Global ecosystems are exhibiting the signature of imminent tipping points but the mechanisms are unknown. Satellite-datasets show forests are experiencing critical slowing down of parameters such as leaf area, biomass, and photosynthesis, wherein their autocorrelation and variance increases to a threshold after which collapse occurs. Structural overshoot could be a mechanism underlying critical slowing down and the subsequent tipping points. Structural overshoot is the anomalous increase in ecosystem biomass and leaf area that results from CO2-fertilization, which is followed by an anomalous mortality overshoot during droughts because the ecosystems have exceeded their carrying capacity, e.g. there were too many leaves to provide with water. Therefore, structural overshoot drives increasing variance and can mechanistically drive mortality events. We review the evidence in support of this hypothesis and propose mechanisms by which ecosystems are more or less susceptible to overshoot and tipping points.
The seminar by Prof. Nate McDowell will take place at S.Marta on 26/11/2024 in aula seminari DIEF (first floor) at 11AM.
For information please contact giovanni.forzieri(at)unifi.it
Bio
Nate Mc Dowell is a staff scientist at the Department of Energy’s Pacific Northwest National Laboratory. Trained initially as a tree physiologist, he applies theory, experiments, models, and observations to understand ecosystem responses to the Earth’s changing environment.
He is currently focused largely on scaling physiological theory and data globally to better understand current and future impacts and associated processes at large-scales.