Sensitivity of Subarctic Trees to Highway-Related Effects on Permafrost

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USU Student Showcase

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Patrick Belmont, Michael Kuhns


Permafrost retention and thawing are important factors in engineering, construction, groundwater dynamics, and biodiversity in high latitude terrestrial environments. Accelerated thawing of permafrost near major highways has been well-documented in North America and Asia. Tree-ring data has been used extensively as a proxy for measuring historical streamflow and climate fluctuations and may prove useful as a proxy for constraining the timing and rate of highway-related permafrost thawing. Generally, during periods of higher effective moisture, trees produce wider rings. During periods of drought ring growth is suppressed, resulting in narrower rings. By combining the ring width measurements from multiple trees with precipitation data, it is possible to reconstruct temporal precipitation patterns and cycles. By extension, it should also be possible to reconstruct other vegetation-relevant signals, such as permafrost thawing, by using known historical precipitation and climate cycle data to filter the tree-ring signal. As permafrost is known to have an effect on groundwater availability, permafrost may exert direct control on tree growth rate. This study tests the hypothesis that tree growth rates increase significantly with proximity to major highways due to permafrost thawing. Further, we expect that trees growing along isolines at progressive distances from the highway (i.e., 5, 10, 15, 20 meters) will have higher correlations with each other than with trees growing closer to or farther from the highway, showing increased rates of growth with proximity to permafrost-melting roadways. Ninety-six black and white spruce trees (Picea mariana and Picea glauca) were cored at sites along the Glenn Highway, in interior Alaska, and chronologies built and correlated with COFECHA (standard tree-ring analysis software). While initial analysis shows that there may be the expected mean annual increase in highway-proximal tree growth, we have not yet applied climate data filters to our tree ring measurements.

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