Distribution Of Soil Microorganisms Research Articles

Влияние на микропластмаси, вермикомпост и зеолит върху микрофлората на почви с различни физични свойства

The effect of additives of different composition and origin - non-organic (microplastics), organic (vermicompost) and mineral (zeolite) on microflora and soil physical conditions of two soil varieties was studied. A laboratory experiment was performed on soil samples, taken from the surface (0-20 cm) soil layer of Vertic Phaeozem (clay textural class), from the experimental field Gorni Lozen under grassland and of Haplic Cambisol (loam textural class), from the experimental station of potatoes Samokov, cultivated land. The concentrations of the additives were 10% by mass of the sample. The amount of main groups of soil microorganisms was determined - ammonifying and cellulolytic microorganisms, mineral nitrogen-utilizing bacteria, actinomycetes and microscopic fungi. The changes of water retention properties of the studied mixtures were analyzed. It was found that the distribution of soil microorganisms was influenced in a different way by the applied additives in the studied soils.

Global distribution modelling of a conspicuous Gondwanian soil protist reveals latitudinal dispersal limitation and range contraction in response to climate warming

AbstractAimThe diversity and distribution of soil microorganisms and their potential for long‐distance dispersal (LDD) are poorly documented, making the threats posed by climate change difficult to assess. If microorganisms do not disperse globally, regional endemism may develop and extinction may occur due to environmental changes. Here, we addressed this question using the testate amoeba Apodera vas, a morphologically conspicuous model soil microorganism in microbial biogeography, commonly found in peatlands and forests mainly of former Gondwana. We first documented its distribution. We next assessed whether its distribution could be explained by dispersal (i.e. matching its climatic niche) or vicariance (i.e. palaeogeography), based on the magnitude of potential range expansions or contractions in response to past and on‐going climatic changes. Last, we wanted to assess the likelihood of cryptic diversity and its potential threat from climate and land‐use changes (e.g. due to limited LDD).LocationDocumented records: Southern Hemisphere and intertropical zone; modelling: Global.MethodsWe first built an updated global distribution map of A. vas using 401 validated georeferenced records. We next used these data to develop a climatic niche model to predict its past (LGM, i.e. 21 ± 3 ka BP; PMIP3 IPSL‐CM5A‐LR), present and future (IPSL‐CMP6A‐LR predictions for 2071–2100, SSP3 and 5) potential distributions in responses to climate, by relating the species occurrences to climatic and topographic predictors. We then used these predictions to test our hypotheses (dispersal/vicariance, cryptic diversity, future threat from LDD limitation).ResultsOur models show that favourable climatic conditions for A. vas currently exist in the British Isles, an especially well‐studied region for testate amoebae where this species has never been found. This demonstrates a lack of interhemispheric LDD, congruent with the palaeogeography (vicariance) hypothesis. Longitudinal LDD is, however, confirmed by the presence of A. vas in isolated and geologically young peri‐Antarctic islands. Potential distribution maps for past, current and future climates show favourable climatic conditions existing on parts of all southern continents, with shifts to higher land from LGM to current in the tropics and a strong range contraction from current to future (global warming IPSL‐CM6A‐LR scenario for 2071–2100, SSP3.70 and SSP5.85) with favourable conditions developing on the Antarctic Peninsula.Main ConclusionsThis study illustrates the value of climate niche models for research on microbial diversity and biogeography, along with exploring the role played by historical factors and dispersal limitation in shaping microbial biogeography. We assess the discrepancy between latitudinal and longitudinal LDD for A. vas, which is possibly due to contrast in wind patterns and/or likelihood of transport by birds. Our models also suggest that climate change may lead to regional extinction of terrestrial microscopic organisms, thus illustrating the pertinence of including microorganisms in biodiversity conservation research and actions.

