The structure of the microbial communities in low-moor and high-moor peat bogs of Tomsk oblast

The number, structure, and physical state of the microbial communities in high-moor and low-moor peat bogs were compared. Distinct differences in these characteristics were revealed. The microbial biomass in the high-moor peat exceeded that in the low-moor peat by 2–9 times. Fungi predominated in the high-moor peat, whereas bacteria were the dominant microorganisms in the low-moor peat. The micromycetal complexes of the high-moor peat were characterized by a high portion of dark-colored representatives; the complexes of the low-moor peat were dominated by fast-growing fungi. The species of the Penicillum genus were dominant in the high-moor peat; the species of Trichoderma were abundant in the low-moor peat. In the former, the bacteria were distinguished as minor components; in the latter, they predominated in the saprotrophic bacterial complex. In the high-moor peat, the microorganisms were represented by bacilli, while, in the low-moor peat, by cytophages, myxobacteria, and actinobacteria. The different physiological states of the bacteria in the studied objects reflecting the duration of the lag phase and the readiness of the metabolic system to consume different substrates were demonstrated for the first time. The relationships between the trophic characteristics of bacterial habitats and the capacity of the bacteria to consume substrates were established.     

Analysis of ecological factors limiting the destruction of high-moor peat

This review presents an analysis of literature data and original studies by the authors aimed at revealing the factors inhibiting the destruction of high-moor (oligotrophic) peat. Each of the ecological factors that prevent the decomposition of the high-moor peat by different groups of microorganisms is considered. The acid reaction, low temperatures, and lack of nutrients were found not to be the primary factors inhibiting the destruction of the peat. The limited content of oxygen in the peatbogs leads to a drastic decrease in the number of mycelial microorganisms and a reduction of the activity of hydrolytic and oxidizing enzymes. The main factor inhibiting the decomposition of sphagnum is its mechanical and chemical stability, since animals crushing sphagnum are absent in the soil, and this moss has polysaccharides of special composition. The toxicity of phenol compounds, which is manifested under the aerobic conditions, prevents the activity of all the hydrolytic enzymes. This is the main reason for the slow decomposition of sphagnum peat and the long-term preservation of the residues of bodies and food in high-moor peatlands.     

The influence of aeration and temperature on the structure of bacterial complexes in high-moor peat soil

The number and taxonomic structure of the heterotrophic block of aerobic and facultative anaerobic bacteria were studied in monoliths from a high-moor peat (stored at room temperature and in a refrigerator) and in the peat horizons mixed in laboratory vessels. The monitoring lasted for a year. In the T0 horizon, spirilla predominated at room and low temperatures; in the T1 and T2 horizons, bacilli were the dominants. The continuous mixing of the peat layers increased the oxygen concentration and the peat decomposition; hence, the shares of actinomycetes and bacilli (bacteria of the hydrolytic complex) increased. In the peat studied, the bacilli were in the active state; i.e., vegetative cells predominated, whose amount ranged from 65 to 90%. The representatives of the main species of bacilli (the facultative anaerobic forms prevailed) hydrolyzed starch, pectin, and carboxymethylcellulose. Thus, precisely sporiferous bacteria can actively participate in the decomposition of plant polysaccharides in high-moor peat soils that are characterized by low temperatures and an oxygen deficit. The development of actinomycetes is inhibited by low temperatures; they can develop only under elevated temperature and better aeration.     

Functioning of microbial complexes in aerated layers of a highmoor peat bog

Monitoring was carried out using the luminescent-microscopic method of the abundance parameters of different groups of microorganisms in a monolith and in the mixed layers of a highmoor peat bog (oligotrophic residual-eutrophic peat soil) in a year-long model experiment. The increase of the aeration as a result of mixing of the layers enhanced the activity of the soil fungi. This was attested to by the following changes: the increase of the fungal mycelium length by 6 times and of the fungal biomass by 4 times and the double decrease of the fraction of spores in the fungal complex. The response of the fungal complex to mixing was different in the different layers of the peat bog. The maximal effect was observed in the T1 layer and the minimal one in the T2 layer. The emission of CO₂ in the mixed samples was 1.5–2 times higher than that from the undisturbed peat samples. In contrast with the fungi, the bacteria and actinomycetes were not affected by the aeration of the highmoor layers.     

