The Effect of Urbanization, Seasonality, and Storm Events On Stream Metabolism at Watershed Scale
Open Access
- Author:
- Wadley, Myriah
- Graduate Program:
- Forest Resources
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 23, 2021
- Committee Members:
- Bradley Cardinale, Program Head/Chair
Jonathan M Duncan, Thesis Advisor/Co-Advisor
Lauren Mc Phillips, Committee Member
Douglas Alan Miller, Committee Member - Keywords:
- metabolism
land-use
urban
watershed
gross primary production
ecosystem respiration
Dead Run 5
ecosystem function
urbanization
restoration - Abstract:
- The primary focus of this thesis is to investigate and quantify the impact of urbanization, restoration and seasonality on stream health and function, often referred to as stream metabolism, in an urban watershed. Stream metabolism measures a stream’s ability to supply and balance energy fluxes at each trophic level, process and transform excess nutrients, and adapt to changes in climate (i.e., warming temperatures, declining precipitation events, increasing droughts) and landscape (i.e., sewer pipe installation and maintenance, increased flashiness due to impervious surfaces, decreased turbidity due to excess sediment from eroded banks) (Hall and Hotchkiss 2017). Metabolism is calculated as Net Ecosystem Production (NEP) using estimates of Gross Primary Production (GPP) and Ecosystem Respiration (ER). This study on Dead Run 5, a 1.53 km2 urbanized watershed of the Lower Gwynn Falls, quantified stream metabolism above and below a recent stream restoration project. These results show the stream as a net heterotrophic system, where more carbon from outside of the stream is added into the system than consumed within it. Seasonal changes to NEP at the reach scale had a negligible effect on overall watershed scale heterotrophy. Despite the structural improvements from the restoration, production rates had little to no change, even though each site sustained healthy average rates of GPP. This study suggests that impacts on watershed-scale metabolism are not completely mitigated by the restoration, despite existing evidence of increased GPP because of reduced canopy cover, increased effective habitat supporting periphyton growth and improved hydrology which decreased stream velocity. This suggests that restorations should apply more watershed Best Management Practices (BMPs) that aim to reduce allochthonous carbon sources which could help to balance GPP, rather than removing riparian canopy during the construction phase of stream restoration.