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Articles 61 - 75 of 75
Full-Text Articles in Forest Sciences
Variation In Personality Among Semi-Wild Myanmar Timber Elephants, Sateesh Venkatesh
Variation In Personality Among Semi-Wild Myanmar Timber Elephants, Sateesh Venkatesh
Theses and Dissertations
This study examines two personality traits: exploration and neophobia, which could influence human-elephant conflicts. Thirty-one semi-wild elephants were tested over two trials using a custom novel puzzle tube containing three tasks and three rewards. Our studies show that elephants do vary significantly between individuals in both exploration and neophobia.
Discerning Competitive Vs. Facilitative Relationships Of Weeds On Forest Restoration Efforts At La Sal Del Rey, Tx, Mylen A. Arias
Discerning Competitive Vs. Facilitative Relationships Of Weeds On Forest Restoration Efforts At La Sal Del Rey, Tx, Mylen A. Arias
Theses and Dissertations
Dryland ecosystems need effective restoration strategies to address severe degradation. It is often assumed that voluntary forb weeds either compete with or have no effect on native seedlings. In contrast, theory and empirical work suggest a potential facilitative role for such forb weeds. We conducted a manipulative weed exclusion experiment at a semi-arid site in South Texas targeted for large scale forest restoration and subsequently dominated by early successional forb weeds to discern the net effect of these weeds on the growth and survival of target thornscrub tree and shrub seedlings. Overall, weed presence did not significantly affect seedling mortality …
Native Plant Allelopathy: A Potential Approach To Limit Invasive Grass Encroachment In Thorn Forest Restoration, Emily A. Mullins
Native Plant Allelopathy: A Potential Approach To Limit Invasive Grass Encroachment In Thorn Forest Restoration, Emily A. Mullins
Theses and Dissertations
Less than 5% of the Tamaulipan thorn forest remains in the United States. For this reason, there have been many attempts at restoration of this ecosystem. Oftentimes these attempts are unsuccessful due to the high prevalence of invasive African grasses that outcompete the seedlings. In an effort to improve the efficacy of these restoration efforts, native plant allelopathy has been examined for its ability to exclude invasive guineagrass. Native species were surveyed and selected species were tested for allelopathy in laboratory bioassays. The species that exhibited allelopathy in the laboratory were then evaluated in pot experiments for their ability to …
Optimizing Species Selection For Forest Restoration In The Lower Rio Grande Valley, Faeqa Mohsin
Optimizing Species Selection For Forest Restoration In The Lower Rio Grande Valley, Faeqa Mohsin
Theses and Dissertations
Over the past four decades, the Lower Rio Grande Valley has been reforested with over 3.3 million native thornscrub plants in old agricultural land through transplanting native species. However, assessments of LRGV forest restoration efforts are scarce, and to address the knowledge gap, this study examined species-specific responses to restoration interventions (RIs) aimed at minimizing seedling mortality for optimizing species selection. A critical period for forest restoration in old croplands is the seedling stage, where high mortality occurs due to the interactive effects of abiotic stress, compromised soil nutrient status from intensive agriculture, and mammalian herbivory. So, we evaluated seedling …
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 …
Assessment Of Long-Term Effects Of Woody Plants Expansion In Humid, Tropical Grassland Of Venezuela, Soraya A. Delgado
Assessment Of Long-Term Effects Of Woody Plants Expansion In Humid, Tropical Grassland Of Venezuela, Soraya A. Delgado
Theses and Dissertations
The invasion of woody plants into grassland communities, or shrub encroachment, is a worldwide phenomenon usually attributed to anthropogenic interference. Most studies have focused on temperate and arctic biomes. Less is known about how shrub encroachment is affecting humid tropical grasslands, which have different climates, higher levels of biodiversity and different histories of human land use. This project quantifies the rate of woody vegetation change in a humid tropical grassland of Venezuela using remote sensing over the past quarter century and ground based measurements of selected individual species. Results of remote sensing indicate high rates of conversion of grasslands to …
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. …
Exploring Data Mining Techniques For Tree Species Classification Using Co-Registered Lidar And Hyperspectral Data, Julia K. Marrs
Exploring Data Mining Techniques For Tree Species Classification Using Co-Registered Lidar And Hyperspectral Data, Julia K. Marrs
Theses and Dissertations
NASA Goddard’s LiDAR, Hyperspectral, and Thermal imager provides co-registered remote sensing data on experimental forests. Data mining methods were used to achieve a final tree species classification accuracy of 68% using a combined LiDAR and hyperspectral dataset, and show promise for addressing deforestation and carbon sequestration on a species-specific level.
Phylogenetic Analyses Of Andean And Amazonian Tree Communities In Ecuador, Samantha J. Worthy
Phylogenetic Analyses Of Andean And Amazonian Tree Communities In Ecuador, Samantha J. Worthy
Theses and Dissertations
The forests of Ecuador are known for their high levels of diversity and endemism, classifying the country as a biodiversity hotspot. Both the western Amazon and Andean montane forests are richly populated with tropical tree species that have been little studied in a community phylogenetic context. The implementation of elevational transects and trait based analyses having proven useful in gaining a better understanding of how environmental factors are affecting the tree community structure in these habitats. The goal of this research was to evaluate the magnitude ofDNA barcode diversity among Amazonian and Andean tree species. Specifically, the objectives were to …
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, …