Research

 

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Successional dynamics of arid ecosystems following environmental change

I am thrilled to have recently started on a project with Jonathan Bakker (University of Washington) and Matt Davies (The Ohio State University) examining compositional trajectories of sagebrush-steppe communities in central Washington state. Sagebrush-steppe is an imperiled arid ecosystem in the Intermountain West threatened by cheatgrass invasion, increased wildfire frequency, overgrazing, climate change, and widespread clearing. Our project combines new and historical data to disentangle the responses of this ecosystem to natural and anthropogenic changes over immediate and long timescales. We are also quantifying the recovery of these communities to various restoration treatments applied at multiple spatial and temporal scales. This project is a multi-agency collaboration between UW, OSU, US Fish & Wildlife Service, Joint Fire Science Program, and the Department of Defense.

 

Assembly and persistence of species-rich communities

My postdoctoral research with Margie Mayfield (University of Queensland) and Janneke HilleRisLambers (University of Washington) focused on quantifying the relative influences of biotic interactions and environmental variation on native and exotic species’ success. Using the diverse annual plant communities of Western Australia’s York gum woodlands as a study system, I am employing experimental and statistical modelling approaches to examine variation in  species’ performance along competitive and environmental gradients (natural and anthropogenic) and how this variation can be explained by species positions in functional trait hierarchies.Manuscripts detailing our findings are currently in preparation.

 

Global change and novel ecosystem functioning

Virtually all of Earth’s ecosystems have been impacted by one or more drivers of global change. I am interested in investigating how these drivers have interacted synergistically to hasten the formation of novel ecosystems. Not only is it important to quantify how novel ecosystems function differently from the original systems they are replacing, it is critical to determine how these ecosystems will function under future climate change scenarios.

My PhD research with Margie Mayfield, Richard Hobbs (University of Western Australia), and John Dwyer (UQ) examined species interactions and links between diversity and function in novel and original York gum woodland annual plant communities arising due to combined effects of invasion, land clearing, and eutrophication. I showed that diversity within the exotic constituent of novel communities is currently under-appreciated, particularly in terms of actual competitive impacts exerted on native species over local scales. While competitive exclusion of native species is an outcome of these interactions (including through litter deposition), neutral and facilitative interactions are just as prevalent, suggesting that many aspects of original community function can be retained or even enhanced. Headed by John Dwyer, we also showed that compositional and functional trait distribution responses to anthropogenic nutrient enrichment were contingent on climate.

While some ecological processes may be resilient to invasion, others may be more sensitive, such as the delivery of pollination services. This research highlights the importance of considering multiple trophic levels when assessing invasion impacts on native community functioning.

 

Using ecology theory to guide and supplement restoration
I am also interested in the role of community ecology theory in implementing practical, on-the-ground ecological restoration. Community ecology theory elucidates the mechanisms of community assembly, functioning, and the relationship between disturbance and species diversity maintenance. When combined with site-specific ecological and cultural information, an understanding of these mechanisms can greatly enhance restoration design.

My Master’s research with Elsa Cleland  (UC San Diego) combined theory and application by using assembly rules to help restore a coastal sage scrub community dominated by invasive annual grasses. By harnessing prior knowledge of invader germination strategies, we turned the seasonal priority effect exerted by invasives on co-occurring natives into a “priority disadvantage”.

While scores of ecologists have heralded the potential utility of theory in restoration settings, the integration of these fields is still relatively uneven. As such, I recently led a review of the ecological restoration literature to pinpoint when and how community ecology theory has been used in restoration settings.

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