Effect of Vegetation Structure on Evapotranspiration and the Prediction of Evapotranspiration
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Authors
Sandquist, Abigail
Issue Date
2025
Type
Dissertation
Language
en_US
Keywords
canopy storage , evapotranspiration , fire , rainfall interception , shrublands
Alternative Title
Abstract
Understanding how vegetation structure controls evapotranspiration is important for predicting how changing climate conditions may influence hydrologic balances in different ecosystems. However, evaluating this topic across diverse ecosystems is often made difficult by the observational challenges associated with great spatiotemporal variability. The work in this dissertation utilizes unique network- and manually-collected ground-based field datasets and remotely sensed data at different spatial and temporal scales to evaluate how varying vegetation structures interact with components of evapotranspiration (ET). The components of ET studied here include canopy rainfall interception loss and storage across diverse forested ecosystems, and transpiration and soil evaporation in semi-arid shrublands. For interception loss, using data from 2073 storms across 22 forested sites, we found storm gross-precipitation depth was the most important variable for predicting the amount of interception loss. We also found that vegetation structure variables, while more important for predicting the percent than the amount of interception losses, had inconsistent relationships with interception losses across sites, suggesting that statistical models with vegetation structure metrics may not be best for predicting interception losses at broad spatial scales.
For canopy storage, using data from 648 storms across 15 forested sites, we found storage values did not vary considerably across sites, and found no consistent, strong relationship across sites between storage variation and the remotely sensed vegetation structure metrics we evaluated. These results suggest the common modeling convention of scaling storage with vegetation metrics is not more appropriate than assuming storage to be constant across forested sites.
For evapotranspiration in semi-arid shrublands, using data from micrometeorology stations at seven paired burned and control plots around the Great Basin, we found dry-season evapotranspiration was 15-77% lower and soil volumetric water content at soil depths ≥35 cm in the control plots was 16-70% of that of the burned plots. These results suggest fire-induced change in vegetation structure led to reduced soil water use and lower evapotranspiration.
Each of the topics in this work fall within the larger challenge in the field of hydrology of reconciling the difference in scales between what we can directly measure at individual sites and smalls scales, and the larger-scale prediction and modeling of water fluxes.