Date of Award
2025
Document Type
Open Access Dissertation
Degree Name
Doctor of Philosophy in Forest Science (PhD)
Administrative Home Department
College of Forest Resources and Environmental Science
Advisor 1
David J. Flaspohler
Committee Member 1
Christopher Webster
Committee Member 2
Kristin Brzeski
Committee Member 3
Kerry Woods
Abstract
This is a multi-taxa study of the ecological factors which differentiate communities of granite bedrock glades from surrounding areas (peripheral and matrix forest). It includes vascular plants, lichens, bryophytes, reptiles and birds. This study demonstrated that the same predictor variables (percent canopy cover and amount of exposed bedrock) were associated with the strongest gradient for all taxonomic groups evaluated.
Microclimates were studied in bedrock glades and surrounding communities by deploying 60 data loggers. Data were collected on vascular plants and cryptogams (lichens and mosses) at the precise logger locations and related to climatic factors. Annual mean temperature, growing degree days, and the 95th percentile of maximum temperature were analyzed as potential drivers for the three habitats. The climate variables demonstrated that bedrock glades were significantly warmer than periphery and matrix forest, 11-20 m and 41-50 m from the edge of the glades respectively.
Models were made for pre-selected southern disjunct species with measured habitat and climatic variables using nonparametric multiplicative regression (NPMR) conducted using Hyperniche (version 2.3). Significant environmental models showed that variables related to lichen guilds, distance to Lake Superior, canopy cover, elevation and distance to human roads and trails were most important for the target animal species. The most important climatic variables in the models were related to soil and ground-level growing degree days, and daily temperature range on the ground.
The impacts of drought have been less studied in terrestrial plant communities than other types of natural disturbance. Most drought studies have focused on regional impacts or used climate modeling over a broad geographic area. In May 2021, prior to drought conditions, 100-m-long transects were established; they were sampled with 1-m² plots in September 2021 after an unusually dry spring and summer. Environmental variables were recorded at two scales (site and plot level), and cover values for alive and top-killed vegetation cover were given for each species. Among the 48 species in our study, 18 experienced at least some top-kill, and 26% of the total vegetation cover was top-killed in 2021.
Nonmetric multidimensional scaling ordination (NMS) was used to describe the variation in top-killed plant data among plots and species. The plots with the highest dead plant cover were on south-facing slopes with no tree canopy cover. This study also reports the first collection of two plant species, Nuttallanthus canadensis (L.) D.A.Sutton (Plantaginaceae), and Opuntia cespitosa Raf. (Cactaceae) from the Lake Superior drainage basin, and both appear to be the northernmost occurrences of these species in eastern North America.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Rutherford, Ryne D., "ECOLOGICAL FACTORS THAT DICTATE THE OCCURRENCE OF UNIQUE BIOTA ON GRANITE BEDROCK GLADES", Open Access Dissertation, Michigan Technological University, 2025.
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