PH对红壤微生物生物量碳和生物量磷的影响

The impact of pH changes on microbial biomass carbon (Cmic) and microbial biomass phosphorus (Pmic) were examined for 3 red soils under citrus production with different lengths of cultivation. Soil pH significantly affected Cmic and Pmic. The Cmie and Pmic changes, as a function of soil pH, appeared to follow a normal distribution with the original soil pH value at the apex and as pH increased or decreased compared to the original soil pH, Cmic and Pmic declined. Moreover, there were critical pH values at both extremes (3.0 on the acidic side and 8.0 to 8.5 on the alkaline side), beyond which most of microorganisms could never survive. The effect of pH on Cmic and Pmic was also related to the original soil pH. The higher the original soil pH was, the less Cmic or Pmic were affected by pH change. It is suggested that soil microorganisms that grow in a soil environment with a more neutral soil pH range (i.e. pH 5.5-7.5) may have a greater tolerance to pH changes than those growing in more acidic or more alkaline soil pH conditions.     

碱稳定污泥污水对土壤可提取有机碳和铜的影响

An incubation experiment was conducted to evaluate the potential for water contamination with sludge-derived organic substances and copper following land application of alkaline-stabilised sewage sludge. Two contrasting sludge-amended soils were studied. Both soils were previously treated with urban and ruralalkaline biosolids separately at sludge application rates of 0, 30 and 120 t ha^-1 fresh product. The air-driedsoil/sludge mixtures were wetted with distilled water, maintained at 40 % of water-holding capacity and equilibrated for three weeks at 4 ℃ before extraction. Subsamples were extracted with either distilled wateror 0.5 mol L^-1 K₂SO₄ solution. The concentrations of organic C in the aqueous and chemical extracts were determined directly with a total organic carbon (TOC) analyser. The concentrations of Cu in the twoextracts were also determined by atomic absorption spectrophotometry The relationship between the two extractable organic C fractions was examined, together with that between extractable organic C concentration and extractable Cu concentration. Application of alkaline biosolids increased the concentrations of soil mobile organic substances and Cu. The results are discussed in terms of a possible increase in the potential for leaching of sludge-derived organics and Cu in the sludge-amended soils.     

Filtration increases the correlation between water extractable organic carbon and soil microbial activity

A study was carried out in order to establish the relationship between the water extractable organic carbon (WEOC) content of soils and soil microbial activity, and to determine how variations in the extraction procedure might influence the quantity of WEOC recovered. Concentrations of WEOC were determined in soils taken from 12 different sites in the south east of Scotland, using a procedure in which samples were shaken with distilled water, centrifuged at 5000g and then filtered through 0.45 μm Millipore filters. Filtration resulted in between 30 and 400 μg C g⁻¹ being extracted using this procedure and the concentration of WEOC in the resultant extracts correlated with soil microbial production of CO₂ and dehydrogenase activity (P<0.001). Without filtration, although more WEOC was extracted (between 31 and 716 μg C g⁻¹), there was no significant correlation with biological activity. There was also no correlation between WEOC and nitrous oxide release during the incubations. Centrifugation at 20,000g for at least 10 min prior to filtration was required to remove particulate organic materials. Storage of samples at 4 °C or for up to 1 week or freezing for up to 3 months was not found to have a large influence on the concentration of WEOC in extracts, although amounts increased with soil:extractant ratio and increasing extraction time (from 15 to 60 min).     

Determination of carbon and nitrogen in microbial biomass of southern-Taiga soils by different methods

The results of methods for determining microbial biomass carbon vary in reproducibility among soils. The fumigation-extraction and substrate-induced respiration methods give similar results for Albic Luvisol and Gleyic Fluvisol, while the results of the rehydration method are reliably higher. In Histic Fluvisol, relatively similar results are obtained using the fumigation-extraction and rehydration methods, and the substrate-induced respiration method gives almost halved results. The seasonal dynamics of microbial biomass carbon also varies depending on the method used. The highest difference is typical for the warm period, when the concentrations found by the extraction and substrate-induced methods poorly agree between two out of three soils studied. The concentration of microbial biomass nitrogen is less sensitive to the analytical method: the differences between the results of the fumigation-extraction and rehydration methods are statistically insignificant in the all soils. To reveal stable relationships between the results of determining microbial carbon and the soil properties and analytical method, a large diversity of soils should be studied. This will allow for proposing of conversion factors for the recalculation of the obtained values to the concentrations of carbon and nitrogen in microbial biomass for different soils (or soil groups) and, hence, the more correct comparison of the results obtained by different methods.     

