TY - JOUR

T1 - Effects of drying/rewetting on soil aggregate dynamics and implications for organic matter turnover

AU - Najera, Francisco

AU - Dippold, Michaela A.

AU - Boy, Jens

AU - Seguel, Oscar

AU - Koester, Moritz

AU - Stock, Svenja

AU - Merino, Carolina

AU - Kuzyakov, Yakov

AU - Matus, Francisco

N1 - Funding information: This research was supported by the German Science Foundation (DFG) priority research program SPP-1803 “Earthshape: Earth Surface Shaping by Biota” (Project Root Carbon KU 1184/36-1), the scholarship program from Leibniz University Hannover IP@Leibniz for a research stay in Leibniz and the national doctoral scholarship CONICYT No. 21160957 of the Chilean government. This study was funded in part by the National Commission of Research of Science and Technology FONDECYT (grant No. 1170119) and by the Network for Extreme Environmental Research (NEXER), Universidad de La Frontera. Acknowledgements We are grateful to the Chilean National Park Service (CONAF) for providing access to the sample locations. We are indebted to the Laboratory of Conservation and Dynamics of Volcanic Soil, BIOREN-UFRO, and the Network of Extreme Environments NEXER project from Universidad de La Frontera-Chile. Many thanks go to the team of the Stable Isotope Center (KOSI) of G?ttingen University. We acknowledge Leibniz University Hannover and Georg-August University Gottingen, Germany, for hosting our research. We thank the reviewers for providing helpful comments on the early version of this manuscript. The publication was supported by the ?RUDN University program 5-100.?

PY - 2020/10

Y1 - 2020/10

N2 - Drying and rewetting (D/W) of soil have significant impacts on soil organic matter (SOM) turnover. We hypothesised that frequent D/W cycles would release the labile organic matter locked away in soil aggregates, increasing the priming effect (PE) (acceleration or retardation of SOM turnover after fresh substrate addition) due to preferential utilisation by microbes. 13C-labelled lignocellulose was added to the soil, and the effects of 0, 1, or 4 cycles of D/W were evaluated at 5 °C and 25 °C after a 27-day incubation of undisturbed soil cores from a temperate forest (Araucaria araucana). Following the incubation, macroaggregates (' 250 μm), microaggregates (250–53 μm), and silt + clay materials (' 53 μm) were separated. For each aggregate size class, three organic matter (OM) fractions (light (fPOM ' 1.6 g cm−3), occluded (oPOM 1.6–2.0 g cm−3), and heavy (Hf ' 2.0 g cm−3) were determined. D/W cycles caused macroaggregates to increase and a decrease in microaggregates (' 15%) at warm temperatures, and preferential use of the novel particulate organic matter (13C labelled), formerly protected fPOM. CO2 efflux was three times higher at 25 °C than at 5 °C. The D/W cycles at 25 °C had a strong negative impact on cumulative CO2 efflux, which decreased by approximately − 30%, induced by a negative PE of −50 mg C kg−1 soil with 1 D/W cycle and − 100 mg C kg−1 soil with 4 D/W cycles, relative to soil under constant soil moisture receiving 13C-labelled lignocellulose, but no cycles. Increasing the temperature and the number of D/W cycles caused a decrease in substrate use efficiency of particulate lignocellulose. In conclusion, D/W cycles at warm temperatures accelerated OM turnover due to preferential use from fPOM, increasing macroaggregates at the expense of microaggregates. A novel pathway of OM release and PE due to the D/W cycles is discussed.

AB - Drying and rewetting (D/W) of soil have significant impacts on soil organic matter (SOM) turnover. We hypothesised that frequent D/W cycles would release the labile organic matter locked away in soil aggregates, increasing the priming effect (PE) (acceleration or retardation of SOM turnover after fresh substrate addition) due to preferential utilisation by microbes. 13C-labelled lignocellulose was added to the soil, and the effects of 0, 1, or 4 cycles of D/W were evaluated at 5 °C and 25 °C after a 27-day incubation of undisturbed soil cores from a temperate forest (Araucaria araucana). Following the incubation, macroaggregates (' 250 μm), microaggregates (250–53 μm), and silt + clay materials (' 53 μm) were separated. For each aggregate size class, three organic matter (OM) fractions (light (fPOM ' 1.6 g cm−3), occluded (oPOM 1.6–2.0 g cm−3), and heavy (Hf ' 2.0 g cm−3) were determined. D/W cycles caused macroaggregates to increase and a decrease in microaggregates (' 15%) at warm temperatures, and preferential use of the novel particulate organic matter (13C labelled), formerly protected fPOM. CO2 efflux was three times higher at 25 °C than at 5 °C. The D/W cycles at 25 °C had a strong negative impact on cumulative CO2 efflux, which decreased by approximately − 30%, induced by a negative PE of −50 mg C kg−1 soil with 1 D/W cycle and − 100 mg C kg−1 soil with 4 D/W cycles, relative to soil under constant soil moisture receiving 13C-labelled lignocellulose, but no cycles. Increasing the temperature and the number of D/W cycles caused a decrease in substrate use efficiency of particulate lignocellulose. In conclusion, D/W cycles at warm temperatures accelerated OM turnover due to preferential use from fPOM, increasing macroaggregates at the expense of microaggregates. A novel pathway of OM release and PE due to the D/W cycles is discussed.

KW - Aggregate stability

KW - Carbon turnover

KW - Drying and rewetting cycles

KW - Particulate soil organic matter

KW - Soil priming effect

UR - http://www.scopus.com/inward/record.url?scp=85084435897&partnerID=8YFLogxK

U2 - 10.1007/s00374-020-01469-6

DO - 10.1007/s00374-020-01469-6

M3 - Article

AN - SCOPUS:85084435897

VL - 56

SP - 893

EP - 905

JO - Biology and Fertility of Soils

JF - Biology and Fertility of Soils

SN - 0178-2762

IS - 7

ER -