Effects of biocidal treatments on metabolism in soil. VI. Fumigation with carbon disulfide

Used in high concentration as a soil fumigant, CS2 was broadly similar to CHCl3 in its effects on metabolism in soil; the amount of N mineralised in 10 days increased roughly 10-fold. the O2 consumption almost tripled and the evolution of CO2 more than doubled. However, the effects of CS2 were consistently slightly less than those of CHCl3. Used at low concentration (10 μg.g−1 soil) on a soil rich in organic matter (2.93% organic C), CS2 stopped nitrification completely, almost without other effect on soil respiration and mineralisation of N. In contrast, when used on a poorer soil (1.07% organic C) even 10 μgCS2.g−1 soil was sufficient to cause a detectable increase in both respiration and mineralisation of N, in addition to stopping nitrification

Soil CO2 emission, microbial biomass, and microbial respiration of woody and grassy areas in Moscow (Russia)

Purpose: Urbanization significantly changes the carbon balance of the terrestrial ecosystem, an important component of which is soil CO2 emission. One of the main sources of soil CO2 emission is microbial decomposition of soil organic matter. In this regard, we hypothesized a relationship between soil CO2 emission and soil microbial properties (biomass, respiratory activity) in Moscow megapolis areas. Materials and methods: Soil CO2 emission was measured monthly (May–October) from the surface (or soil respiration, RS) and after the sequential removal of the two top 10-cm soil layers at woody (forest park, public garden) and grassy (grassland, arable) areas. Soil temperature (ST) and soil water content were recorded in 0–10-, 10–20-, and 20–30-cm layers, from which samples were taken to measure microbial biomass carbon (Cmic) and basal (microbial) respiration (BR). Results and discussion: RS ranged from 0.3 to 14.7 μmol СО2 m−2 s−1, with average values of 1.0, 5.4, 7.5, and 8.8 μmol СО2 m−2 s−1 for arable, forest park, public garden, and grassland, respectively. Removing the topsoil layer in woody areas resulted in higher CO2 release to the atmosphere than in grassy ones. Topsoil Cmic was on average 110, 331, 517, and 549 μg C g−1 and BR was 0.42, 0.87, 0.47, and 0.92 μg C-СО2 g−1 h−1 for arable, forest park, public garden, and grassland, respectively. Subsoil Cmic and BR were 1.5–3 times and 30–62% lower than in topsoil. RS in woody areas was more strongly dependent on ST than in grassy areas. Strong positive correlation between RS and topsoil Сmic and Corg (R2 = 0.98–0.99) was found. Conclusions: The RS of different Moscow’s areas might be predicted on the base of soil Cmic or Corg experimental data. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature

Microbial C-availability and organic matter decomposition in urban soils of megapolis depend on functional zoning

Urbanization has various strong effects on soil processes. Despite an increasing number of studies focused on soil carbon (C) distribution and stocks within cities, the C and nutrient availability to microorganisms and their capacity to decompose organic matter remain nearly unknown. The factors responsible for these processes in megacities are characterized by a very high spatial heterogeneity and therefore, their effects should be investigated as related to specific environmental conditions – common for urban functional zones. This study focuses on the examination of the texture, C, available phosphorus (AP) and potassium (AK), mineral nitrogen, pH, and heavy metals (HMs) contents considering microbial C-availability (ratio of microbial biomass to C) and organic matter decomposition (BR) in soils of Moscow megapolis. The sampling sites were referred to recreational, residential and industrial zones. In the industrial and residential zones, the pH, AK, AP, and HMs were increased compared to recreational. Concurrently, the microbial С-availability and BR were much less in these zones. The high pH and AP content had negative effects on the BR for all soils. Soil segregation into groups (C-poor and C-rich, light texture and heavy texture) reduced heterogeneity and showed the additional patterns. In C-poor soils, the AP effect on BR was confirmed, but not of pH. The AK and Cu contents had negative effects on C-availability for C-poor and light soils, respectively. We conclude that careful control of the soil phosphorus and potassium contents as well as texture is necessary for planning the soil construction in megacities to consider their optimal functioning. © 2019, Soil Science Society of Pakistan

