Modeling the Interconnected Effects of Fuel Treatments on Forests, Water, and Fire

This defense will be presented in person at Bren. Join us in Bren Hall 3526 (Pine Room) or watch online using this link and passcode fire

ABSTRACT

Fuel treatments, the reduction of forest biomass through mechanical removal or burning, are a flexible forest management tool used to address a variety of human and environmental concerns. Treatments can be used to reduce high severity fire, improve forest productivity and drought resilience, and increase streamflow. However, the effects of fuel treatments can be inconsistent and uncertain and are sensitive to both the treatment and the biophysical environment in which the treatment is done, and these uncertainties may be exacerbated by climate change. Climate change is already increasing wildfire size and frequency, drought, and strain on water supply in much of the Western US. Given that fuel treatments are likely to play a key role in current and future forest management, it is critical that we understand the full range of fuel treatment interactions with climate and effects on forests, water, and fire. Existing ecohydrologic models are limited in their ability to model fuel treatment effects because they do not account for both the within forest stand ecohydrologic effects of changes in forest structure and the watershed scale variation in radiation, water availability, and other factors. The ability to simulate heterogenous vegetation at fine scales is key to implementing fuel treatments like forest thinning. To address this lack I adapted the Regional Hydro-Ecological Simulation System (RHESSYs) to include a new multiscale routing (MSR) approach, RHESSys-MSR. In addition to allowing modeling of within forest stand heterogeneity, MSR enables an additional layer of hydrologic routing, on top of existing topographic hillslope routing. The first chapter of this thesis describes the implementation of RHESSys-MSR and the second two apply this model to investigate fuel treatment effects in a changing climate. In the first application of these methods, I simulate a large set (13,500) of model scenarios varying treatment type, biophysical and climatic conditions for a Central California Sierra forest stand. Results show that plant accessible water storage capacity and vegetation type are dominant environmental controls on the effects of fuel treatments. More broadly I find that estimating the effect of fuel treatments based on only a single biophysical variable fails to capture the extent of possible treatment effects. In the second application, I investigate the interactions between projected climate change and fuel treatment area on the effects of treatments on forest health, fire risk, and streamflow at the watershed scale. Results show that projected climate change has a nontrivial influence on net treatment effects, even compared to a maximized area treated. Fuel treatments and their effects are complex, spanning the environmental domains of forests, water, fire, and climate. Treatments are further complicated by the wide variety in the treatment itself, varying in how forest structure is affected, where it’s implemented, and how often. Model applications like RHESSys-MSR are critical to reducing this uncertainty and developing place-based estimates of fuel treatment effects that can support forest managers. The persistent challenges in understanding fuel treatments and their effects make any progress all the more essential, and as this research and more contributes to this understanding, we can make better and more informed forest management decisions into the future.

BIO

William is a graduate of Santa Clara University (BS Environmental Science, 2013) and Indiana University (MS Geography, 2016). William’s research interests are centered around ecohydrologic modeling but extend to fire, forest management, and climate change. As a part of the interdisciplinary SERI-Fire team he was able to contribute to the broader research into managing wildfire under a changing climate, and the overarching research which incorporated both the biophysical and human aspects of wildfire management. William has contributed to development of the RHESSys model and built an interest in developing modeling methods and building tools to improve how we pursue ecohydrologic modeling. His research is an extension of these interests, and focuses on modeling the effects of fuel treatments, and improving our understanding of those effects across varied biophysical and climatic conditions. William will continue to pursue research modeling the effects of fuel treatments and fire in a postdoctoral position at the University of Nevada, Reno.