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This paper reports current research concerning Oribatid populations occurring in three ecosystems (an oak forest, a meadow and a poplar plantation). The main criterion used in the faunistic analysis is the relative density; this is expressed as a percentage and conventionally represented by ten classes (Fig. 1). The specific components of each habitat are compared at first wholly (Fig. 2) and then on the more rational basis or the Oribatid mites group peculiar to each milieu or in common with all the habitats (Tab. 1). The study of the relative density sums indicates the interspecifics quantitative connections, but also the similarities and the divergences between the three habitats (Tab. 2, Fig. 3). In the same way, the relationships between the three communities are established on the basis of the species list; those results show not only the connecting species but also the discriminating species (Fig. 4). The conclusions obtained are validated by considering various concepts such as the diversity, the constraint index and the specificity. [ABSTRACT FROM AUTHOR]

A system for measuring the period of inundation of permanent plots in the Skallingen salt marsh in SW Jutland is described and some results presented. Results are compared to those obtained by the normal method of measuring inundation time. It is necessary to measure inundation on each permanent plot. [ABSTRACT FROM AUTHOR]