Mikhail Nikolaevich Maslov

A comparative description of the structural and functional organization of plant litter and forest floor in the course of natural postagrogenic reforestation in the chronory series of ecosystems for 12, 40 and 100 years is given. As the age of the stand increases, an increase in the total reserves and diversity of litter types, a decrease in the proportion of easily decomposable components, and a decrease in their pH and ash content are found. The change of ground cover is accompanied by the replacement of grass cover with grass-shrub, which indicates a decrease in the trophicity of ecosystems. The characteristics of the litter are adequately reflected by the composition of the ground cover. As the stand is restored, a regular decrease in the decomposition intensity of the ground detritus and the speed of the biological cycle occurs. Spatial differentiation of litter types serves as a trigger for the subsequent divergence of soil organic profiles.

The characteristic of typical and humus petrozems of the most high-altitude belt zone of the Khibiny, formed under three predominant types of plant groups corresponding to different stages of primary succession, is presented. For these soils, there is no differentiation of the profile by the content of most elements, with the exception of phosphorus, which is concentrated in the surface organogenic horizons. According to many chemical and phy sicalchemical properties, the soils of the char belt are close to Entic Folic Podzols formed in the underlying mountain-tundra belt under shrubby vegetation. The biological activity of petrozems below or is comparable with this parameter in the soil of shrub tundra. It was found that as the structure of vegetation becomes more complex, the activity of microorganisms increases and the organic matter of the soil stabilizes. Overall, the microbial community of petrozems well adapted to extreme conditions.

Under the conditions of a laboratory incubation experiment, the effect of the introduction of crop residues (rye straw) and mineral nitrogen fertilizer on the formation of nitrous oxide by Albic Retisols was studied. It was found that the increase in the carbon content of microbial biomass is linearly related to the mass of introduced plant residues. An important indicator characterizing the system under study is the C:N ratio of microbial biomass and its dynamics both with changes in the amount of crop residues introduced and over time. At the ratio C:N = 40 in plant residues at the early stages of their decomposition in the soil, the predominant process of microbial nitrogen immobilization is replaced by the predominance of the process of mineralization of organic nitrogen compounds. It is shown that the maximum immobilization "capacity" of microbial biomass in relation to nitrogen is achieved at a ratio of C:N in the substrate equal to 20-40. The dependence of the intensity of nitrous oxide emission by soils on the amount of crop residues introduced has been established. It is shown that the maximum values of the emission factor are characteristic of the experimental variants with the introduction of a substrate enriched with nitrogen (C:N = 7,5-10), which may be associated with better decomposition of plant residues under conditions of better nitrogen supply.