EGU2020-3736
https://doi.org/10.5194/egusphere-egu2020-3736
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Modelling respiration pulses at rewetting as a stochastic process

Stefano Manzoni1,2, Arjun Chakrawal1,2, Thomas Fischer3, Amilcare Porporato4, and Giulia Vico5
Stefano Manzoni et al.
  • 1Stockholm University, Department of Physical Geography, Stockholm, Sweden (stefano.manzoni@natgeo.su.se)
  • 2Bolin Centre for Climate Research, Stockholm, Sweden
  • 3Central Analytical Laboratory, Brandenburg University of Technology, Cottbus, Germany
  • 4Department of Civil and environmental Engineering, Princeton University, Princeton, USA
  • 5Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden

Respiration pulses at rewetting are prominent features of soil responses to soil moisture fluctuations. These pulses are much larger compared to respiration rates under constant soil moisture, pointing to variations in water availability as drivers of the enhanced CO2 production. Moreover, the respiration pulses tend to be larger when soil moisture before rewetting is lower. Thus, both the pre-rainfall soil moisture and the variation in soil moisture control the size of the respiration pulse. While these patterns are known from empirical studies, models have struggled to capture the relations between rainfall statistical properties (frequency of occurrence and rain event depths) and the occurrence and size of respiration pulses, framing the scope of this contribution. Specifically, we ask – how are the statistical properties of respiration pulses related to rainfall statistics?

Because rainfall can be regarded as a stochastic process generating variations in soil moisture, also respiration pulses at rewetting can be modelled through a probabilistic model. Here we develop such a model based on the premises that rainfall can be described as a marked Poisson process, and that respiration pulses increase with increasing variations of soil moisture (i.e., larger pulses after larger rain events) and decreasing pre-rain soil moisture (i.e., larger pulses after a long dry period). This model provides analytical relations between the statistical properties of soil respiration (e.g., long-term mean and standard deviation) and those of rainfall, allowing to study in a probabilistic framework how respiration varies along existing climatic gradients or in response to climatic changes that affect rainfall statistics.

Results show that the long-term mean CO2 production during respiration pulses increases with increasing frequency and depth of rainfall events. However, the relative contribution of respiration pulses to the total microbial respiration decreases with rainfall frequency and depth. Similarly, also the variability of the size of respiration pulses, as measured by their standard deviation, decreases with increasing rainfall frequency and depth. As a consequence, climatic changes exacerbating rainfall intermittency – longer dry periods and more intense rain events – are predicted to increase both the relative contribution of respiration pulses to total microbial respiration and the variability of the pulse sizes.

How to cite: Manzoni, S., Chakrawal, A., Fischer, T., Porporato, A., and Vico, G.: Modelling respiration pulses at rewetting as a stochastic process, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3736, https://doi.org/10.5194/egusphere-egu2020-3736, 2020

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Presentation version 1 – uploaded on 29 Apr 2020
  • AC1: Display highlights, Stefano Manzoni, 29 Apr 2020

    Approach: novel perspective on heterotrophic respiration based on the theory of stochastic processes

    Advantage: analytical relations between statistical properties of respiration and statistical properties of rainfall, suitable approach for climate change scenarios

    Prediction: respiration pulses contribute more to total heterotrophic respiration under more intermittent rainfall

    Implications: processes associated with pulses will gain importance under climate change—e.g., nutrient mineralization can become de-coupled from plant uptake

    • CC1: Reply to AC1, Ana López Ballesteros, 06 May 2020

      Dear Stefano et al., congrats for your work! Just in case you want to have a look to some data acquired in Spanish semi-arid sites, where most of the soil CO2 effluxes happen after rainfall events. We also saw that only heterotrophic respiratory activity re-activated after rewetting while photosynthesis and autotrophic respiration were not affected by "normal" rainfall events (< 20mm). 

      López-Ballesteros, A., Serrano-Ortiz, P., Sánchez-Cañete, E. P., Oyonarte, C., Kowalski, A. S., Pérez-Priego, Ó., & Domingo, F. (2016). Enhancement of the net CO 2 release of a semiarid grassland in SE Spain by rain pulses. Journal of Geophysical Research: Biogeosciences, 121(1), 52–66. https://doi.org/10.1002/2015JG003091

      Vargas, R., Sánchez-Cañete P., E., Serrano-Ortiz, P., Curiel Yuste, J., Domingo, F., López-Ballesteros, A., & Oyonarte, C. (2018). Hot-Moments of Soil CO2 Efflux in a Water-Limited Grassland. Soil Systems, 2(3), 47. https://doi.org/10.3390/soilsystems2030047

       

      • AC2: Reply to CC1, Stefano Manzoni, 06 May 2020

        Thanks for your interest and for the references - they will be useful as we revise the manuscript in Biogeosciences!