Amount Of Microbial Biomass Research Articles

Antibiotics and their associations with antibiotic resistance genes and microbial communities in estuarine and coastal sediment of Quanzhou Bay, Southeast China

The antibiotic concentrations spanned from 11.2 to 173.8 ng/g, with quinolones and tetracyclines being observed to be prevalent. The amount of microbial biomass as determined by Phospholipid fatty acid (PLFA) ranged from 2.92 to 10.99 mg kg−1, with G- bacteria dominating. A total of 254 distinct ARGs and 10 MEGs were identified, with multidrug ARGs having the highest relative abundance (1.18 × 10−2 to 3.00 × 10−1 copies/16S rRNA gene copies), while vancomycin and sulfonamide resistance genes were the least abundant. Results from canonical-correlation analyses combined with redundancy analysis indicated that macrolides were significantly related to the shifts of microbial community structure in sediments, particularly in G+ bacteria that were more sensitive to antibiotic residues. It was observed that sulfonamide ARGs had a greater correlation with residual antibiotics than other ARGs. This study provided a field evidence that multiple residual antibiotics from coastal sites could cause fundamental shifts in microbial community and their associated ARGs.

Moisture-induced electrical power generation with waste activated sludge

Moisture-induced power generation from pure bacterial cultures has been demonstrated, but the feasibility of extending this renewable energy harvesting method to mixed bacterial cells from environmental samples is uncertain. Herein, waste active sludge (WAS) from wastewater treatment reactors was used to fabricate whole-cell film-based moisture-induced electricity generators (MEGs). Electrical power could be harvested from all four representative WAS samples, which were obtained from wastewater treatment reactors or plants treating liquid-ammonia mercerization, municipal, beer brewery, and printing-dyeing wastewaters. The highest performing MEGs were obtained from anammox activated sludge with an open circuit voltage of 0.45 ± 0.02 V and a maximum power density of 5.24 μW/cm2, which outperformed those MEGs with pure bacterial cultures. Physicochemical characterizations combined with partial least-squares path modeling suggested that the amount of microbial biomass and hydrophilicity of the as-prepared WAS films were the most important factors in determining the performance of the WAS-based MEGs. Extracellular polymer substances were essential in creating a water gradient inside the WAS, which was a crucial mechanism for generating electricity from MEGs based on WAS. This study not only provides a new approach for developing materials for moisture-induced energy harvesting but also presents a novel avenue for resource utilization of WAS.

An Optimized Active Sampling Procedure for Aerobiological DNA Studies.

The Earth's atmosphere plays a critical role in transporting and dispersing biological aerosols. Nevertheless, the amount of microbial biomass in suspension in the air is so low that it is extremely difficult to monitor the changes over time in these communities. Real-time genomic studies can provide a sensitive and rapid method for monitoring changes in the composition of bioaerosols. However, the low abundance of deoxyribose nucleic acid (DNA) and proteins in the atmosphere, which is of the order of the contamination produced by operators and instruments, poses a challenge for the sampling process and the analyte extraction. In this study, we designed an optimized, portable, closed bioaerosol sampler based on membrane filters using commercial off-the-shelf components, demonstrating its end-to-end operation. This sampler can operate autonomously outdoors for a prolonged time, capturing ambient bioaerosols and avoiding user contamination. We first performed a comparative analysis in a controlled environment to select the optimal active membrane filter based on its ability to capture and extract DNA. We have designed a bioaerosol chamber for this purpose and tested three commercial DNA extraction kits. The bioaerosol sampler was tested outdoors in a representative environment and run for 24 h at 150 L/min. Our methodology suggests that a 0.22-µm polyether sulfone (PES) membrane filter can recover up to 4 ng of DNA in this period, sufficient for genomic applications. This system, along with the robust extraction protocol, can be automated for continuous environmental monitoring to gain insights into the time evolution of microbial communities within the air.