Microbiocenosis of Cryofrost Soils in the South of the Vitim Plateau

The microbial communities in soils of cryomorphoses in the south of the Vitim Plateau have been studied. The objects of study were gley cryoturbated chernozems and humus-quasi-gley carbonated soils. In the course of the study, experimental sites with pronounced cryogenic phenomena were selected. The intensity of microbiological activity was determined by the carbon content of microbial biomass, the number of microorganisms in the dominant groups of microbial communities. Determination of the number of microorganisms in soils was carried out by direct microscopy, which makes it possible to carry out a more accurate count of bacteria in the soil, taking into account adsorbed cells. Cells were preliminarily desorbed on an ultrasonic disperser. The carbon of microbial biomass was determined by the rehydration method. Data were obtained characterizing the direction and intensity of microbiological processes along the horizons of soil profiles of heaving mounds and thermokarst depressions. The number of microorganisms and the dominant groups of bacterial communities of soils formed under the conditions of the ultracontinental climate of Buryatia and relatively close-lying permafrost are presented. It was revealed that bacterial microflora predominates in the soils of heaving mounds and thermokarst depressions. The intra-profile heterogeneity in the distribution of soil microorganisms indicates that, as a habitat, the soil is strongly differentiated in all directions. This differentiation along the vertical of heaving mound and thermokarst depression was reflected in the concept of soil horizons as special ecological niches and the possibility of using microbiological indications of heaving and subsidence occurring during heaving.

Distribution of soil microorganisms in different complex soil layers in Mu Us sandy land.

The soft rock in Mu Us Sandy Land has rich resources and high content of clay minerals. The combination of soft rock with sand can play a certain role in sand fixation and promote the green development of ecological environment. In this paper, the aeolian sandy soil in Mu Us Sandy was taken as the research object, and it was mixed with soft rock to form composite soil. The four volume ratios of soft rock to sand were respectively 0:1, 1:5, 1:2 and 1:1. And CK, P1, P2 and P3 were used to represent the above four volume ratios in turn. By means of quantitative fluorescent PCR and high throughput sequencing, 16S rRNA gene abundance and community structure were investigated. The results showed that the soil organic carbon (SOC) and total nitrogen (TN) contents in 0-30cm soil layer were higher. Compared with CK, the SOC of P2 was improved by 112.77% and that of P1 was 88.67%. The content of available phosphorus (AP) and available potassium (AK) was higher in 30-60cm soil layer, and P3 was more effective. The abundance of 16S rRNA gene in the mixed soil bacteria ranged from 0.03×109 to 0.21×109 copies g-1 dry soil, which was consistent with the changes of nutrients. Under different soil layers, the three dominant bacteria in the mixed soil were the same, namely Phylum Actinobacteriota, Phylum Proteobacteria and Phylum Chloroflexi, and there were more unique genera in each soil layer. Both bacteria ɑ and β diversity showed that the community structure of P1 and P3 in 0-30cm soil layers was similar, and that of P1 and P2 in 30-60cm soil layers was similar. AK, SOC, AN (ammonium nitrogen), TN and NN (nitrate nitrogen) were the main factors contributing to the differentiation of microbial community structure under different compound ratios and soil layers, and Phylum Actinobacteria has the largest correlation with nutrients. The results showed that the soft rock could improve the quality of sandy soil, and that the growth of microbial growth was dependent on the soil physicochemical characteristics. The results of this study will be helpful to the study of the microscopical theory for the control of the wind-blown sand and the ecology of the desert.

Investigation of Environmental Effect of Plants in Smoking Area through Analysis of Cadmium and Microorganisms

Objectives:The purpose of this study was to investigate the effect of plants on smoking area and its environment. For this purpose, two different smoking areas (with and without plants) were selected, and the number of smokers and spitting behaviors were monitored. Soil and leaves samples of each smoking area were taken to analyze the concentration of cadmium and distribution of soil microorganisms. Through this investigation, the role of plants in smoking area for the cadmium and microorganisms was estimated. Methods:In the selected smoking areas, number of smokers and the number of spitting behaviors were monitored. Cadmium (Cd) concentrations of leaves, topsoil and rhizosphere obtained from the smoking areas were analyzed with inductively coupled plasma mass spectrometry (ICP-MS). The microorganisms in soil samples were analyzed using denaturing gradient gel electrophoresis (DGGE) and 16s rRNA amplicon sequencing based metagenomics.Results and Discussion:In the case of smoking area with plants, number of smokers and number of total spitting behaviors were 176.67 ± 7.85 and 918.67 ± 40.8 times per hour, respectively. In smoking area without plants, the 153.67 ± 5.44 (smokers) and (829.8 ± 29.36 (spitting behavior) per hour were observed. Among the collected samples from the smoking areas, the highest Cd values (347.117 ± 24.542 μg/kg) were found in leaves of smoking area. In the case of smoking area without plants, the top soil samples showed the highest Cd concentration (295.77 ± 16.64 μg/kg). The results indicate that Cd released from cigarette ash, saliva and smoke can be accumulated in plants and soil. The results suggested that the presence of plants in the smoking area protect the accumulation of Cd in surrounding environments (soil and atmosphere). The metagenomic analysis of the soil samples showed that smoking and spitting behavior also affected microbial system in the smoking areas. The results showed that the microorganisms in smoking area were closely related to the heavy metal removing activities. Conclusion:Results suggested that the cadmium distribution in the smoking areas was significantly affected by the presence of live plants. In addition, the presence of plants in the smoking area induced the difference species microorganisms. These results suggested that the presence of plants in smoking area can protect the spread of cadmium to the surrounding environment.

