Soil respiration (SR) is characterized by high spatial and temporal variability, which entails a significant uncertainty in estimates of CO2 emission from soils at the levels of individual ecosystems, regions, and the world as a whole. The primary objective of this study was to quantify the contribution of temporal and spatial variability to SR at the annual and seasonal scales by analyzing year-round SR monitoring data from November 2024 to October 2025 in six different biotopes in the southern Moscow region, which belongs to the temperate continental climate zone. We measured SR three–four times per month, using the chamber method with parallel monitoring of soil hydrothermal characteristics. The biotopes differed in vegetation type (forest, meadow, and agrocenosis) and soil (Entic Podzol (Arenic) and Haplic Luvisols (Siltic). It was revealed that differences between the average SR values in paired comparisons of the studied biotopes were more often statistically significant in the warm (May–October) and summer (June–August) periods and were least pronounced in the cold season and spring. The use of the nonparametric analysis of variance (PERMANOVA) showed that the contribution of the time factor (seasonality) to the total SR variability over the annual measurement cycle was 85

The stability of soil organic matter (SOM) is the trade-off between its bioenergetic profits for microorganisms and the energy barrier for its decomposition. The energy density and activation energy, which determine the SOM stability in topsoil (0–30 cm), belowground biomass and litter in forest and grassland ecosystems, were determined by thermogravimetryand differential scanning calorimetry. Organic matter was fractionated into pools based on their thermal stability — labile, stable, and persistent. The activation energy of thermal decomposition of persistent SOM was 2.8 times higher than for labile SOM. There was more labile SOM per unit of thermally stable SOM in forest soil than in grassland. Therefore, the higher bioenergetic availability of SOM in forest ecosystems suggested a faster carbon turnover compared to grassland soils. Forest soil accumulated 1.5 times more organic carbon than grassland soil. The ratio of energy density to activation energy characterized the potential bioenergetic advantage of organic substrate decomposition by microorganisms, could be used to characterize the SOM quality as an addition to the widely used C:N ratio. The transformation of forest and grassland litter and belowground biomass into SOM was accompanied by a decrease in activation energy and an increase in energy density. These identified processes underline the leading role of progressive decomposition and selective stabilization of microbial metabolites for the SOM formation

Soil respiration (SR) is one of the largest fluxes in the global carbon cycle, exceeding anthropogenic CO2 emission by more than an order of magnitude. Estimation of the heterotrophic component of SR is necessary to assess the carbon balance on the ecosystem and on the regional, national, and global scales. Within the framework of the most important national innovation project “Development of a System of Ground-based and Remote Monitoring of Carbon Pools and Greenhouse Gas Fluxes on the Territory of the Russian Federation,” the first Russian national network is organized to monitor CO2 emission from soils and other linked parameters. The SR values and the relationship with the temperature of the upper 5- to 10-cm layer of soil (TS) are analyzed for the first time on the territory of Russia based on methodologically identical field measurements conducted simultaneously in the summer period (June–August 2023) at 75 monitoring sites in the different ecosystems in the main Russian bioclimatic zones from the tundra to the semidesert. The positive effect of soil temperature on the mean summer SR rate and the maximum monthly SR values is observed in the interval of mean TS from 10 to 20°C. Among the ecosystems studied, the lowest SR values are recorded in tundra and bog ecosystems, while the highest values are in the forest–steppe. Amongst the forest ecosystems, the lowest SR rates are characteristic of larch forests, while the highest SR values are observed in broadleaved forests of the forest–steppe zone. To clarify the regularities obtained, it is necessary to expand studies in all bioclimatic zones, but mainly in agrocenoses, tundra, and steppe ecosystems.

