Soil enzymes participate in the carbon cycle, at the same time being indicators of the intensity of ongoing processes of humification, decomposition and mineralization of organic matter, and carbon accumulation in soils. The study of soil enzyme interactions with the carbon cycle in forest ecosystems in different regions of Russia remains a relevant topic in connection with the greenhouse gas problem. The purpose of this work was to assess the soil enzyme activity in the forests of the Saralinsky section of the Volga-Kama Nature Reserve. On the territory of the Saralinsky site, linden forests make up 42 % of the forest area, pine and birch forests 25 % and 24 %, respectively. About 7 % of the territory is occupied by aspen forests. Forests of middle-aged and older age groups predominate. On the territory of the Saralinsky section 7 test plots have been established under forests of the predominant species and age groups. Soil samples were taken from five sections at each plot. The activity of invertase, catalase, and phosphatase in the humus horizons of the soils was determined. It has been established that catalase and invertase exhibit a strong correlation with the humus content in soils (correlation coefficients of 0.769 and 0.882, respectively), phosphatase is a weak one (0.349). The correlation between invertase and catalase was strong (coefficient 0.840), and the correlation between invertase and phosphatase was average (coefficient 0.508). The invertase activity in the humus horizons of the Saralinsky site ranged from 0.44 to 5.19 mg of glucose per 1 g of soil in 4 hours; catalase activity was from 1.03 to 3.63 ml of 0.1 N KMnO4 per 1 g of soil in 20 minutes; and phosphatase activity was from 2.93 to 9.63 mg of P2O5 per 10 g of soil in 24 hours. According to the Zvyagintsev scale, the soils of the Saralinsky site were very poor in catalase, phosphatase enrichment ranged from medium to rich, and invertase enrichment ranged from very poor to medium. According to the Anova test (Type I), the invertase, catalase, and phosphatase activity in the studied soils was significantly influenced by the type of dominant species, age group, and the combined effect of these factors. According to the Tukey HSD test, the activity of all three enzymes was significantly higher in the soils under deciduous forests compared to middle-aged pine forests, characterized by a slower carbon cycle. A significant difference in enzyme activity between soils of linden, birch, and aspen forests of the same age group was observed only for phosphatase.For catalase and invertase, there was a clear tendency towards an increase in enzyme activity with the age of the forest in linden, birch, and pine forests. For phosphatase, only under birch and pine forests. However, the Tukey HSD test statistically proved an increase in the activity of soil enzymes only during the transition from middle-aged pine forests to over-mature pine forests for all enzymes and for invertase during the transition from middle-aged linden forests to over-mature linden forests. Thus, the activity of all three enzymes was interconnected with the biological carbon cycle in soils under forest plantations. However, according to the studies, the greatest correlation with forest parameters and humus content in the soil was noted for invertase, which should be recommended for biomonitoring of soils in forest ecosystems.