The research was carried out on the waste rock dump of the Kedrovsky pit of the Kuznetsk coal basin (Kemerovo Region – Kuzbass) 25 km north of the city of Kemerovo (northern forest-steppe subzone). Monitoring sites, experimental and control, were established in a mixed pine-birch stand of natural origin. The experimental site is located on the railtransported outer dump Yuzhny where no potentially fertile layer was placed. The pinebirch stand grows along the foot of the northern slope of the Yuzhny dump. The control site is situated in a natural forest area 5 km north-west of the Kedrovsky pit. The woody vegetation is mainly by silver birch, Scots pine, and common aspen. Herbaceous plants form grassforms meadow communities. Soils in the control site are Grey-Luvic PHAEOZEMS / Luvic CHERNOZEMS (WRB). The article presents the results of an analysis of seasonal variations of the main ecological and trophic groups of microorganisms (microorganisms that utilize organic forms of nitrogen, microorganisms that utilize mineral forms of nitrogen, microscopic fungi) and the activity of soil enzymes (proteases and phosphatases). The studies have shown that the numerical composition of soil microorganisms, both in the dump and in the control, varies significantly during a year and depends largely on the soil moisture content and temperature. We have also identified some patterns in this variation. During the growing season, the numbers of microorganisms that utilize organic nitrogen and microorganisms that utilize mineral nitrogen in Technosols around pine and birch crown periphery differed significantly from those in the control. The numbers of microscopic fungi were mostly at the same level, but significant differences were established between soils in the control site and in the dump under pine (at p < 0.05). Some correlations were revealed between the number of microorganisms and enzymatic activity: a reliable negative correlation was found in Technosols under pine between the number of microorganisms utilizing organic nitrogen and phosphatase activity (r = 0.48, at p < 0.05); reliable positive correlations were found around pine crown perimeters in the control site between the content of protease and phosphatase (r = 0.48, at p < 0.05) and around birch crown perimeters in the control site between the number of microscopic fungi and protease activity (r = 0.54, at p < 0.05).