Regime of precipitation and temperature conditions are key factors that regulate the rate of decomposition of soil organic matter in terrestrial ecosystems. The aim of this work was to assess the effect of the duration of dry periods in summer and different depths of snow cover in winter on heterotrophic soil respiration. The studies were carried out as part of a 2–year field manipulation experiment organized on gray soil (Haplic Luvisol) in the temperate continental climate conditions (southern Moscow region). Three variants were organized: (1) simulation of mild weather with uniform watering of the soil in summer and the absence of freezing in winter, (2) simulating two summer dry periods lasting 1–2 months with natural winter snow cover, (3) simulation of extreme weather with one long (~3 months) dry period in summer and complete removal of snow cover in winter. Heterotrophic soil respiration was measured by the closed chamber method on bare fallow during 2 years of continuous experiment and 1 more year after its completion. Medians of heterotrophic soil respiration for the entire period of the experiment in the three above–mentioned variants of the experiment were 38, 27 and 19 mg C/(m2 h), respectively. Two short dry periods led to an increase in heterotrophic soil respiration by 7–10%, which is associated both with the drying and rewetting cycles of the soil and with an increase in the average summer temperature of a 20–cm soil profile by 1.5°C. The prolonged dry period caused a decrease in heterotrophic soil respiration by 12–16% as a result of low soil moisture. Soil freezing led to a strong decrease in winter CO2 emission from soil, which reached 34–55% in the control variant and 57–72% when the snow cover was removed. The frost period (November–March) contributed from 25–34% without of soil freezing to 14–19% when its presence to the annual CO2 flux. We conclude that the change in the winter temperature regime of the soil due to manipulations with the snow depth led to a more significant change in the annual heterotrophic soil respiration than the lack of precipitations in the summer season.

Steppe ecosystems, occupying about 8% of the terrestrial area, are an essential element of the global carbon cycle in the atmosphere–vegetation–soil system. The carbon (C–CO2) balance of natural steppe ecosystems in Russia is estimated based on the geoinformation–analytical method and employing the database of empirically measured values of the net primary production and a climate-driven regression model that makes it possible to estimate the intensity of carbon dioxide flux from soils into the atmosphere. Natural steppes in Russia serve as a significant sink of carbon dioxide from the atmosphere. The average intensity of this carbon flux can be estimated at 231 ± 202 gC/m2 per year. The estimated annual accumulation of carbon dioxide in the natural steppe ecosystems of Russia is 111 ± 97 MtC. According to the estimates, the steppe ecosystems under study provide from 8 to 19% of the atmospheric carbon sink to the terrestrial ecosystems of Russia.

The separation of soil organic matter (SOM) into pools and fractions allows to understand the nature and functions of SOM as well as to characterize its quality, composition and properties. The study presents an analysis of approaches, methods and results of determining various pools and fractions of SOM using the gray and agrogray soils (Haplic Luvisol) under contrasting types of land use (Moscow region, Russia). Conservative properties and storage functions of SOM were proposed to be estimated by its granulometric and densimetric pools, and dynamic properties and emission functions were proposed to be estimated by microbial and potentially mineralizable pools. It was shown that the ratio of different pools in the SOM composition depends on the type of land use and it is controlled by the composition and amount of plant materials entering into soil. The microbial biomass is a dynamic pool of organic carbon in the soil and determins the degree of biological activity of soil organic matter. Different aggregate fractions make different contributions to the formation of the total Cmic pool depending on the type of land use. The arable soil is characterized by a low content of Cmic; the soil is also depleted in organic matter, which is represented mainly by biologically stable components. The recarbonization of arable soils by grassing or reforestation will lead to real carbon sequestration with its accumulation in a biologically active form. We conclude that the separation of structural and process pools, the determination of their sizes and ratios should be considered an essential component of the programs for monitoring the quality and functions of SOM and carbon sequestration processes.

Field observations of soil respiration (SR) in different types of terrestrial ecosystems are very relevant because of high temporal and spatial variations of SR rate. The intra-annual dynamics of SR is mainly determined by the changes in hydrothermal conditions during the year and is often described with temperature sensitivity coefficient ( Q 10 ), which usually has a fixed value in many of the used models. This study is focused on the assessment of seasonal and interannual dynamics of SR temperature sensitivity in two grasslands in the southern Moscow oblast (temperate continental climate) based on continuous 25-year-long all-year-round measurements of CO 2 emission from soils. The grasslands have been formed on two different soil types: sandy soddy-podbur (Entic Podzol (Arenic)) and gray loamy soil (Haplic Luvisol (Loamic)). The SR rate has been continuously measured from December 1997 to November 2022 with an interval of 7–10 days using the technique of closed static chambers. The temperature sensitivity of SR, estimated from the entire set of data, is higher in Haplic Luvisol as compared with Entic Podzol (3.47 vs. 2.59). The Q 10 values for SR in both soils are 1.2–1.4-fold lower in dry years as compared with wet years. The interannual variation of Q 10 values in grassland ecosystems amounts to 21–36% depending on the considered temperature range. A statistically significant positive correlation between the Q 10 values in the temperature range ≥1°С and wetness indices is observable in both grasslands. A differentiated approach integrating different values of temperature coefficients for SR into the used models is necessary to improve the predictions of C budget in ecosystems.

