Date Approved

8-2020

Graduate Degree Type

Thesis

Degree Name

Biology (M.S.)

Degree Program

Biology

First Advisor

Dr. Robert Hollister

Second Advisor

Dr. Gary Greer

Third Advisor

Dr. Megan Woller-Skar

Fourth Advisor

Dr. Timothy Evans

Academic Year

2019/2020

Abstract

High latitude regions are warming faster than most regions. Studies documenting change in plant cover due to warming have reported that graminoids, deciduous shrubs, and evergreen shrubs are increasing in some regions of the Arctic, but not at others. Mixed responses to warming have caused researchers to shift towards an emphasis on functional traits of individual species rather than their growth forms. This thesis focuses on ten measured plant functional traits for twelve arctic species at three regions spanning a latitudinal gradient in northern Alaska (Utqiaġvik, Atqasuk, and Toolik Lake). We compare mean trait values across the three regions for each species and find considerable variability within a growth form. Quantification of intraspecific variation (ITV) in the three populations showed high amounts of variation for some traits (>50% for normalized difference vegetation index (NDVI) and photosynthetic capacity (Amax)) but not for other traits (<15% for plant height, leaf area, specific leaf area (SLA), leaf thickness, and leaf dry matter content (LDMC)). Amount of ITV also varied across regions. To better understand why trends in plant cover and functional traits vary across regions, change in cover (measured three times from 2008 to 2018) was also compared with observed trait values (measured in 2018) for twelve dominant species. Canonical correspondence analysis (CCA) suggested a relationship between change in species cover and functional traits. Species increasing in cover were associated with photosynthetic capacity (Amax) and species decreasing in cover were associated with LDMC. Investigation of community-weighted trait means (CWM) showed that whole community rather than species-specific trait values may be more indicative of future change. CWM changed significantly over time for all traits at Utqiaġvik and Atqasuk, but not Toolik Lake. Non-significant results in direct cover-trait relationships also suggest that multiple traits rather than a single trait may be responsible for shifts in plant cover, supporting a multidimensional approach to future trait-based studies. Additionally, studies investigating the impact of warming on vegetation that incorporate ITV will be able to provide more accurate predictions for future change.

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