No 9 (2023)

An increase in the concentration of carbon dioxide in the atmosphere is a trigger for the activation of all processes of the carbon cycle, including soil respiration (SR), since it causes not only an increase in the greenhouse effect of the atmosphere, but also its fertilization. The consequence of fertilization is the tendency to increase the world’s net primary production of photosynthesis (NPP) and heterotrophic respiration of soils (RH). The increase in global terrestrial carbon sink was accompanied by an increase in CO₂ in the atmosphere. The global increase in RH is due to global losses of soil organic carbon and is confirmed by models according to which the average residence time of organic carbon in the soil pool has decreased by 4.4 years over the past century. To assess the level of C sequestration in soils, it is necessary to determine the balance between the RH of the soil and the amount of new soil C-sink in the form of net biome production (NBP) – resistant to mineralization. Carbon sink into net ecosystem production (NEP) determines short-term unsustainable carbon sequestration.

The Far East has been and remains the part of Russia least studied with respect to carbon fluxes. We reviewed the results of in situ measurements of carbon emission from the surface of forest soils obtained at 26 points in the southern part of the Far East on the territory of 4 constituent entities of Russia. The measurements were taken in different forest formations (larch, cedar, oak, ash, and elm forests), including forests in the permafrost zone. Information on seasonal and daily dynamics of emission is presented. Equations are presented for 14 sites to estimate the emission from the air temperature of the nearest weather station. Annual fluxes vary by measurement points in the range of 5.5–10.1 t C/ha, with a maximum value in the old-growth cedar-fir forest of southern Primorye. The contribution of the summer season to the annual flux is 49–81%. In the western part of the territory under consideration (Buryatia), carbon emission from the soil surface strongly depends on soil temperature and moisture. In over moistened soils, the emission is significantly affected by the groundwater level (R² = 0.42). In Primorye forests, the soil moisture factor ceases to have a significant effect on the emission. Discussion of the results in the context of modern studies in other regions shows comparability of the survey estimates and possibility of their use for analysis of global trends and regularities. Translated with www.DeepL.com/Translator (free version).

Experimental data on soil respiration are need for estimating role of industrial logging on carbon cycle of forest ecosystems. Investigations were carried out during snowless periods 2019–2021 years on felled area of pine forest 10 years after clear cutting (Komi Republic, Russia). The soil type is a Gleyic Folic Albic Podzol (Arenic). Emission CO₂ was measured by LI COR 8100. The characteristic of weather conditions and soil temperature dynamic at 10 cm depth were given. The weather conditions were strongly influenced on soil respiration rate. More intensive CO2 flux from soil surface was observed in warm summer with insufficient precipitation. The mean month CO₂ emission was less by 1.3–1.9 times in apiaries, parts of felled area with low soil cover damages, comparing to skidding tracks where logged trees were extracted. The significant positive correlation (R² = 0.12–0.86) was detected between soil temperature at 10 cm depth and soil respiration investigated technological elements. A reliable interrelation between CO₂ flux and moisture of forest floor was observed in skidding tracks in a year with abundant precipitation while in a dryer year it wasn’t. It is differ from apiaries where found reverse dependencies. Apiaries emitted in atmosphere 303–379 g С m^–2 with soil respiration during snowless period, skidding tracks – 419–573 g С m^–2 which is 60–75 tons of CO₂ in terms of the area of the entire felled area (5 ha). The growing season formed most part (86–90%) of carbon efflux from May to October and input of summertime was 56–65%. The data obtained will serve to determine the role of timber harvesting in the carbon cycle of taiga forests.

The results of the assessment of soil respiration (CO₂ emission from soil) in three regions (Chuvash Republic, Ryazan and Kursk regions) are presented. Agrarian (crop and livestock) and natural ecosystems are combined into seven groups: croplands, pastures, hayfields, abandoned lands, forests, stockyards and open compost storages.CO₂ emissions were measured in 2020–2022 using the close chamber method. Ecosystems were ranked by increasing rate of CO₂ emission from soil in the following order: croplands (0.03–0.24 g C–CO₂ m^–2 h^–1) < pastures (0.07–0.33 g C–CO₂ m^–2 h^–1) ≤ hayfields (0.06–0.35 g C–CO₂ m^–2 h^–1) ≤ ≤ forests (0.07–0.28 g C–CO₂ m^–2 h^–1) ≤ abandoned lands (0.08–0.37 g C–CO₂ m^–2 h^–1) \( \ll \) stockyards (0.21–8.61 g C–CO₂ m^–2 h^–1) \( \ll \) compost storages (1.15–13.85 g C–CO₂ m^–2 h^–1). Estimates of CO₂ emissions from pasture, hayfield, forest, and abandoned land soils were not statistically different in most cases. The dependence of soil respiration rate on hydrothermal (temperature and humidity of the upper soil layer, air temperature) and agrochemical (content of total carbon and total nitrogen in the upper soil layer, pH) indicators by geographical regions and by types of ecosystems was analyzed. The most important among the evaluated factors at both ecosystem and regional levels is soil temperature at the 10 cm depth (r = 0.41–0.88, p < 0.05). Moisture conditions do not play a significant role in the formation of carbon flux. On the regional scale, the stocks of carbon and nitrogen are significant (r = 0.33–0.92, p < 0.05), which are more dependent on the geographical location of sites than on the characteristics of economic activity. The considered indicators determine the variance of CO₂ emission from soils of the studied ecosystems by 17–78%.

