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Articles 1 - 12 of 12
Full-Text Articles in Forest Sciences
Patterns, Mechanisms, And Characterization Of Carbon Cycling Stability Following Partial Forest Disturbance, Kayla C. Mathes
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 (Rs) 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
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 …
Advancing Forest Structure-Function Relationships: Linking Above- And Belowground Structure To Soil Respiration, Laura J. Hickey
Advancing Forest Structure-Function Relationships: Linking Above- And Belowground Structure To Soil Respiration, Laura J. Hickey
Theses and Dissertations
Variation in the soil-to-atmosphere C flux, or soil respiration (Rs), is influenced by a suite of biotic and abiotic factors, including soil temperature, soil moisture, and root biomass. However, whether canopy structure is tied to soil respiration through its simultaneous influence over these drivers is not known. We assessed relationships between measures of above- and belowground vegetation density and complexity, and evaluated whether Rs is linked to remotely sensed canopy structure through pathways mediated by established biotic and abiotic mechanisms. Our results revealed that, at stand-scale, canopy rugosity–a measure of complexity–and vegetation area index were coupled to soil respiration through …
A Spatiotemporal Assessment Of Fish Assemblage Response To Land-Use Change And The Evaluation Of Edna Metabarcoding For Describing Diverse Fish Communities, Timothy M. Owen
Theses and Dissertations
Fish assemblages are often assessed as a biological proxy for environmental health. While humans value healthy environments for the ecosystem services and recreational opportunities they provide, it is increasingly evident that such resources can be paradoxically degraded by anthropogenic activities. In this investigation, we studied the relationship between different intensities of anthropogenic land-use change and habitat-driven fish assemblage response across multiple spatiotemporal scales. Secondarily, we explored the efficacy of eDNA metabarcoding against conventional electrofishing techniques for the purpose of describing complete fish communities. This study was conducted in the Tuckahoe Creek basin near Richmond, Virginia. This James River tributary serves …
Senescent Trees Stabilize Aboveground Wood Net Primary Production Immediately After Disturbance, Maxim S. Grigri
Senescent Trees Stabilize Aboveground Wood Net Primary Production Immediately After Disturbance, Maxim S. Grigri
Theses and Dissertations
In the United States, forests sequester 17% of national carbon (C) emissions annually (UGCRP, 2018), however shifting forest disturbances threaten the stability of this essential C sink. Unlike the high severity, stand-replacing disturbances that were widespread a century ago, today’s eastern temperate forests experience frequent low-to-moderate severity disturbances from invasive pests and pathogens with mixed effects on net primary production (NPP). Carbon cycling stability after disturbance has been reported, however, the mechanisms underlying immediate NPP stability or decline are not well understood. Through weekly measurements of production in a landscape scale experiment, we show that the sustained growth of senescent …
Interspecific Gene Flow Potentiates Adaptive Evolution In A Hybrid Zone Formed Between Pinus Strobiformis And Pinus Flexilis, Mitra Menon
Theses and Dissertations
Species range margins are often characterised by high degrees of habitat fragmentation resulting in low genetic diversity and higher gene flow from populations at the core of the species range. Interspecific gene flow from a closely related species with abutting range margins can increase standing genetic diversity and generate novel allelic combinations thereby alleviating limits to adaptive evolution in range margin populations. Hybridization driven interspecific gene flow has played a key role in the demographic history of several conifer due to their life history characteristics such as weak crossability barriers and long generation times. Nevertheless, demonstrating whether introgression is adaptive …
Mechanisms Underlying Production Stability In Temperate Deciduous Forests, Shea B. Wales
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
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 …
Natural And Anthropogenic Drivers Of Tree Evolutionary Dynamics, Brandon M. Lind
Natural And Anthropogenic Drivers Of Tree Evolutionary Dynamics, Brandon M. Lind
Theses and Dissertations
Species of trees inhabit diverse and heterogeneous environments, and often play important ecological roles in such communities. As a result of their vast ecological breadth, trees have become adapted to various environmental pressures. In this dissertation I examine various environmental factors that drive evolutionary dynamics in threePinusspecies in California and Nevada, USA. In chapter two, I assess the role of management influence of thinning, fire, and their interaction on fine-scale gene flow within fire-suppressed populations of Pinus lambertiana, a historically dominant and ecologically important member of mixed-conifer forests of the Sierra Nevada, California. Here, I find evidence …
The Effect Of Chronic Nutrient Addition From Wastewater On Forest Ecosystems At The Rice Rivers Center, Michael Beck
The Effect Of Chronic Nutrient Addition From Wastewater On Forest Ecosystems At The Rice Rivers Center, Michael Beck
Theses and Dissertations
Wastewater application to land can be a useful tool for mitigating impacts of nutrient enrichment on aquatic systems. A land application treatment system at VCU’s Rice Rivers Center in Charles City County, VA provided an opportunity to study the impact of wastewater addition on the biogeochemistry of forests representative of the Mid-Atlantic Coastal Plain. Nutrient concentrations in throughfall and leachate were measured at Treatment and Control sites to assess differences in nutrient deposition and retention. Wastewater amended plots from the Walter L. Rice education building received 20-fold (N) and 6-fold (P) higher inputs relative to Control plots and plots located …
The Effects Of Disturbance And Species Specific Interactions On Diversity In An Agent Based Forest Simulation, Matthew E. Mills
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
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, …