older pool of carbon that would otherwise be inaccessible to microbes, an effect that persists throughout the incubation. However, as the bias in ∆¹⁴C-CO₂ from air-drying and rewetting is small, measuring ∆¹⁴C-CO₂ in incubations of archived soils appears to be a promising technique for constraining soil carbon models.

Organisation(s)

Institute of Soil Science
Section Soil Chemistry

External Organisation(s)

Max Planck Institute of Biogeochemistry (MPI-BGC)
Lawrence Berkeley National Laboratory
University of California at Irvine

Type

Article

Journal

Journal of Geophysical Research: Biogeosciences

Volume

126

ISSN

2169-8953

Publication date

14.09.2021

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Soil Science, Forestry, Water Science and Technology, Palaeontology, Atmospheric Science, Aquatic Science, Ecology

Sustainable Development Goals

SDG 13 - Climate Action

Electronic version(s)

https://doi.org/10.1029/2020JG006119 (Access: Open)