24 Aug 2021

24 Aug 2021

Review status: a revised version of this preprint is currently under review for the journal BG.

SOC stabilization mechanisms and temperature sensitivity in old terraced soils

Pengzhi Zhao1, Daniel J. Fallu2, Sara Cucchiaro3,4, Paolo Tarolli3, Clive Waddington5, David Cockcroft5, Lisa Snape6, Andreas Lang6, Sebastian Doetterl7, Antony G. Brown2,8, and Kristof Van Oost1 Pengzhi Zhao et al.
  • 1Georges Lemaître Centre for Earth and Climate Research, Earth and Life Institute, UCLouvain, 1348 Louvain-la-Neuve, Belgium
  • 2Tromso University Museum, UiT The Artic University of Norway, Kvaløyen 30, 9013 Tromsø, Norway
  • 3Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, Via delle Scienze, 206, 33100 Udine, Italy
  • 4Department of Land, Environment, Agriculture and Forestry, University of Padova, viale dell’Università 16, 35020 Legnaro, Italy
  • 5Archaeological Research Services, Ltd, Angel House, Portland Square, Bakewell DE45 1HB, UK
  • 6Department of Geography and Geology, University of Salzburg, Salzburg, 5020, Austria
  • 7Department of Environmental Systems Science, ETH Zurich, Universitätstrasse 16, 8092 Zürich, Switzerland
  • 8Geography and Environmental Science, University of Southampton, Highfield SO17 1BJ, Southampton, UK

Abstract. Being the most common and widest spread man-made landform, terrace construction has resulted in an extensive perturbation of the land surface. Our mechanistic understanding of soil organic carbon (SOC) (de-) stabilization mechanisms and of the persistence of SOC stored in terraced soils, however, is far from complete. Here we explored the factors controlling SOC stability and temperature sensitivity (Q10) of abandoned prehistoric agricultural terrace soils in NE England, using soil fractionation and temperature sensitive incubation in combination with measurements of terrace soil burial age. Results showed that although buried terrace soils contained 1.7 times more unprotected SOC (i.e., coarse particulate organic carbon) than non-terraced soils at comparable soil depths, a significantly lower potential soil respiration was observed, relative to a control (non-terraced) profile. This suggests that burial of former topsoil due to terracing provided a mechanism for enhanced C stabilization. Furthermore, we observed a shift in SOC fraction composition from particulate organic C towards mineral protected C with increasing burial age. This clear shift to more processed recalcitrant SOC with soil burial age also contributes to SOC stability in terraced soils. Temperature sensitivity incubations revealed that the dominant controls on Q10 depend on the terrace soil burial age. At relatively younger ages of soil burial, the reduction of substrate availability due to SOC mineral protection with ageing attenuates the intrinsic Q10 of SOC decomposition. However, as terrace soil becomes older, SOC stocks in deep buried horizons are characterized by a higher temperature sensitivity, potentially resulting from the poor SOC quality (i.e., soil C : N ratio). In conclusion, terracing in our study site has stabilized SOC as a result of soil burial during terrace construction. The depth-age patterns of Q10 and SOC fraction composition of terraced soils observed in our study site differ from those seen in non-terraced soils and this has implications when assessing the effects of climate warming or terrace abandonment on the terrestrial C cycle.

Pengzhi Zhao et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-205', Anonymous Referee #1, 01 Sep 2021
  • RC2: 'Comment on bg-2021-205', Anonymous Referee #2, 08 Sep 2021

Pengzhi Zhao et al.

Pengzhi Zhao et al.


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Short summary
We investigate the factors controlling SOC stability and temperature sensitivity of abandoned prehistoric agricultural terrace soils. Results suggest that the burial of former topsoil due to terracing provided a SOC stabilization mechanism. Both the soil C : N ratio and SOC mineral protection regulate soil SOC temperature sensitivity. However, which mechanism predominantly controls SOC temperature sensitivity depends on the age of the buried terrace soils.