Winter is a critical season for land‐surface feedbacks and ecosystem processes; however, most high‐latitude paleo‐environmental reconstructions are blind to cold season conditions. Here we introduce a winter‐sensitive, paleo‐proxy record that is based on the relative frequency of tangential rows of traumatic resin ducts (TRDs) in the annual growth rings of mountain hemlocks (
Much of the precipitation delivered to western North America arrives during the cool season via midlatitude Pacific storm tracks, which may experience future shifts in response to climate change. Here, we assess the sensitivity of the hydroclimate and ecosystems of western North America to the latitudinal position of cool‐season Pacific storm tracks. We calculated correlations between storm track variability and three hydroclimatic variables: gridded cool‐season standardized precipitation‐evapotranspiration index, April snow water equivalent, and water year streamflow from a network of
- NSF-PAR ID:
- 10035994
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Global Change Biology
- Volume:
- 23
- Issue:
- 11
- ISSN:
- 1354-1013
- Page Range / eLocation ID:
- p. 4896-4906
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Tsuga mertensiana ) growing near treeline in Southeast Alaska. Hemlocks produce a row of TRDs in the earlywood portion of their annual rings in response to cambial damage incurred during winter. Multidecadal bouts of TRD production were followed by growth‐leader replacement, reaction wood formation, and divergence in radial growth between storm‐damaged trees and less exposed mountain hemlock forests. These patterns are consistent with TRDs being a response to tree damage caused by ice and snowstorms, a conclusion supported by the krummholz tree architecture at these sites. This relationship is further corroborated by significant correlations between our TRD record and the strength of the wintertime Aleutian Low (AL) pressure system that is linked to tree‐damaging agents like wind, precipitation, and ice storm strength in Southeast Alaska. The combined TRD/krummholz architecture record indicates that abrupt shifts between strong and weak AL phases occurred every several decades since CE 1700 and that the 1800s had relatively long AL phases with heavy snowpacks. In addition to describing the magnitude and tempo of wintertime climate change in Northwestern North America, these results suggest that North Pacific Decadal Variability underlies the long‐term dynamics of treeline ecosystems along the northeast Pacific coast. -
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