The floristical variation of tundra vegetation along environmental gradients has been studied on the basis of numerical multivariate methods. The results may be briefly summarized as follows: tundra vegetation is characterized by a high degree of structural order: the community-types are sharply defined in terms of diffferential species, and they are disposed on the ground according to very regular patterns. The relation between variation in the vegetation cover and variation of environmental factors are strong, so that the vegetation pattern fairy well reflects the microgeomorphological pattern induced by physical forces. Such a pattern is mostly evident only at a decimetric scale: the use of sample sizes smaller than the ones hitherto adopted in the study of tundra vegetation is suggested as more appropriate to achieve data sets with higher predictive values in respect with the variation of the ecological factors.
