TY - JOUR

T1 - Substrate quality effects on stabilized soil carbon reverse with depth

AU - Li, Mengmeng

AU - Meador, Travis

AU - Sauheitl, Leopold

AU - Guggenberger, Georg

AU - Angst, Gerrit

N1 - Funding Information: This research was funded by the Czech Ministry of Education, Youth, and Sports (grant numbers: LM2015075 and EF16_013/0001782 – SoWa Ecosystems Research), and the Czech Science Foundation (grant numbers 19-00533Y, 18-24138S, and 19-17139S). We thank Kateřina Lapáčková, Hana Turoňová, Ljubov Poláková, and Viola Rünzi for help in the laboratory and Kevin E. Mueller, Daquan Sun, Ondrej Mudrák, and Jan Frouz for discussing some of the data presented in this manuscript.

PY - 2022/1/15

Y1 - 2022/1/15

N2 - High-quality plant inputs to the soil with low lignin to nitrogen ratios have been conceptualized to foster the formation of soil organic matter (SOM) and carbon (C) in stabilized soil compartments, such as aggregates and organo-mineral associations (MAOM), in dependence of the soil's capacity to store additional C (i.e., C saturation deficit). Yet, evidence for these conceptualizations from field experiments is scarce and it is unclear whether factors commonly not included in laboratory experiments (such as soil depth) may modulate the influence of substrate quality on SOM formation. We, thus, tested the effect of substrates with different qualities (from European alder and Scots pine) on C stocks in bulk soil, free particulate and aggregate-occluded organic matter, and MAOM in soils at various ages after reclamation and at different soil depths in a common-garden field experiment. Our results revealed that substrate quality generally acted in the predicted way in the upper investigated soil layer (0–5 cm depth), i.e., high-quality substrates increased C stocks in MAOM. Surprisingly, the effect of substrate quality reversed with depth (5–15 cm; i.e., low-quality litters were associated with higher C stocks in MAOM), potentially due to a higher sensitivity (or “priming”) of native SOM in response to high-quality substrates at depth or a lower probability of such substrates reaching deeper soil layers. These patterns appeared to be largely independent of the soils’ theoretical capacity to stabilize additional C, which was exceeded in all investigated soils. Based on the results of our field experiment, we highlight the need to refine recent conceptualizations by focusing on environmental factors that are commonly not accounted for in laboratory-scale experiments and that may alter the direction in which substrate quality acts to influence the formation of SOM.

AB - High-quality plant inputs to the soil with low lignin to nitrogen ratios have been conceptualized to foster the formation of soil organic matter (SOM) and carbon (C) in stabilized soil compartments, such as aggregates and organo-mineral associations (MAOM), in dependence of the soil's capacity to store additional C (i.e., C saturation deficit). Yet, evidence for these conceptualizations from field experiments is scarce and it is unclear whether factors commonly not included in laboratory experiments (such as soil depth) may modulate the influence of substrate quality on SOM formation. We, thus, tested the effect of substrates with different qualities (from European alder and Scots pine) on C stocks in bulk soil, free particulate and aggregate-occluded organic matter, and MAOM in soils at various ages after reclamation and at different soil depths in a common-garden field experiment. Our results revealed that substrate quality generally acted in the predicted way in the upper investigated soil layer (0–5 cm depth), i.e., high-quality substrates increased C stocks in MAOM. Surprisingly, the effect of substrate quality reversed with depth (5–15 cm; i.e., low-quality litters were associated with higher C stocks in MAOM), potentially due to a higher sensitivity (or “priming”) of native SOM in response to high-quality substrates at depth or a lower probability of such substrates reaching deeper soil layers. These patterns appeared to be largely independent of the soils’ theoretical capacity to stabilize additional C, which was exceeded in all investigated soils. Based on the results of our field experiment, we highlight the need to refine recent conceptualizations by focusing on environmental factors that are commonly not accounted for in laboratory-scale experiments and that may alter the direction in which substrate quality acts to influence the formation of SOM.

KW - C saturation, C stocks

KW - common garden

KW - lignin:N

KW - MAOM

KW - oPOM

UR - http://www.scopus.com/inward/record.url?scp=85116546267&partnerID=8YFLogxK

U2 - 10.1016/j.geoderma.2021.115511

DO - 10.1016/j.geoderma.2021.115511

M3 - Article

AN - SCOPUS:85116546267

VL - 406

JO - GEODERMA

JF - GEODERMA

SN - 0016-7061

M1 - 115511

ER -