Seasonal responses in microbial biomass carbon, phosphorus and sulphur in soils under pasture

The response of the soil microbial biomass to seasonal changes was investigated in the field under pastures. These studies showed that over a 9-month period, microbial biomass carbon, phosphorus and sulphur (biomass C, P, S), and their ratios (C:P, C:S, and P:S) responded differently to changes in soil moisture and to the input of fresh organic materials. From October to December (1993), when plant residues were largely incorporated into the soils, biomass C and S increased by 150–210%. Biomass P did not increase over this time, having decreased by 22–64% over the dry summer (July to September). There was no obvious correlation between biomass C, P, and S and air temperature. The largest amounts of biomass C and P (2100–2300μg and 150–190μgg^–1 soil, respectively) were found in those soils receiving farmyard manure (FYM or FYM+NPK) and P fertilizer, whereas the use of ammonium sulphate decreased biomass C and P. The C:P, C:S, and P:S ratios of the biomass varied considerably (9–276:1; 50–149:1; and 0.3–14:1, respectively) with season and fertilizer regime. This reflected the potential for the biomass to release (when ratios were narrow) or to immobilize (wide ratios) P and S at different times of the year. Thus, seasonal responses in biomass C, P, and S are important in controlling the cycling of C, P, and S in pasture and ultimately in regulating plant availability of P and S. The uptake of P in the pasture was well correlated with the sum of P in the biomass and soil available pools. Thus, the simultaneous measurement of microbial biomass P and available P provide useful information on the potential plant availability of P. Received: 25 May 1996     

添加生物质炭对红壤水稻土有机碳矿化和微生物生物量的影响

通过室内培育试验,研究了添加生物质炭对江西红壤水稻土有机碳矿化和微生物生物量碳、氮含量的影响。结果表明:红壤有机碳矿化速率在培育第2天达最大值后迅速降低,培养7天后下降缓慢并趋于平稳;添加生物质炭降低了土壤有机碳的矿化速率和累积矿化量,培养结束时,不加生物质炭的对照处理中有机碳的累积矿化量分别比添加0.5%和1.0%生物质炭的处理高10.0%和10.8%。此外,生物质炭的加入显著提高了土壤微生物生物量,添加0.5%生物质炭处理的土壤微生物生物量碳、氮含量分别比对照高111.5%～250.6%和11.6%～97.6%,添加1.0%生物质炭处理的土壤微生物生物量碳、氮含量分别比对照高58.9%～243.6%和55.9%～110.4%。相同处理中,干旱的水分条件下(40%田间持水量)微生物生物量要高于湿润的水分条件(70%田间持水量)。同时,添加0.5%和1.0%的生物质炭使土壤代谢熵分别降低2.4%和26.8%,微生物商减少了43.7%和31.7%。     

Turnover time of microbial biomass carbon in Japanese upland soils with different textures

We investigated the turnover time of microbial biomass-C in Japanese upland soils with various textures and examined the soil physicochemical properties influencing their turnover time. Samples from five different soil types (sand-dune regosol, light-colored Andosol, humic Andosol, brown forest soil, and dark red soil) were taken from upland concrete-frame plots in the experimental field of Chiba University. Each soil amended with [U -¹³C] glucose was incubated for 80 d at 25°C. Microbial biomass-C and -¹³C in soil were periodically determined by the fumigation-extraction method. The longest turnover time of microbial biomass-C was observed in the dark red soil (215 d) followed by the humic Andosol (134 d), brown forest soil (97 d), and light-colored Andosol (83 d) and the shortest in the sand-dune regosol (45 d). The turnover time of microbial biomass-C was significantly correlated with the value of soil clay (R: 0.917*), CEC (R: 0.921*), and macroaggregate (R: 0.907*) contents, but not with the total-C content. The amount of microbial biomass-C showed a close correlation with the turnover time of microbial biomass-C, suggesting that the turnover time of microbial biomass-C is an important factor influencing the accumulation of microbial biomass-C in soil.     

