EGU2020-10528
https://doi.org/10.5194/egusphere-egu2020-10528
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Soil carbon dynamic after freezing/thawing and drying/wetting in a temperate forest soil: Dual labeling of 13C and 14C

Francisco Nájera1,2, Michaela Dippold3, Jens Boy4, Oscar Seguel2, Moritz Köster3,5, Svenja Stock3, Carolina Merino6,7,8, Yakov Kuzyakov9,10, and Francisco Matus7,8
Francisco Nájera et al.
  • 1Universidad La Frontera, Chemical Sciences and Natural Resources, Chile (francisco.matus@ufrontera.cl)
  • 2Facultad de Ciencias Agronómicas, Universidad de Chile, Chile.
  • 3Biogeochemistry of Agroecosystems, Department of Crop Science, Georg-August-Universität Göttingen, Germany.
  • 4Institute of Soil Science, Leibniz Universität Hannover, Germany
  • 5Instiute of Geography, University of Bern, Bern, Switzerland
  • 6Center of Plant, Soil Interaction and Natural Resources Biotechnology. Scientific and Technological Bioresource Nucleus (BIOREN), Universidad de la Frontera, Temuco, Chile.
  • 7Laboratory of Conservation and Dynamic of Volcanic Soils, Department of Chemical Sciences and Natural Resources, Universidad de La Frontera, Temuco, Chile
  • 8Network for Extreme Environmental Research (NEXER) Universidad de La Frontera, Temuco, Chile.
  • 9Soil Science of Temperate Ecosystems, Büsgen Institute, Georg-August-Universität Göttingen, Germany.
  • 10Agro-Technological Institute, RUDN University, 117198 Moscow, Russia

Temperate forests in Chile have experienced increasing temperatures and extreme climatic events, such as severe drought and short winters in unique Araucaria araucana forest in Nahuelbuta National Park. Therefore, it is relevant to understand the impact of drying and rewetting (D/R) or freezing and thawing (F/T) on SOM turnover in these ecosystems. Particularly important is the destabilization of soil organic matter (SOM) by microbial activity, which is highly heterogeneous and influenced by soil properties and water cycles. Drying and rewetting or F/T cycles accelerate particulate organic matter (POM) decomposition by aggregate disruption, thereby, decreasing carbon (C) availability for soil microorganism. We hypothesized that frequent D/R and F/T cycles release labile organic C locked away in the aggregates for microbial consumption. We assumed that a repeated number of D/R and F/T cycles enhance the preferential C utilization of fresh organic substrate. In the present study an incubation experiment was conducted for 27 days to assess the effect of F/T (-18 ºC to room temperature) and D/R (-500 kPa to 33 kPa, field capacity) cycles on labelled 14C glucose and 13C lignocellulose decomposition, soil aggregates size and POM fractions distributions. CO2 efluxes and priming effect (PE), i.e. the turnover acceleration or retardation of native C mineralization, C use efficiency (CUE) and C allocation in soil aggregate classes as POM-light, POM-occluded and heavy fractions were also determined. Labelled glucose was mainly allocated in macro (> 250 mm) and microaggregates (< 250 mm) as part of the POM-light fraction. In contrast, labelled lignocellulose was allocated in microaggregate in the POM-occluded and heavy fraction. CUE was similar amongst all treatments. The PE was negative in soil with and without cycles and it was much more pronounced (-125 mg C kg-1 soil) for F/T cycles than D/R (-50 mg C kg-1 soil) at the end of incubation. The C:N ratio of soil following mining theory is further discussed. We conclude that D/R cycles clearly retarded the native C mineralization by preferential use of labelled 13C-lignocellulose, while F/T cycles led to preferential use of 14C-glucose.

How to cite: Nájera, F., Dippold, M., Boy, J., Seguel, O., Köster, M., Stock, S., Merino, C., Kuzyakov, Y., and Matus, F.: Soil carbon dynamic after freezing/thawing and drying/wetting in a temperate forest soil: Dual labeling of 13C and 14C, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10528, https://doi.org/10.5194/egusphere-egu2020-10528, 2020

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