Date of Award

2019

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

Yvette Dickinson

Committee Member 1

Christopher R. Webster

Committee Member 2

Robert E. Froese

Committee Member 3

Erik A. Lilleskov

Committee Member 4

Amy M. Marcarelli

Abstract

The objective of this dissertation is to assess plant community response across a range of silvicultural disturbances and test ecological hypotheses to better inform ecologists and forest managers. To provide context for the utility of revising silvicultural systems, I review natural disturbance regimes and historical practices that have shaped contemporary Great Lakes northern hardwood forests (Chapter 2). Further, I identify important ways to expand the silvicultural toolbox and better emulate natural disturbance regimes. Building on this theoretical underpinning, I investigate the initial regeneration and plant community response to two novel silvicultural experiments: the Northern Hardwood Experiment for Enhancing Diversity (NHSEED) near Alberta, Michigan, and a strip clearcut experiment near Mountain Iron, Michigan. Three themes emerged from the findings in this dissertation. First, seedlings and saplings receive few benefits from reduced canopy cover if they cannot overcome additional limitations. For example, yellow birch (Betula alleghaniensis Britt.) seedling density was better predicted by conspecific overstory basal area and litter depth variation than silvicultural treatments (Chapter 3), and sugar maple recruitment into the sapling size class in clearcut strips may be limited by deer browse (Chapter 5). Second, silvicultural disturbances tend to favor low-mass fruit, long-lived fruit, or vegetative reproduction, except for sugar maple which relies on robust advance regeneration to benefit from overstory disturbances (Chapters 3, 4 and 5). Third, the relationship between disturbance severity and diversity is not conclusive. Initial responses to silvicultural disturbances did not follow the intermediate disturbance hypothesis, which proposes that diversity is maximized at intermediate levels of disturbance intensity or frequency (Chapter 4). Moreover, taxonomic and phylogenetic diversity do not always respond similarly to disturbances (Chapter 4), suggesting that both indices should be incorporated into informed management decisions. Integrating these findings into management planning may allow better predictions to silvicultural disturbances now and in the future.

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