苏打盐碱水灌溉的土壤添加石膏肥和有机肥后水溶性碳和微生物碳研究

Microbial biomass carbon (MBC), a small fraction of soil organic matter, has a rapid turnover rate and is a reservoir of labile nutrients. The water-extractable carbon pools provide a fairly good estimate of labile C present in soil and can be easily quantified. Changes in soil MBC and water-extractable organic carbon pools were studied in a 14-year long-term experiment in plots of rice-wheat rotation irrigated with canal water (CW), sodic water (SW, 10-12.5 mmol c L-1 residual sodium carbonate), and SW amended with gypsum with or without application of organic amendments including farmyard manure (FYM), green manure (GM), and wheat straw (WS). Irrigation with SW increased soil exchangeable sodium percentage by more than 13 times compared to irrigation with CW. Sodic water irrigation significantly decreased hot water-extractable organic carbon (HWOC) from 330 to 286 mg kg-1 soil and cold water-extractable organic carbon (CWOC) from 53 to 22 mg kg-1 soil in the top 0-7.5 cm soil layer. In the lower soil layer (7.5-15 cm), reduction in HWOC was not significant. Application of gypsum alone resulted in a decrease in HWOC in the SW plots, whereas an increase was recorded in the SW plots with application of both gypsum and organic amendments in both the soil layers. Nevertheless, application of gypsum and organic amendments increased the mean CWOC as compared with application of gypsum alone. CWOC was significantly correlated with MBC but did not truly reflect the changes in MBC in the treatments with gypsum and organic amendments applied. For the treatments without organic amendments, HWOC was negatively correlated with MBC (r = 0.57*) in the 0-7.5 cm soil layer, whereas for the treatments with organic amendments, both were positively correlated. Irrigation with SW significantly reduced the rice yield by 3 t ha-1 and the yield of rice and wheat by 5 t ha-1 as compared to irrigation with canal water. Application of amendments significantly increased rice and wheat yields. Both the rice yield and the yield of rice and wheat were significantly correlated with MBC (r = 0.49**-0.56**, n = 60). HWOC did not exhibit any relation with the crop yields under the treatments without organic amendments; however, CWOC showed a positive but weak correlation with the crop yields. Therefore, we found that under sodic water irrigation, HWOC or CWOC in the soils was not related to MBC.     

Effect of forest and soil type on microbial biomass carbon and respiration

The aim of study was to evaluate the variation of soil microbial biomass carbon (C_mic) and microbial respiration (M_R) in three types soil (Chromic Cambisols, Chromic Luvisols and Eutric Leptosols) of mixed beech forest (Beech- Hornbeam and Beech- Maple). Soil was randomly sampled from 0–10 cm layer (plant litter removed), 90 soil samples were taken. C_mic determined by the fumigation-extraction method and M_R by closed bottle method. Soil C_org, N_tot and pH were measured. There are significant differences between the soil types concerning the C_mic content and M_R. These parameters were highest in Chromic Cambisols following Chromic Luvisols, while the lowest were in Eutric Leptosols. A similar trend of C_org and N_tot was observed in studied soils. Two-way ANOVA indicated that soil type and forest type have significantly effect on the most soil characteristics. Chromic Cambisols shows a productive soil due to have the maximum C_mic, M_R, C_org and N_tot. In Cambisols under Beech- Maple forest the C_mic value and soil C/N ratio were higher compared to Beech-Hornbeam (19.5 and 4.1 mg C g^–1, and 16.3 and 3.3, respectively). This fact might be indicated that Maple litter had more easy decomposable organic compounds than Hornbeam. According to regression analysis, 89 and 68 percentage of C_mic variability could explain by soil C_org and N_tot respectively.     

