Influencing Factors of Plant Succession Along a Chronosequence at Grinnell Glacier, Glacier National Park, MT, USA

Keywords: Glacier foreland, Succession, Chronosequence
Session Type: Virtual Guided Poster Abstract
Day: Monday
Session Start / End Time: 2/28/2022 05:20 PM (Eastern Time (US & Canada)) - 2/28/2022 06:40 PM (Eastern Time (US & Canada))
Room: Virtual 40

Abstract

Patterns of plant colonization on terrain exposed by retreating glaciers provides insight into the drivers, mechanisms, and trends of primary succession and ecosystem recovery in dynamic alpine environments. The purpose of this research is to investigate biotic and abiotic characteristics of primary succession at Grinnell Glacier — a LIA glacier in Glacier National Park, MT. Specific objectives were to assess trends in species richness, percent cover, Shannon’s diversity, and species evenness, (1.) across a chronosequence, (2.) among different landforms, and (3.) among GIS-derived site conditions (e.g., elevation, precipitation, and solar irradiance). Fifty-six sample plots (2 m x 2 m) were placed across terrain exposed between 1850 and 2015 using a random sample stratified by terrain date. Species richness, percent vegetation cover, Shannon’s diversity, and species evenness were calculated for each plot.
Preliminary results reveal that plant colonization took at least 27 years since exposure to begin colonizing on roche moutonnées, and 36 years on bedrock with surface till. Vegetation cover increased overall the longer a plot was exposed, but the relationship was weak. Furthermore, Shannon’s diversity index and species evenness did not appear to be strongly influenced by time since deglaciation, implying other factors, such as macro- and micro- scale site characteristics influenced the rate and patterns of succession. A PCA biplot and regression plots revealed elevation and precipitation influence all four measured vegetative characteristics, further influencing successional patterns. Landform characteristics (e.g., consolidation) are likely to play an essential role in determining plant succession trends and patterns at Grinnell Glacier.