Estimation of turnover time of microbial biomass potassium in paddy field soil

ABSTRACT Soil microbial biomass (microbial biomass) contains substantial amounts of potassium (K) as a reservoir of K in soils. However, information about K dynamics and K flux through the microbial biomass are lacking. In the present study, the turnover time of microbial biomass K was estimated for the first time using paddy field soils. The paddy field soils, either amended with substrates of carbon, nitrogen, and phosphorus, or not, were aerobically incubated for 60 days, during which the amounts of microbial biomass K were periodically determined by the chloroform fumigation-extraction procedure. Microbial biomass K increased to twice (51.4–72.3 mg K kg−1 soil) of that in the unamended control 5 days after addition of the substrates and gradually decreased to the values in the control (25.2–44.0 mg K kg−1 soil) until 60 days of the incubation. The turnover time of microbial biomass K was estimated from the declines in the substrate amended soils. The turnover time of microbial biomass K ranged from 80.4 to 98.5 days, which roughly corresponded to the cultivation period of rice (about 100 days). These results indicated that microbial biomass K plays important roles in the supply of K source as well as the reservoir of K in paddy field soil.

Mineral weathering and lessivage affect microbial community and enzyme activity in mountain soils

The aim of the study was to assess if pedogenic processes such as mineral weathering and lessivage, other than organic matter accumulation, can affect soil microbial population and enzyme activities. This study examines six soil profiles located in a karst region of the North-Eastern Italian Alps and characterized by a vertical textural differentiation due to lessivage. For each soil, four pedological layers were recognized according to the dominant soil forming process: i) the top soil (Tp layer), formed by A and AB horizons, characterized by organic matter accumulation; ii) the subsurface eluviated layer (Elu layer), comprising AE and EB horizons; iii) the layer dominated by the in-situ mineral weathering (Wh layer), made by Bw horizons; iv) the deepest layer (Ls), subjected to clay illuviation and comprised by Bt horizons. In the upper layers (Tp and Elu), because of the low pH, weathering also occurred, as indicated by the presence of disordered smectite and by the high values of pedogenic Fe oxi-hydroxides to pseudo-total Fe ratio.The microbial biomass content and structure, and the enzyme activities significantly differed in the four pedological layers. The amount of microbial biomass was, as expected, most abundant in the Tp layer, where bacteria and actinomycetes abounded. Conversely, in Elu and Wh we observed a fungal-to-bacterial biomass ratio significantly higher than in Tp and Ls; in Elu, also the gram (+)/gram (−) ratio was the highest. In the upper layer, the interaction between enzymes and minerals like disordered smectite and pedogenic Fe-oxides appeared as responsible for the inhibition of the total enzyme activity per unit of organic C, and of the lipase activity. In Ls layer, where clay illuviation and high organo-minerals interaction occurred, the potential hydrolysis of organic matter was low, as revealed by the SEI/TOC ratio, the reduced lipase activity, and the inhibited activity of α-fucosidase and α-mannosidase. Even if the activity of most enzymes depends on the substrate availability, which decreases with soil depth, those involved in lipid degradation displayed the maximum activities in Elu and Wh layers, where a relative increase of the fungal population was observed. In conclusion, our findings showed that the soil functionality, expressed by the microbial community structure and enzymes activity, can vary according to organic matter–mineral interaction following the weathering and lessivage gradients along the soil profiles.

Role of the bryophytes in substrate revitalization on a post-technogenic salinized territory

