In the Theoretical Ecosystem Ecology group of the Max Planck Institute for Biogeochemistry, we study interactions and feedbacks between the carbon cycle and the climate system. We develop theoretical concepts and numerical software, and collect diverse data from ecosystems, to understand how climate affects metabolic rates in ecosystems and how changes in these metabolic rates affect the climate system.

Research themes

Timescales of carbon and element cycling in the terrestrial biosphere

We have made relevant contributions to the undesrtanding of the timescales at which carbon is cycled in natural systems. Our group developed mathematical and computational methods to obtain the age and the transit time of elements in mass balanced systems (compartmental systems) (Sierra et al., 2017; Metzler & Sierra, 2018; Metzler et al., 2018). We have applied these methods to study for how long can trees survive without new photosynthetic inputs (Herrera-Ramírez et al., 2020); to determine the age of soil carbon and the time that new carbon remains stored as soil organic matter (Sierra et al., 2018; Xiao et al., 2022; Sierra et al., 2024; Wang et al., 2024); to determine the time it takes for carbon to transit through a tropical rain forest (Sierra et al., 2021); and how the transit time of carbon for the entire terrestrial biosphere has changed during the industrial period (Sierra et al., 2023).

We are currently using measurements of radiocarbon in carbon dioxide to determine the transit time of carbon in ecosystems, and to compare these measurements with ecosystem models.

Control of the carbon-climate system and carbon cycle management

Our gains in conceptual understanding of carbon-climate interactions has allowed us to explore new concepts and methods to manage the carbon cycle for the purpose of climate change mitigation. We proposed a new definition of Carbon Sequestration (CS) to better quantify for how long carbon that is kept out of the atmosphere helps to mitigate climate change (Sierra et al., 2021; Crow & Sierra, 2022). We also develope a new concept called the Climate Benefit of Sequestration (CBS) that allow us to quantify how much warming is avoided when carbon is stored inside an ecosystem (Sierra et al., 2021).

We also proposed ideas about how to effectively control the carbon-climate system using knowledge on the rates at which carbon is transferred among different reservoirs within the Earth system such as the biosphere, the atmosphere and the oceans (Sierra et al., 2021). We believe that it is possible to express the problem of carbon cycle management as a congestion problem of networks, in which we assume that fossil fuel carbon is accumulating in the atmosphere because it cannot be processed fast enough by the land and the oceans.

Current Projects

Measurement and global interpretation of greenhouse gases at the ATTO tower in the Amazon rain forest

This is a collaborative project with the MPI for Chemistry in Mainz and multiple Brazilian investigators around the Amazon Tall Tower Observatory ATTO. We are contributing to this project with the collection of atmospheric flask samples for analyses of greenhouse gases and ¹⁴CO₂. We also collect data and calculating the age structure of carbon stocks and fluxes in a central Amazon forest.

Hawaiʻi Partnership for Climate-Smart Commodities

The main aim of this project is to develop equitable practices, data systems, and decision support tools to promote and actuate meaningful climate benefits in agroecosystems guided by Hawaiʻi-based producers and ancestral practitioners. The project is led by Prof. Susan Crow from the University of Hawai'i.

Utilizing ¹⁴C technology to decipher the sources of methane in wetlands and their response to global change

This project aims to investigate methane production pathways and regulatory mechanisms by employing techniques such as ¹³C and ¹⁴C analyses of methane and biomarkers of methanogens and methanotrophs. The project takes place in wetlands of the Zoige region in the Tibetan Plateau. The project is a collaboration with Prof. Xiaojuan Feng of the Institute of Botany, Chinese Academy of Sciences.

Drought Impact on the Climate Benefit of Carbon Sequestration

This project, led by Estefania Muñoz, aims at improving the understanding of the role of soil moisture on the amount of carbon stored in ecosystems and the time this carbon remains stored. The project is based at CREAF in Spain.

Previous Projects

Stochastic understanding of ecosystem productivity under elevated CO₂ and changes in rainfall regimes

In the project, we use models and observations to address the question: does a stochastic treatment of rainfall and atmospheric CO₂ concentration lead to different predictions of CO₂ fertilization effects in ecosystems compared to strictly deterministic approaches?

Nonlinearities and Alternative States of Biogeochemical cycling in terrestrial ecosystems

In this project we attempt to better link mathematical models of biogeochemical cycling with a theoretical framework of ecosystem function; in particular, a theory that encompasses the prediction of the residence time of biogeochemical elements in terrestrial ecosystems and possible alternative states of biogeochemical cycling.

Geo-ecosystems in transition on the Tibetan Plateau (TransTiP)

TransTiP is a Sino-German Reserach Training Group that studies ecosystems in transition in the Tibetaen Plateu. Our group participates in this project developing models of carbon fluxes in permafrost soils.

