Scaling approaches to the modelling of water, sediment and nutrient fluxes within semi-arid landscapes, Jornada Basin, New Mexico
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Overland flow generated by high-intensity rainstorms has been suggested as having an important role in desertification, resulting in a significant vegetation change from productive grassland to desert shrubland in the south-western part of the United States. For the quantification of overland flow and associated nutrient and sediment fluxes, there are significant scale issues involved that required resolution. To address these issues, a fieldwork-integrated modelling approach was employed to enable the quantification of water, sediment and nutrient fluxes within and between shrubland and grassland associations in a semi-arid ecosystem, the Jornada Basin in the Chihuahuan Desert, New Mexico. The aim of this thesis is the evaluation of scaling approaches to the numerical modelling of these fluxes combined with the appropriate application of scaling tools for model parameterisation. Special emphasis is placed on the investigation of parameter and process scaling and the applicability of scaling tools to interpolate and extrapolate field data, disaggregate remotely sensed data and aggregate model parameters. Extensive field studies were carried out to acquire detailed understanding of the spatial distribution of hydrological, soil- and nutrient-related model parameters within black grama grassland and creosote, tarbush and mesquite shrublands. The statistical and geostatistical analysis of the field data resulted in the development of scaling techniques that enabled the spatially realistic reproduction of the small-scale variability and connectivity features of model input parameters. Spatially distributed, process-orientated models with a 2-m resolution were employed to enable an adequate representation of model input parameters and an appropriate reproduction of overland flow characteristics and sediment- and nutrient-transport processes. Based on these results, the models were upscaled to a resolution of 10-m under specific evaluation of process and parameter scaling issues. The upscaled model versions were then employed for the flux quantification within and percentage change of fluxes between shrubland and grassland associations. The modelling studies provided important insights in the stability of grassland-shrubland boundaries as a function of nutrient depletion and water-resource enrichment for the grassland by the action of overland flow. It was hypothesised, that external forces such as overgrazing or climatic variations might potentially disturb this stability, which consequently leads to the invasion of shrubs into the grassland. The modelling results suggest that landscape linkages through the redistribution of water and soil resources across vegetation-transitions zones at the landscape scale play a significant role in desertification processes.
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Scaling approaches to the modelling of water, sediment and nutrient fluxes within semi-arid landscapes, Jornada Basin, New Mexico, Eva Nora Müller
- Sprache
- Erscheinungsdatum
- 2007
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- Titel
- Scaling approaches to the modelling of water, sediment and nutrient fluxes within semi-arid landscapes, Jornada Basin, New Mexico
- Sprache
- Englisch
- Autor*innen
- Eva Nora Müller
- Verlag
- Logos-Verl.
- Erscheinungsdatum
- 2007
- ISBN10
- 3832517545
- ISBN13
- 9783832517540
- Kategorie
- Biologie
- Beschreibung
- Overland flow generated by high-intensity rainstorms has been suggested as having an important role in desertification, resulting in a significant vegetation change from productive grassland to desert shrubland in the south-western part of the United States. For the quantification of overland flow and associated nutrient and sediment fluxes, there are significant scale issues involved that required resolution. To address these issues, a fieldwork-integrated modelling approach was employed to enable the quantification of water, sediment and nutrient fluxes within and between shrubland and grassland associations in a semi-arid ecosystem, the Jornada Basin in the Chihuahuan Desert, New Mexico. The aim of this thesis is the evaluation of scaling approaches to the numerical modelling of these fluxes combined with the appropriate application of scaling tools for model parameterisation. Special emphasis is placed on the investigation of parameter and process scaling and the applicability of scaling tools to interpolate and extrapolate field data, disaggregate remotely sensed data and aggregate model parameters. Extensive field studies were carried out to acquire detailed understanding of the spatial distribution of hydrological, soil- and nutrient-related model parameters within black grama grassland and creosote, tarbush and mesquite shrublands. The statistical and geostatistical analysis of the field data resulted in the development of scaling techniques that enabled the spatially realistic reproduction of the small-scale variability and connectivity features of model input parameters. Spatially distributed, process-orientated models with a 2-m resolution were employed to enable an adequate representation of model input parameters and an appropriate reproduction of overland flow characteristics and sediment- and nutrient-transport processes. Based on these results, the models were upscaled to a resolution of 10-m under specific evaluation of process and parameter scaling issues. The upscaled model versions were then employed for the flux quantification within and percentage change of fluxes between shrubland and grassland associations. The modelling studies provided important insights in the stability of grassland-shrubland boundaries as a function of nutrient depletion and water-resource enrichment for the grassland by the action of overland flow. It was hypothesised, that external forces such as overgrazing or climatic variations might potentially disturb this stability, which consequently leads to the invasion of shrubs into the grassland. The modelling results suggest that landscape linkages through the redistribution of water and soil resources across vegetation-transitions zones at the landscape scale play a significant role in desertification processes.