This work aims to investigate the role of the bryophyte cover in substrate revitalization on a post-technogenic salinized territory. The influence of the moss cover on the organic carbon content, actual acidity, redox potential, and the content of the main ecological and trophic groups of microorganisms in the substrate of the tailings storage of the Stebnyk Mining and Chemical Enterprise "Polymineral" was investigated. Bryophytes significantly affect the tailings storage saline substrates. They colonize areas with a very strong and strong degree of salinity, which are unsuitable for other plants. It was indicated that pioneer moss species promote the accumulation of organic matter in saline substrates of the tailings storage. Under moss turfs, the amount of organic carbon increased 2.2–5.0 times, compared with its content in the uncovered substrate. The high variability of the organic matter content is determined by the species characteristics of mosses, primarily their life form. The dense-turf species Didymodon rigidulus and Pthychostomum pseudotriquetrum var. bimum accumulated the most organic matter. The thickness of the litter under the moss turf of these species was much greater than in Barbula unguiculata and Funaria hygrometrica, which form loose turf. We assessed the specificity of the accumulation of organic carbon in the turfs of the studied mosses. It founded that most organic matter accumulated in the dead parts of the moss turf. In the green parts of the shoots of these moss species the amount of organic carbon was 3–4 times less, which indicates a relationship between litter capacity and content of carbon in the substrate under moss turfs. We investigated the influence of mosses on the actual acidity of the tailings storage substrate. Moss turfs promote the increase of acidity of the aqueous solution of the tailings substrate by 0.2–0.5 units. The tailings storage substrates are characterized by a reduction regime. The redox potential of the substrate under moss cover significantly depended on the species characteristics of mosses. Under the moss cover, the redox potential increased by 1.2–1.4 times, compared with the index for the substrate without moss cover. We studied the influence of moss cover on microbial biomass and the quantity of some ecological-trophic groups of microorganisms in the substrates of the tailings storage. The amount of microbial biomass under moss turfs increased depending on the degree of the substrate salinization and the species characteristics of the mosses. In areas with a very high degree of salinization under the moss turfs of Didymodon rigidulus and Funaria hygrometrica, the microbial biomass index increased almost two times, compared with the uncovered substrate. We found a significant increase in the quantity of the main ecological and trophic groups of microorganisms (saprophytes, cellulose-destroying bacteria, oligonitrophils and nitrogen fixers) in the substrate under the moss cover. Thus, pioneer moss species have a complex effect on the saline substrate of tailings storage. They accumulate organic matter, increase the acidity of the upper layer, improve the redox regime of the substrate and promote the development of soil microbiota.

Tillage System and Crop Sequence Affect Soil Disease Suppressiveness and Carbon Status in Boreal Climate.

The soil-borne plant pathogens cause serious yield losses and are difficult to control. In suppressive soils, disease incidence remains low regardless of the presence of the pathogen, the host plant, and favorable environmental conditions. The potential to improve natural soil disease suppressiveness through agricultural management practices would enable sustainable and resilient crop production systems. Our aim was to study the impact of autumn tillage methods and crop sequence on the soil carbon status, fungistasis and yield in boreal climate. The disease suppression was improved by the long-term reduced and no tillage management practices with and without crop rotation. Compared to the conventional plowing, the non-inversion tillage systems were shown to change the vertical distribution of soil carbon fractions and the amount of microbial biomass by concentrating them on the soil surface. Crop sequence and the choice of tillage method had a combined effect on soil organic carbon (SOC) sequestration. The improved general disease suppression had a positive correlation with the labile carbon status and microbial biomass. From the most common Fusarium species, the predominantly saprophytic F. avenaceum was more abundant under non-inversion practice, whereas the opposite was true for the pathogenic ones. Our findings furthermore demonstrated the correlation of the soil fungistasis laboratory assay results and the prevalence of the pathogenic test fungus Fusarium culmorum on the crop cereals in the field. Our results indicate that optimized management strategies have potential to improve microbial related soil fungistasis in boreal climate.

Soil microbial biomass increases along elevational gradients in the tropics and subtropics but not elsewhere

AbstractAimOur aim is to use elevational gradients to quantify the relationship between temperature and ecosystem functioning. Ecosystem functions such as decomposition, nutrient cycling and carbon storage are linked with the amount of microbial biomass in the soil. Previous studies have shown variable relationships between elevation and soil microbial biomass (SMB). Understanding the biological mechanisms linking SMB with elevational gradients will shed light on the environmental impacts of global warming.LocationGlobal.Time period2002–2018.Major taxa studiedSoil microbes.MethodWe performed a global meta‐analysis of the relationships between SMB and elevation. Data were collected from 59 studies of 73 elevational transects from around the world.ResultsWe found no consistent global relationship between SMB and elevation. SMB increased significantly with elevation in the tropics and subtropics, but not in other climate zones. However, we found consistent positive relationships between SMB, soil organic carbon and total nitrogen concentrations.Main conclusionsOur results suggest that global warming will impact tropical and subtropical ecosystems more severely than colder regions. Tropical ecosystems, already at risk from species extinctions, will likely experience declines in SMB as the climate warms, resulting in losses of fundamental ecosystem functions such as nutrient cycling and carbon storage.

