Towards the quantitative modeling of pedogenesis - a review

The historical development of our pedogenetic model is reviewed, and trends or directions toward the future are discussed. Pedogenetic models are characterized with respect to relative degree of computation, complexity, and level of organization. These three characteristics are used as a framework for classification. Early qualitative models have well served the purpose of soil survey to describe the distribution of soils in landscapes. Further development of qualitative models will contribute to the understanding of soil genesis in areas where soil surveys are not completed. In the developed countries, however, the scientific questions have changed dramatically. Greater interest lies in understanding the physical and chemical processes of soil formation acting within relatively short time frames and assessing the interactions between natural processes and environmental change or anthropogenic impacts. Quantification of pedogenetic processes is a life-line to other environmental disciplines, and a mechanistic understanding would, in an ideal situation, describe and predict the behavior of a system for a limited number of years under changing environmental conditions. A proposed approach to mathematical simulation of the dynamic pedogenetic processes is to integrate soil physical, chemical, and other ecological system models into a quantitative pedogenetic model. Models may be developed as research tools in data-intensive studies at the pedon or horizon level, or for the purpose of simulating a soil system at the catena or soil region level. Specific kinds of pedogenetic models have specific implications with respect to the availability and spatial variability of the data needed for development and testing.