- Title
- Spatial description of soil properties through landscape-pedogenesis modelling
- Creator
- Cohen, Sagy
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2010
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Soil is one of the most important substances or zones in the natural system both as a substratum for life and as a component in a variety of processes. Soil characteristics play a major role in most geomorphological and hydrological processes. Describing soil spatial and temporal dynamics has been therefore important but is yet to be adequately achieved. In recent years there is a growing recognition that a mechanistic landscape-pedogenesis approach is needed in order to fully capture soil dynamics. However this approach has not been fully implemented due to the immense complexities in integrating soil and landscape processes and the many uncertainties within this merger. In this work an interdisciplinary approach is adopted in which geomorphological processes at a landscape scale are mechanistically linked to pedological processes at a profile scale. The complexities of this merger are reduced by a novel mathematical approach which couples physically-based equations and transition matrices. The resulting model (mARM3D) explicitly describes the soil profile for every point on the landscape while remaining computationally efficient. This allows simulation of large-scale and long-term soil evolution as a function of a various processes. In this thesis the model physics was kept simple, simulating only surface armouring (selective erosion) and mechanical weathering. This simplicity is important for the model development as it allows easier interpretation of cause and effect in the results. The modelling approach and physics are described in detail in this thesis. The model is evaluated and found to provide a good match to a traditional physically-based model and to laboratory weathering results. The model is used to study three major pedological concepts. The first concept is the depth dependency of bedrock and soil weathering. The effect of weathering rate changes within the soil-profile is examined by simulating long-term soil evolution with two well known soil production functions, the exponential decline and the “humped”. The results show that the differences between the two weathering functions affected not only the soil vertical and spatial distribution but also the local erosion regime. The second concept examined is the relationship between soil and topography. This was initially studied with a new methodology of spatially-explicit calculation of the area-slope equation and hypsometric integral. With this methodology the soil-topography relationship is identified but cannot be quantitatively described. Using the model the area-slope-soil relationship is quantitatively calculated for the first time. The results show that the area-slope-soil relationship has a similar scaling under different conditions. This prompts a possible analytical solution for this relationship which may have important implications for soil mapping and various modelling frameworks (e.g. landform evolution). The third concept examined is the effect of climatic changes on long-term soil evolution. Soil evolution is simulated with mARM3D using a Late Quaternary (400,000 year) climate oscillation input. The results show, for the first time, that the affect of climatic forcing on soil evolution has very distinct spatial and temporal trends. The magnitude in which the climatic forcing affects soil evolution varies considerably in space to the extent where different parts of the hillslope have opposite evolutionary trends. The results also show that the timescale of soil adjustment to climatic changes is substantial and spatially variable. These results have great implications for pedogenesis and long-term soil-related modelling. The study, presented here, is an initial stage in the development of this modelling framework. The last chapter provides a strategic plan for the future development and usage of the mARM3D model.
- Subject
- soil evolution modelling; geomorphology; pedogenesis; landform evolution; area-Slope; soil distribution
- Identifier
- uon:6605
- Identifier
- http://hdl.handle.net/1959.13/804405
- Rights
- Copyright 2010 Sagy Cohen
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
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| View Details Download | ATTACHMENT01 | Abstract | 1 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Thesis | 16 MB | Adobe Acrobat PDF | View Details Download |