Assessing Stream Function Across an Agricultural Gradient in Three Ecoregions of Alberta

• Author / Creator

  Barrie, Emily

• Streams provide essential ecosystem services including nutrient cycling and uptake, organic matter processing and ecosystem production and respiration. Stream ecosystem functioning provides an integrated metric of biological structures and processes that can respond to anthropogenic land use activities including removal of riparian areas and nutrient enrichment. Agricultural land use is common in the Boreal Transition, Parkland and Grassland ecoregions of Alberta, where streams are exposed to a range of land use intensities and levels of nutrient loading. Two key indicators of ecosystem function are stream metabolism and organic matter processing, which incorporate carbon cycling and community structure. This thesis aims to describe the direct and indirect effects of anthropogenic land use on stream metabolism and decomposition in streams within agriculturally-impacted areas of Alberta. I studied 34 streams along a gradient of nutrients over three years in spring, summer and fall. Metabolism was measured with the single station open-channel method over 3–5-day deployments in each season. Variation in stream physicochemical properties was analyzed across regions and seasons, and direct impacts on metabolism were studied through generalized linear mixed modelling and indirect impacts through structural equation modelling. Stream metabolism was driven primarily by water temperature and dissolved organic carbon concentrations and does not appear to be strongly influenced by increased concentrations of nutrients. Land cover has indirect impacts on metabolism by controlling changes in light and dissolved organic carbon availability. Decomposition was measured in-stream using litterbags deployed from June to September. Decomposition was assessed through decay rates and stoichiometry. Contrary to metabolism, decomposition was directly correlated with increasing total nitrogen concentrations, which increased microbial decay rates and lowered litter carbon:nutrient ratios. This research showcases the diverse impacts of anthropogenic land use on stream function and the importance of nutrient criteria and riparian management for preserving ecological integrity.

• Subjects / Keywords

  • stream
  • ecology
  • ecosystem metabolism
  • decomposition

• Graduation date

  Fall 2021

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-2xge-7034

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.