Is there a density compensation effect in plant communities in extreme habitats

The occurrence of a density compensation effect (DCE) has been estimated in north Caucasian areas of extreme habitats occupied by communities of vascular plants, mosses, and lichens. The species densities have been estimated according to their frequency. The correlation between species number and frequency in the studied areas has failed to confirm the assumption that extreme environmental conditions alone is responsibile for the DCE, at least locally.