The paper considers the results of calculations of the heterotrophic (HR) and total soil respiration for Entic Carbic Podzol under a coniferous-broad-leaved forest in the South of the Moscow region (54.89° N, 37.56° E), performed using the soil model Romul_Hum and a new version of the system of models EFIMOD3. The results of soil respiration modeling had a good correlation with the field measurement data. The Romul_Hum model simulates better the intensity of HR of the studied soil in wet than in dry years when it lightly overestimates the HR values. In the spatially detailed modeling of heterotrophic and root respiration using the EFIMOD3, the variability of carbon pools and fluxes associated with the distribution of the litterfall and hydrothermal conditions under the forest canopy was taken into account. The data obtained show that the intensity of HR at the beginning and middle of the growing season differs by about a factor of two, and HR values between different parts of the simulation site at the same time differ by more than 3.5 times. Spatial and temporal variability of the soil respiration affects the accuracy of estimates of C stocks in forest ecosystems. The used models are effective tools to analyze changes in soil carbon stocks, soil respiration, and carbon sink estimation in forest ecosystems, including tasks of forest management.

The values of heterotrophic (HR) and total soil respiration for the Entic Carbic Podzol under a coniferous–broadleaved forest in the south of Moscow oblast (54.89° N, 37.56° E) calculated using the Romul_Hum model and a new version of the EFIMOD3 system of models are reported. The results of soil respiration modeling correlate well with the field measurement data. The Romul_Hum model better simulates the HR intensity of the studied soil in wet years as compared with dry years, when it somewhat overestimates the HR values. The spatially explicit modeling of HR and root respiration using EFIMOD3 takes into account the variation of carbon pools and fluxes associated with the distribution of the plant litterfall and hydrothermal conditions under the forest canopy. The results show that the HR intensity differs approximately twofold in early and middle growing season, and the HR values in individual parts of the simulation site at the same dates differ more than 3.5-fold. The spatial and temporal variation of soil respiration influences the accuracy of estimates for the carbon budget in forest ecosystems. The used models are efficient tools for analyzing the changes in carbon stocks and soil respiration and estimating carbon sink in forest ecosystems, including the tasks related to forest management.

Temperature and moisture are the main external factors controlling organic matter decomposition and mineralization in soil. The effect of temperature (8 and 22°C) and moisture (15, 30, and 45 mass %) of gray forest soil (Luvic Retic Greyzemic Phaeozems (Loamic)) on decomposition of tree residues (leaves, small twigs, thin roots) and agricultural plants (clover aboveground mass and roots, barley straw and roots) has been studied in two long-term experiments. Coarsely crushed (10–2 mm) plant residues were added to the soil in dry form in an amount of 1% of the soil mass. The decomposition of soil organic matter and plant residues were assessed by the quantification of C–CO2 emitted from the soil. The efficiency and rate of decomposition of soil organic matter and plant residues depended on the type of decomposed material rather than on the temperature and moisture levels. The predominant decomposition of easily decomposable components hid the temperature response of stable compounds and low-quality plant residues. The slowly decomposable plant residues were more sensitive to soil wetting. Temperature coefficients Q10 of mineralization of soil organic matter and plant residues were on average 1.66 ± 0.41 and 1.39 ± 0.06, respectively. Moisture coefficients W10 in the gravimetric moisture intervals of 15–30 and 30–45% were 1.22 ± 0.09 and 1.21 ± 0.05 for soil and 1.29 ± 0.20 and 1.25 ± 0.13 for plant residues respectively.

In tropical forests, especially in the Southeast Asia, there are only fragmentary estimates of coarse woody debris (CWD) pools and dynamics. Our study examines the volume and structural diversity of CWD in forests not affected by commercial felling in the territories of the Bidoup Núi Bà and Bù Gia M 0̂.̂3̂êm̂·̂â p National Parks of the Republic of Vietnam. In the lowland Dipterocarp forests of Bù Gia M 0̂.̂3̂êm̂·̂â p National Park, the average volume of CWD was almost two times lower than the average CWD stock in the mixed montane forests of Bidoup Núi Bà national park: 44 m3 ha–1 versus 78 m3 ha–1. The mass of CWD depended linearly on its volume and averaged 24 t ha–1. The projective cover of CWD averaged 269 m2 ha–1. Snags prevailed among the substrate categories (position types), accounting for 42 and 31 0̂.̂3̂êm̂·̂â p forests, respectively. The proportion of large branches in the montane forests of Bidoup Núi Bà National Park was 8 0̂.̂3̂êm̂·̂â p it reached 33 0̂.̂3̂êm̂·̂â p National Park—in 73