Distribution of Soil Microorganisms in Field under Potatoes due to Fertilizer and Organics

Background: Using organic manure derived from animal or vegetable matter is often associated with balanced crop production. The influence of organics and fertilizers on soil sustainability during cultivation of potatoes in field was studied. Methods: Vegetable experiment comprising 10 years (2011-2021), having a control variant (no fertilization), independent mineral, organics (compost) and their combination (50:50%). Changes in the amount and distribution of microbial groups in experimental variants and associated untreated controls were evaluated. Total bacterial number, spore-forming bacteria, fungi, nitrogen-utilizing bacteria and actinomycetes were assessed. Result: Applied organics and fertilizers had statistically proven a positive effect on growth parameters of potatoes. Organics and fertilizers supplied with mineral and foliar feeding registered taller plants with increased number of branches, number and mass of leaves and stem and root masses, compared to potatoes with organic and organic-mineral combination. Application of compost led to a significant increase in populations of all physiological groups of microorganisms excluding spore-forming bacteria and bacteria utilizing mineral nitrogen, which is a good indicator of increased soil microbial activity in respective treatments. Mineral fertilization had a positive effect on total number of bacteria and on absorption of mineral nitrogen. The treatment in variant (50:50 %) at rhizosphere soil was associated with organic manure application and at non-rhizosphere soil with mineral fertilizer.

Disturbances consistently restrain the role of random migration in grassland soil microbial community assembly

Random migration often plays important roles in soil microbial community assembly. However, it remains unexplored that whether its role is affected by anthropogenic disturbances, and whether the effects of different disturbances are consistent. Here, we report a novel and general pattern that different disturbances consistently restrain the role of migration in soil bacterial community assembly. We mimicked 16 types of anthropogenic disturbances relevant to a Eurasian steppe ecosystem, including removing different number of plant functional groups, mowing, adding nitrogen, adding phosphorus, watering, warming, and some of their combinations. The estimated migration rates in soil bacterial community assembly with Stephen Hubbell’s neutral model decreased by 0.19–6.29% under these disturbances. The relative change in migration rate was correlated with the deterministic change in community composition and the relative change in soil pH. Our results suggested that the intensifying anthropogenic disturbances may restrain the random dispersal, colonization and distribution of soil microorganisms.

Aggregate-related microbial communities and nutrient stoichiometry under different croplands

Ecological stoichiometry is an important indicator presenting multiple elements balance in agro-ecosystems. However, information on microbial communities and nutrient stoichiometry in soil aggregate fractions under different croplands (rice, maize, and soybean fields) remains limited. Thus, this study investigated water-stable aggregate structure and their internal nutrient stoichiometry under different croplands and ascertain their interaction mechanism with microbial communities. The results showed that no significant difference on the carbon-to-nitrogen ratio (C:N) in soil aggregate fractions was observed, while the carbon-to-phosphorus ratio (C:P) and the nitrogen-to-phosphorus ratio (N:P) were ranked as rice field > maize field > soybean field, and were higher in mega-aggregates (ME, > 1 mm). General fatty acid methyl ester (FAME), Gram-positive bacteria (G+), and Gram-negative bacteria (G−) were predominant microbial communities in all croplands and tented to condense into coarse-aggregates. Redundancy analysis (RDA) demonstrated that N:P ratio was primary environmental controls on the distribution of soil microorganisms. In the Sanjiang Plain, N was the nutrient element limiting agro-ecosystem productivity, and rice cultivation is expected to improve the N-limited nutrient status.