An Ecological Observatory System for Colombia: a prototype for monitoring changes in biodiversity and ecosystem function

The objective of this project is to develop a research plan to promote and design the implementation of an Ecological Observatory System that monitors changes in ecosystem and climate in Colombia.

National carbon stocks of mangroves in Colombia: capacity building for their inclusion in climate change mitigation strategies

In this project we are developing a model for the estimation of carbon stocks in Colombian mangroves, and will explore policy mechanisms to include these ecosystems in the climate change mitigation strategy of Colombia.

References

1. Sierra, C. A., Ahrens, B., Bolinder, M. A., Braakhekke, M. C., von Fromm, S., Kätterer, T., Luo, Z., Parvin, N., & Wang, G. (2024). Carbon sequestration in the subsoil and the time required to stabilize carbon for climate change mitigation. Global Change Biology, 30(1), e17153. https://doi.org/https://doi.org/10.1111/gcb.17153
2. Wang, G., Wang, M., Xiao, L., Sierra, C. A., Chang, J., Shi, Z., & Luo, Z. (2024). Fast Transit of Carbon Inputs in Global Soil Profiles Regardless of Entering Depth. Earth’s Future, 12(2), e2023EF003982. https://doi.org/10.1029/2023EF003982
3. Sierra, C. A., Quetin, G. R., Metzler, H., & Müller, M. (2023). A decrease in the age of respired carbon from the terrestrial biosphere and increase in the asymmetry of its distribution. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 381(2261), 20220200. https://doi.org/10.1098/rsta.2022.0200
4. Crow, S. E., & Sierra, C. A. (2022). The climate benefit of sequestration in soils for warming mitigation. Biogeochemistry, 161, 71–84. https://doi.org/10.1007/s10533-022-00981-1
5. Xiao, L., Wang, G., Wang, M., Zhang, S., Sierra, C. A., Guo, X., Chang, J., Shi, Z., & Luo, Z. (2022). Younger carbon dominates global soil carbon efflux. Global Change Biology, 28(18), 5587–5599. https://doi.org/https://doi.org/10.1111/gcb.16311
6. Sierra, C. A., Metzler, H., Müller, M., & Kaiser, E. (2021). Closed-loop and congestion control of the global carbon-climate system. Climatic Change, 165(1), 15. https://doi.org/10.1007/s10584-021-03040-0
7. Sierra, C. A., Crow, S. E., Heimann, M., Metzler, H., & Schulze, E.-D. (2021). The climate benefit of carbon sequestration. Biogeosciences, 18(3), 1029–1048. https://doi.org/10.5194/bg-18-1029-2021
8. Sierra, C. A., Estupinan-Suarez, L. M., & Chanca, I. (2021). The fate and transit time of carbon in a tropical forest. Journal of Ecology, 109(8), 2845–2855. https://doi.org/10.1111/1365-2745.13723
9. Sierra, C. A., Estupinan-Suarez, L. M., & Chanca, I. (2021). The fate and transit time of carbon in a tropical forest. Journal of Ecology, 00(n/a), 11. https://doi.org/https://doi.org/10.1111/1365-2745.13723
10. Herrera-Ramírez, D., Muhr, J., Hartmann, H., Römermann, C., Trumbore, S., & Sierra, C. A. (2020). Probability distributions of nonstructural carbon ages and transit times provide insights into carbon allocation dynamics of mature trees. New Phytologist, 226(5), 1299–1311. https://doi.org/10.1111/nph.16461
11. Metzler, H., Müller, M., & Sierra, C. A. (2018). Transit-time and age distributions for nonlinear time-dependent compartmental systems. Proceedings of the National Academy of Sciences, 115(6), 1150–1155. https://doi.org/10.1073/pnas.1705296115
12. Metzler, H., & Sierra, C. A. (2018). Linear Autonomous Compartmental Models as Continuous-Time Markov Chains: Transit-Time and Age Distributions. Mathematical Geosciences, 50(1), 1–34. https://doi.org/10.1007/s11004-017-9690-1
13. Sierra, C. A., Hoyt, A. M., He, Y., & Trumbore, S. E. (2018). Soil Organic Matter Persistence as a Stochastic Process: Age and Transit Time Distributions of Carbon in Soils. Global Biogeochemical Cycles, 32(10), 1574–1588. https://doi.org/10.1029/2018GB005950
14. Sierra, C. A., Müller, M., Metzler, H., Manzoni, S., & Trumbore, S. E. (2017). The muddle of ages, turnover, transit, and residence times in the carbon cycle. Global Change Biology, 23(5), 1763–1773. https://doi.org/10.1111/gcb.13556