Effects of drying/rewetting on soil aggregate dynamics and implications for organic matter turnover
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ORIGINAL PAPER
Effects of drying/rewetting on soil aggregate dynamics and implications for organic matter turnover Francisco Najera 1,2 & Michaela A. Dippold 3 & Jens Boy 4 & Oscar Seguel 2 & Moritz Koester 3 & Svenja Stock 3 & Carolina Merino 5,6,7 & Yakov Kuzyakov 8,9 & Francisco Matus 6,7 Received: 3 June 2019 / Revised: 17 April 2020 / Accepted: 24 April 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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. 13Clabelled 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. Keywords Soil priming effect . Particulate soil organic matter . Drying and rewetting cycles . Aggregate stability . Carbon turnover
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00374-020-01469-6) contains supplementary material, which is available to authorized users. * Francisco Matus [email protected] 1
Doctorado en Ciencias de Recursos Naturales, Facultad de Ciencias Químicas y Recursos Naturales, Universidad de La Frontera, Temuco, Chile
2
Facultad de Ciencias Agronómicas, Universidad de Chile, Santiago, Chile
3
Biogeochemistry of Agroecosystems, Department of Crop Science, Georg-August Göttingen Universität, Gottingen, Germany
4
Institute of Soil Science, Leibniz Universität Ha
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