Effect of Grazing on Litter Decomposition and Extracellular Enzyme Activity across Agro-climatic Subregions in Alberta

• Author / Creator

  Chuan, Xiaozhu

• Grasslands cover approximately 40% of the Earth’s terrestrial surface and provide a wide range of ecologically and economically important services such as forage production, carbon (C) and nitrogen (N) storage, and wildlife habitat. Livestock grazing is a ubiquitous use of grasslands around the globe; however, the direct and indirect effects of grazing on ecosystem processes including C and nutrient cycling, are still overlooked. To better understand how livestock grazing and associated shifts in plant community compositions affect ecosystem function, we studied decomposition of litter of different grass species and extracellular enzyme activity (EEA) over 18-months using litterbags, placed inside and outside of long-term grazing exclosures at 15 sites across three grassland subregions, including the Central Parkland, Foothills Fescue and Mixedgrass Prairie. Overall, livestock grazing increased litter decomposition rates and EEAs in litter samples, though this response varied among subregions and individual enzymes; decomposition was most rapid in the Foothills Fescue followed by the Parkland and Mixedgrass subregions. While grazing enhanced enzymes activities regulating C cycling, it decreased those associated with N and P cycling decomposing litter. No effects of grazing on soil EEAs were detected. Litter types also altered litter decomposition rates and EEAs regardless of subregion or grazing effects. P. pratensis had particularly high decomposition rates and EEAs, especially in the Foothills, and a similar pattern existed for B. gracilis in the Mixedgrass, suggesting increases in these grazing tolerant species may alter biogeochemical cycling, and therefore C accumulation. Results from this study suggest that grazing could play a critical role in regulating litter decomposition and C cycling in the northern temperate grassland.

• Subjects / Keywords

  • Carbon Cycling
  • Extracellular Enzyme Activity
  • Grazing
  • Nutrient Cycling
  • Grasslands
  • Litter Decomposition

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3CR5NS3C

• 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.