Post Doc - Short Talks

Courtney Collins bio: (talk title: Disentangling direct and indirect effects of global change above and below-ground in tundra ecosystems)

Global change threatens the stability of terrestrial ecosystems by reducing biodiversity, disrupting biogeochemical cycles and altering species interactions both within and across trophic levels. One of the most critical and complex barriers to predicting how ecosystems will respond to global change is the need to parse apart direct environmental effects and indirect effects of shifts in community composition and species’ interactions. I address these issues using conceptually driven research questions paired with large and global datasets to disentangle the interacting effects of global change on plant-soil-microbial interactions. My research has a strong theoretical grounding in ecosystem, community, and population ecology, and I incorporate advanced statistical techniques to link ecological processes across scales from the microbial to ecosystem level. I combine both experimental data from field, greenhouse, and laboratory studies and publically available data from global monitoring networks.  My major research objectives are to: 1) Determine the direct and indirect effects of global change on plant and soil microbial community structure and ecosystem function and 2) Quantify the primary mechanisms driving these global change impacts. I primarily focus on Arctic and alpine tundra ecosystems, as they are some of the most rapidly changing areas of the planet, allowing me to study the real-time impacts of global change. However, my research framework and quantitative approaches can be applied to any terrestrial ecosystem

Brenton Twist's Bio: (talk title: 'The Role of Coralline Algae in Kelp Forest Recovery')

Dramatic shifts from healthy kelp forests to urchin-dominated barrens have become prevalent in recent years, severely impacting ecosystems and local economies. Research to-date has focused mostly on top-down effects and their impacts on recovery with little attention paid to bottom-up effects, such as those derived from coralline algal communities present in these systems. Coralline algae play critical and species-specific roles in nearshore ecosystems, inducing invertebrate larval settlement and influencing kelp spore settlement and germination. Furthermore, coralline communities can differ significantly between urchin barren and kelp forest habitats, perhaps helping to maintain either ecosystem state. The settlement patterns of the red urchin and several common kelp species were assessed on a range of molecularly identified coralline algal species in the laboratory. Fewer differences in urchin metamorphosis and juvenile canopy-forming kelp density were observed than expected across coralline species. This perhaps suggests the generality of urchin and canopy-forming kelp recruitment to barrens, regardless of coralline composition. A secondary sub-canopy kelp species, however, preferentially settled on articulated coralline species not typically found in urchin barren habitats, suggesting that benthic coralline communities would need to recover before this sub-canopy species could return. These results could have important implications for kelp forest recovery following changes in coralline community structure in urchin-dominated barrens. 

Nathalie Isabelle Chardon's bio: (talk title: Predicting shrub distribution and abundance in Greenland with high resolution spatial models')

Improving Species Distribution Models (SDMs) and Species Abundance Models (SAMs) is critical for predicting biodiversity changes, yet it remains relatively unexplored if SDMs and SAMs can explain local-scale patterns in new data. I use field surveys of Betula nana and Salix glauca occurrence and abundance in two separate fjords in Southwest Greenland to construct high resolution (90 m) SDMs and SAMs. I then validate the models’ predictive ability of local-scale patterns with the survey data from the fjord not used in model training, a rare yet important approach to understand model performance. I find substantial differences in model performance when compared to a traditional split-sample validation approach, highlighting the usefulness of using a separate survey for realistic performance measures.