Comportement des microarthropodes du sol en climat méditerranéen français

Abstract

The french mediterranean region may be considered interesting in respect to different levels. Though biogeographically, it is constituted by cosmopolitan and holarctic collembola and ori- batids mites which are the «common component» of soil microfauna, its climate, particularly its drought summer season, induces original strategies. Seasonnal cycles are thus observed whereas in more septentrional regions populations fluctuations seem to be random. The two main groups of microfauna oribatids mites and collembola do not exhibit the same behaviour. The farmer, more resistant to dryness, remain present all the year long migrating into the deep soils layers when the soil water content gands too low, the later pass the summer in egg stage, as an exception, two species are able to resist by a process of déshydratation comparable to anhydrobiosis. This physiological possibilities characterize the collembolan microfauna of Provence. These demographic variations are unlike those in other temperate zone but similar, although less marked to those in arid and semi-arid zones (in Australia or California for example). There is an alternation bandween, on one hand common «winter populations», the number and composition of which are quite variable, like an ’K’ strategy, and on the other hand «reserve populations» which are subjected to exceptional hygrométrie conditions worthy to be compared to the deserts ones and which is an V strategist. This dualism is the most important feature of collembolan populations in xeric regions. © 1984 Taylor & Francis Group, LLC.