FOREST SOIL COLLEMBOLA - DO TREE INTRODUCTIONS MAKE A DIFFERENCE

In Portugal, autochthonous forests have been gradually replaced by exo tic tree species. Riparian areas are, because of their sui generis cha racteristics, places where this replacement has been more notorious. A ssuming that tree species, with similar chemical composition, support similar soil arthropod communities, this study aimed to evaluate if tr ee species replacement would affect soil Collembola populations. There fore, Collembola populations from areas where the introduced Eucalyptu s globulus and Acacia dealbata were dominant were compared with those from native Alnus glutinosa and Populus nigra stands. Alnus glutinosa and Acacia dealbata are nitrogen fixing species whereas leaves of Euca lyptus globulus and Populus nigra have been referred by some authors a s having low food value. No significant differences were detected amon g tree species in terms of number of taxa. However, stands of poplar a nd eucalyptus had significantly lower densities of Collembola than ald er and acacia. The results suggest that the geographical origin of tre e species is relatively unimportant for soil biota and that Collembola soil communities may be controlled by leaf chemistry and soil physica l and chemical characteristics.