Digital Commons Network^™

Patterns, Mechanisms, And Characterization Of Carbon Cycling Stability Following Partial Forest Disturbance, Kayla C. Mathes

Theses and Dissertations

Among the most essential questions in the era of climate change is how the forest carbon (C) cycle will respond to an increase in the extent of biotic disturbances from insects and pathogens. While research has focused on stand-replacing disturbance regimes, less is known about C cycling stability following partial disturbances that produce gradients of disturbance severity. Belowground C cycling responses to disturbance are especially poorly understood, even though temperate forest soils contain up to 50% of total ecosystem C and soil respiration (R_s) accounts for more than half of temperate forest C loss. Interpreting trends and mechanisms …

Coupled Structure-Function Responses To Disturbance: High Structural Complexity Resistance Supports Primary Production Resistance, Kerstin M. Niedermaier

Theses and Dissertations

The capacity of forests to resist structural change and retain material legacies–the biotic and abiotic resources that persist through disturbance–is crucial to sustaining ecosystem functioning after disturbance. However, the role of forest structure as both a material legacy and feature supporting carbon (C) cycling stability following disturbance has not been widely investigated. We used a large-scale disturbance manipulation to ask whether LiDAR-derived canopy structures as material legacies drive 3-year responses of NPP to a range of disturbance severity levels. As part of the Forest Resilience Threshold Experiment (FoRTE) in northern Michigan, USA we simulated phloem-disrupting disturbances at a range of …

Successional Changes In Carbon Storage Are Sustained In A Temperate Forest Across Different Initiating Disturbances, Cameron Clay

Theses and Dissertations

Managing forests for carbon (C) sequestration requires an understanding of how disturbance history shapes C pools and fluxes over successional time. At the University of Michigan Biological Station, we examined how two stand establishing disturbances influenced C pools and fluxes over 100+ years of succession, comparing these secondary forests with “legacy” late-successional stands encompassing ages and compositions that would be present in the absence of region-wide stand-replacing disturbance. Our work utilized measurements taken between 2014 and 2020 from separate experimental forest chronosequences initiated following clear-cut harvesting only or clear-cut harvesting and fire, along with three >130-yr-old late successional stands comprising …

Plant-Pollinator Associations In An Eastern Serpentine Savannah And The Effects Of Overbrowsing, Allyson Richins

Theses and Dissertations

Chapter 1: Native plant response to deer overbrowsing in a serpentine savannah

Plants are particularly vulnerable to physical disturbance in low productivity areas, due to a high cost of replacing lost plant tissue. In the eastern United States, serpentine grasslands are fragmented ecosystems with high concentrations of rare endemic plant species, low concentrations of soil nutrients, and uncontrolled deer overpopulation. This study assessed functional responses of native angiosperms in a rare eastern serpentine savannah to selective deer browsing. Plant count, flower count, floral area, vegetative area, and plant height of 10 serpentine plant species were compared inside and outside of …

Mechanisms Underlying Production Stability In Temperate Deciduous Forests, Shea B. Wales

Theses and Dissertations

A persistent and reliable future terrestrial carbon (C) sink will depend on how stable forest production is under more variable climate conditions. We examined how age, forest structure, and disturbance history relate to the interannual variability of above-ground wood net primary production (NPPw). Our site in northern Michigan spans two experimental forest chronosequences and three late successional stands; the chronosequences have distinct disturbance histories, originating following either clear cut harvesting (“Cut Only”) or clear cut harvesting and fire (“Cut and Burn”), and range from 21 to 108 years old. Annual NPPw was estimated using dendrochronology and site specific allometric equations. …

Forest Structural Complexity And Net Primary Production Resilience Across A Gradient Of Disturbance In A Great Lakes Ecosystem, Lisa T. Haber