Changes of the content of oil products in the oil-polluted peat soil of a high-moor bog in a field experiment with application of lime and fertilizers

A field model experiment on stimulating the activity of native oil microorganisms–decomposers was performed on an oil-polluted area in a high-moor bog under its total flooding in the northern taiga (Western Siberia). For two summer months, the doses of lime and nitrogen, phosphorus, and potassium fertilizers applied have caused a decrease in the oil products (OP) content by 54% relative to their initial amount. The decrease of the OP content in the soil profiles was nonuniform, and at the depth of 30–50 cm it was accompanied by the acidification of peat. The stimulation of the activity of aboriginal microorganisms by applying lime and mineral fertilizers led to the development of migration processes with the participation of oil and products of its transformation. These processes differed from those in the soil without application of lime and fertilizers. An original technology of applying lime and fertilizers providing minimal disturbances the upper 50-cm peat layer is suggested.     

Microbial communities and transformation of carbon compounds in bog soils of the taiga zone (Tomsk oblast)

Two types of bogs were studied in Tomsk oblast—Maloe Zhukovskoe (an eutrophic peat low-moor bog) and Ozernoe (an oligotrophic peat high-moor bog). The gram-negative forms of Proteobacteria were found to be dominant and amounted to more than 40% of the total population of the microorganisms investigated. In the peat bogs, the population and diversity of the hydrolytic microbial complex, especially of the number of micromycetes, were lower than those in the mineral soils. The changes in the quantitative indices of the total microbiological activity of the bogs were established. The microbial biomass and the intensity of its respiration differed and were also related to the depth of the sampling. In the Zhukovskoe peat low-moor bog, the maximal biomass of heterotrophic microorganisms (154 μg of C/g of peat) was found in the aerobic zone at a depth of 0 to 10 cm. In the Ozernoe bog, the maximal biomass was determined in the zone of anaerobiosis at a depth of 300 cm (1947 μ g of C/g of peat). The molecular-genetic method was used for the determination of the spectrum of the methanogens. Seven unidentified dominant forms were revealed. The species diversity of the methanogens was higher in the oligotrophic high-moor bog than in the eutrophic low-moor bog.     

Microbial transformation of nitrogen compounds in soils of the southern taiga

The intensity of the processes of nitrogen mineralization, fixation, and denitrification was assessed in the high-moor peat gley, white-podzolic, pale-podzolic, burozem, low-moor peat, and soddy-gley soils of the Central Forest Biosphere Reserve (CFBR). The actual and potential activities of the nitrogen fixation and denitrification were determined using the gas-chromatographic method, and the intensity of the ammonification was determined using ion-selective electrodes. The maximum intensity of the nitrogen fixation was observed in the low-moor peat and soddy-gley soils, which are characterized by a high content of organic matter. High denitrification activity was found in the low-moor peat soil (0.31 nmol N₂O/g per h); this was determined by the excessive moistening of this soil. The processes of organic nitrogen mineralization were the most intensive in the upper (L and F) subhorizons of the litter.     

Morphology and properties of the soils of permafrost peatlands in the southeast of the Bol’shezemel’skaya tundra

The morphology and properties of the soils of permafrost peatlands in the southeast of the Bol’shezemel’skaya tundra are characterized. The soils developing in the areas of barren peat circles differ from oligotrophic permafrost-affected peat soils (Cryic Histosols) of vegetated peat mounds in a number of morphological and physicochemical parameters. The soils of barren circles are characterized by the wellstructured surface horizons, relatively low exchangeable acidity, and higher rates of decomposition and humification of organic matter. It is shown that the development of barren peat circles on tops of peat mounds is favored by the activation of erosional and cryogenic processes in the topsoil. The role of winter wind erosion in the destruction of the upper peat and litter horizons is demonstrated. A comparative analysis of the temperature regime of soils of vegetated peat mounds and barren peat circles is presented. The soil–geocryological complex of peat mounds is a system consisting of three major layers: seasonally thawing layer–upper permafrost–underlying permafrost. The upper permafrost horizons of peat mounds at the depth of 50–90 cm are morphologically similar to the underlying permafrost. However, these layers differ in their physicochemical properties, especially in the composition and properties of their organic matter.     

Migration of oil and its components along the profile of high-moor peat soil under model experimental conditions

It was found in a model experiment that high-moor peat has a high sorption capacity for oil, as well as for its most migration-capable components (aromatic hydrocarbons and their derivatives). Benzene was more involved in migration with water than phenol, which can be related to the formation of molecular complexes with fulvic acids. The results obtained agree with the low contamination of surface waters near oil spills in high-moor peatlands.     