Lime Application Affects Soil Cadmium Availability and Microbial Community Composition in Different Soils

The effect of pH increases following lime (Ca(OH)2) addition on soil cadmium (Cd) availability is examined in three soils. The effect of Ca(OH)2 addition (0–7.5 t ha−1) on crop Cd uptake and microbial community composition is evaluated in pot experiments with Chinese cabbage (Brassica chinensis L.) and rice (Oryza sativa L.). The soil pH increases significantly (by 1.21–2.57) after Ca(OH)2 addition, which may be caused by both biological and chemical factors. The soil water‐exchangeable Cd content decreases substantially from 11.7 to 1.4% with Ca(OH)2 application, and the iron and manganese oxide Cd fractions increase from 24.7 to 37.5%. Ca(OH)2 significantly reduces the exchangeable Cd in acidic soil but has limited effects in neutral soil. Ca(OH)2 can inhibit soil Cd activity and plant Cd absorption in acid soil. With increasing Ca(OH)2 addition, the abundance of microorganisms tends to decrease, especially in the acidic soil, whereas it tends to increase in neutral soil. Principal components analysis and redundancy analysis among the soil environmental factors and the soil microbial phospholipid fatty acids show highly variable microbial community composition among soils and treatments. Soil pH has substantial effects on soil fungi, actinomycetes, and other microorganisms, the abundance of which decreases with increasing soil pH. The continuous use of Ca(OH)2 has no significant effects on the abundance and distribution of soil microorganisms.

Impacts of Cropping Systems on the Distribution of Soil Microorganisms in Mid-mountainous Paddy

Soil microbes are widely well known to play an important role for sustainable agriculture in terms of crop healthy cultivation and environmental conservation. In this context, the distributional characteristics of soil microbes according to cropping systems were investigated under rice (R)-rice (R), rice (R)-barley (B)-rice (R), and soybean (S)-barley (B)-soybean (S) cropping condition to get basic informations for sustainable agriculture, where barley was grown for winter, in mid-mountainous loam paddy located at the altitude of 285 m above sea level in Sangju area from 2014 to 2015. Estimating from microbial communities by fatty acid methyl ester (FAME) method, a total biomass of bacteria, actinomycetes, and fungi in R-B-R plot was 37% and 40% higher than that in S-B-S and R-R plots, respectively (p < 0.05). In especial, bacteria and fungi were more in R-B-R plot than those in any other ones. B. japonicum, AMF, and mesophilic Bacillus sp. were also greater in S-B-S plot than those. In the community distribution, however, bacteria and actinomycetes showed comparatively high values in S-B-S plot relative to either R-R or R-B-R plot including rice, in which fungi outstanding. In the correlation between microbial biomass and soil properties changed by the cropping, bacteria was positively correlated with C:N ratio; actinomycetes with exchangeable Ca; fungi with available <TEX>$P_2O_5$</TEX> (p < 0.05). While these microbes showed negative response to water stable aggregates of soil.

The activity and community structure of total bacteria and denitrifying bacteria across soil depths and biological gradients in estuary ecosystem.

