Measuring and modeling microclimate impacts of Sequoiadendron giganteum

Abstract

The University of Portland (UP) in Portland, Oregon (USA) removed four giant sequoias (Sequoiadendron giganteum) from UP’s campus in 2017 for a construction project. The loss of these trees provided an opportunity to measure how sequoias influence microclimates, with a goal of quantifying their roles in mitigating urban heat island (UHI) effects, and thus promoting preservation of these and similar trees everywhere. Our study applied a widely-used computational fluid dynamics model called ENVI-met to isolate effects of sequoias on microclimates, and validated results by making field measurements before and after UP removed the four sequoias. Our study is likely the most thorough to ever measure and model microclimate effects of sequoias, or potentially any other large trees. Results show model simulations of plant metabolic processes and their influences on air temperatures, surface temperatures, winds, and carbon dioxide concentrations, with validation statistics ranking model performance comparable to or superior to previous ENVI-met studies. Applications include new methods for running and validating microclimate models, which could lead to better decisions about what kinds of trees to plant where, and greater protection for trees, which can reduce the UHI effect and its detrimental influences on energy demand, human comfort, and human health.