Fungal and Bacterial Respiration in Urban Technosols vs. Natural Soils

Fungi and bacteria are the main decomposers of soil organic matter, however, in urban Technosols their role is still poorly understood. The respiration of active and potential active parts of fungi and bacteria was assessed for Technosols of Russian cities (Sergiev-Posad, Moscow, Kursk) compared to the undisturbed natural analogues (Retisols and Chernozems). The technique of determination of fungi and bacteria respiration applying selective antibiotics was adjusted for urban Technosols. The bactericide (streptomycin) applied for respiration inhibition in the Technosols should be added in the concentration by several thousand fold less (0.0005–0.3 mg g −1 ) than for the references (4–15 mg g −1 ). Such specific feature related to neutral and alkaline pH properties of urban soils (7.0–7.9). The fungi-to-bacteria ratio was found to be 1.4, 3.2 and 3.4 for Technosols of SergievPosad, Moscow and Kursk, respectively, and 3.4–3.9 for the references. In Technosols of Sergiev-Posad and Kursk the fungi and bacteria respiration after adding easily available nutrient substrate (glucose) decreased by 1.3–6.8 times compared to natural analogues. The differences in averaged fungal respiration between urban and natural soils were more explicit than for bacterial. Consequently, urbanization influences on the fungi and bacteria functioning related to soil organic matter decomposition: in urban soils it was significantly deteriorated. © 2020, Springer Nature Switzerland AG

Soil microbial activity along an altitudinal gradient: Vegetation as a main driver beyond topographic and edaphic factors

An altitudinal gradient in the mountains constitutes a unique ‘open-lab’ to examine environmental hypotheses and analyse the expected effects of global warming. The distribution of carbon (C)-, nitrogen (N)-, and phosphorus (P)-acquiring enzyme activity, microbial catabolic activity as represented by a community-level physiological profile (CLPP), and microbial functional diversity (HCLPP) within mountainous ecosystems consisting of mixed, fir and deciduous forests, as well as subalpine and alpine meadows (1260–2480 m a.s.l., Mt. Tkachiha, the Northwest Caucasus, Russia) has been studied. Concerning potential drivers, vegetation (plant projective cover, plant functional group composition, plant richness and diversity) and edaphic (soil nutrients: total and available C and N, total P, pH, texture, temperature, microbial biomass C) and topographic (elevation, slope, mean annual temperature calculated using biannual monitoring data) properties have been considered. The distribution patterns of the studied hydrolytic enzymes along an altitudinal gradient cannot be explained solely by elevation change and soil nutrient content. The activity of soil leucine aminopeptidase depends on vegetation type and graminoid abundance. β-D-glucosidase activity was mainly driven by the quality of soil organic matter (SOM), demonstrating a significant relation with the soil C:N ratio. The chitinase and phosphatase turned out soil temperature-sensitive enzymes. The CLPP depends on the available N content in the soil. The HCLPP distribution with altitude was driven by available N and forbs abundance represented by the widest spectrum of plant families and species. An altitudinal gradient determines the spread of the vegetation zone. In turn, vegetation properties, such as plant functional group composition, species richness and diversity, play a significant role in the distribution of soil microbial activity along an altitudinal gradient that controls the decomposition of SOM and nutrient cycling. Thus, the significant role of vegetation in the distribution of soil microbial activity across a wide range of natural ecosystems and in consideration of topographic and edaphic factors has been demonstrated. © 2021 Elsevier B.V

Carbon dioxide emission and soil microbial respiration activity of Chernozems under anthropogenic transformation of terrestrial ecosystems

The total soil CO2 emission (EM) and portion of microbial respiration were measured (in situ; May, June, July 2015) in Chernozems typical of virgin steppe, oak forest, bare fallow and urban ecosystems (Kursk region, Russia). In soil samples (upper 10 cm layer), the soil microbial biomass carbon (Cmic), basal respiration (BR) and fungi-to-bacteria ratio were determined and the specific microbial respiration (BR / Cmic = qCO2) was calculated. The EM was varied from 2.0 (fallow) to 23.2 (steppe) g СО2 m-2 d-1. The portion of microbial respiration in EM was reached in average 83, 51 and 60% for forest, steppe and urban, respectively. The soil Cmic and BR were decreased along a gradient of ecosystems transformation (by 4 and 2 times less, respectively), while the qCO2 of urban soil was higher (in average by 42%) compared to steppe, forest and fallow. In urban soil the Cmic portion in soil Сorg and Сfungi-to-Сorg ratio were by 2.6 and 2.4 times less than those for steppe. The relationship between microbial respiration and BR values in Chernozems of various ecosystems was significant (R2 = 0.57)