Effect of biobed composition, moisture, and temperature on the degradation of pesticides

Biobeds retain and degrade pesticides through the presence of a biobed mixture consisting of straw, peat, and soil. The effects of biobed composition, moisture content, and temperature on pesticide degradation were investigated in laboratory studies. Straw produced the main microbial activity in the biobed mixtures as strong positive correlations were observed between straw, respiration, and phenoloxidase content. Most pesticides investigated were dissipated by cometabolic processes, and their dissipation was correlated with respiration and/ or phenoloxidase content. More pesticides were more dissipated at biobed moisture levels of 60% water holding capacity (WHC) than at 30% and 90% WHC, while 20 degrees C gave higher dissipation rates than 2 and 10 degrees C. A straw:peat:soil ratio of 50:25:25% v/v is recommended in field biobeds since this produces high microbial activity and low pH, favorable for lignin-degrading fungi and phenoloxidase activity.     

Gas Diffusion Coefficient of Undisturbed Peat Soils

Determination of the gas diffusion coefficient D _s of peat soils is essential to understand the mechanisms of soil gas transport in peatlands, which have been one of major potential sources of gaseous carbons. In the present study, we aimed at determining the D _s of peat soils for various values of the air-filled porosity a and we tested the validity of the Three-Porosity Model (Moldrup et al. 2004) and the Millington-Quirk model (1961) for predicting the relative gas diffusivity, the ratio of D _s to D ₀, the gas diffusion coefficient in free air. Undisturbed peat soil cores were sampled from aerobic layers in the Bibai mire, Hokkaido, Japan. The MQ model reproduced the measured D _s/ D ₀ curves better than the TPM. The TPM, a predictive model for undisturbed mineral soils, overestimated the D _s/ D ₀ values for peat soils, implying that in the peat soils the pore pathways were more tortuous than those in the mineral soils. Since the changes in the D _s/ D ₀ ratios with the a values of a well-decomposed black peat soil tended to be more remarkable than those of other high-moor peat soils, the existence of a positive feedback mechanism was assumed, such that peat soil decomposition itself would increase the soil gas diffusivity and promote soil respiration.     

Biological activity of soddy-calcareous soils and cultural layers in Alanian settlements of the Kislovodsk basin

Microbiological investigations of cultural layers were performed in a settlement of the Alanian culture—Podkumskoe-2 (the 2nd–4th centuries AD). The present-day soddy-calcareous soils (rendzinas) used for different purposes were also studied near this settlement. The most significant changes in the initial characteristics of the soil microbial communities occurred under the residential influence more than 1500 years ago; these changes have been preserved until the present time. In the areas subjected to the anthropogenic impact, the total microbial biomass (the weighted average of 3720 μg C/g soil) was lower than that in the background soil. The minimal values of the microbial biomass were found in the soil of the pasture—2.5 times less than in the background soil. The urease activity of the cultural layer was higher than that of the soils nearby the settlement. Elevated values of the cellulose activity were also recorded only in the cultural layers. The current plowing has led to a significant decrease in the mycelium biomass of the microscopic fungi. In the soil of the fallow, the weighted average value of the fungal hyphae biomass along the profile was twice lower than that in the background soil and cultural layers of the settlement. The pasture first affected the active microbial biomass and, to a lesser extent, the amount of microscopic fungi.     

Micromycetes in podzolic and bog-podzolic soils in the middle taiga subzone of northeastern European Russia

The qualitative and quantitative characteristics of the mycobiota in podzolic and bog-podzolic soils were studied in the middle taiga subzone (the Republic of Komi). The complex of micromycetes was found to include 73 species of 18 genera from the Zygomycota and Ascomycota orders and from the formal class of anamorphic fungi. The latter has the following specific features: many forms of sterile mycelium, the predominance of Penicillium species (25), the constant presence of Mucor and Trichoderma species, and single Aspergillus species. With increasing moisture in the sequence of the podzolic, surface-gleyic podzolic, peaty podzolic-gleyic, and peat podzolic-gley soils, the dominant soil fungi are preserved, but the species composition of the micromycete complexes becomes poorer due to the removal of rare species. In the podzolic and bog-podzolic soils, fungi absolutely predominate in the microbial biomass. They accounted for more than 99% of the total biomass, 1–6% of the latter is the biomass of spores, and more than 94% falls on mycelium. In these soils, the reserves of bacterial biomass, as compared to those of fungi, are lower by two orders of magnitude.     