Spatial variability in the carbon of microbial biomass and microbial respiration in soils of the south of Moscow oblast

Soil samples from the upper 10-cm-thick layer of the humus horizon (without forest litter) were taken in Podol’sk and Serpukhov districts (1130 and 1080 km², respectively) of Moscow oblast. At each sampling site, ecosystem (forest, plowland, or fallow), soil (soddy-podzolic, soddy-gley, bog-podzolic, meadow alluvial, gray forest, and anthropogenically transformed soils of lawns and industrial zones), predominant vegetation, and topography (floodplain and low, medium, and upper parts of watersheds) were determined. The carbon content of the microbial biomass (C_mic) was determined by the method of substrate-induced respiration; we also determined the rate of basal (microbial) respiration (BR) and the organic carbon content, pH, and particle-size distribution. Overall, 237 samples from Serpukhov district and 45 samples from Podol’sk district were analyzed. The BR/C_mic ratios (respiration quotient qCO₂) and C_mic/C_org ratios were calculated. The C_mic content in the soils ranged from 43 to 1394 μg C/kg; the BR varied from 0.06 to 25 μg CO₂-C/g per h, qCO₂, from 0.34 to 6.52 μg CO₂-C/mg C_mic per h; and the C_mic/C_org ratio, from 0.19 to 10.65%. It was found that the most significant factors affecting the variability of the C_mic and BR are the parameters of ecosystem (50% and 80%, respectively) and soil (30% and 9%, respectively). The most significant variability of these indices was found in forest soils; it was mainly controlled by the soil texture (33 and 23%) and the C_org content (19 and 24%). The C_mic parameter made it possible to differentiate the soils of the territory for the purposes of their evaluation, monitoring, and biological assessment more clearly than the BR value and the soil chemical characteristics.     

Effect of plant roots on carbon metabolism of soil microbial biomass

The utilization of plant- and soil-C by the microbial biomass in the rhizosphere of maize plants was investigated as a function of root proximity. The plants were cultivated in pots with divided root chambers and their shoots supplied with ¹⁴CO₂ for 23 days. Subsequently the individual soil zones were analyzed for organic C, ¹⁴C, biomass C and biomass ¹⁴C. Plant roots induced a 197% increase in microbial biomass and a 5.4% decrease in soil organic C compared with an 1.2% decrease in the unplanted control soil. The contributions of plant- and soil-C to this increased microbial growth amounted to 68% and 32% respectively. Biomass-¹⁴C corresponded to 1.6% of the total photosynthetically fixed ¹⁴C, to about 15% of the organic ¹⁴C-input into the rhizosphere and to 58% of the plant carbon remaining in soil after the removal of roots. 20% of this biomass-¹⁴C was found outside the immediate root zone. These results demonstrate that growing roots are a significant C-source for the microbial biomass and render an additional fraction of soil-C available to microbial utilization. The efficiency of C-utilization by the rhizosphere biomass is lower than values obtained with liquid cultures in laboratory experiments. The supply of plant-C to the microbial biomass outside the immediate root vicinity indicates that the overall volume of the maize rhizosphere is greater than what has been supposed so far.     

Relationships of soil microbial biomass carbon and organic carbon with environmental parameters in mountainous soils of southwest China

The relationships between microbial biomass C, organic C, and environmental parameters were studied in soils under corn (Zea mays. L) in the mountainous areas of southwest China. Three yellowish-red (Ultisols), yellow (Ultisols) and yellowish-brown (Alfisols) soils were relatively weathered, leached and impoverished, with most having a low input of aboveground corn residues. Seasonal changes in soil microbial C at 0-10 cm depth were significant at each sampling site, with the highest value (120 g C m^-2) in winter, and lowest value in summer (21 g C m^-2). Microbial biomass C was significantly and negatively correlated with site elevation and positively correlated with mean annual temperature. The seasonal change in microbial biomass C was significantly correlated with total soil organic C. The decline in microbial biomass C estimated as a percentage of the total soil organic C was negatively correlated with the elevation above sea level, ranging from 3.9ǂ.9% below 600 m to 1.4ǂ.5% above 1,500 m, suggesting higher turnover rates of soil microbial biomass C at warmer air temperatures. Temperature influenced the decomposition of organic C in soils mainly through its effects on microbial biomass C, and the microbial biomass C/organic C ratio appears to be a sensitive index of the change in organic matter content of soil.     