Impact of flow hydrodynamics and pipe material properties on biofilm development within drinking water systems

ABSTRACT The aim of this study was to investigate the combined impact of flow hydrodynamics and pipe material on biofilm development in drinking water distribution systems (DWDS). Biofilms were formed on four commonly used pipe materials (namely polyvinyl chloride, polypropylene, structured wall high-density polyethylene and solid wall high-density polyethylene) within a series of purpose built flow cell reactors at two different flow regimes. Results indicate that varying amounts of microbial material with different morphologies were present depending on the pipe material and conditioning. The amount of microbial biomass was typically greater for the biofilms conditioned at lower flows. Whereas, biofilm development was inhibited at higher flows indicating shear forces imposed by flow conditions were above the critical levels for biofilm attachment. Alphaproteobacteria was the predominant bacterial group within the biofilms incubated at low flow and represented 48% of evaluated phylotypes; whilst at higher flows, Betaproteobacteria (45%) and Gammaproteobacteria (33%) were the dominant groups. The opportunistic pathogens, Sphingomonas and Pseudomonas were found to be particularly abundant in biofilms incubated at lower flows, and only found within biofilms incubated at higher flows on the rougher materials assessed. This suggests that these bacteria have limited ability to propagate within biofilms under high shear conditions without sufficient protection (roughness). These findings expand on knowledge relating to the impact of surface roughness and flow hydrodynamics on biofilm development within DWDS.

Transformation of Nitrogen Compounds in Soils of Mountain Tundra Ecosystems in the Khibiny

The content of nitrogen compounds and processes of nitrogen mineralization and nitrification were studied in the soils of four tundra ecosystems in the Khibiny Mountains. The results obtained demonstrate the differences between soils of heath and meadow ecosystems in the concentrations of extracted inorganic and organic nitrogen and in the activity of nitrogen transformation. The relationships between the activity of organic nitrogen mineralization and the C/N ratio in organic matter, as well as between the activity of mineralization and the amount of microbial biomass in the soils, differ among the soils. At the high C/N ratios, microorganisms assimilate more available nitrogen, which leads to a decrease in the intensity of organic N mineralization. In soils of meadow communities, as compared to the heath ones, the activity of N mineralization responds more rapidly to changes in the microbial biomass, the C/N ratio and proportion of microbial nitrogen in the labile nitrogen pool. The microbial community in the studied soils of the mountain tundra ecosystems substitutes the nitrogen mineralization for nitrogen immobilization at the C/N ratio in organic matter of about 20.5 and the carbon content in the microbial biomass of about 1000 mg/kg.

Responses of Soil Macrofaunal Community and Diversity under Different Types of Vegetation on Soil Nutrient Pools in winter in Emei Mountain, China

To study its community characteristics under different types of vegetation in winter, soil macro fauna were collected and identified by hand picking in Emei Mountain in December, 2016. Soil nutrient pools and the amounts of microbial biomass were measured, and the diversity indices of soil macro fauna were calculated. We identified 667 soil macro fauna individuals belonging to 26 orders, 11 classes, and 4 phyla. The highest values of the Pielou (J) and Shannon-Wiener (H′) diversity indices were established in the 0.5 cm soil layer of the evergreen broad-leaved forest (2.22 and 0.76, respectively). The lowest values these indices had in the 5–10 cm soil layer of the coniferous and broad-leaved mixed forest (0.51 and 0.17, respectively). The correlation analysis results showed that the numbers of soil macro fauna group were significantly correlated to soil temperature and MBC contents, and the number of soil macro fauna individuals was significantly correlated with soil water content. Therefore, vegetation type and soil microbial dynamics have a strong effect on the diversity of soil macro fauna communities, which further affect the soil nutrient cycle and ecological processes.