The distribution of soil microorganisms often shows variations along soil depth, and even in the same soil layer, each microbial group has a specific niche. In particular, the estuary soil is intermittently flooded, and the characteristics of the surface soil layer are different from those of other terrestrial soils. We investigated the microbial community structure and activity across soil depths and biological gradients composed of invasive and native plants in the shallow surface layer of an estuary ecosystem by using molecular approaches. Our results showed that the total and denitrifying bacterial community structures of the estuarine wetland soil differed according to the short depth gradient. In growing season, gene copy number of 16S rRNA were 1.52(±0.23) × 10(11), 1.10(±0.06) × 10(11), and 4.33(±0.16) × 10(10) g(-1) soil; nirS were 5.41(±1.25) × 10(8), 4.93(±0.94) × 10(8), and 2.61(±0.28) × 10(8) g(-1) soil; and nirK were 9.67(±2.37) × 10(6), 3.42(±0.55) × 10(6), and 2.12(±0.19) × 10(6) g(-1) soil in 0 cm, 5 cm, and 10 cm depth layer, respectively. The depth-based difference was distinct in the vegetated sample and in the growing season, evidencing the important role of plants in structuring the microbial community. In comparison with other studies, we observed differences in the microbial community and functions even across very short depth gradients. In conclusion, our results suggested that (i) in the estuary ecosystem, the denitrifying bacterial community could maintain its abundance and function within shallow surface soil layers through facultative anaerobiosis, while the total bacterial community would be both quantitatively and qualitatively affected by the soil depth, (ii) the nirS gene community, rather than the nirK one, should be the first candidate used as an indicator of the microbial denitrification process in the estuary system, and (iii) as the microbial community is distributed and plays a certain niche role according to biogeochemical factors, the study of the microbial community even in surface soil should be performed in detail by considering the soil depth.

Vertical Distributions in Number of Soil Microorganism with Caragana in the Hobq of Inner Mongolia

The study investigated the vertical distribution of soil microorganism on Caragana rhizosphere at Hobq of ORDOS. The result showed that microbial vertical distribution was obvious. The order of vertical distribution in number of aerobic bacteria were 0-10cm&gt;20-30cm&gt;10-20cm&gt;30-40cm, and there were significant differences between microorganisms in 0-10cm, 10-20cm and 30-40cm underground; the number of aerobic bacteria in 0-10cm underground was higher than 10-20cm, 20-30cm and 30-40cm by 1.48,1.41 and 1.86. The order of vertical distribution in number of fungi were 0-10cm&gt;10-20cm&gt;20-30cm&gt;30-40cm, and there were significant differences between 0-10 cm and 20-30cm、30-40cm, and between 10-20 cm and 20-30cm、30-40cm. the number of fungi in 0-10cm underground was higher than 10-20cm, 20-30cm and 30-40cm by 1.01, 3.60 and 5.37. The order of vertical distribution in number of Actinomycetes was 0-10cm&gt;10-20cm&gt;20-30cm&gt;30-40cm, and the differences between 0-10 cm and 10-20cm, 20-30cm, 30-40cm were significant; the number of Actinomycetes in 0-10cm underground was higher than 10-20cm, 20-30cm and 30-40cm by 1.54,1.66 and 2.60. The distribution and quantity of soil microorganisms might be influenced by organic matter contents.

Landscape-scale geographic variations in microbial biomass and enzyme-labile phosphorus in manure-amended Hapludults

Long-term nutrient management practices have lasting effects on the geographic distribution of soil microorganisms, loci of enhanced activity, and non-mobile nutrients such as phosphorus (P) to ultimately influence nutrient use efficiency by crops and edge-of-field losses. We determined the distribution of soil microbial biomass, phosphomonoesterases' activity, and P forms in a 10-ha no-till field that received annual additions of dairy manure at 0, 15, and 30 kg P ha−1 at the field scale for 16 consecutive years. The spatial structure of soil microbial indices and extractable P fractions were characterized based on their semivariance distributions for each manure treatment. The buildup in soil P occurred, although replacement was done at a crop removal rate. Manure additions resulted in overall mean increases in total labile P of 73 % and 156 % and alterations in the soil microbial ecosystem that depended on manure inorganic-to-enzyme-labile P composition in soils treated with 15 and 30 kg P ha−1, respectively. Distinct clusters of phosphate- and enzyme-labile organic P were observed within manure treatments, where accumulation of the latter forms was associated with high soil microbial biomass C and reduced acid phosphomonoesterase activity. The geographic variability highlighted the critical need for improving methods of field-scale application of manure and non-mobile nutrients. In addition, current soil testing methods that depend upon composite representative samples for estimating microbiological parameters linked to nutrient turnover and P requirements for optimal crop production should be modified to include site-specificity in sampling and interpretation approaches.

