No evidence for increased loss of old carbon in a temperate organic soil after 13 years of simulated climatic warming despite increased CO2 emissions

Briones, M. J.I., Garnett, M. H. and Ineson, P. (2021) No evidence for increased loss of old carbon in a temperate organic soil after 13 years of simulated climatic warming despite increased CO2 emissions. Global Change Biology, 27(9), pp. 1836-1847. (doi: 10.1111/gcb.15540) (PMID:33528070)

Abstract

Determining the temperature sensitivity of terrestrial carbon (C) stores is an urgent priority for predicting future climate feedbacks. A key aspect to solve this long‐standing research gap is to determine whether warmer temperatures will increase autotrophic activities leading to greater C storage or promote heterotrophic activities that will drive these systems to become C sources. We experimentally addressed this critical question by subjecting intact plant‐soil systems in a UK upland ecosystem to simulated climate warming under natural field conditions. We report the results of a 13‐year field‐based climate manipulation experiment combining in situ respiration measurements with radiocarbon (14C) analyses of respired CO2, dissolved organic carbon (DOC), soil and the tissue contents of the dominant soil fauna (enchytraeids). We found that warming during the growing season produced the largely expected increases in ecosystem respiration (63%) and leaching of DOC (19%) with no evidence for thermal acclimation or substrate exhaustion over the whole 13‐year experimental period. Contrary to expectations, we found no evidence to support an increased release of old soil C after more than a decade of simulated climatic change, and indeed, 14C analyses indicated that warming caused a significant shift towards mineralisation of more recent plant‐derived C inputs. Further support came from the radiocarbon analyses of the enchytraeid tissues, which showed a greater assimilation of the more recent (plant‐derived) C sources following warming. Therefore, in contrast to subarctic ecosystems, our results suggest that changes in C storage in this UK upland soil are strongly coupled to plant activities and that increasing temperatures will drive the turnover of organic material fixed only within recent years, without resulting in the loss of existing old carbon stores.

• Item Type: Articles
• Additional Information: Research Funding: UK Natural Environment Research Council. Grant Number: NRCF010001, Spanish Ministry of Education, Xunta de Galicia.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Garnett, Dr Mark
• Authors: Briones, M. J.I., Garnett, M. H., and Ineson, P.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Global Change Biology
• Publisher: Wiley
• ISSN: 1354-1013
• ISSN (Online): 1365-2486
• Published Online: 02 February 2021
• Copyright Holders: Copyright © 2021 John Wiley and Sons Ltd
• First Published: First published in Global Change Biology 27(9): 1836-1847
• Publisher Policy: Reproduced in accordance with the publisher copyright policy