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Micro-organisms and nutrients were determined in soil samples (top 20 cm) collected underneath and outside the canopy of Adesmia bedwellii in mid fall (April 1997), after 8 months of drought, and in mid spring (October 1997) after heavy winter rains associated with the 1997-ENSO in a Chilean coastal desert site. Bacteria and fungi were two orders of magnitude higher in mid spring, but no seasonal effects were detected for chemical parameters. Micro-organisms, organic matter and nitrogen content were significantly higher underneath shrub canopies, especially in mid fall. Micro-organism abundances were positively correlated with nitrogen levels and soil moisture. (C) 1999 Academic Press.