TY - JOUR

T1 - Re-visiting soil carbon and nitrogen stocks in a temperate heathland seven years after the termination of free air CO2 enrichment (FACE)

AU - Li, Qiaoyan

AU - Ambus, Per Lennart

AU - Michelsen, Anders

AU - Schmidt, Inger Kappel

AU - Beier, Claus

AU - Dietzen, Christiana A.

AU - Reinsch, Sabine

AU - Arndal, Marie Frost

AU - Larsen, Klaus Steenberg

N1 - Funding Information: We gratefully acknowledge funding provided for this project by the Villum Foundation, the INCREASE project (EC FP7, Grant Agreement 227628) and AnaEE Denmark (https://anaee.dk/). Additional funding was provided by China Scholarship Council (201904910587). SR was supported by the Natural Environment Research Council award number NE/R016429/1 as part of the UK–ScaPE Programme Delivering National Capability. Many thanks to Mads Madsen Krag, Senhao Wang, Haifeng Zheng, David Pessanha Siqueira and Linsey Marie Avila (University of Copenhagen) for their crucial help during fieldwork, and to Wenyi Xu and Maja Holm Wahlgren (University of Copenhagen) for their assistance during sample processing. Finally, we would like to thank the journal reviewers for very helpful and constructive comments to this manuscript. Funding Information: We gratefully acknowledge funding provided for this project by the Villum Foundation, the INCREASE project (EC FP7, Grant Agreement 227628) and AnaEE Denmark (https://anaee.dk/). Additional funding was provided by China Scholarship Council (201904910587). SR was supported by the Natural Environment Research Council award number NE/R016429/1 as part of the UK–ScaPE Programme Delivering National Capability. Many thanks to Mads Madsen Krag, Senhao Wang, Haifeng Zheng, David Pessanha Siqueira and Linsey Marie Avila (University of Copenhagen) for their crucial help during fieldwork, and to Wenyi Xu and Maja Holm Wahlgren (University of Copenhagen) for their assistance during sample processing. Finally, we would like to thank the journal reviewers for very helpful and constructive comments to this manuscript. Publisher Copyright: © 2022 The Author(s)

PY - 2022

Y1 - 2022

N2 - The response of soil carbon to global climate change remains one of the largest uncertainties for future climate projection. In this study, we re-sampled the soil in a long-term, field-scale, multi-factorial climate experiment, CLIMAITE (Free Air CO2 Enrichment (FACE), warming and drought in all combinations in a Danish heathland ecosystem) in 2020, seven years after the experiment was terminated. We aimed to study the dynamics of the soil carbon after the cessation of long-term multi-factorial climate manipulation, with special attention to the fate of the additional soil carbon (19% increase) that was sequestered in plots exposed to elevated CO2 concentrations (eCO2). Soil carbon pools in former eCO2 plots, as well as in drought and warming plots, had normalized again by 2020. However, the difference in soil isotopic composition between ambient and former eCO2 plots remained, indicating similar loss fractions from older and newer soil carbon pools in the eCO2 plots as well as stimulation of the decomposition of old soil carbon via priming. Throughout the study period, soil nitrogen dynamics tracked the changes in soil carbon, suggesting that nitrogen from deeper soil layers was transported upwards to meet increasing plant demand during eCO2 but was lost again from the topsoil after termination of the FACE treatment. Our findings show that the soil carbon and nitrogen pools in this ecosystem are highly dynamic and may respond strongly and rapidly to changes in major ecosystem drivers, and that revisiting climate experiments after the cessation of treatments may provide valuable insights into the dynamics, stability and resilience of major element pools in ecosystems.

AB - The response of soil carbon to global climate change remains one of the largest uncertainties for future climate projection. In this study, we re-sampled the soil in a long-term, field-scale, multi-factorial climate experiment, CLIMAITE (Free Air CO2 Enrichment (FACE), warming and drought in all combinations in a Danish heathland ecosystem) in 2020, seven years after the experiment was terminated. We aimed to study the dynamics of the soil carbon after the cessation of long-term multi-factorial climate manipulation, with special attention to the fate of the additional soil carbon (19% increase) that was sequestered in plots exposed to elevated CO2 concentrations (eCO2). Soil carbon pools in former eCO2 plots, as well as in drought and warming plots, had normalized again by 2020. However, the difference in soil isotopic composition between ambient and former eCO2 plots remained, indicating similar loss fractions from older and newer soil carbon pools in the eCO2 plots as well as stimulation of the decomposition of old soil carbon via priming. Throughout the study period, soil nitrogen dynamics tracked the changes in soil carbon, suggesting that nitrogen from deeper soil layers was transported upwards to meet increasing plant demand during eCO2 but was lost again from the topsoil after termination of the FACE treatment. Our findings show that the soil carbon and nitrogen pools in this ecosystem are highly dynamic and may respond strongly and rapidly to changes in major ecosystem drivers, and that revisiting climate experiments after the cessation of treatments may provide valuable insights into the dynamics, stability and resilience of major element pools in ecosystems.

KW - C stable isotope

KW - Drought

KW - Elevated CO

KW - FACE experiment

KW - Soil carbon and nitrogen dynamics

KW - Warming

U2 - 10.1016/j.geoderma.2022.116185

DO - 10.1016/j.geoderma.2022.116185

M3 - Journal article

AN - SCOPUS:85140597526

VL - 428

JO - Geoderma

JF - Geoderma

SN - 0016-7061

M1 - 116185

ER -