Viability of bacteria in peatlands

The viability of bacteria in oligotrofic bogs and fens was determined by the luminescent microscopy method with the help of a two-component fluorescent dye (L7012 LIVE/DEAD). Living bacterial cells were found in the entire peat profiles. Their portion was maximal (up to 60%) in the upper layers and did not exceed 25% in the lower layers. The portion of dead bacterial cells varied from 3 to 19%, and dormant cells constituted 25 to 95% of the total number of bacterial cells. The numbers of dormant cells increased down the profiles irrespectively of the peat type. The portion of nanoforms did not exceed 5% of the total. The cells of the nanoforms, unlike the bacteria of typical sizes, were characterized by their high viability (93–98%).     

Markers of Soil Organic Matter Transformation in Permafrost Peat Mounds of Northeastern Europe

For the paleoreconstruction of permafrost peat mounds and the identification of plant communities participating in the formation of peat, the contents of n-alkanes (C₂₀–C₃₃) have been determined, and relative changes in the stable isotope compositions of carbon and nitrogen and the C/N ratio have been analysed. Several indices (CPI_alkanes, P_aq, P_wax) have been calculated to assess the degree of decomposition of the peats studied and the contributions of different plant species to their formation. It has been found that shortand long-chain n-alkanes are concentrated in high-moor peat, while medium-chain alkanes are typical for transitional peat. Integrated analysis of the studied markers has shown that the botanical and material composition of peat, anaerobic conditions of bog formation, and permafrost play an important role in the preservation of organic carbon in permafrost peat mounds. Alternation of plant associations is the main reason for changes in n-alkane concentrations, C/N ratios, and δ13C values.     

Laboratory experiments on drought and runoff in blanket peat

Global warming might change the hydrology of upland blanket peats in Britain. We have therefore studied in laboratory experiments the impact of drought on peat from the North Pennines of the UK. Runoff was dominated by surface and near‐surface flow; flow decreased rapidly with depth and differed from one type of cover to another. Infiltration depended on the intensity of rain, and runoff responded rapidly to rain, with around 50% of rainwater emerging as overland flow. Drought changed the structure of the peat and the subsequent behaviour of the peat in response to rain. Surface runoff was reduced, infiltration increased and flow increased within the deeper peat layers. Old and new water produced from the peat during simulated storms was identified by bromide tracing; the amount of old mobile water flushed out of the top few centimetres was small and there was less from deeper peat layers. No significant difference in the old and new water mixing processes could be identified between the control plots and the drought treatment plots. Lissamine staining showed preferential bypass flow through macropores in the peat, though only in the top 5 cm. Following drought, however, macroporosity increased within the upper peat layers, and preferential flow extended deeper than in controls. Peat structure recovered somewhat after drought, but the effects of the drought were long‐lasting. If these effects extend to the field during drier summers then we can expect changes to the hydrology and associated chemistry of blanket peat catchments in the British uplands.     

冻融对老龄苹果园土壤微生物数量及酶活性的影响

以山东蒙阴、莱州和栖霞3地老龄苹果园土壤为材料,分别在冬前和冬后采集0~30 cm(上层)与30~60 cm(下层)土层土样,探讨了冻融作用对老龄苹果园土壤微生物数量和酶活性的影响。结果显示:3地苹果园0~30 cm土层各理化性状均显著高于30~60 cm土层,其中速效钾含量差异最显著;冻融处理后,3地上下层土壤细菌、真菌和放线菌数量均显著性降低,且上层土壤降低最显著,其中蒙阴苹果园上层土壤细菌、真菌和放线菌分别降低了40.6%、43.6%和55.7%,3地上下层土壤细菌/真菌比值显著提高、尖孢镰孢菌基因拷贝数大幅下降;冻融处理后,3地上下层土壤脲酶、磷酸酶和蔗糖酶活性均有所降低,且表现出显著性差异,但三地上下层土壤CEC变化趋势不同,其中蒙阴苹果园上层CEC降低了41.7%,下层CEC提高了19.2%,栖霞苹果园则相反。综上,3地老龄苹果园土壤经过冻融处理后,显著降低了上下层土壤微生物数量,显著提高了上下层土壤细菌/真菌比值,优化了土壤微生物群落结构,有利于缓解苹果园连作障碍。     

Mechanisms of N2O and NO production in the soil profile of a drained and forested peatland, as studied with acetylene, nitrapyrin and dimethyl ether