Soil organic matter largely controls the ecosystem functions of soil and is a source of energy and a nutrient substrate for the soil microbial community as well. The postagrogenic dynamics of organic matter stock (content of organic carbon, Corg; total nitrogen, Ntot; and their ratio, C/N), basic soil properties, and indicators of soil microbial and enzyme activities are analyzed for the chronosequence of Retic Albic Podzol (southern taiga zone, Kostroma oblast, Russia). Different plots of the chronosequence have been withdrawn from agricultural use 11, 16, and 40 years ago. The stratification ratios (SRs) 0–5 : 5–10, 0–10 : 10–20, and 0–10 : 20–30 cm layers for Corg and Ntot contents are also estimated. A statistically significant increase in the contents of Corg and Ntot during the postagrogenic succession is observed in the topsoil layer of the old arable horizon (0–5 and 5–10 cm) as well as an increase in the stratification of their distribution, especially after a closed tree canopy has developed on the former arable land. Postagrogenic succession promotes an increase in the soil basal respiration rate and the content of microbial biomass, the maximum values of which are most often recordable in the soil under a 40-year-old secondary small-leaved forest. During the natural reforestation of the former arable lands, a statistically significant increase in the phosphatase activity is observed within the entire old arable horizon. The peaks of oxidoreductase activity correspond to the stages of succession with the maximum uptake of easily decomposable plant litter. Over the 40 years of postagrogenic succession, all analyzed parameters (except for pHKCl) have increased in a statistically significant manner at all considered depths of the old arable layer, with the highest annual increase in 0–5-cm layer, most enriched for organic matter.

Soil respiration is one of the main fluxes in the global carbon cycle and has high temporal and spatial variability. Respiration of a soddy-weakly-podzolic soil (Entic Podzol Arenic) in forest and meadow coenoses of the south-taiga zone was continuously monitored on a year-round basis for 21 years; the collected data allows us to assess the temporal variability of CO2 fluxes from soils at different temporal levels: monthly, seasonal, and annual. The total respiration of the soddy-weakly-podzolic soil varies most significantly at the monthly averaging level (coefficient of variation, CV = 25–56%); while the annual respiration variability is 20–22%. At the seasonal averaging level, winter CO2 fluxes from soils have the highest variability (CV = 39–44%); in contrast, during other calendar seasons, soil respiration variability remains roughly at the same level: 26–29%. The effect of the coenosis type on total CO2 fluxes from the soddy-weakly-podzolic soil is statistically significant both at the annual averaging level and in all calendar seasons of the year, except for winter. The most stable parameter that characterizes the seasonal distribution of CO2 fluxes throughout the year is the contribution of the warm period (May–October) to the total annual CO2 flux from soils (73–77% on average). In both studied coenoses, its variability over the 21-year observation period was 8%. This parameter can be used to estimate annual CO2 fluxes from soils based on field measurements performed during the growing season. Results of numerical experiments show that continuous measurements of CO2 emissions from soils for 5 consecutive years reduce the variability of annual and seasonal CO2 fluxes from soils by more than half compared with 1‑ or 2-year measurement periods. Accordingly, a 5-year observation period can be recommended as the optimal one: its duration is sufficient to obtain adequate values of annual and seasonal CO2 fluxes from soils in the south-taiga zone.