Soil Microbial Communities of Eastern Antarctica

Investigation of microbial communities of Antarctica soils is a very important field of research that expands our knowledge of microbial participation in primary soil formation and specific features of their communities in extreme habitats, and it is of considerable interest in directed search of for microorganisms as potential biotechnological objects. The results of long-term (2012–2017) complex studies on soil microbial communities of the Russian East Antarctica polar stations at Shirmakher oasis (Novolazarevskaya station), the Larsemann Hills (Progress station), and the Tala Hills (Molodezhnaya station) are presented in this review. The assessment of biomass of soil microorganisms by the methods of direct microscopy has been carried out for the first time for this region. The general amount of microbial biomass is small; the fungi dominate (77–99%). The unique features of Antarctic soils are the high content and morphological diversity of small forms of microorganisms: fungi are presented by mainly single-celled structures (small spores and yeasts), while bacteria by ultrafine (filtering) forms. At the same time, microorganisms can significantly contribute to such important ecological functions of soil as the emission of greenhouse gases, especially during the warm season with the stable positive temperatures of the soil. This should be considered during creation of models and forecasts of global warming. The use of various isolation techniques for the analysis of the soil microbial population, together with the succession approach, significantly expand the information about taxonomic diversity of cultivated fungi and bacteria in Antarctica soils.

The Organic Matter Pool, Composition and Transformation in Soils of Middle Siberia

The structure and agrogenic transformation of organic substance in chernozems of Middle Siberia are considered (within Krasnoyarsk Krai, Khakassia and Tuva). The comparative-geographic, comparative-analytical and stationary observation methods are used in this work. These investigations are based on ideas of academician I.V. Tyurin, who had a Krasnoyarsk period in his creative work. All of the forms of humic compounds of chernozem type are presented in the studied soils. The mineralized (transformed) pool of organic matter in chernozems (19-28 t C/ha) is characterized by set of the plant residues, microbial biomass and a mobile humus. The entrance of plant residues into the soil of a graminae-fallow-hoed crop rotation makes 3.32 t C/ha per year, graminae-grass - 3.89 C/ha per year. The contribution of living roots reaches 40-70% of year stocks of the plant residues. The entrance of additional portions of "fresh" plant material with straw and green manure increases the mineralized pool of the organic matter and its decomposition intensity. The amount of microbial biomass in an arable layer of chernozems fluctuates from 1.5 to 3.0 t C/ha. The decomposition of plant residues occurs at k = 0.37-0.44. The share of a mobile humus (water- and alkaline-soluble compounds) as a part of the mineralized chernozems OM reaches 69-77%. The seasonal variability of mobile humus concentration is determined by the unequal rate of plants death, the entrance into the soil and decomposition of plant residues, different intensity of their transformation in neoformed humic substances. Losses of humus mobile compounds in soils of Krasnoyarsk Krai (0.23 t C/ha per year) contain about 7% of his expenses on the forming of net primary production and are compensated here by a neoformed humus at 91%, in soils of Khakassia - at 34%, Tuva - only at 16%.

Soil carbon sequestration and nutrient status of tropical rice based cropping systems: Rice-Rice, Rice-Soya, Rice-Onion and Rice-Tobacco in Sri Lanka

