Date of Completion

2016

Document Type

Honors College Thesis

Department

Geography

Thesis Type

College of Arts and Science Honors, Honors College

First Advisor

Shelly Rayback

Keywords

Dendrochronology, Forestry, Climate, Blue Intensity Analysis, Red Spruce, Eastern Hemlock

Abstract

The Northern Forest is a complex, heterogeneous environment which is undergoing changes in response to anthropogenic forcing factors. It is, therefore, necessary to quantify how trees have responded to environmental conditions in the past and may respond in the future. Traditional tree-ring width analysis enables the creation of temporally-expansive, annually-resolved records of yearly variability in tree growth. These tree-ring archives are well suited for researching which climate drivers have impacted forest growth most significantly and for identifying changes in the temporal stability of the climate signal over the 20th and 21st century. To perform this analysis, tree-ring width chronologies were developed for an eastern hemlock (Tsuga canadensis) stand, located at the Abbey Pond site in East Middlebury, Vermont, and red spruce (Picea rubens) stand, located in the Cape National Research Area (NRA) site, near Goshen Four Corners, Vermont, using increment cores sampled in 2010. A subset of each chronology was analyzed using blue intensity analysis (BIA), a novel dendrochronological technique which has been developed as a proxy for maximum latewood density (MXD) analysis. MXD has been utilized extensively in summer temperature reconstructions as it is capable of capturing a stronger, summer temperature signal. This study represents the first attempt to use BIA with eastern hemlock and red spruce trees and the first study within the US Northeast to incorporate BIA into dendroclimatological analysis. A combination of temperature, precipitation, and novel climate datasets were assembled to explore the drivers of growth of each forest stand. Several climate datasets, namely total percent cloudiness, total percent possible sunshine, and sunshine hours, to the best of our knowledge, have not been incorporated into past dendrochronology studies conducted in Vermont or the Northeastern US. Linear mixed model analysis was used to determine how much variability in annual growth could be attributed to climate drivers. 34% of the variance (R2 = 0.34) in the Abbey Pond TRW chronology was accounted for using summer (JJA) precipitation and June PDSI as predictors of growth. 35% of the variance in the Abbey Pond BIA chronology was accounted for using minimum September temperatures and total percent cloudiness (TPC). Previous year temperatures in July and August and present year minimum temperatures in September accounted for 33% of the annual variance in the Cape NRA TRW chronology. Minimum spring temperatures were only able to account for 6.8% of the annual variance in the Cape BIA chronology.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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