SOME CONSIDERATIONS ON METHODS FOR SPATIALLY AGGREGATING AND DISAGGREGATING SOIL INFORMATION

Some possible approaches to the aggregation and disaggregation of soil data and information are presented as an opener to the more detailed discussion. The concepts of hierarchy, grain, extent, scale and variab ility are discussed. Slight modifications to the Hoosbeek-Bryant schem e to deal with spatial and temporal scales and various types of quanti tative models are suggested. Approaches to aggregation or upscaling ar e reviewed. The contributions of representative elementary volume (REV ), variograms, fractal theory, multi-resolution analysis using wavelet s, critical point phenomena, renormalisation groups and transfer funct ions are discussed followed by a brief presentation of some ecological approaches including extrapolation by lumping, extrapolation by incre asing model extent and extrapolation by explicit integration. A clear distinction must be made between additive and nonadditive variables. T he scaling of the former is much less problematic than the latter. Cor roboration of any approach by testing against the aggregated values se ems problematic. Methods of disaggregation or downscaling including tr ansfer functions, mass-preserving or pycnophylactic methods are also d iscussed. In order to make quantitative advances, nested sampling or r eanalysis of data in land information systems to obtain variance infor mation over a complete range of scales is required. Finally an appeal is made for work to begin on a quantitative scale-explicit theory of s oil variation.