Talk Title: Empirical Constraints on the Long-Term Dynamics of Terrestrial Ecosystems

Changes in vegetation over decades to centuries are among the largest uncertainties in our understanding of the response of terrestrial ecosystems to environmental forcing. Slow processes, such as changing plant demographic rates or evolutionary changes in plant traits, can set the pace of ecosystem change, but we usually don't have data to constrain them. I will present two cases where our team has empirically constrained such processes with surprising results. First, we found that the population dynamics of individual tree species had a disproportionate impact on the trajectory of aboveground biomass in the Midwest over the last 10,000 years. Second, we found that evolutionary changes over the last century in the traits of a coastal sedge were large enough to influence the resilience of salt marshes to rising sea-levels. In two different systems, we found that biological details currently missing from most predictive models played important roles in pacing long-term ecosystem dynamics.

About the Presenter:

Jason McLachlan is an associate professor in Notre Dame’s Department of Biological Sciences. His research aims to improve understanding of vegetation response to environmental change over long time periods with the goal of improving predictive forecasts of the biosphere. He is the lead of the PalEocological Observatory Network (PalEON) and he chairs the education section of the Ecological Forecasting Initiative, working to improve diversity and inclusion in ecological forecasting (and data science, more generally).