水旱轮作与林地利用方式对中国滨海滩涂土壤微生物生物量碳的影响

Rice-wheat rotation and poplar afforestation are two typical land use types in the coastal reclaimed flatlands of eastern China.This study investigated two rice-wheat rotation lands(one reclaimed from 1995 to 2004 and cultivated since 2005, RW1, and the other reclaimed from 1975 to 1995 and cultivated since 1996, RW2) and a poplar woodland(reclaimed from 1995 to 2004 and planted in2004, PW1) to determine the effects of land use types and years of cultivation on soil microbial biomass and mineralizable carbon(C) in this coastal salt-affected region. The results showed that the soil in PW1 remained highly salinized, whereas desalinization was observed in RW1. The total organic C(TOC) in the top soil of PW1 and RW1 did not show significant differences, whereas at a soil depth of 20–30 cm, the TOC of RW1 was approximately 40%–67% higher than that of PW1. The TOC of 0–30-cm soil in RW2 was approximately 37% higher than that in RW1. Microbial biomass C(MBC) and mineralizable C(MNC) exhibited the trend of RW2 RW1 PW1. Sufficient nutrition with more abundant C substrates resulted in higher MBC and MNC, and soil respiration rates were negatively correlated with C/N in RW1 and RW2. Nutrient deficiency and high salinity played key roles in limiting MBC in PW1. These suggested that rice-wheat rotation was more beneficial than poplar afforestation for C accumulation and microbial biomass growth in the coastal salt-affected soils.     

Soil-released carbon dioxide from microbial biomass carbon in the cultivated soils of karst areas of southwest China

 Soil microbial biomass and the emission of CO₂ from the soil surface were measured in yellow soils (Ultisols) of the karst areas of southwest China. The soils are relatively weathered, leached and impoverished, and have a low input of plant residues. The measurements were made for a 1-year period and show a reciprocal relationship between microbial biomass and surface CO₂ efflux. The highest (42.6±2.8 mg CO₂-C m^–2 h^–1) and lowest (15.6±0.6 mg CO₂-C m^–2 h^–1) CO₂ effluxes are found in the summer and winter, respectively. The cumulative CO₂ efflux is 0.24 kg CO₂-C m^–2 year^–1. There is also a marked seasonal variation in the amount of soil microbial biomass carbon, but with the highest (644±71 μg C g^–1 soil) and lowest (270±24 μg C g^–1 soil) values occurring in the winter and summer, respectively. The cumulative loss of soil microbial biomass carbon in the top 10 cm of the soil was 608 μg C g^–1 year^–1 soil over 17 sampling times. The mean residence time of microbial biomass is estimated at 105 days, suggesting that the carbon in soil microbial biomass may act as a source of the CO₂ released from soils. Received: 13 July 1999     

中国土壤微生物量的大小

The microbial biomass C, N and P of soils all over China were determined in this study to study their affecting factors. The results, about 100-417 mg C kg^-1 soil, 18-51 mg N kg^-1 soil and 4.4-27.3 mg P kg^-1 soil, showed the biomass C, N and P in linear relationship with the soil total organic C, toal N and soil organic P. The ratios of C: N and C:P, ranging from 5.6 to 9.6 and from 11.2 to 48.4 respectively, were affected by soil pH, texture, crop rotation, macroclimate, etc. The ratio of C:N in soil biomass increases gradually from the north to the south in China.     

