PS 34-56 - Arctic-alpine vegetation responses to global change following glacial retreat: Primary succession in the Central Brooks Range, Alaska

Wednesday, August 9, 2017
Exhibit Hall, Oregon Convention Center


Shawnee A. Gowan, University of Alaska Fairbanks; Donald A. Walker, University of Alaska


Background/Question/Methods:  The majority of Alaska’s glaciers have been retreating since approximately 1700 A.D. Numerous studies have examined plant community succession on glacial forelands, but there is little information on pioneer stages of succession involving mainly cryptogamic species (bryophytes and lichens), and how these set the stage for colonization by higher plants. Additionally, little is known about recent responses to accelerating climate change. I will examine primary succession following recent rapid retreat of small cirque glaciers of the central Brooks Range, where detailed lichenometric dating studies were conducted in the 1970s. I hypothesize: (1) Patterns in vegetation community development during primary succession are predictable based on indicative pioneer communities and substrate type. (2) Lichen growth rates and community compositions markedly differ from the 1970’s, reflecting localized climate change. I will establish permanent plots primarily on moraines formed following the Little Ice Age glacial advance. I will measure maximum lichen thallus diameters of six species, on different aged surfaces, and update the lichenometric curve to determine if recent warming has affected lichen growth rates. I will also conduct the first detailed community analysis for the area of vascular plants, bryophytes, and lichens. My research will focus on Grizzly Glacier, a well-studied, relatively accessible glacier near Atigun Pass. If resources permit, I will include more glaciers to examine variation on different substrates. These data will be compared to primary succession data collected in 2016 from alpine-inland and maritime-tidewater glacial forelands in an attempt to explain variation within a shared regional environment, and between differing environments and locations.

Results/Conclusions: Trends in early successional colonization patterns on a maritime glacial foreland documented in 2016, show rapid increase in biodiversity and plant cover up to 120m in front of the glacial terminus, followed by a decrease in diversity and overall cover to 500m. This contrasted sharply with a slow accumulation of diversity and cover to 120m in front of an inland-alpine glacier, with steep acceleration past 500m from the terminus. This suggests that major environmental factors such as substrate, elevation, precipitation and annual temperature drive pioneer stages of primary succession, as expected. Even so, certain species of lichens, bryophytes and vascular plants occur as major players across many regions, and appear to be characteristic for plant communities developing later in succession. Such a relationship suggests that major environmental variation may not always be a barrier, and some pioneer species may be indicative of the trajectory of community assembly.