Using diverse lidar scans to examine the effects of disturbance on forest structural complexity metrics in a northern California mixed hardwood forest

Student: Randi Carter

Faculty Mentor: Lisa Bentley

Biology

College of Science, Technology, and Business

Quantifying changes to forest structure after disturbances is integral to assessing forest health, evaluating the efficacy of management prescriptions, and predicting future changes following subsequent disturbances. Often, forest structure is characterized via understory vegetation structural complexity (VSC) metrics. Over the past decade, active remote sensing methods, such as LiDAR, have facilitated the accessibility of accurate fine-scale VSC measurements. Due to the increased frequency of disturbance driven by climate change (i.e., wildfire, drought), changes to forest structure post-disturbance are well researched, but it is less clear how structure changes with repeated disturbances. As such, my goal was to quantify changes in VSC metrics in the forest understory following multiple disturbances at two sites in northern California mixed hardwood forests using LiDAR data at different spatial scales. At both sites, similar trends and proportional increases in forest structure heterogeneity were observed with terrestrial and airborne LiDAR data. These results imply that, in general, thinning (via wildfire or prescriptions) does increase complexity in the understory in oak-woodland ecosystems, with regular thinning or fire needed to reach management goals of reducing understory fuel loads. Nevertheless, specific thinning treatments might not consistently change structural complexity in certain oak-woodland forest stands; perhaps vegetation alliance mediates responses to disturbance. Additionally, my results indicate that VSC metrics can be applied across multiple spatial scales, with considerations made for point density and occlusion. This research is crucial to inform effective management strategies and deepen our understanding of forest dynamics following disturbance.