High elevation forests in the Sierra Nevada face threats from climate change that could lead to ecological impacts and changes in carbon storage. Forests above 2000 m elevation are experiencing increasing tree mortality due to wildfire and insect outbreaks, and forest stand structure has changed over the last century with the death of large trees and more dense forests of smaller trees. Because high elevation forests are more limited by cold temperatures and short growing seasons, changes in forest structure may be driven by different processes than the lower elevation forests in the Sierra Nevada. Additionally, models built for a wider region may not perform as well at high elevations, where fine-scale topographic complexity and variable forest structure make spatial extrapolations from standard forest inventory processes difficult; these complex areas also have more limited data availability due to the remote locations. How forest structural changes influence carbon storage in high elevation forests is unknown, as are the drivers of change along elevational and latitudinal gradients.

I am addressing these research gaps using NASA satellite data in combination with aerial lidar and multiple sources of field measurements to train models specifically for high elevation forests. I am mapping current aboveground biomass in high elevation forests and also the change in biomass over 35 years and in response to disturbance events. I am analyzing the drivers of change in high elevation forests and how they interact in different topographic and spatial settings. I expect to reveal the spatial distribution of aboveground biomass along with the nature of threats, forming a foundation for predicting future change.

Project Webpage

https://swinsem.github.io/research.html