Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 18 of 18 for “"Net ecosystem exchange"”.
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Ecosystem-atmosphere exchange of carbon dioxide and water vapour in typical East-Asian croplands
… and environmental changes, the role of cropland ecosystems in the surface-atmosphere energy and matter exchange has drawn a lot of attention. This thesis investigated the potential change on ecosystem-atmosphere exchange of heat, water vapour and carbon dioxide if crop species planted or …
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Investigation of covariability between energy fluxes and CO2 exchange over a semi-arid savanna (Kruger National Park) by Eddie Covariance Technique
… studying the connection between energy flows and Net Ecosystem Exchange (NEE) at the semi-arid savanna of Kruger National Park to gain a more detailed and accurate understanding of these processes, especially in semi-arid savannas that are susceptible to changes in environmental factors. By …
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Spatial and temporal dynamics of the terrestrial carbon cycle : assimilation of two decades of optical satellite data into a process-based global vegetation model
… data produces more realistic carbon fluxes of net primary production (NPP), soil respiration, carbon released by fire and the net land-atmosphere flux than the potential vegetation model. It also produces a good fit to the interannual variability of the CO2 growth rate. Compared to the original …
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Modeling Neotropical Ecosystems during the Last Glacial Maximum
… has long motivated research on Neotropical ecosystems, though regionally-focused modeling studies remain relatively sparse and limited in scope. Three individual projects were performed to address potential issues in the modeling of Neotropical ecosystems in past and present contexts with …
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Non-growing season CO2 fluxes of a boreal fen – key drivers and responses to anomalous winter conditions
… to a significant amount of the full-year ecosystem carbon balance. Year-round net ecosystem exchange (NEE) data from 17 years was used to analyse the non-growing season carbon dioxide (CO2) fluxes together with environmental and meteorological variables at Siikaneva fen in Southern …
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Forest respiration from eddy covariance and chamber measurements under high turbulence and a bark beetle epidemic
… carbon, water, and energy fluxes, and a global network of >500 sites (www.fluxnet.ornl.gov) has resulted in major advances in understanding ecosystem-scale biogeochemical cycling. However, long-term sums of net ecosystem exchange, photosynthesis and respiration fluxes have uncertainties because …
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Advection at a forest site – an updated approach
The exchange of carbon dioxide (CO2) across the vegetation-atmosphere interface of a spruce forest was investigated. Horizontal and vertical advection are recognized as important terms of the Net Ecosystem Exchange (NEE) budget in addition to the commonly measured turbulent flux and storage flux. …
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Phenology Effects on Carbon and Water Dynamics in a Pristine Boreal Fen A multi-decadal analysis from 2005-2007 & 2014-2022
… it is evident that climate change affects these networks of interactions, it is only poorly understood to what extent, as site-specific empirical evidence over multiple decades is lacking. This study investigates the role of phenology (leaf area index: LAI) for peatland C (net ecosystem exchange: …
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Assessing the condition of the Flow Country peatlands to support their future protection: Monitoring blanket bog functioning during drought and mapping post-wildfire recovery
… year. During that period, most sites acted as net sources of CO2 to the atmosphere. Net Ecosystem Exchange (NEE) was limited by water availability, with ericoid shrubs showing the highest drought resilience, followed by graminoids and Sphagnum mosses.<br/>An exhaustive optimal vegetation index …
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The modeled effects of fire on carbon balance and vegetation abundance in Alaskan tundra
… fire frequency. Whether tundra remains a global net sink of carbon could depend upon the effects of fire on vegetation, specifically concerning the speed at which vegetation reestablishes, the stimulation of growth after fire, and the changes that occur in species composition during succession. …
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Quantifying terrestrial ecosystem carbon dynamics with mechanistically-based biogeochemistry models and in situ and remotely sensed data
<p>Terrestrial ecosystem plays a critical role in the global carbon cycle and climate system. Therefore, it is important to accurately quantify the carbon dynamics of terrestrial ecosystem under future climatic change condition. This dissertation evaluates the regional carbon dynamics by using …
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Quality Assurance for Eddy Covariance Measurements of Turbulent Fluxes and its Influence on the Energy Balance Closure Problem
… to study the surface energy balance and the exchange of gaseous air constituents. Due to improvements in the construction of adequate sensors and the progress in computer technology during the last decades this method is now well-established. However, a general failure to close the energy …
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CO2 and Isotope Flux Measurements above a Spruce Forest
… of the turbulent carbon dioxide (CO2) exchange by the eddy covariance (EC) method has become a fundamental tool for the quantitative determination of the atmospheric CO2 net ecosystem exchange (NEE) and the investigation of the carbon mass balances of ecosystems. Such measurements …
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Ground vegetation gross primary production dynamics of a drained peatland forest ecosystem
… and impacts of the partial harvest; forest floor net exchange (NEFF) and respiration (RFF) were measured on an hourly interval with an automated closed flux chamber method were analysed. These measurements were conducted in a forestry drained peatland before (pre-harvest, 2013 – 2015) and after …
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Adoption of footprint methods for the quality control of eddy-covariance measurements
… on a large number of sites organised in a network. Their results may serve as a tool for an improved determination of yearly sums of the net ecosystem exchange, because fluxes originating from sectors of minor quality could be excluded from the analysis. Because of these important …
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Modeling the exchange of energy and matter within and above a spruce forest with the higher-order closure model ACASA
… for the detailed simulation of all relevant exchange processes above and within a forest canopy. The Advanced Canopy-Atmosphere-Soil Algorithm (ACASA) model incorporates such an advanced turbulence scheme, the third-order turbulence closure. This study presents the application of the ACASA …
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Ecosystem Models in a Bayesian State Space Framework
… the temporal dynamics of carbon in terrestrial ecosystems. In Chapter 1, I provide an introduction to Ecological Forecasting, State Space Models, and the challenges of using State Space Models for Ecosystems. In Chapter 2, we provide a brief background on State Space Models and common methods of …
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The potential implications of bioenergy crop production for water and energy balance and carbon and nitrogen dynamics in the United States
… and quality in the US; (3) what is the potential net ecosystem carbon exchange (NEE) and N2O emission with the expansion of bioenergy grasses in the US; and (4) how does application of N fertilizer affect NEE and N2O emission with the expansion of bioenergy grasses in the US. Chapter 1 includes a …