Spatial heterogeneity of a microbial community in a sandy soil ecosystem

Abstract A fieldwork was carried out in Caesarea sand dunes, Israel, to determine the influence of fine-scale landscape-patch abiotic-factor heterogeneity on microbial activity in a Mediterranean region. Soil organisms in terrestrial systems are unevenly distributed in time and space, and are often aggregated. Spatio-temporal patchiness in the soil environment is thought to be crucial for the maintenance of soil biodiversity, providing diverse microhabitats that are tightly interwoven with resource partitioning. Determination of a ‘scale unit’ to help understand ecological processes has become one of the important and most debatable problems in recent years. To better understand the distribution of soil microbial communities at multiple spatial scales, a survey was conducted to examine the spatial organization of the community structure in two sandy soil ecosystems. One-hundred forty-four soil samples were collected from two patches 4000 m apart from each other. Basal respiration (CO 2 evolution without the addition of any external substrate), microbial biomass, functional diversity, and community-level physiological profile (CLPP) in soil were measured with a MicroResp™ system. Soil abiotic analysis was performed by soil standard analytical methods. The results demonstrated that bacterial distributions can be highly structured, even within a habitat that appears to be relatively homogeneous at the plot and field scale. Different subsets of the microbial community were distributed differently across the plot. This is due to spatial heterogeneity associated with soil physical, chemical, and biological properties. Although spatial variability in the distribution of soil microorganisms is generally regarded as random, this variability often has a predictable spatial structure. This study provided evidence that a spatially explicit approach to soil ecology can enable the identification of factors that drive the spatial heterogeneity of populations and activities of soil organisms, at scales ranging from meters to hundreds of meters. Furthermore, there is increasing evidence that spatial soil ecology can yield new insights into the factors that maintain and regulate soil biodiversity, as well as on how the spatial distribution of soil organisms influences plant growth and plant community structure.

Evaluation of tyramide solutions for an improved detection and enumeration of single microbial cells in soil by CARD-FISH

Several tyramide solutions were evaluated for the application of fluorescence in situ hybridization with catalyzed reporter deposition (CARD-FISH) in soil. Fluorescently labeled tyramide solutions were synthesized and compared to commercially available tyramides for the detection and quantification of single microbial cells. Among the tyramide solutions tested, a succinimidyl ester of fluorescein diluted with dimethylformamide containing iodophenolboronic acid (SFX-DMF-IPBA) gave the best results, yielding highly reproducible cell numbers and detection rates of archaea and bacteria along with negligible non-specific signals. The addition of organic and inorganic compounds to the amplification reagents had a positive impact on the detection of prokaryotic cells. The applicability of SFX-DMF-IPBA for CARD-FISH in soil was further evaluated in soils of different texture. Cell numbers and detection rates of bacteria and archaea remained on a high level independent of the clay or organic matter content. Based on the results obtained in this study, the choice of the tyramide solution used for CARD-FISH has a significant influence on the detection and quantification of single microbial cells in soil. Therefore, we suggest the application of the presented tyramide signal amplification procedure including the tyramide solution SFX-DMF-IPBA for comprehensive CARD-FISH studies investigating the abundance and spatial distribution of soil microorganisms.

Characterization of microorganisms in the soils with sewage irrigations

The purpose of this study was to examine the influence of sewage irrigation on the quantity and distribution of soil microorganisms, and to explore the relationship between the content of soil nutrients and the quantity of different microorganism. The results showed that the quantities of the soil actinomycetes, fungi, nitrite oxidizing bacteria (NOB), nitrate bacteria (NB) and denitrifying bacteria (DB) were reduced, while those of soil bacteria, ammonia oxidizing bacteria (AOB) and aerobic cellulose decomposing bacteria (CDB) were increased after sewage irrigation. The distribution of fungi, azotobacter (AB) and cellulose decomposing bacteria (CDB) in the soil rhizosphere of soybean, corn and rice were significantly altered after sewage irrigation. The quantity of soil microorganism in the soil after sewage irrigations was significantly correlated with the soil content of organic substance, ammonia nitrogen and available phosphorous. These results provided theoretical basis for the application and standard establishment of sewage irrigation in the farmland. Key words: Sewage irrigation, soil microorganisms, soil nutrient, Kuihe River, farmland.

