Using Dendrochronology to Measure Sitka Spruce ( Picea sitchensis) Reforestation in the Post-glacial and Isostatic Rebound Dominated Landscape of Southeast Alaska

Document Type

Student Presentation

Presentation Date

April 2017

Faculty Sponsor

David Wilkins


Retreat of the Davidson Glacier in southeastern Alaska has been documented since the late 1800’s. John Muir in 1879, as well as members of the Harriman Expedition in 1899, noted its terminus very near to sea level. Since that time, the Davidson has steadily retreated to its current location, roughly 4 km from the ocean. Uplifting and emerging land resulting from post-Little Ice Age deglaciation is being recorded at 22 to 24 mm per year, making isostatic rebound in southeast Alaska one of the highest measurable rates in the world today, rapidly exposing land for reforestation. The post-glacial landscape is occupied predominantly by Sitka spruce (Picea sitchensis) with secondary reforestation of spruce also occurring near sea level. This study uses dendrochronology and tree-ring analysis to identify stages of reforestation from both the receding glacier’s terminus and isostatic rebound regression along the shoreline. An initial analysis of Sitka spruce stand ages along a transect line from sea level to the glacier indicates a trend towards older trees occupying an area 800 meters from todays shoreline. Stand age then decreases to germination near the glacier. Matching reforestation ages to the retreat of the Davidson Glacier with an isostatic rebound effect will constrain the timing of deglaciation in this area of southeast Alaska.

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