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| Titel |
Modelling Framework to Assess Ecohydrological Processes Responsible for Shrub Encroachment in Semi-Arid Landscapes on the Example of the Chihuahuan Desert in New Mexico |
| VerfasserIn |
Peter Bíró, Eva Müller, John Wainwright |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250046060
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| Zusammenfassung |
| The transformation of productive grassland to desert shrubland due to overgrazing by cattle has occurred for more than 100 years in the Chihuahuan Desert in New Mexico (USA). Degradation processes have been reported to continue despite the removal of the livestock. Overland flow generated by short, high-intensity convective rainstorm events has been suggested to have an important role in these land-degradation processes by means of redistribution of fine soil particles and nutrients. With focus on a grass-shrub transition zone, feedback mechanisms between vegetation dynamics, soil resources and hydrological transport processes are investigated in this study.
A newly created model framework for assessing the interactions of grass and shrub growth as a function of resource availability under dryland conditions will be presented. Modelling results will provide aspects to answer the following questions:
• How is it possible to better the understanding of shrub encroachment into a grassland area under semi-arid conditions?
• How are the contributing processes interlinked?
The model framework is spatially distributed and captures processes occurring during an overland flow event as well as processes taking place over the time frame of a yearly vegetation period in two soil layers. It consists of three main components: (i) soil moisture is calculated as a function of runoff, infiltration, soil water movement and evapotranspiration; (ii) sediment and nutrient redistribution is calculated as a function of runoff; (iii) vegetation coverage is calculated as a function of resource dependant growth, mortality and dispersal.
This structure allows the incorporation of ecohydrological feedbacks between vegetation and soil in regard of the changing amount of available resources and their redistribution.
Model runs have been performed on the hillslope scale (25 ha) where parameterisation is possible with measured data for a typical shrub site and a grass site, respectively. Subsequently the model settings have been upscaled and the focus was on areas of a bigger extent across the vegetation transition (25 sqkm) enclosing sites with different grass-shrub coverages.
Thus, outcomes will enable an evaluation of effects of changing resource and rainfall characteristics on development of grass and shrub coverage on the plot and hillslope scale across a moving vegetation boundary. |
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