TY - JOUR

T1 - Substrate quality of drained organic soils – Implications for carbon dioxide fluxes

AU - Säurich, Annelie

AU - Tiemeyer, Bärbel

AU - Dettmann, Ullrich

AU - Fiedler, Sabine

AU - Don, Axel

N1 - Funding Information: This study was carried out as part of the German Agricultural Soil Inventory, funded by the German Federal Ministry of Food and Agriculture. We would like to thank Frank Hegewald, Thomas Viohl, Peter Braunisch, Viridiana Alc?ntara-Shivapatham, Arndt Piayda, Mareille Wittnebel, Ang?lica Jaconi, Sebastian Willi Oehmke, Nicole Altwein, Roland Prietz, Arne Heidkamp, Anna Jacobs, Stefan Burkart, Joonas Sandman and Josefin S?urich for their help during sampling, tending to the incubation device and invaluable encouragement and support. Open Access funding enabled and organized by Projekt DEAL.

PY - 2021/10/23

Y1 - 2021/10/23

N2 - Background: Peatlands only cover a minor fraction of the global terrestrial surface, but due to drainage, they are major contributors to carbon dioxide (CO2) emissions from soils. Previous studies have shown that hydrological conditions, nutrient availability and anthropogenic disturbance play an important role in the mineralisation of organic matter. Furthermore, microbial turnover depends on peat quality, which is determined by its botanical origin and degree of transformation under natural conditions. Aims: The objective of this study was to shed light on the interdependence between mineralisation rates, secondary transformation of peat and chemical composition by examining the differences between bog and fen peat and between strongly degraded topsoil and well-preserved subsoil. Methods: Bog and fen peat from ten different peatlands under grassland use in Germany were analysed for their chemical composition using standard 13C nuclear magnetic resonance (NMR) spectroscopy and wet chemical extractions for fibre analysis. The radiocarbon age was determined as well. The results were combined with CO2 fluxes from a previous incubation study. Results: Topsoils had higher shares of proteins and lipids, and lower shares of carbohydrates and aromatics than subsoils. Bog peat subsoils were characterised by higher shares of carbohydrates and lower shares of aromatics than fen peat subsoils. Topsoils were more similar to each other in their chemical composition than the subsoils. Considering all samples, aromatics and phenolics were negatively correlated with CO2 fluxes. Measured CO2 fluxes from topsoils were significantly higher than from subsoils. However, no influences of chemical composition on CO2 fluxes were detected when examining topsoils and subsoils separately. Even though aromatics and phenolics showed positive relationships with radiocarbon age, differences in age alone were unable to explain the higher amounts of these compounds in the subsoil. Conclusions: The results imply that chemical composition of topsoil peat is not the reason for higher mineralisation rates compared to subsoil peat, but rather a consequence of decomposition and transformation. Thus, peat mineralisation of drained organic soils under agriculture might not slow down over time due to gradually decreasing peat quality but could increase further.

AB - Background: Peatlands only cover a minor fraction of the global terrestrial surface, but due to drainage, they are major contributors to carbon dioxide (CO2) emissions from soils. Previous studies have shown that hydrological conditions, nutrient availability and anthropogenic disturbance play an important role in the mineralisation of organic matter. Furthermore, microbial turnover depends on peat quality, which is determined by its botanical origin and degree of transformation under natural conditions. Aims: The objective of this study was to shed light on the interdependence between mineralisation rates, secondary transformation of peat and chemical composition by examining the differences between bog and fen peat and between strongly degraded topsoil and well-preserved subsoil. Methods: Bog and fen peat from ten different peatlands under grassland use in Germany were analysed for their chemical composition using standard 13C nuclear magnetic resonance (NMR) spectroscopy and wet chemical extractions for fibre analysis. The radiocarbon age was determined as well. The results were combined with CO2 fluxes from a previous incubation study. Results: Topsoils had higher shares of proteins and lipids, and lower shares of carbohydrates and aromatics than subsoils. Bog peat subsoils were characterised by higher shares of carbohydrates and lower shares of aromatics than fen peat subsoils. Topsoils were more similar to each other in their chemical composition than the subsoils. Considering all samples, aromatics and phenolics were negatively correlated with CO2 fluxes. Measured CO2 fluxes from topsoils were significantly higher than from subsoils. However, no influences of chemical composition on CO2 fluxes were detected when examining topsoils and subsoils separately. Even though aromatics and phenolics showed positive relationships with radiocarbon age, differences in age alone were unable to explain the higher amounts of these compounds in the subsoil. Conclusions: The results imply that chemical composition of topsoil peat is not the reason for higher mineralisation rates compared to subsoil peat, but rather a consequence of decomposition and transformation. Thus, peat mineralisation of drained organic soils under agriculture might not slow down over time due to gradually decreasing peat quality but could increase further.

KW - bog

KW - fen

KW - fibre analysis

KW - mineralisation

KW - NMR

KW - peat

KW - radiocarbon age

UR - http://www.scopus.com/inward/record.url?scp=85111103323&partnerID=8YFLogxK

U2 - 10.1002/jpln.202000475

DO - 10.1002/jpln.202000475

M3 - Article

AN - SCOPUS:85111103323

VL - 184

SP - 543

EP - 555

JO - Journal of Plant Nutrition and Soil Science

JF - Journal of Plant Nutrition and Soil Science

SN - 1436-8730

IS - 5

ER -