Universiteit Leiden

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This Week’s Discoveries | 17 december 2019

dinsdag 17 december 2019
Niels Bohrweg 2
2333 CA Leiden
De Sitterzaal

First lecture

Global mycorrhizal plant distribution linked to terrestrial carbon stocks

Nadia Soudzilovskaia (CML)
Nadia is an Assistant Professor in Stress Ecology at the Environmental Biology Department of CML.
Nadia works at the intersection of ecology and environmental sciences. Her research aims to obtain a quantitative, process-based understanding of plant-soil interaction dynamics along natural and human-induced gradients of environmental stresses, in order to unravel mechanisms enabling provisioning of soil-related ecosystem services at regional and global scale.

Vegetation impacts on ecosystem functioning are mediated by mycorrhizas, plant-fungal associations formed by most plant species. Ecosystems dominated by distinct mycorrhizal types differ strongly in their biogeochemistry. Quantitative analyses of mycorrhizal impacts on ecosystem functioning are hindered by the scarcity of information on mycorrhizal distributions. I will present first global, high-resolution maps of the distribution of mycorrhizal types, and show that human-induced transformations of Earth’s ecosystems have reduced ectomycorrhizal vegetation, with potential ramifications to terrestrial carbon stocks. Arbuscular, ectomycorrhizal, and ericoid mycorrhizal vegetation store, respectively, 241±15, 100±17, and 7±1.8 GT carbon in aboveground biomass, and the impacts of CO2 fertilization on vegetation are constrained by soil nitrogen or phosphorus availability, with N-or P-limitation modulated by the type of mycorrhizal association. Soil carbon stocks in both topsoil and subsoil are positively related to the community-level biomass fraction of ectomycorrhizal plants, though the strength of this relationship varies across biomes. This work provides a benchmark for spatially explicit and globally quantitative assessments of mycorrhizal impacts on ecosystem functioning and biogeochemical cycling.

Second lecture

Lorentz, Millikan and postwar reconciliation

Dirk van Delft (LION)
Dirk van Delft is a guest researcher at the Lorentz-Instituut of LION and special professor (emeritus) in the history of science at Leiden University. He just published an extensive biography of H.A. Lorentz, in collaboration with Frits Berends.

Hendrik Lorentz (1853-1928) and Robert Millikan (1868-1953) were outstanding physicists: they both won the Nobel Prize. After a short overview of Lorentz’ career, the presentation will focus on his contacts with Millikan in the 1920s. After World War I, Lorentz and Millikan tried hard to pour oil on the troubled waters, partly in their capacity as members of the International Committee on Intellectual Cooperation (ICIC) of the League of Nations – the direct precursor of present-day UNESCO

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