• Login
    View Item 
    •   Home
    • University of Alaska Fairbanks
    • UAF Graduate School
    • College of Natural Sciences and Mathematics
    • View Item
    •   Home
    • University of Alaska Fairbanks
    • UAF Graduate School
    • College of Natural Sciences and Mathematics
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of Scholarworks@UACommunitiesPublication DateAuthorsTitlesSubjectsTypeThis CollectionPublication DateAuthorsTitlesSubjectsType

    My Account

    Login

    First Time Submitters, Register Here

    Register

    Statistics

    Display statistics

    Seedling recruitment, genetic diversity, and secondary growth of deciduous shrubs in Arctic tundra disturbed by retrogressive thaw slump thermokarst on Alaska's North Slope

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    Huebner_D_2020.pdf
    Embargo:
    2022-05-05
    Size:
    11.79Mb
    Format:
    PDF
    Download
    Author
    Huebner, Diane C.
    Chair
    Bret-Harte, M. Syndonia
    Committee
    Wagner, Diane
    Wolf, Diana E.
    Douhovnikoff, Vladimir
    Keyword
    shrubs
    Alaska
    North Slope
    seedlings
    genetics
    tundra plants
    climate
    shrub growth
    Metadata
    Show full item record
    URI
    http://hdl.handle.net/11122/11274
    Abstract
    Since the 1970s, Arctic temperatures have risen by 2.7 °C, more than twice that of lower latitudes. Productivity of tundra vegetation is historically nutrient-limited, largely due to low rates of decomposition in soils underlain by permafrost, where cold temperatures limit nutrient uptake by plants. However, climate warming is implicated in the recent expansion of tall (≥ 0.5 m) deciduous woody shrubs across the Arctic. Among the largest tundra plants, deciduous shrubs exert strong controls on hydrology, heat balance, nutrient cycling, and food webs. These shrubs may be key players in carbon storage and re-stabilization of thaw-deformed permafrost landscapes (thermokarst), however, shrub-climate feedbacks are complex and their magnitude remains uncertain. Warming associated with recent thermokarst activity includes large (≥ 1 ha) de-vegetated depressions on hillslopes caused by mass soil thaw, known as retrogressive thaw slumps (RTS). RTS have increased on Alaska's North Slope by two-thirds since the 1980s. Within a few decades, some RTS near Toolik Lake support tall willow (Salix spp.) and dwarf birch (Betula nana) colonies. This study quantified three aspects of plant response in RTS of different ages (chronosequences) at two North Slope lakes: 1) recruitment (seedlings m⁻² and percent germination of soil seedbanks), 2) clonal (asexual) growth of dominant vegetation (willow), and 3) secondary growth (annual rings) of dwarf birch and willow. I hypothesized that conditions in RTS support greater recruitment, genetic diversity, and growth than conditions in undisturbed moist acidic tussock tundra, and that the climate signal (June mean temperature) is amplified in RTS shrub ring widths. The study found higher seedling density and seedbank viability associated with warm, nutrient-rich bare soil in recent RTS. Willow species richness was higher in RTS than in undisturbed tundra, but all willows showed high heterozygosity and low clonal spread regardless of disturbance. Ramets (branches) within clones were more widely spaced in RTS, suggesting that RTS can fragment and disperse asexual propagules. Shrub rings in RTS were wider than in undisturbed tundra, but climate sensitivity to warmer temperatures was not amplified in the growth rings of most RTS shrubs. Most RTS shrubs had wider rings associated with greater September precipitation in the previous year, while shrubs growing outside of RTS did not, which suggests protective effects of early snow accumulations in RTS depressions. These results demonstrate that some North Slope RTS support greater seedling recruitment and shrub growth than undisturbed tundra and may enhance tundra shrub growth.
    Description
    Thesis (Ph.D.) University of Alaska Fairbanks, 2020
    Table of Contents
    Chapter 1. General introduction -- Chapter 2. Microsite conditions in retrogressive thaw slumps may facilitate increased seedling recruitment in the Alaskan Low Arctic -- Chapter 3. Recruitment dynamics and population structure of willows in tundra disturbed by retrogressive thaw slump thermokarst on Alaska's North Slope -- Chapter 4. Secondary growth responses of deciduous shrubs in retrogressive thaw slump thermokarsts in the Alaskan Low Arctic -- Chapter 5. General Conclusion.
    Date
    2020-05
    Type
    Thesis
    Collections
    College of Natural Sciences and Mathematics

    entitlement

     
    ABOUT US|HELP|BROWSE|ADVANCED SEARCH

    The University of Alaska Fairbanks is an affirmative action/equal opportunity employer and educational institution and is a part of the University of Alaska system.

    ©UAF 2013 - 2021 | Questions? ua-scholarworks@alaska.edu | Last modified: September 25, 2019

    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.