European Soil Bureau (ESBN) > Pedotransfer rules
The fourth component of the European Soil Database is a series of pedotransfer rules (PTR) allowing to derive a number of additional properties for practical purposes. These are based on expert judgement, mainly qualitative, and assume that a due weight is given to the confidence level of individual inferred attributes.
A set of tools was conceived within Arc/Info to manage and use a rules database for the inference of new information from that available within an Info database. These tools may be considered as a prototype of an expert system shell and were used in the above context. Several hundred rules were defined by Van Ranst et al., (1995) in the form of IF <condition> AND <condition> ... THEN <inferred value>. At this stage, although rules are applied to spatial objects (soil units) and the system does not take spatial relationships between objects into consideration.
Output attributes were selected on the basis of the environmental parameters needed for the problems faced, e.g., hydrology of soil types for predicting catchment response to rainfall and standard percentage of run-off; location and sensitivity of wetlands; soil buffering capacity for predicting soil susceptibility; ecosystem and surface water deposition; vulnerability of ground -and surface- water to pollution by agrochemicals and farm waste; soil erosion potential, etc.
The output attributes are class values in view of the low level of precision of some input attributes. The thresholds selected for class intervals were chosen as a compromise between currently established values used in Soil Science, and the level of precision at the scale of input data (in this case 1:1,000,000). As a result, the adopted values may not always correspond to the thresholds necessary for environmental problems.
The pedotransfer rules DB remains one of the fundamental tools for deriving useful information from existing soil databases. However it is important to appreciate that most of the PTRs were developed using a knowledge base for Western Europe (EU-12) only (King et al., 1994; Van Ranst et al., 1995) and it would be inappropriate to apply them to the extended Euro-Asian Soil Geographical Database (v4.0).
Recent implementation of complex pedotransfer rule based evaluations of soil erosion (Kirkby et al., 2004) and topsoil organic carbon content (Jones et al., 2004) have demonstrated the great potential of such ’expert-based’ approaches compared to more deterministic modelling exercises. The current lack of reliable, comparable and compatible input data for sophisticated deterministic models leaves the pedotransfer approach as the only realistic means to derive policy-relevant information from the SGDBE.
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