Monday, November 01, 2010, 12:00PM - 1:00PM
Soil, through its various properties, is a key factor in the hydrological, geomorphic and biogeochemical cycles. Quantifying its spatio-temporal dynamics is therefore imperative for deciphering past and predicting future trends in terrestrial, aquatic and atmospheric systems. However, explicit quantification of soil is challenging as soil is a complex and dynamic substance, constantly evolving in response to changing environmental conditions. Field-based description of soil properties by sampling and analysis is extremely limited in both its spatial extrapolation and temporal interpretation. At the same time numerical modeling of soil has mainly focused on in situ description of various pedogenesis processes (mainly chemical). In recent years there is an increasing effort toward mechanistic modeling of soil in the context of landscape processes. These so called soil-landscape models are an important advance in soil modeling but so far limited in their ability to explicitly simulate the soil-landscape interaction, largely due to computational constraints.
The mARM4D model is a spatially and temporally explicit soil-landscape evolution model. To achieve computational efficiency the model is based on a novel mathematical algorithm that express the processes physics with multi-dimensional transition matrices. This allows for detailed description of soil properties (e.g. 10’s of grading size-classes), spatial domain (10,000’s of pixels with 10’s soil-profile layers) and temporal change (millions of iterations). At its current configuration mARM4D simulate the soil-landscape interaction as a function of (1) selective fluvial sediment transport, (2) diffusive sediment transport, (3) Aeolian deposition and (4) physical weathering of bedrock and soil particles. Additional processes (e.g. translocation, chemical weathering) are gradually introduced to the modeling framework.
Three case studies will be presented:
- The affect of various soil production and soil weathering functions (exponential decline with depth, the “humped”, constant and age-dependent) on soil profile morphology and surface soil-grading;
- The affect of late-Quaternary climate fluctuations on soil evolution;
- Comparison between diffusive and fluvial soil-transport processes at a semi-arid field-site.