The Effects of Vegetation on Ecosystem Services Provisioning by Stormwater Bioretention

Abstract

Vegetation plays an integral role in the provision of ecosystem services by stormwater biore- tention, influencing a diversity of services from flood regulation to sense of place. This dissertation explores the myriad ways plants influence these services, with a focus on indi- vidual plant traits, suites of traits that reflect underlying plant adaptive strategies, emergent landscape-scale factors like pattern, and ecological attributes like nativeness. The first chap- ter reviews key topics like stormwater bioretention, ecosystem services provisioning, and vegetative characteristics (e.g., plant adaptive strategy), and provides a roadmap for my dissertation. The second chapter investigates whether current plant selection practices for stormwater bioretention introduce adaptive strategy biases that may impact ecosystem ser- vices provisioning. Findings suggest that planting guidance in arid regions favors stress tolerant species whereas planting guidance in humid regions favors competitive species rela- tive to the native species pool. Across all climate zones, there is a notable anti-ruderal bias, which could limit bioretention resilience by reducing its capacity for self-repair. The third chapter explores how these biases influence hydrologic services in different climate zones, using saturated hydraulic conductivity (Ksat) as a performance metric. My results indicate that stress-tolerant bias in arid climates increases Ksat whereas competitive bias in humid climates has no measurable effect. Notably, overall Ksat values were higher than design standards, potentially due to the exclusion of ruderals, the only plant group that reduced Ksat to a level consistent with engineering targets. The final two chapters of my dissertation examine the effects of vegetation on the provisioning of cultural services such as aesthetics using new design tools like virtual reality and mental modeling. My results indicate that plant adaptive strategy influences aesthetics through individual plant traits and landscape characteristics. Competitive plant bias was associated with lower aesthetic value due to re- duced biodiversity, whereas stress tolerant and ruderal biases tended to enhance aesthetic value. Collectively these results suggest that plant adaptive strategy has far reaching im- plications for ecosystem services provisioning by stormwater bioretention (e.g., impacting a range of services from hydrologic to cultural). This research highlights the importance of factoring ecological principles into plant selection practices for stormwater bioretention and provides valuable insights to engineers and landscape architects seeking to leverage those principals to develop more multifunctional and resilient stormwater infrastructure.