Simulated Livestock Soil Compaction, Plant Defoliation and Litter Removal Effects on Extracellular Enzyme Activity and Vegetation Across a Moisture Gradient in Southern Alberta, Canada

• Author / Creator

  Barszczewski, Sara Janina Bodnar

• Preservation of grasslands is vital for the continuation of the numerous ecosystem goods and services (EG&S) provided by these ecosystems, including forage for livestock, nutrient cycling, carbon sequestration and habitat for flora and fauna. All EG&S in grasslands are supported by microbial biological functions and the vegetation community. Recent attention on adaptive multi-paddock (AMP) grazing, which focuses on effects to the soil and plant community through trampling and compaction of litter into the soil surface, have raised questions about the relative roles of the different mechanisms through which cattle affect grasslands, namely, compaction, defoliation and subsequent depletion of litter. Few studies have been conducted that isolate the mechanisms through which grazing may alter grasslands, particularly in western Canada. This study investigated relationships of soil biological activity, vegetation production and diversity with individual grazing mechanisms across a moisture gradient. We conducted a plot-level factorial study that simulated cattle trampling and defoliation as well as litter depletion at three locations with different climates and vegetation types in Alberta rangelands. In the first year of study, litter was removed or retained to examine the importance of litter presence, which generally decreases with heavy grazing. To simulate seasonal defoliation and trampling, plots were clipped and compacted, or not, in the spring or the fall of the first and second year of study. Data were collected in the second and third year of study. Extracellular enzyme activity (EEA) is a measure of enzyme availability and used in this study as a metric of microbial community function at each site. Enzymes are used to degrade specific substances by plant and soil microbes, and were measured in this study in both soil and litter.
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  Our study determined that litter manipulation had a strong influence on EEA in both soil and litter, as litter presence affects moisture, though patterns fluctuated between sites. Response of both soil and litter EEA to defoliation and compaction treatments did not present consistent patterns. Production and structure of the vegetation community are known to be key influences on biodiversity; our study determined that defoliation, particularly in the fall, had a greater influence on vegetation production and diversity than trampling in either season. Response of species with different grazing tolerance indicates variation in the effects of grazing mechanisms on species with varied grazing tolerances. The results of this study demonstrate the key role that litter presence plays in biological function and influence of defoliation on the vegetation community in grasslands. From this study, the implications for grassland preservation and management are on the importance of litter management for decomposition and nutrient cycling. This study highlights the importance of monitoring effects of seasonal grazing in grasslands, as production and structure of the vegetation community are affected variably at different locations.

• Subjects / Keywords

  • Litter
  • Canada
  • Soil
  • Extracellular enzyme activity
  • Trampling
  • Vegetation
  • Grassland
  • Grazing
  • Rangeland
  • Defoliation

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-a3hp-pk42

• License

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