Date of Award

2017

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Forestry (MS)

Administrative Home Department

School of Forest Resources and Environmental Science

Advisor 1

Yvette L. Dickinson

Committee Member 1

Christopher R. Webster

Committee Member 2

Tara L. Bal

Abstract

Gap partitioning theory predicts that changes in microenvironment conditions found within a forest opening promote diversity in forest ecosystems. Under this theory we would expect to see variations in tree and understory diversity throughout and surrounding a forest opening. In order to test this theory, we examined manmade openings with legacy-tree retention in a northern hardwood forest located in the Upper Peninsula of Michigan. This work is part of an ongoing study that was started in 2003 with the creation of 49 openings centered on a reserve dominant or co-dominant yellow birch (Betula alleghaniensis Britt.). The primary objective of this research was to assess if opening size, plot location and/or plot transect azimuth had an influence on the dependent variables that we measured (herbaceous-layer species, cover groups, and sapling). Twenty reference sites were also selected from the surrounding forest and centered on a dominant or co-dominant yellow birch. At each site, the following variables were measured; herbaceous-layer species percent cover, cover groups (tree seedling (< 50 cm), exposed soil, forest litter, exposed rock, woody shrubs, herbaceous plants, grass, sedge, rush, non-vascular plants, and woody debris), and sapling height (≥ 50 cm).

We found that both opening size and plot location were influential on our measured variables to varying degrees. We found no evidence that transect azimuth was a significant predictor of any of the dependent variables. Opening size was significant when analyzing species diversity and evenness. Plot location was also significant when measuring species diversity as well as richness. Correlations with cover groups varied and some groups were not found to be associated with any of the opening measures (size, location, transect azimuth).

Mean tallest tree sapling height was not found to be significantly different among opening sizes, but sapling height was significantly shorter in the references sites than any of the harvested openings. We also found that saplings under the legacy tree were the tallest on average when compared to the opening and the surrounding forest. Maples were by far the most abundance sapling species with sugar maple (Acer saccharum Marsh.) being the most common. Continued monitoring of sapling survival and growth will be important to gain a better understanding of tree diversity in openings with legacy- tree retention and have a better understanding of the future forest composition.

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