Cultivation and Grazing Impacts on Extracellular Enzyme Activity in Alberta Grasslands

• Author / Creator

  Kaliaskar, Dauren

• Grasslands cover a quarter of the planet’s terrestrial surface and constitute 70% of the world’s agricultural land area. Grasslands provide clean water, facilitate effective nutrient cycling, and provide necessary habitat and forage for livestock and wildlife. In addition, grasslands have the potential to mitigate greenhouse gas emissions by sequestering carbon (C) and nitrogen (N) in soil. Grazing is one of the most common uses of grasslands and may alter C and nutrient mineralisation. Therefore, understanding the impact of different grazing systems (i.e. continuous and rotational) on C and nutrient cycling, as well as past management practices (cultivation), climate and soil properties, is of significant interest. This study examined the role of grazing systems on soil biogeochemical cycling by measuring extracellular enzyme activity (EEA), which is an indicator of soil biological activity. The activities of six soil extracellular enzymes were analysed that are involved in C (xylosidase, β-glucosidase, cellobiosidase), nitrogen (N) (N-acetyl-β glucosaminidase, urease), and phosphorus (phosphatase) cycling. Soil samples were tested from 12 pairs of field sites (i.e., ranches) with varying grazing practices (i.e., AMP or non-AMP grazing, with divergent stocking rates) for at least five years prior. An information theoretic model selection approach was used to determine those independent variables (disturbance regime, climate, soil) that explained the variability of each EEA. Results showed that a long resting period (mainly present in AMP ranches) increased β-glucosidase activity, while a high stocking rate increased urease activity. In contrast, soils with known previous cultivation had lower xylosidase and phosphatase activities, suggesting a legacy effect of previous cropping. The main environmental factors regulating enzyme activity were available soil N and climatic aridity. Overall, grazing practices, as represented by grazing systems, appear capable of altering C and nutrient cycling, with AMP grazing increasing C mineralisation iniiithese Alberta grasslands. This finding highlights the importance of grazing practices that maintain soil biological activity.

• Subjects / Keywords

  • soil enzymes
  • Alberta
  • grassland
  • grazing
  • adaptive multi-paddock

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-w2en-7x26

• License

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