Regional and local changes in the climate have been driving rapid glacial retreat in many glaciers since the Little Ice Age. This retreat provides a unique opportunity to study succession across the chronosequences of glacier forelands. Patterns of plant colonization and succession on terrain exposed by retreating glaciers give insight into factors influencing alpine ecosystem change and recovery. Understanding these patterns and processes is important for conserving alpine landscapes and flora as glaciers disappear. This study sought to investigate how various biotic and abiotic factors influence plant successional patterns in the dynamic alpine environment of Sperry Glacier, a Little Ice Age, mid-latitude cirque glacier in Glacier National Park, Montana. Through field data collection, additional Geographic Information System (GIS) derived variables, and subsequent geostatistical analysis, I specifically assessed: (1.) vegetative trends (percent cover, species richness, Shannon's diversity, species evenness, composition, and species turnover) over a 170-year chronosequence, and (2.) vegetative trends over field and GIS-derived site conditions (e.g., surface fragmentation, concavity, flow accumulation, and solar irradiance). Sixty-one plots (each 8 square meters) were placed throughout the glacier foreland using a random sample stratified by terrain date. Percent cover, species richness, Shannon's diversity, and species evenness were calculated for each plot. All sampled vegetation was identified with taxonomic resolution down to species whenever possible. I assessed vegetative trends across terrain age ranges using Kruskal-Wallis and Dunn's tests. I used two models, generalized linear models (GLMs) and Classification and Regression Trees (CARTs), to assess field and GIS-derived biophysical correlates (e.g., surface fragmentation, concavity, terrain variables, and solar irradiance with vegetative trends), followed by Kruskal-Wallis tests, Dunn's tests, and scatterplots. Species richness and vegetation cover were greater on older terrain. Plant composition changed over terrain age, with Penstemon ellipticus favoring older terrain and Boechera lemmonii favoring moderately aged terrain. Moderate drainage and concave plots, which were important in the GLMs, explained increased species richness and Shannon's diversity across different site conditions. The CARTs were able to predict species richness, vegetation cover, Shannon's diversity, and species evenness with surface fragment sized from gravel to cobble, topographic position index, and flow accumulation. These findings show that both temporal and biophysical site conditions influence successional trends across the foreland, though different vegetation measures are most influenced differently. / Master of Science / Regional and local changes in the climate have been driving rapid glacial retreat in many glaciers since the Little Ice Age. This retreat provides a unique opportunity to study succession across glacier foreland terrain that has been uncovered for different lengths of time. Patterns of plant colonization and succession on terrain exposed by retreating glaciers give insight into factors influencing alpine ecosystem change and recovery. Understanding these patterns and processes is important for conserving alpine landscapes and flora as glaciers disappear. This study sought to investigate how various biotic and abiotic factors influence plant successional patterns in the dynamic alpine environment of Sperry Glacier, a Little Ice Age, mid-latitude glacier in Glacier National Park, Montana. Through field data collection, additional Geographic Information System (GIS) derived variables, and subsequent geostatistical analysis, I specifically assessed: (1.) vegetative trends (percent cover, species richness, Shannon's diversity, species evenness, composition, and species turnover) over terrain uncovered between zero and 170-year, and (2.) vegetative trends over field and GIS-derived site conditions (e.g., surface fragmentation, concavity, flow accumulation, and solar irradiance). Sixty-one plots (each 8 square meters) were randomly placed within each terrain age range throughout the glacier foreland. Percent cover, species richness, Shannon's diversity, and species evenness were calculated for each plot. Shannon's diversity is a measurement of a community's diversity and uses both species richness and evenness to calculate diversity. All sampled vegetation was identified with taxonomic resolution down to species whenever possible. I assessed vegetative trends across terrain age using several statistical comparison tests. I used two types of statistical models to assess field and GIS-derived biophysical correlates (e.g., surface fragmentation, concavity, terrain variables, and solar irradiance with vegetative trends), followed by comparison tests and scatterplots. Species richness and vegetation cover were greater on older terrain. Plant composition changed over terrain age, with the species Penstemon ellipticus (rocky ledge penstemon) favoring older terrain and Boechera lemmonii (Lemmon's rockcress) favoring moderately aged terrain. Moderate drainage and concave plots explained increased species richness and Shannon's diversity across different site conditions. Species richness, vegetation cover, Shannon's diversity, and species evenness could be predicted with surface fragments sized from gravel to cobble, topographic position index, and flow accumulation. These findings show that both temporal and biophysical site conditions influence successional trends across the foreland, though different vegetation measures are most influenced differently.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/115411 |
| Date | 12 June 2023 |
| Creators | Schulte, Ami Nichole |
| Contributors | Geography, Resler, Lynn M., Pingel, Thomas, Gielstra, Dianna |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Coverage | Montana, United States |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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