October 24, 2017 4:00PM - 5:00PM
Jane Foster from the University of Vermont presents "Landsat time series predict wood growth from tree-rings using departures in mean phenology."
The terrestrial carbon cycle is perturbed when disturbances remove leaves from the forest canopy. Yet the significance of episodic defoliation to models that predict forest growth remains unknown. In this talk, I will describe research in which we use new cloud computing tools to quantify the effect of canopy defoliation on forest growth. Our approach uses dense Landsat time-series to quantify departures in mean phenology that in turn predict changes in leaf biomass. We reconstruct a foliar biomass index (FBMI) from 1984-2016, and predict plot-level wood growth over 28 years on 156 tree-ring monitoring plots in Minnesota, USA. Our analysis accesses the entire Landsat archive using Google Earth Engine, which allows this pixel-level approach to be applied at any location; a feature we demonstrate with published wood-growth data from distant flux tower sites. We are finding that Landsat FBMI is a remarkably strong predictor of aggregate wood-growth, explaining up to 80% of annual growth variation for some deciduous plots. Insights emerging from these models can clear up sources of persistent uncertainty and open a new frontier for models of forest productivity.
Natural Resources Building, Room 225Get Directions