Against the backdrop of global warming, urban ecosystems are becoming increasingly vulnerable to climate stresses. Strategies for climate adaptation developed for almost every major city in the world pay considerable attention to urban green infrastructure as a nature-oriented solution for carbon sequestration. However, the influence of urban climate conditions on the spatial and temporal heterogeneity of CO₂ emissions from urban soils remains poorly understood, which can lead to inaccurate estimates and probably inflated expectations of urban green infrastructure in the context of carbon neutrality. Studies of CO₂ emission dynamics with parallel observation of soil temperature and moisture were conducted at three green infrastructure sites in the Moscow metropolis, which differ in contrasting mesoclimatic conditions, in 2019–2022. Plots with different vegetation types were compared for each site, which allowed us to assess the internal heterogeneity of soil and microclimatic conditions. Soil temperature and moisture were determined to 70% of the total variance of CO₂ emissions. At the same time, mean annual soil temperature in the center was almost 3–6°C higher and moisture was 10–15% lower compared to the periphery. Soils under lawns and bushes were, on average, 1–2°C warmer and 10–15% wetter than under trees. Soil CO₂ emission under lawns was, on average, 20–30% higher than that under woody plantings in the same plot. At the same time, the differences between the plots with the same vegetation in the center and on the periphery reached 50%, which confirms the high vulnerability of urban soil carbon stocks to mesoclimatic anomalies and the high risks of increased CO₂ emission by urban soils against the background of climate change.

The effect of individual trees on soil and litter respiration in forests polluted with heavy metals from copper smelter emissions was investigated for the first time. We tested the hypothesis that polluted sites exhibit a d-ecrease in the portion of spatial variance of soil respiration associated with the distance to the tree trunk compared to the background area. The study was conducted in the southern taiga spruce-fir and birch forests exposed to long-term pollution from the Middle Ural Copper Smelter in Revda City, Sverdlovsk region, Russia. Measurement points were placed near spruce and birch trees at different distances from the tree trunk (tree-base site, middle of the crown projection, and canopy gap), and total CO₂ emission, litter respiration, litter contribution to soil respiration, litter-specific respiratory activity, and litter stock were measured at each point. In the background area, soil respiration decreased from the tree trunk to the canopy gap. The hypothesis was partially confirmed, as the variance portion associated with distance to tree trunks decreased in spruce forests with increasing pollution but did not change in birch forests. A change in spruce forests was due to a decline in litter-specific respiratory activity, while litter stock was considerably higher in the tree-base site than in the canopy gap. It is proposed to locate measurement points in the middle of the crown projection, at a sufficient distance from tree trunks and outside the canopy gaps, to minimize bias in soil respiration estimates.

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.

Within the territory of MSU Agrobiostation “Chashnikovo”, assessment of carbon stock for soil, typical for coniferous-broad-leaved forests subzone – coniferous forests, small-leaved forests, agrocenoses, fallow lands and floodplain meadows – was given. The next indexes were studied for litters: typology, stock, detritus content and ratio of sub-horizons thickness (deposit) – these indexes are indicators of organic matter decomposition intensity. For mineral soil profile, the assessment of general organic carbon stock in 0–30 and 0–100 cm layers, as well as stock of biologically active carbon in 0–20 cm layer (by calculation according to the content of total carbon), are given. Maximum organic matter accumulation in litters and moderate accumulation – in mineral profile, was obtained for coniferous forests soddy-podzolic soils. The litter carbon stock value in spruce forests differ by almost 10 times, depending on location in tessera. Minimal carbon accumulation by litters is obtained for meadow ecosystem soils – upland meadows as well as flood-plain meadows. Alluvial soils of flood-plain meadows are characterized by highest stock of general carbon, as well as carbon of biologically active soil organic matter. Potential of CO₂ production by soil, determined by data, including structural and functional litter indexes and organic matter biologically active carbon stock (0–20 cm layer), depends on combination of row of factors: vegetation type, hydromorphism degree, and agricultural use character in present or past. Coniferous forest soils comparing with small-leaved forest soils are characterized by less rate of litter decomposing due to plant remains biochemical features, thereby these soils are assumed to less CO₂ production potential. Soils of natural grass ecosystems, especially flood-plain meadows, are characterized by maximal potential production of carbon dioxide, resulting from intensive plant residues decomposition and high stock of biologically active organic matter carbon.

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.