Non-native plant occurrence and human disturbance at freshwater springs in Alberta, Canada

This thesis investigates the factors that affect non-native plant occurrence at freshwater springs in southern Alberta, Canada, with special focus on the effect of human disturbance, and the life history traits of commonly-occurring native and non-native plant taxa. Non-native species richness and abundance were higher at springs with greater human disturbance, and at springs within regions of the province that support greater land use relative to livestock grazing. Non-metric multidimensional scaling demonstrated that commonly-occurring non-native plant taxa were associated with springs that experienced greater human disturbance. Autecological investigation revealed that both native and non-native plant taxa commonly exhibited life history traits that confer greater tolerance to various types of disturbance, including grazing. Overall, these results demonstrate that springs ecosystems that experience greater human disturbance are vulnerable to invasion by non-native plants, which could reduce biodiversity and ecosystem services provided by these distinctive, insular ecosystems.