Carbon sequestration increases soil fertility and reduces global warming by storing atmospheric carbon in soils. This study aimed to quantify and compare soil organic C fractions and C stocks in 4 different rice based cropping systems and investigate their variation as affected by crop rotation with upland crops. Soil nutrient availability and their relationship with chemical C fractions were also examined. Total organic C (TOC), microbial biomass C (MBC), water soluble C (WSC), KMnO4 oxidizable C, pH and available macronutrients were analyzed at 0–15 and 15–30cm depths in Rice-Rice11RR; Rice-Rice, RS; Rice-Soya, RT; Rice-Tobacco, RO; Rice–Onion. (RR), Rice-Soya (RS), Rice-Tobacco (RT) and Rice–Onion (RO) rotations on Alfisols of Sri Lanka. The data were analyzed by analysis of variance (ANOVA) on a completely randomized design (CRD) under 4 treatments with 6 replicates for each treatment. Results showed that carbon fractions and nutrient availability among different cropping systems varied significantly from one another. Under all cropping systems a higher content of all C fractions was observed in the 0–15cm layer, except for WSC which was higher in the 15–30cm layer because it moves to the deeper layers. The top soil layer also had a higher amount of MBC than the deeper layer, because the amount of microbial biomass and rate of microbial activity decline rapidly below the surface layer. Highest dry matter return to soil (147g/m2) in the RR system as paddy stubble accounted for highest amount of TOC in soil. RS system also had a higher TOC content due to the organic residues collected in soil as roots and leaf litter (67.7g/m2) as all dry leaves have fallen on to the soil at the time of harvesting of soyabean. However in RO system hardly any residues are added because the entire crop is removed at harvest and a significantly lower organic C content was recorded. Also the soil in RO and RT were tilled more than that used for soyabean during temporary bed preparation resulting in a relatively faster decomposition leaving significantly lower levels of C compared to RS. Change of cropping systems from RR to other annual crops such as RT and RO reduced the soil C sequestration to a significant level after 10years of cultivation. However crop rotation change from RR to RS has maintained similar levels of C (65.18t/ha) in RS and (63.48t/ha) in RR. This indicated that C sequestration capacity is species specific and differences are mainly due to remaining crop residues and specific soil tillage practices used for upland crops. The study also showed that soil nutrient availability among the cropping systems varied significantly. Correlation analysis between chemical C fractions and major nutrient cations showed that there are significant correlations exist among them. The study confirmed that tropical rice based cropping systems have a great potential in storing and maintaining C in soils and thereby to facilitate nutrient availability.

Effects of biopellets composed of microalgae and fungi on pharmaceuticals present at environmentally relevant levels in water

Removal of seven pharmaceuticals (acetaminophen, carbamazepine, diclofenac, metoprolol, naproxen, ranitidine and sulfamethoxazole) from water was investigated using three different microbial treatments with: (1) the microalga Chlorella vulgaris, (2) the fungus Aspergillus niger and (3) biopellets composed of both microorganisms. The three-day experiment was performed under laboratory conditions and pharmaceuticals were spiked at the environmentally relevant concentration of 10μgL−1. The biopellets and fungal treatments resulted in significantly lower ranitidine concentration compared with the initial value. Also, treatment with biopellets resulted in significantly lower final ranitidine concentrations compared to those found after control and microalgal treatments. Low removal rates were obtained for other substances, possibly because the amount of microbial biomass used was 16–500-fold lower than that normally used in activated sludge processes in wastewater treatments plants. Thus, the pharmaceutical removal potential, elimination potential and performance of biopellets should be further investigated at higher biomass concentrations.

Impact of Fertilization on Microbial Biomass Carbon and Nitrogen from Soil in Vegetable Greenhouse

In this study, columns packed of a greenhouse soil with various soil fertile levels (low, medium and high) were carried out under greenhouse condition. The leaching experiment lasted 51 days. There were four fertilization treatments including no fertilizer [CK], chemical fertilizer [NPK], organic manure [M], organic manure and chemical fertilizer [M+NPK]. Microbial biomass C and N were measured. The results were as follows: organic or inorganic fertilizer increased the contents of soil microbial biomass C and N, and combination of chemical fertilizer and organic fertilizer significantly elevated the amount of soil microbial biomass C and N compared to organic or inorganic fertilizer treatment. There were significant differences in the amount of microbial biomass C and N among different fertile level soil under different fertilization practices in 0-20 and 20-40cm soil layers. Our study showed that application of manure and chemical fertilizer at proper rates according to soil fertile status is beneficial to increase the amount of microbial biomass C and N.

