I’m recently finished my PhD at the University of Toronto-Scarborough under the amazing supervision of Dr. Marc Cadotte and Dr. Marney Isaac. My PhD research spanned the fields of invasion ecology, biological control, ecosystem functioning, functional diversity and stakeholder valuation of ecosystem services.
PhD Thesis Project: The consequences of plant invasion in the peri-urban environment: A case study of the invasive vine Vincetoxicum rossicum
Ch 1: The effect of the invasive vine Vincetoxicum rossicum on biodiversity and ecosystem functionality
This project involved the establishment of 350 permanent field plots at 14 sites throughout Rouge National Urban Park in Toronto. The aim of this study was to examine the effect of increasing abundance of the invasive V. rossicum on multiple ecosystem functions (i.e. soil nutrient content, pollinator diversity, productivity, floral production, etc). Here I analyzed biodiversity-ecosystem function relationships across a V. rossicum “invasion gradient”. This study demonstrated significantly negative ecological impacts of V. rossicum invasion, on both biodiversity and ecosystem functions. This work is being prepped for submission to the peer-review journal Ecology Letters. The ultimate objective of this research is to develop a long-term data set to examine the advancement of V. rossicum throughout the Park, shifts in biodiversity-ecosystem function relationships over time as well as to establish baseline ecological conditions that will be used to evaluate ecological dynamics following the introduction of Hypena opulenta as a control agent for V. rossicum. We foresee this project serving as the foundation of a long-term ecological restoration efforts within Rouge National Urban Park.
Ch 2: Can a moth strangle the Dog-strangler? An experimental application Hypena opulenta as a bio-control agent for the invasive Dog-strangling vine (Vincetoxicum rossicum)
This project involved an experimental release of the biological control agent, Hypena opulenta, within a highly invaded ecosystem in Kirkfield, Ontario. As V. rossicum is highly invasive in both shade and sun conditions, we sought to examine the agent’s relative effectiveness in each of those conditions. We found that defoliation of V. rossicum by H. opulenta and larvae dispersal was significantly greater in shaded forest plots. Further, contrary to expectations, we found that V. rossicum’s seed productivity in shaded plots was enhanced by defoliation of H. opulenta. This finding has strong implications for the widespread release of H. opulenta in that we may see a significant increase in the seed output of V. rosssicum following defoliation. This likely warrants further testing to evaluate how V. rossicum responds to various densities of H. opulenta and timing of release. This work was presented at an internal colloquium at the University of Toronto-Scarborough in May, 2017 and is about to be submitted to Biological Invasions.
A second component of this work was to evaluate the potential effects of V. rossicum defoliation on soil processes, which was conducted at a separate research site due to the sensitivity of our control agent. By artificially defoliating V. rossicum we were able to conduct experiments to assess soil processes as well as take soil samples to measure soil properties (soil efflux, available nitrogen, decomposition, etc). There is significant variability in the literature regarding the impacts of defoliation on soil properties and processes, even more so with respect to the defoliation of invasive species (i.e. uncertainty surrounding the relationship between defoliation and the exudation of allelopathic chemicals). Yet, species specific knowledge is highly valuable in the context of local control efforts for invasive species. We did measure a surge in soil NH4 following defoliation, suggesting root exudation following defoliation, but other soil properties and processes were not significantly affected by our treatment. Although our inferences here are limited by the absence of the biological control agent and associated ecological inputs, our finding suggests that defoliation of V. rossicum will have a marginal impact on soil properties and processes. This has strong positive implications for the potential ecological restoration efforts within invaded ecosystems. This work is in preparation to be submitted to the Journal Invasive Plant Science and Management in March, 2018.
Ch 3: On the distribution of different forms of ecological rarity in herbaceous plants and their importance for ecosystem functioning
This projects integrates species abundance and functional trait data for plant species in Rouge National Urban Park to characterize the “functional rarity” of plants species within meadow communities. Further, we employ a null model approach to examine the relationship between functional rarity, taxonomic rarity and ecosystem functionality. This study presents evidence that while the majority of ecosystem functions appear to be driven by dominant species, certain rare species prove to make significant contributions to ecological functionality. Data analysis was conducted using recently developed packages for R statistical software and metrics developed in Violle et al. 2017 (in list of publications below). This work will contribute to the emerging field of functional ecology and will help to broaden perspectives on the characterization of species rarity. This research is in preparation for submission to Functional Ecology.
Ch 4: Ecological engagement determines ecosystem service valuation: A case study from Rouge National Urban Park in Toronto, Canada
This project aimed to investigate stakeholder valuation of ecosystem services (ESs), and perceptions of threats to their conservation within Rouge National Urban Park (NUP). Many of Rouge NUP’s ESs are threatened by the advancement of the non-indigenous invasive species (NIS), Vincetoxicum rossicum. The aim of our study was to: 1) assess the distribution, within a stakeholder group (Park users), of ESs valuations for an urban protected area; and 2) determine whether “ecological engagement” (operationalized as Park user awareness of V. rossicum) affects ESs valuation and perceptions of V. rossicum’s impact on the provisioning of ESs. The overall value placed on nearly all of the ESs derived from the Park was significantly higher for ecologically engaged (EE) Park users as compared to non- EE users, yet both groups ranked climate regulation, carbon storage and agricultural production as the least important. Interestingly, non-EE users tended to give recreation (a ‘cultural’ ES) the highest importance value. Conversely, EE users tended to assign pollination (a ‘supporting’ ES), the highest importance. We conclude that examination of EE can reveal differential ES valuations and perceptions of the impact of NIS. Furthermore, we believe such examination can inform conservation management plans and public engagement strategies. This work has been accepted for publication in the peer-reviewed journal, Ecosystem Services, and is currently in press.