Tree-ring reconstruction of historic insect outbreaks annual technical report, Lake Clark National Park and Preserve

Sherriff, Rosemary; Berg, Ed

Tree-ring data have been widely used in temperate and high-latitude forested ecosystems to address issues of past disturbance (insects, fire) and long-term climate variability. Regional warming is thought to have triggered the recent spruce bark beetle outbreaks on the Kenai and Alaska Peninsulas. Beetle kill has affected coastal forests extending from north of Lake Clark National Park and Preserve (NPP) south to Tuxedni Bay, as well as stands in Lake Clark Pass and surrounding Lake Clark. As part of this multi-year project, we are using tree-ring records to determine whether bark beetle outbreaks occurred historically in Lake Clark NPP. The objectives of the project are to 1) reconstruct historic patterns of insect outbreaks in forests of Lake Clark NPP; and 2) evaluate the relationship between insect outbreaks and regional climate using existing tree-ring chronologies and long-term climate data. We collected cores from live and dead trees in July 2005 from seven sites in Lake Clark NPP and two sites in Pedro Bay. Current spruce bark beetle activity and/or damage was evident at the Tlikakila River, Currant Creek, Chinitna Bay and Pedro Bay sites. Damage from another, unidentified bark engraver beetle was evident on dead standing and downed trees at the Two Lakes, Telaquana Lake, and Lachbuna Lake sites. To date, we have mounted and sanded tree cores from all nine sites. We have visually counted tree rings and recorded growth changes potentially due to beetle activity and other sources of damage from three of the nine sites (Lachbuna Lake, Telaquana Lake – Braden Cabin, and Two Lakes). The oldest cores processed to date are from Two Lakes and show live tree ages that range from the early 1600s through the 1900s. Visual inspection of cores from the three sites that have been processed show multiple suppression periods since the mid 1800s. These patterns suggest evidence for insect activity at multiple time periods from the mid 1800s to present, although the exact dates, magnitude of growth changes, and synchroneity of patterns will be examined in the next phase of the project, during 2006. The results of this project will provide both baseline conditions and a historic context for long-term monitoring of forested ecosystems in the Park.

Tree-ring reconstruction of historic insect outbreaks annual technical report, Lake Clark National Park and Preserve

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