Ratios between estimates of microbial biomass content and microbial activity in soils

The content levels and activities of the microbiota were estimated in topsoils and in one soil profile at agricultural and forest sites of the Bornhöved Lake district in northern Germany. Discrepancies between data achieved by fumigation-extraction (FE) and substrate-induced respiration (SIR), both used for the quantification of microbial biomass, were attributed to the composition of the microbial populations in the soils. In the topsoils, the active, glucose-responsive (SIR) versus the total, chloroform-sensitive microbial (FE) biomass decreased in the order; field maize monoculture (field-MM)>field crop rotation (field-CR) and dry grassland>beech forest. This ratio decreased within the soil profile of the beech forest from the litter horizon down to the topsoil. Differences between microbial biomass and activities suggested varying biomass-specific transformation intensities in the soils. The metabolic quotient (qCO₂), defined as the respiration rate per unit of biomass, indicates the efficiency in acquiring organic C and the intensity of C mineralization, while biomass-specific arginine-ammonification (arginine-ammonification rate related to microbial biomass content) seems to be dependent on N availability. The qCO₂, calculated on the basis of the total microbial biomass, decreased for the topsoils in the same order as did the ratio between the active, glucose-responsive microbial biomass to the total, chloroform-sensitive microbial biomass, in contrast to qCO₂ values based on the glucose-responsive microbial biomass, which did not. There was no difference between the levels of biomass-specific arginine-ammonification in topsoils of the fertilized field-CR, fertilized field-MM, fertilized dry grassland and eutric alder forest, but levels were lower in the beech forest, dystric alder forest, and unfertilized wet grassland topsoils. Ratios between values of different microbiological features are suggested to be more useful than microbiological features related to soil weight when evaluating microbial populations and microbially mediated processes in soils.     

Effect of temperature on EDTA‐extractable copper in soils

Abstract

Two contrasting soils were extracted with 0.05 M EDTA in 1 M CH₃ COONH₄ at pH 6, before and after incubation for 4 weeks at constant (10, 20 or 30°C) or fluctuating (10/30, mean 20°C) temperatures. Less copper was extracted from soils which were incubated at fluctuating temperature than from those maintained at a constant 20 C. Where incubation temperature was constant, extractable copper increased or decreased with increasing temperature depending on the soil and how it was treated. Recovery of added copper was low initially but increased during the incubation. Maximum recovery was associated with low incubation temperature in one soil, but high temperature in the other. The amounts of copper extracted were slightly increased by γ‐irradiation of the soils. Extractable copper was also increased by increasing the temperature at which the extraction was performed.     

Spatial structure of microbial biomass and activity in prairie soil ecosystems

Management of soil ecosystems requires assessment of key soil physicochemical and microbial properties and the spatial scale over which they operate. The objectives were to determine the spatial structure of microbial biomass and activity and related soil properties, and to identify spatial relationships of these properties in prairie soils under different management histories. Soil were sampled along a transect at 0.2 m intervals in each of five long-term treatments, namely, undisturbed, cattle grazed at two intensities, and cultivated with either wheat (Triticum aestivum L.) or cotton (Gossypium hirsutum L.). Contents of organic carbon (C_org), dissolved organic C (DOC), soluble nitrogen (N_sol), and microbial biomass C (C_mic) and N (N_mic) as well as dehydrogenase activity (DH) in 70 samples were evaluated. Results showed that long-term soil management altered the spatial structure and dependence of C_org and microbial biomass and activity. Cultivation has contributed to high nugget variance for C_org, C_mic, N_mic and DH which interfered with detection of spatial structure at the sampling scale used. Contents of C_org were spatially connected to microbial biomass and activity and to DOC in the uncultivated but not in the cultivated soils, indicating that various factors affected by management may operate at different spatial scales.     

Anaerobic methane oxidation in soils and water ecosystems

The process of anaerobic methane oxidation has been studied for over 30 years on the example of bottom marine sediments and fresh water ecosystems. This paper presents a review of the results of these investigations. It is also demonstrated that this process can proceed not only in submerged but also in drained peat and automorphic sod-podzol soils. The latter soils continue to absorb methane after anaerobic conditions are created and an inhibitor of methane monooxygenase (acetylene) is introduced. Oxidated compounds (nitrates, sulphates) are stimulatory to gas absorption; deoxidated nitrogen compounds (ammonium chloride) do not produce significant changes. Incubation with the addition of nitrates and sulphates in an atmosphere of argon and methane results in an increase in the fraction and abundance of archaea in the soil. This is in agreement with the data obtained for aquatic inhabits.