 Acetylene, dimethyl ether (DME) and 2-chloro-6-trichloromethyl pyridine (nitrapyrin) were used as inhibitors to study the contributions of nitrification and denitrification to the production of N₂O and nitric oxide (NO) in samples taken from the soil profile of a peatland drained for forestry. Acetylene and DME inhibited 60–100% of the nitrification activity in field-moist samples from the 0–5 cm and 5–10 cm peat layers, whereas nitrapyrin had no inhibitory effect. In the 0–5 cm peat layer the N₂O production could be reduced by up to 90% with inhibitors of nitrification, but in the 5–10 cm peat layer this proportion was 20–30%. All the inhibitors removed 96–100% of the nitrification potential in peat-water slurries from the 0–5 cm peat layer, but the 5–10 cm layer had a much lower nitrification activity, and here the efficiency of the inhibitors was more variable. Litter was the main net source of NO in the peat profile. NO₃ ^– production was lower in the litter layer than in the peat, whereas N₂O production was much higher in the litter than in the peat. Denitrification was the most probable source of N₂O and NO in the litter, which had a high availability of organic substrates. Received: 14 July 1997     

Comparative Analysis of the Number and Structure of the Complexes of Microscopic Fungi in Tundra and Taiga Soils in the North of the Kola Peninsula

The number, biomass, length of fungal mycelium, and species diversity of microscopic fungi have been studied in soils of the tundra and taiga zones in the northern part of the Kola Peninsula: Al-Fe-humus podzols (Albic Podzols), podburs (Entic Podzols), dry peaty soils (Folic Histosols), low-moor peat soils (Sapric Histosols), and soils of frost bare spots (Cryosols). The number of cultivated microscopic fungi in tundra soils varied from 8 to 328 thousand CFU/g, their biomass averaged 1.81 ± 0.19 mg/g, and the length of fungal mycelium averaged 245 ± 25 m/g. The number of micromycetes in taiga soils varied from 80 to 350 thousand CFU/g, the number of fungal propagules in some years reached 600 thousand CFU/g; the fungal biomass varied from 0.23 to 6.2 mg/g, and the length of fungal mycelium varied from 32 to 3900 m/g. Overall, 36 species of fungi belonging to 16 genera, 13 families, and 8 orders were isolated from tundra soils. The species diversity of microscopic fungi in taiga soils was significantly higher: 87 species belonging to 31 genera, 21 families, and 11 orders. Fungi from the Penicillium genus predominated in both natural zones and constituted 38–50% of the total number of isolated species. The soils of tundra and taiga zones were characterized by their own complexes of micromycetes; the similarity of their species composition was about 40%. In soils of the tundra zone, Mortierella longicollis, Penicillium melinii, P. raistrickii, and P. simplicissimum predominated; dominant fungal species in soils of the taiga zone were represented by M. longicollis, P. decumbens, P. implicatum, and Umbelopsis isabellina.     

Evaluation of phosphorus mobilization potential in rewetted fens by an improved sequential chemical extraction procedure

After rewetting of peatlands, phosphorus (P) pore‐water concentrations were up to three orders of magnitude greater than under pristine conditions. It was hypothesized that different mobilization processes such as ion‐exchange reactions, biotic/abiotic redox reactions, acidification and ongoing anaerobic decomposition of particulate organic matter by hydrolytic cleavage and fermentation might be responsible. To identify P pools in peat samples of varying degrees of decomposition, we modified and improved a sequential chemical extraction method that allowed conclusions on potential mobilization mechanisms in rewetted peatlands. The results indicated that the earlier drainage of rewetted fens strongly increased the P mobilization potential in the upper decomposed peat layers. Accordingly, the amount of P bound to redox‐sensitive (bicarbonate/dithionite soluble) compounds (BD‐P) was, on average, one order of magnitude greater in decomposed peat of rewetted fens (5.4–14.3 μmol P g^?1 dry matter or DM) than in underlying less‐decomposed peat layers (0.2–1.9 μmol P g^?1 DM) or slightly decomposed peat derived from pristine fens (0.4–2.0 μmol P g^?1 DM). The BD‐P fraction found in the upper very decomposed peat layers appears to be most important for P mobilization in rewetted fens and accounted for 85% of the variability of P mobilization rates. Despite uncertainties regarding P diagenetic processes in peat, as well as the development of microbial decomposition processes, in the long‐term, high pore‐water P concentrations can be expected in rewetted fens for decades to come.