HR: 0800h
AN: H51C-1146    [Abstracts]
TI: Interactions between Vegetation and Land Surface Evolution in Arid and Semiarid Systems
AU: * Saco, P M
EM: patricia.saco@newcastle.edu.au
AF: The University of Newcastle, University Drive, Callaghan, NSW 2308 Australia
AU: Willgoose, G
EM: g.willgoose@geography.leeds.ac.uk
AF: University of Leeds, Earth and Biosphere Institute, School of Geography, Leeds, LS2 9JT United Kingdom
AU: Hancock, G
EM: gggh@alinga.newcastle.edu.au
AF: The University of Newcastle, University Drive, Callaghan, NSW 2308 Australia
AB: Ecological, hydrological and geomorphological processes are tightly coupled and the understanding of their complex interactions represents a research challenge that is at the heart of the emerging fields of ecohydrology and ecogeomorphology. The coupling between ecology and hydrology is particularly strong in drylands, in which water limited conditions are the main constraint for vegetation growth and survival. Arid and semiarid ecosystems comprise about 30$%$ of the Earth's surface. Various forms of environmental perturbations like climate change and anthropogenic activities can lead to desertification or degradation of these ecosystems. The vegetation of water-limited ecosystems is commonly patterned, that is, arranged in a two phase mosaic composed of patches with high biomass cover interspersed within a low-cover or bare soil component. These patterns play an important role in controlling erosion. Human impacts or climate change may alter these systems, disrupting vegetation and triggering erosion. The resulting geomorphic changes are likely to have feedbacks including runaway desertification. Models that couple erosion and vegetation evolution can be used as a tool to understand the dynamics of arid and semi arid systems and the impact of climate change and human disturbance. However, the few existing models that explore the interactions between vegetation and sediment movement do not account for the feedbacks between ecohydrologic and geomorphic processes as is the objective of our research. A new modeling framework that couples the SIBERIA landform evolution model with a dynamic vegetation model for water limited ecosystems will be presented. The model explicitly accounts for the dynamics of runon-runoff areas that controls the evolution of the spatial distribution of vegetation in water limited ecosystems. The model reproduces the dynamics of banded vegetation patterns (tiger bush) characteristic of areas with mild slopes as well as more complex two-phase patterns that are characteristic of steeper areas. Complex spatially distributed feedbacks into slope evolution are also apparent. Preliminary results on the long term topographic evolution of hillslopes with these different dynamic vegetation patterns as well as the geomorphic consequences of disrupting or eliminating the vegetative cover will be presented.
DE: 1809 Desertification
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1851 Plant ecology
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting