Bioindication of the Dark Gray Soil State in the Pine Forests of the Krasnoyarsk Forest-Steppe under Anthropogenic Influence

Abstract

The biological activity of dark gray soil was studied in a 100-year-old pine forb-green-moss forest of the Pogorelsky pine forest of the Krasnoyarsk forest-steppe. In 2017, selective cuttings were carried out in the pine forest, and in May 2022 there was a strong fire. To improve reforestation and increase the biological productivity of the soil, bio-fertilizer based on sawdust-soil substrate with the addition of urea and mycoproduct (SSSU + M) was applied to cut and burned areas. On the experimental plots (Paseka, Volok, Fon), an annual count of self-seeding of pine was carried out. Bioindication of the soil condition was assessed based on the total number and ratio of ecological-trophic groups of microorganisms, enzyme activity, microbial biomass content, intensity of basal respiration and specific respiration of microbial biomass. The application of biofertilizer to the cut areas alkalized the soil by 0.2–0.4 units, retained moisture, increased the content of nitrogen (by 5–14%) and microbial biomass (by 1.2–1.6 times), compared with the control options. The impact of biofertilizers on the germination and growth of self-seeding of pine was noted in the second year after application – in the experimental plots of self-seeding it was 4–6 times greater than in the control ones. The entry of burnt plant residues, coals and ash into the soil in the first week after the fire led to an increase in some microbiological indicators, the activity of urease and invertase, and the activation of carbotrophic microorganisms. However, by the end of the growing season, a decrease in microbiological activity was noted, which indicated a post-pyrogenic depression of microbocenoses. The introduction of biofertilizer on the burnt surface of the plots leveled the effect of pyrogenic effects and stimulated the formation of shoots of scots pine, the number of which was significantly higher than in the control plots. It was found that the universal bioindicators that adequately reflect the state of the soil after all anthropogenic impacts were microbial biomass, specific microbial respiration, enzymatic activity and the total number of microorganisms. A specific bioindication of the soil condition after the fire was an increase in the proportion of bacteria Serratia plymuthica, Bacillus mycoides and fungi of the genera Trichoderma, Penicillium and Mortierela.