8:30 am - 9:30 am
849 General Services Building (GSB), General Services Building, University of Alberta, Edmonton AB
A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Dauren Kaliaskar. This seminar is open to the general public to attend.
Thesis Topic: Cultivation and Grazing Impacts on Extracellular Enzyme Activity in Alberta Grasslands
MSc with Dr. Scott Chang.
Grasslands have the potential to mitigate greenhouse gas emissions by sequestering carbon (C) and nitrogen (N) in soil; such functions maybe altered by grazing and cultivation in managed grasslands. Understanding the impact of different grazing systems (i.e., adaptive multi-paddock (AMP), and continuous, rotational (non-AMP) grazing) and cultivation on extracellular enzyme activities (EEA) related to C and nutrient cycling, particularly in relation to climate and soil properties, is of significant interest. The activities of six soil extracellular enzymes were analysed that are involved in C (xylosidase, β-glucosidase, cellobiosidase), N (N-acetyl-β glucosaminidase, urease), and phosphorus (phosphatase) cycling. Soil samples were collected from 12 pairs of ranches with varying grazing practices (i.e., AMP or non-AMP grazing, as well as divergent stocking rates) for at least five years. An information theoretic model selection approach was used to determine those independent variables (disturbance regime, climate, soil properties) that explained each EEA. Results showed that a lengthy rest to grazing period ratio (mainly present in AMP ranches) increased β-glucosidase activity, while high stocking rate increased urease activity. In contrast, soils previously cultivated had lower xylosidase and phosphatase activities, suggesting a legacy effect of past cultivation. The main factors regulating enzyme activities were available soil N and climatic aridity. Overall, grazing practices appear to be capable of altering C and nutrient cycling in these Alberta grasslands. This study highlights the importance of grassland management in influencing biological activity.