The aim of the study: Analysis of carbon stocks in soils and vegetation on the territory of the Pilot Carbon Polygon “Ugra”. Location and time of the study. Kaluga region, Ugra National Park, March–October, 2020. Methodology. The study was carried out on soils of four land use types: i) arable lands, ii) abandoned arable lands under grassland vegetation, iii) young forest vegetation (25–30 years old), and iv) mature mixed forest (75–80 years old). Two-four plots were located in each land use type. Soil samples were taken up to 50 cm by 10 cm layers. The content of organic carbon (Corg), total nitrogen (N), and the C/N ratio were determined. Considering soil density, the Corg and N stocks were calculated in the top 20 and top 50 cm. In the top 20 cm, the particle size distribution, pH(KCl), water holding capacity (WHC), and microbial properties (basal respiration, BR and content of microbial biomass, Cmic) were determined. Based on the forest inventory, the carbon stocks in phytomass and mortmass (dead trees) were estimated. Main results. The Retisols of the Carbon Polygon “Ugra” are characterized by a sandy loamy texture and slightly acidic (arable and abandoned lands) or acidic (forest areas) reaction. Microbial activity in the top 20 cm of soil decreases in the following order: abandoned lands under grassland > young forest stands (25–30 years old) > arable lands > mature mixed forest. The BR variability was determined by 86–90 % by the Cmic content. The highest Corg stock in the 0–50 cm layer was in the arable soils (65.4±4.4 t C/ha), and the lowest Corg stock (41.4±0.4 t C/ha) was observed in the soils under young forest. The C/N ratio in the top 10 cm varied from 8.9 to 17.6 and depended on the composition of plant litter at the soil surface. The main C pool in the forest ecosystems, regardless of their age, was the phytomass of woody plants. This C pool exceeded the total Corg stocks in the 50-cm soil layer by 1.6 and 4 times in young forest and mature mixed forest, respectively. The total C stocks in the mature mixed forest were 3 times larger than in young forest stands. Conclusions. The C stocks and the state of the soils of the Carbon Polygon “Ugra” depend on the current land use type, which in turn determines the composition of plant residues input on and in the soil. This is the reason for the most distinct differences between the studied soils in terms of Corg and N content, C/N ratio, and microbial characteristics. The age of forest stands is a key factor determining the total C stocks in soils and forest biomass.

The bark of coniferous trees (BCT) is an essential component of the litter in boreal forests. The effects of temperature and mineral additives (N and P) on the rate of BCT decomposition (DecR), its constant (k), total loss of C–CO2, and the changes in BCT chemical composition are assessed in a long-term (12 months) laboratory experiment with soil–bark substrates (SBSs) using three contrasting temperatures (2, 12, and 22°C) and sufficient moisture. The temperature coefficient (Q10) for the mean DecR during the experiment varies from 1.1 to 2.5 depending on temperature range and SBS composition. The effect of temperature was the most pronounced during the first and second months of the experiment, explaining 47% of the DecR variation. At later stages of the experiment, the SBS composition affected by the addition of mineral N and P compounds is the key factor influencing the BCT decomposition; it explains 18–63% of the DecR variance. The maximum losses of C–CO2 (158–187 g С/(kg bark), or 34–41% of the initial С content) are observed at 22°C. Irrespectively of the temperature, the most significant loss of ethanol-soluble compounds (56–64%) is recorded in the variant with the mineral N additive, whereas the cellulose content most significantly decreases (by 64–69%) in the variant with combined application of N and P and is almost independent of temperature. The loss of lignin was insignificant, amounting to only 3–12% of its initial content. The addition of mineral N and P is a key factor stimulating the BCT decomposition, considerably shortening the decomposition time and improving the quality of the resulting substrates.

The land use type and agricultural practices significantly affect the aggregate state and many physical properties of soils. In this study, we provide a comparative assessment of the bulk density, water holding capacity of disturbed samples (WHC), and structural state (dry sieving method) of Luvic Greyzemic Chernozems under different land uses (long-used arable land, newly developed arable land, 27-yr-old abandoned land, and virgin steppe) in the Cis-Altai forest-steppe soil province of Western Siberia. At each site, three mixed samples were taken from the layers of 0–5, 5–10, 10–20, and 20–30 cm of the humus horizon. The influence of land use on the bulk density was only seen for the upper 5-cm layer, in which the decompaction after 27 years of abandonment was statistically significant. Differences in the bulk density between the two croplands and between the abandoned and virgin lands were insignificant. Changes in the WHC under the impact of land use were manifested for the upper 20-cm layer. In six years of using the previously abandoned land for growing cereals, the aggregate-size distribution of the soil became almost identical to that in the old-arable soil. Judging the amount of agronomically valuable aggregates and the structural coefficient value, the aggregate state of all the studied soils can be assessed as excellent. Thus, Luvic Greyzemic Chernozems of the forest-steppe zone in Western Siberia are characterized by the high tolerance towards agrogenic impact and retain their natural crumb–granular structure for a long time of their using for crop production.

