Mapping of reference area representativity using a mathematical soilscape distance

The applicability of detailed soil surveys limited to small reference areas to larger regions should be assessed using easily available data. This is done in this paper by computing at each site of the large region a mathematical distance between local soilscapes and those in the reference area. Soilscapes are represented by a cover frequency vector of elementary landscape classes (combinations of soil-forming factor classes) calculated within an area defined around the site under consideration. The application of this technique to four reference areas located in the Hérault–Libron–Orb valleys in the south of France demonstrated that: (1) the proposed soilscape distance was in good agreement with the degree of representativity of a reference area (i.e. percentage of soil classes already encountered in the reference area), (2) representative areas of different size and purity can be delineated from a soilscape distance map by applying a distance threshold, (3) expertise in delineating a reference area has a strong influence on its performances, i.e. size vs. purity of representative area. This suggests that the soilscape distance tested in this paper could be integrated in a classification procedure defining the optimal size and location of future reference areas.