COS 267-4 - A paleolimnological reconstruction of Eastern Spruce Budworm (Choristoneura fumiferana) outbreak dynamics and vegetation changes in Newfoundland

Background/Question/Methods

Insect defoliator outbreaks have helped regulate boreal ecosystem activity and maintain other natural processes that keep forests productive and healthy. However, the effects of climate change, human interference, and current harvesting practices are producing rapid, unnatural changes to both the forest mosaic and outbreak dynamics, increasing outbreak frequency and intensity. Eastern Spruce Budworm (ESB) has had a significant impact on Canada’s boreal ecosystems. The future pattern of insect defoliator outbreaks and biophysical conditions required are difficult to predict based on past monitoring data alone. This study analyzed and quantified sedimentary proxies of ESB from within four sediment cores collected from lakes across Newfoundland using paleolimnological techniques. We tested current methodologies for isolating moth wing scales from sediments to quantify: (1) the frequency and intensity of historical ESB outbreaks in Newfoundland and (2) the difference between outbreak dynamics at low and high elevations within Gros Morne National Park (GMNP). Additionally, sedimentary pollen data explore the historical impacts of ESB and other pest defoliators on Newfoundland forests. Using this data, we compare how elevation, climate, human intervention strategies (i.e., spraying), and vegetation dynamics interact with/influence ESB outbreak dynamics over time.

Results/Conclusions

Our results confirm and further develop new methodologies for isolating ESB wing scales from sediment, including sediment deflocculation and wing scale extraction using a density separation method. Isolated wing scales were well-preserved and taxonomically distinct, with enough abundance to quantify historical population dynamics. The cores were sectioned at 0.25 cm intervals, achieving records with high-temporal resolution: Gull Pond (low elevation GMNP) ~1 yr/slice, Small Lake (high elevation GMNP) ~5 yrs/slice, Little Crow Lake ~3 yrs/slice, and No Name Pond ~3-4 yrs/slice. Given that outbreaks have been assumed to occur in ~30-year intervals; we have been able to quantify wing scale abundance to more accurately determine historic outbreak dynamics in Newfoundland. At higher elevations, Small Lake is predicted to have lower diversity and abundance of conifer species, and respectively, less intense historical ESB outbreaks relative to Gull Pond. Currently, on Newfoundland’s west coast, ESB populations are rapidly increasing. While not confirmed, there is a high probability that an outbreak has begun. GMNP has opted out of the government’s insect management strategies, including pesticide spraying. These results would allow better insight into past outbreak dynamics and better inform management decisions concerning ESB moving forward.