The succession of natural vegetation on the former arable soils triggers the processes of postagrogenic restoration of soil ecological functions specific of a particular bioclimatic zone. We analyze the postagrogenic dynamics of a set of soil characteristics in the upper (0–5 and 5–10 cm) layers of former arable horizon by the case study of the chronosequence of Retic Albic Podzols (agrosoddy podzols, southern taiga, Kostroma oblast, Russia) withdrawn from agricultural use 15, 20, and 45 years ago. The following soil characteristics are determined: pHKCl; the contents of soil organic carbon (SOC), total nitrogen (TN), and dissolved carbon and nitrogen (DOC and DON); basal respiration (BR) rate; carbon of microbial biomass (Cmic); and relative indicators of the state of microbial community. In addition, absolute (HIX1) and relative (HIX2) humification indices of dissolved organic matter (DOM) are assessed for the soil layer of 0–5 cm in the studied soil chronosequence, as well as the stratification ratio (SR (0–5 : 5–10)). The following changes are observed in the upper layers of the former arable horizon over 45 years of postagrogenic succession: (1) a statistically significant decrease in the pHKCl and humification index of DOM; (2) an increase in the SOC, TN, and Cmic contents and BR rate; and (3) a considerable stratification according to the SOC and TN contents and microbial properties. The highest values of SR for the SOC and TN are observed in the soil of the old-aged forest; for the microbial properties, in the 45-yr-old abandoned soil. Thus, the main characteristics and ecological functions of Retic Albic Podzol gradually restore during the secondary succession on the former arable land in the southern taiga zone.

The postagrogenic dynamics of organic carbon (C org ), total nitrogen (N tot ), and density fractions of organic matter (OM) in the dark gray soil (Haplic Phaeozem, Belgorod oblast, Les na Vorskle (Forest on Vorskla) Reserve) and migrational–mycellary Chernozem (Haplic Chernozem, Kursk oblast, Streletskaya Steppe Reserve) were examined. The most significant postagrogenic changes in all the studied soil properties were observed in the top 0–5 cm layer. The contents of C org and N tot in this layer of the Phaeozem chronosequence increased by 1.2–1.3 times over 45 years after cessation of farming. The contents of C org and N tot in the top 0–5 cm layer of Chernozem chronosequence increased by 1.9–2.0 times over 60 years of the postagrogenic development. The accumulation of C org took place in all density fractions. In both chronosequences, the free fraction of organic matter (density <1.6 g cm –3 ) increased, while the occluded fraction (density <2.0 g cm –3 ) virtually did not change. In 60 years after the cessation of farming on Chernozem, all the studied parameters became close to those in the Chernozem under natural steppe. In the Phaeozem, these parameters recovered by no more than 60% of the level typical for the natural soil over 45 years after the cessation of farming. Thus, the postagrogenic restoration of organic matter and all its fractions in the forest-steppe zone was much faster in the Chernozem in comparison with the Phaeozem.

Validating methodology for quantifying of carbon (C) loss from dead wood is critical for understanding C turnover in forest ecosystems. We compared estimates of CO(2)fluxes with a closed dynamic chamber method using an infrared gas analyzer with: 1) small chambers installed on the downed woody debris (DWD) surface and 2) DWD segments placed in large chambers. The fluxes were measured from 6 intermediately decayed DWD fragments, wood and bark ofBetula pubescensandPopulus tremulaand calculated on the surface area, volume and mass bases. For most DWD fragments, the tendency with an underestimation of CO(2)flux in the first approach up to 90% was observed due to a barrier effect of a thick bark layer and possible gas leakages. Our results demonstrate the importance of taking into account contribution of bark into total DWD respiration rates especially in upscaling the piece-level results into ecosystem level.

The aim of this study was to validate the ROMUL and Romul_Hum simulation models based on the data of long-term measurements of soil respiration performed by the Institute of Physicochemical and Biological Problems in Soil Sciences of the Russian Academy of Sciences in the south of Moscow oblast (54°50′ N, 37°34′ E). We estimated the dynamics of carbon stocks and soil CO 2 emission for three scenarios of plant litterfall compiled with the account of experimental data on the composition and mass of litterfall entering the gray forest soil (Albic Luvisol) under secondary deciduous forest. The calculations of long-term series of temperature and moisture content in the forest litter and upper organo-mineral soil horizons in simulation experiments are based on the real data on air temperature and precipitation for 1973–2016. The correspondence of simulation results to the data of field measurements was better for the Romul_Hum model, which comprises a description of the effects related to the vital activity of soil fauna, leading to the formation of different fractions of soil organic matter. The best correspondence of simulated values of CO 2 emission, carbon stocks, and the C : N ratios in gray forest soil horizons to field data was for the litter scenarios, which excluded the fraction of small branches. The revealed differences between the simulated and real values of soil parameters are explained by specific features of the input and transformation of different litterfall fractions, which are not always taken into account during soil sampling. The results of the study attract the attention to the uncertainties of estimates of carbon budget in forest ecosystems due to the difficulties of accounting both large wood residues (dead tree and coarse branches debris) and smaller wood fractions in the litterfall.