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2. The reduction in the quantity of information, expressed by a reduction in the number of attributes, even when they were the more informative attributes, produced a loss in the ecological significance of the land classification. Therefore, the use of ISA in land classification requires as much information as possible. 3. The first RAO axes obtained from non floristic data do not have the relationship that Hill showed with floristic data. Therefore, the second axis at the first ISA level is used in lower levels of the ISA. 4. The statistical validation of the 3 most important approaches, using the <strong>Natural</strong> Vegetation in order to test them, showed that the "Two-step" structure had the highest correlation coefficient. . Meanwhile, the standard ISA structure presented lover significance. Nevertheless, the differences between them were small and were not atatistically significant. As the statistical differences are not as high as expected, the Standard ISA is equally applicable because the posslble loss in objectivity of "Two-step" is not compexmated by the increase in the statistical significance of its results. BUNCE, R.G.H. & SMITH, R.S. 1978. An ecological survey of Cumbria. (Working paper no. 4) Kendal: Clunbria C.C. and Lake District Special Planning Board. BIJNCB, R.G.H., BARB, C.J. & WEIFTAKER, H.A. 1983. A stratification system for ecological sampling. In: Ecological mapping from ground, air and space, edited by R.M. Fuller, 39-46. CITE S~rmposium no. 10). Cambridge: Institute of Terrestrial Ecology. FOURT, D.F., DONALD, D.G.M., JE-FFERS, J.N.R. 8 BINNS, W.O. 1971. Corsican pine (Pinus nzgra var. maritima (Ait .) Melville) in Southern Britain. A study of growth and site factors. Forestry, 44, 189-207. BILL, M.O. 1973. Reciprocal averaging: an eigenvactor method of ordination. J. Ecol., 61, 237-249. BILL, M.O., BUNCE, R.G.H. k SRAW, M.W. 1975. Indicator species: analysis, a divisive polythetic method of classification, and its application to a survey of native pinetoo& in Scotl8nd. J. Ecol., 63, 597-613.