TY - JOUR

T1 - Tracing organic carbon and microbial community structure in mineralogically different soils exposed to redox fluctuations

AU - Winkler, Pauline

AU - Kaiser, Klaus

AU - Jahn, Reinhold

AU - Mikutta, Robert

AU - Fiedler, Sabine

AU - Cerli, Chiara

AU - Kölbl, Angelika

AU - Schulz, Stefanie

AU - Jankowska, Martha

AU - Schloter, Michael

AU - Müller-Niggemann, Cornelia

AU - Schwark, Lorenz

AU - Woche, Susanne K.

AU - Kümmel, Steffen

AU - Utami, Sri R.

AU - Kalbitz, Karsten

N1 - Funding information: The study was funded by Deutsche Forschungsgemeinschaft—DFG within the research unit FOR995 Biogeochemistry of Paddy Soil Evolution (Grants FI 803/8-1; JA 523/16-1; KA 1737/10-1; SCHL 446/7-1; SCHW 554/20-1,2; KO 1035/35-1,2) initiated by Ingrid Kögel-Knabner. The authors declare that there are no conflicts of interest. We gratefully acknowledge the support of Jorin Schoorl, Susanne Horka, Alexandra Boritzki, Christine Krenkewitz, Gudrun von Koch, Simal Dhimal, Heike Maennicke, Marianne Benesch, Bruno Glaser, Gisle Vestergaard, Gabi Albert, and Madina Burkitbayeva during laboratory work and data analyses.

PY - 2019/3/15

Y1 - 2019/3/15

N2 - Submerged rice cultivation is characterized by redox fluctuations and results in the formation of paddy soils, often accompanied by soil organic carbon (SOC) accumulation. The impact of redox fluctuations and the underlying soil type on the fate of organic carbon (OC) in paddy soils are unknown. Hence, we mimicked paddy soil development in the laboratory by exposing two soil types with contrasting mineral assemblages (Alisol and Andosol) to eight anoxic–oxic cycles over 1 year. Soils regularly received 13 C-labeled rice straw. As control we used a second set of samples without straw addition as well as samples under static oxic conditions with and without straw. Headspaces were analyzed for carbon dioxide and methane as well as their δ 13 C signatures, whereas soil solutions were analyzed for redox potential, pH, dissolved iron, and dissolved organic carbon (DOC and DO 13 C). At the end of the experiment, when eight redox cycles were completed, mineral-associated organic matter (MOM) was isolated by density fractionation and characterized for δ 13 C, non-cellulosic carbohydrates, and lignin-derived phenols. Moreover, changes in the soil’s microbial community structure were measured. For both soil types, headspace data confirmed less respiration in straw-amended soils with redox fluctuation than in those under static oxic conditions. The δ 13 C data revealed that, irrespective of soil type, straw carbon allocation into MOM was larger in soils with redox fluctuation than in those with static oxic conditions. A net increase in MOM after the one-year incubation, however, was only observed in the respective Andosol, probably due to abundant reactive minerals capable of OC uptake. In the Alisol, straw OC most likely exchanged initial MOM. A potential for lignin accumulation in the MOM of soils incubated with straw and redox fluctuation was observed for both soil types. Lignin and carbohydrates suggest a plant origin of MOM formed under redox fluctuation. The initially similar bacterial community composition of the Alisol and Andosol changed differently under redox fluctuation. The stronger change in the Alisol indicates less protective microbial habitats. In summary, the overall turnover of straw OC in soils under redox fluctuation seems to be independent of soil type, while net accumulation of SOC as well as the evolution of the bacterial community structure may in part depend on soil type, suggesting an impact of the soil’s mineral composition.

AB - Submerged rice cultivation is characterized by redox fluctuations and results in the formation of paddy soils, often accompanied by soil organic carbon (SOC) accumulation. The impact of redox fluctuations and the underlying soil type on the fate of organic carbon (OC) in paddy soils are unknown. Hence, we mimicked paddy soil development in the laboratory by exposing two soil types with contrasting mineral assemblages (Alisol and Andosol) to eight anoxic–oxic cycles over 1 year. Soils regularly received 13 C-labeled rice straw. As control we used a second set of samples without straw addition as well as samples under static oxic conditions with and without straw. Headspaces were analyzed for carbon dioxide and methane as well as their δ 13 C signatures, whereas soil solutions were analyzed for redox potential, pH, dissolved iron, and dissolved organic carbon (DOC and DO 13 C). At the end of the experiment, when eight redox cycles were completed, mineral-associated organic matter (MOM) was isolated by density fractionation and characterized for δ 13 C, non-cellulosic carbohydrates, and lignin-derived phenols. Moreover, changes in the soil’s microbial community structure were measured. For both soil types, headspace data confirmed less respiration in straw-amended soils with redox fluctuation than in those under static oxic conditions. The δ 13 C data revealed that, irrespective of soil type, straw carbon allocation into MOM was larger in soils with redox fluctuation than in those with static oxic conditions. A net increase in MOM after the one-year incubation, however, was only observed in the respective Andosol, probably due to abundant reactive minerals capable of OC uptake. In the Alisol, straw OC most likely exchanged initial MOM. A potential for lignin accumulation in the MOM of soils incubated with straw and redox fluctuation was observed for both soil types. Lignin and carbohydrates suggest a plant origin of MOM formed under redox fluctuation. The initially similar bacterial community composition of the Alisol and Andosol changed differently under redox fluctuation. The stronger change in the Alisol indicates less protective microbial habitats. In summary, the overall turnover of straw OC in soils under redox fluctuation seems to be independent of soil type, while net accumulation of SOC as well as the evolution of the bacterial community structure may in part depend on soil type, suggesting an impact of the soil’s mineral composition.

KW - Microbial community

KW - Mineral-associated organic matter

KW - Mineralization

KW - Paddy soils

KW - Redox fluctuation

KW - Soil organic matter formation

UR - http://www.scopus.com/inward/record.url?scp=85061336465&partnerID=8YFLogxK

U2 - 10.1007/s10533-019-00548-7

DO - 10.1007/s10533-019-00548-7

M3 - Article

AN - SCOPUS:85061336465

VL - 143

SP - 31

EP - 54

JO - Biogeochemistry

JF - Biogeochemistry

SN - 0168-2563

IS - 1

ER -