A comparison of contents of group A and B trichothecenes and microbial counts in different cereal species

Concentrations of trichothecenes and the amounts of microbial biomass were compared in grain of bread wheat, durum wheat, triticale, rye, oat and barley. Grain samples came from lines regionalised in Poland grown under identical climatic and agricultural conditions in 2007. Among the six analysed cereals, the highest mean concentration of toxic metabolites of 151.89 µg/kg was found for grain of Triticum durum, whereas the lowest was for barley grain (25.56 µg/kg). The highest contamination with microscopic fungi was recorded in case of barley and rice grain (mean concentrations of ergosterol were 12.53 mg/kg and 11.24 mg/kg, respectively). In case of the analysed cereals, the total microbial biomass expressed in the amount of ATP turned out to be the highest (4.7 × 105 relative light units [RLU]) for rye and oat (3.2 × 105 RLU). The results of the applied classical discrimination analysis indicate a significant diversification of species in terms of all the 11 analysed metabolites.

전북지역 과수원의 토양특성이 미생물 분포에 미치는 영향

This study was conducted to investigate impacts of soil properties on microbial distribution in Jeonbuk orchard fields. Soil samples were collected from 110 sites cultivated with different fruit plants. The population of aerobic bacteria and fungi and the content of soil microbial biomass carbon (C) were found to increase with increasing silt content in the soils. Different activity of dehydrogenase was not observed among the different textures of soil. Microbial distribution, amount of microbial biomass C, and dehydrogenase activity in the soils were not significantly different among the topographic sites. However, in pear and grape fruit plant fields, coliform group of bacteria was found in relatively higher population, 133.0x10 3 CFU g -1 and 107.4x10 3 CFU g -1 , respectively. Microbial groups were simplified and their density was reduced with increasing the cultivation periods of fruit plants. The soil microbial distribution was proportionally correlated with some of soil properties such as soil pH, soil organic matter (SOM) content, and exchangeable Mg content; in particular, the population of Bacillus sp. was proportionally correlated with soil pH and exchangeable Mg content. The amounts of microbial biomass C and the dehydrogenase activity in the soils were significantly correlated with the contents of SOM and exchangeable Ca ion (p<0.01).

Experimental warming effects on the microbial community of a temperate mountain forest soil

Soil microbial communities mediate the decomposition of soil organic matter (SOM). The amount of carbon (C) that is respired leaves the soil as CO2 (soil respiration) and causes one of the greatest fluxes in the global carbon cycle. How soil microbial communities will respond to global warming, however, is not well understood. To elucidate the effect of warming on the microbial community we analyzed soil from the soil warming experiment Achenkirch, Austria. Soil of a mature spruce forest was warmed by 4 °C during snow-free seasons since 2004. Repeated soil sampling from control and warmed plots took place from 2008 until 2010. We monitored microbial biomass C and nitrogen (N). Microbial community composition was assessed by phospholipid fatty acid analysis (PLFA) and by quantitative real time polymerase chain reaction (qPCR) of ribosomal RNA genes. Microbial metabolic activity was estimated by soil respiration to biomass ratios and RNA to DNA ratios. Soil warming did not affect microbial biomass, nor did warming affect the abundances of most microbial groups. Warming significantly enhanced microbial metabolic activity in terms of soil respiration per amount of microbial biomass C. Microbial stress biomarkers were elevated in warmed plots. In summary, the 4 °C increase in soil temperature during the snow-free season had no influence on microbial community composition and biomass but strongly increased microbial metabolic activity and hence reduced carbon use efficiency.

Efeito da cinza de biomassa na dinâmica do C e N do solo de uma plantação de Pinus pinaster

Effects of wood ash (loose and pelleted) on chemical properties and microbial activity in an Arenosol from a Pinus pinaster plantation were assessed through laboratory incubation. Wood ash was applied at a rate of 0, 4 and 8 g kg-1 soil both alone or together with N. Loose ash significantly increased pH values and extractable nutrients from the soil. Net nitrification was stimulated by it application. Amounts of microbial biomass C were lower in soils with loose ash than in the control. Basal respiration was not affected by treatments. Effects increased with the increment of applied ash and when applied together with N. Application of pelleted ash produced smaller changes in soil chemical characteristics, net nitrification and C dynamic. Results suggest that, in N limited soils, wood ash should be applied in the pelleted form because changes in chemical soil properties are slower and the potential loss of N is much less as compared to the loose ash. Pelleted ash should be applied together with N fertilizer to improve soil N availability.