Investigating Riparian Resilience to the Climate Crisis through a Critical Zone Lens

ABSTRACT

Riparia are important hydrological microrefugia in semi-arid environments, sustained by groundwater during drought. This dissertation adopts an ecohydrological perspective to investigate riparian resilience to the climate crisis. I use a process-based ecohydrological model that simulates water and forest responses to climate, and design a novel calibration method to incorporate field data in Sagehen Creek Experimental Watershed, Sierra Nevada, CA. Chapter 1 shows how subsurface lateral inputs buffer riparian water stress against drought, except during wet and warm snow droughts when they’re more adversely affected than upslope forests. Chapter 2 generalizes these results across subsurface variability to reveal complex interactions between shallow storage and drainage that influence the benefit of lateral inputs to riparian trees in response to changing precipitation and snowmelt. Chapter 3 extends these concepts of hillslope ecohydrology to forest management and implements innovative modeling techniques that allow the realistic simulation of forest density reduction on vegetation regrowth and water yield. I consider both upslope and riparian forest treatments in order to develop scaling relationships of treatment effects on water yield from tree to stand to hillslope to watershed. Overall, this dissertation demonstrates the conditions that create and maintain riparian hydrological microrefugia and their resilience to climate.

BIO

Louis Graup graduated from Temple University in Philadelphia, PA in 2016 with a Bachelor of Science in Applied Mathematics. His undergraduate research in mathematical modeling and his post-graduate job as a Quantitative Financial Analyst translate naturally to his dissertation work in ecohydrological modeling. His doctoral research at the Bren School has explored ecohydrological patterns and processes of forest water stress in the California Sierra Nevada. In his career, Louis hopes to raise awareness about riparian ecosystems and restoration using art and science communication.