Theses and Dissertations

Forests are an important component of the global carbon (C) cycle and contribute to climate change mitigation through atmospheric C uptake and storage in biomass and soils. However, the forest C sink is susceptible to disturbance, which modifies physical and biological structure and limits spatial extent of forests. Unlike severe, stand-replacing disturbances that reset forest successional trajectories and may simplify ecosystem structure, moderate severity disturbances may instead introduce complexity in ways that sustain net primary production (NPP), leading to the phenomenon of “NPP resilience.” In this study, we examined the linkage between disturbance severity and ecosystem biological and physical structural …

The Effects Of Disturbance And Species Specific Interactions On Diversity In An Agent Based Forest Simulation, Matthew E. Mills

Theses and Dissertations

In ecology literature, there is much data which suggests that conspecific negative density dependence (CNDD) and abiotic disturbances increase biodiversity in forests. This thesis elucidates the notion that not only do these two forces increase diversity, but they may also interact with one another in order to achieve higher levels of biodiversity. Abiotic disturbances, like fires and hurricanes, can indirectly impact conspecific effects because when these forces remove individuals from the landscape, the role of the conspecific effects will change. The interaction of these two factors in biodiversity are explored in an agent based forest simulation through a resource surface. …

Forest Stand Structure And Primary Production In Relation To Ecosystem Development, Disturbance, And Canopy Composition, Cynthia M. Scheuermann

Theses and Dissertations

Temperate forests are complex ecosystems that sequester carbon (C) in biomass. C storage is related to ecosystem-scale forest structure, changing over succession, disturbance, and with community composition. We quantified ecosystem biological and physical structure in two forest chronosequences varying in disturbance intensity, and three late successional functional types to examine how multiple structural expressions relate to ecosystem C cycling. We quantified C cycling as wood net primary production (NPP), ecosystem structure as Simpson’s Index, and physical structure as leaf quantity (LAI) and arrangement (rugosity), examining how wood NPP-structure relates to light distribution and use-efficiency. Relationships between structural attributes of biodiversity, …

Coarse Woody Debris And The Carbon Balance Of A Moderately Disturbed Forest, Amy V. Schmid

Theses and Dissertations

Landscapes are comprised of multiple ecosystems shaped by disturbances varying in severity and source. Moderate disturbance from weather, pathogens, insects, and age-related senescence, in contrast to severe disturbances that fell trees, may increase standing woody debris and alter the contribution of coarse woody debris (CWD) to total ecosystem respiration (R_E). However, woody debris dynamics are rarely examined following moderate disturbances that substantially increase standing dead wood stocks. We used an experimental manipulation of moderate disturbance in an upper Great Lakes forest to: 1) examine decadal changes in CWD stocks through a moderate disturbance; 2) quantify in situ CWD …

Forest Net Primary Production Resistance Across A Gradient Of Moderate Disturbance, Ellen Goodrich-Stuart

Theses and Dissertations

The global carbon (C) balance is vulnerable to disturbances that alter terrestrial C uptake and loss. Moderate disturbances that kill or defoliate only a subset of canopy trees such as insect defoliation, drought, and age-related senescence are increasing in extent and frequency; yet, little is known about the effect of moderate disturbance on forest production and the mechanisms sustaining or supporting the recovery of the C cycle across a range of moderate disturbance severities. We used a broad plot-scale gradient of upper canopy tree mortality within a large manipulation of forest disturbance to: 1) quantify how aboveground wood net primary …

Canopy Disturbance And Reproduction In Cornus Florida L., Daniel Carr

Theses and Dissertations

This study examined aspects of local reproductive variation in the flowering dogwood (Cornus florida L.) coincident with recent differences in primary canopy architecture. The dogwood trees in this study were impacted by a hurricane that created numerous treefall gaps, which created fine scale heterogeneity in the primary canopy. Fine scale disturbances in a forest can result in changes for multiple members of the forest community, including the reproductive responses of the trees and interspecific pollination mutualisms. Previously determined differences in offspring genetic structure suggested that pollen movement among genetically unstructured maternal individuals was significantly impacted between open, or disturbed, canopy …