Diversity of soil microorganisms in natural Populus euphratica forests in Xinjiang, northwestern China

To better understand the distribution of soil microorganisms in Populus euphratica forests in Xinjiang, northwestern China, we studied and compared the populations and numbers of bacteria, fungi and actinomycetes in the soil at four different age stages of natural P. euphratica forests, i.e., juvenile forests, middle-aged forests, over-mature forests and degraded forests. Results showed that there were clear differences in the amount of microorganism biomass and composition rates across the four forest stages. Dominant and special microorganisms were present in each of the four different soil layers. The vertical distribution showed that the microorganism biomass decreased with increasing soil depth. The population of microorganisms was the lowest at 31–40 cm of soil depth. The microorganisms consisted of bacteria, actinomycetes, as well as fungi. Bacteria were the chief component of microorganisms and were widely distributed, but fungi were scarce in some soil layers. Aspergillus was the dominant genus among the 11 genera of fungi isolated from the soil in different age stages of P. euphratica forests.

The influence of topography on the spatial distribution of fertility indices in an ameliorated agrolandscape in the area of terminal moraines

The effect of geomorphic conditions on the morphological, chemical, and physical properties; the biochemical activity; and the distribution of soil microorganisms in the plow horizon of ameliorated swampy podzolic soils has been studied along the catena on a gentle slope of the northeastern aspect of a moraine hill. The indices of soil fertility gradually improve from the top of the hill to the adjacent hollow. In this direction, the soil acidity becomes weaker under the impact of liming, the soil texture becomes somewhat heavier, and the contents of humus and the major nutrients increase in parallel with the increase in the number of soil microorganisms and their enzymatic activity.

Horizontal Distribution Patterns of Testate Amoebae (Protozoa) in a Sphagnum magellanicum Carpet.

The distribution of soil microorganisms is generally believed to be patchy and to reflect habitat heterogeneity. Despite this general rule, the amount of existing data on species distribution patterns is scarce. Testate amoebae (Protozoa; Rhizopoda) are an important component of soil microbial communities and are increasingly used in ecological and paleoecological studies of Sphagnum-dominated peatlands, but data on the spatial structure of communities are completely lacking. This is an important aspect since quantitative models used for paleoecological reconstruction and monitoring are based on species assemblages. We explored the distribution patterns of testate amoebae distribution in a macroscopically homogeneous Sphagnum carpet, down to a scale of several centimeters. Distributions maps of the species and spatially constrained sample groups were produced. Multivariate and individual spatial autocorrelations were calculated. The importance of spatial structure was quantified by canonical correspondence analysis. Our ultimate goal is to find the finest resolution of environmental monitoring using testate amoebae. The distribution patterns differed among species, resulting in a complex spatial structure of the species assemblage in a whole. Spatial structure accounted for 36% of the total variation of species abundance in a canonical correspondence analysis constrained by spatial variables. This structure was partly correlated to altitude (microtopography) at a very fine scale. These results confirmed the existence of significant broad- and fine-scale spatial structures within testate amoebae communities that could in part be interpreted as effects of ecological gradients. This shows that, on a surface area of 0.25 m(2), ecological conditions which look uniform from a macroscopic point of view are not perceived as such by Sphagnum-inhabiting organisms. Therefore, testate amoebae could prove very useful to monitor fine-scale ecological processes or disturbances. Studies of the species' spatial distribution patterns in combination with autoecological studies are needed and should be included in the toolbox of biomonitoring itself.

土壌における微生物の垂直分布について

Vertical distribution of microorganisms in soils was studied. The largest populations of bacteria (108/g of dried soil), actinomycetes (107/g) and fungi (105/g) were observed in soils from the top layer (0∼30cm in depth) of black color loam. Reduced numbers of bacteria and actinomycetes, but few fungi, were detected in soils of the second upper layer (50cm∼5m) of black loam. Bacteria (106/g) were also found even in silty sand soils of 40m depth. Vertical distribution of actinomycetes was examined in detail in soils of 0∼100cm depth taken at a 10cm interval. The actinomycete population was the largest in soils of the surface layer (0∼10cm), and decreased gradually as the depth increased. A comparative survey of all the isolates showed that ca. 80% of different kinds of actinomycete cultures were isolated from surface soils. It was demonstrated that actinomycetes peculiar to individual soil layers existed.