ECOSYSTEM SERVICES APPROACH IN TERRESTRIAL ECOTOXICOLOGY: ASSESSING PRAIRIE GRASSLAND SOIL RESILIENCE AND VULNERABILITY TO ECOLOGICAL DISTURBANCES AND CHEMICAL STRESSORS
Date
2024-12-13
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0003-2640-8947
Type
Thesis
Degree Level
Doctoral
Abstract
Pyric herbivory, where fire meets grazing, shapes grasslands by enhancing habitat heterogeneity and soil function. However, it may come with hidden costs when the fire and grazing pressure interact to disturb aboveground and belowground processes, making grassland soils more vulnerable to environmental stressors like pesticides. This study reveals that in rough fescue prairie grassland, fire followed by cattle grazing not only depletes soil nutrients and alters vegetation structure in the burnt patches but also significantly lowers the abundance of soil arthropods, particularly Collembola (springtails) due to changes in litter cover and soil organic carbon. Although carbon storage increased by 17% in the burnt areas, the 74-93% decrease in Collembola abundance signals a deeper ecological imbalance. By introducing the novel ecosystem services approach, “Eco-indicator Sensitivity Distribution (EcoSD),” we assessed the vulnerability of soil ecological indicators to chemical exposure. EcoSD identified nitrogen cycling as the most sensitive process disrupted by contaminants like cadmium. Additionally, soil previously exposed to fire followed by cattle grazing experienced heightened susceptibility to chlorpyrifos toxicity, particularly affecting ecological indicators such as Oribatid mites and soil microbial functions. These findings highlight the ecological imbalance introduced by fire in burnt patches under pyric herbivory. While the interaction of prescribed fire and grazing in burnt patches enhanced specific ecological processes like carbon sequestration, the increased ecological risks to soil arthropods in the burnt patches after three to four years emphasize the need for sustainable land management practices that balance the effects of fire and grazing to meet management goals and protect soil health. This study advocates for a comprehensive evaluation of soil health in Canadian grasslands facing ecological disturbances and chemical stressors. By integrating ecosystem services approaches like EcoSD into chemical risk assessments, we can better protect and sustain natural ecosystems like grasslands amidst growing climate and environmental challenges.
Description
Keywords
Ecosystem services, ecological risk assessment, grassland, soil ecotoxicology
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Toxicology Centre
Program
Toxicology