Project
Carbon cycling in the terrestrial biosphere
The terrestrial biosphere exchanges more carbon with the atmosphere than any other part of the Earth System. This exchange is highly variable from minute-to-minute, month-to-month, year-to-year, and even decade-to-decade. We study the processes that control the build-up and release of carbon in forests all over the world, from Tropical primary forests to newly forming shrubs in northern Tundra’s. Driven by observations from the ground (forestry surveys), the air (atmospheric tall towers, see Figure), and from space (biomass amounts and greenness), we develop the biogeochemical model SiB4 to simulate decades of hourly photosynthesis and respiration. SiB4 is used to answer burning questions on the global forest response to ongoing warming, to more frequent heat waves, and to extreme droughts and CO2 fertilization. The Theme is co-led by Wouter Peters and Ingrid Luijkx, and includes the following activities:
Forest managers have long used biomass surveys to monitor the growth and removal of trees (biomass) on their lands. Such surveys feed national forest statistics and carbon bookkeeping models. We try to integrate this long-term development of forest carbon stocks, with short-term carbon exchange captured by SiB4. Their combination should give an optimal state-of-the-carbon-cycle for forests, to be compared to atmospheric observations that record the sources and sinks. PhD student Marnix van de Sande leads this project, in collaboration with Profs Pieter Zuidema and Gert-Jan Nabuurs.
Extreme events in the carbon cycle occur every year, whether it is from European droughts (2022), Canadian wildfires (2023), or El Niño impacts on the Amazon (2023/2024). We try to quickly diagnose such events and their impacts, as they present an ideal opportunity to test our knowledge and skills as represented in our models. Through the high-resolution CarbonTracker system (CTE-HR) Dr. Auke van der Woude contributes 0.1x0.1 degree global biosphere simulations with SiB4 to the low latency carbon team every 3 months.
In a closely linked activity, PhD student Ruben van ‘t Loo makes actual carbon cycle forecasts using ECMWF seasonal ensemble forecasts and SiB4. The aim is to test the seasonal dynamics of our model not in reanalyses, but in near-future events. This encapsulates the uncertainty in both the environmental drivers (weather) and response (vegetation). This combination is needed to improve land-surface interactions of climate models, and could also provide actionable information to forest- and water- managers.
Arctic cycling of CO2, CH4, and N2O is rapidly changing. Next to increasing greenness, there is also permafrost thaw, wildfires, and increased human influence on what used to be a pristine and icy landscape. PhD student Sebastiaan de Haas studies this area specifically, employing machine-learning, data assimilation, and moisture tracking techniques to integrate multiple sources of information. This work is part of EMBRACER, an NWO funded project with a large Dutch consortium that investigates Earth system feedbacks on timescales from decades to millennia. Dr Imme Benedict is a co-investigator on this project.