淹水培养条件下土壤微生物生物量碳、氮和可溶性有机碳、氦的动态

以洞庭湖区2个典型水稻土（红黄泥和紫潮泥）为对象,研究了25℃、淹水培养条件下稻草-硫铵配施和单施硫铵处理土壤微生物生物量碳、氮（SMBC、SMBN）和可溶性有机碳、氦（SDOC、SDON）的动态变化．结果表明,SMBC、SMBN和SDOC、SDON在培养前期达到峰值,之后降低,并趋于稳定．添加底物后,2种土壤不同处理土壤微生物生物量碳与有机碳（SMBC／TC）和土壤微生物生物量氮与全氮（SMBN／TN）的平均值都在2％-3％之间变化;可溶性碳与全碳（SDOC／TC）的平均值为1％左右,可溶性氮与全氮（SDON／TN）平均值为5％-6％．2种土壤中SMBC峰值单施硫铵处理最大,但与稻草-硫铵配施处理差异均不显著;SMBN、SDOC和SDON峰值稻草-硫铵配施最大．稻草．硫铵配施与单施硫铵处理中,低肥力红黄泥的SMBN、SDOC和SDON峰值差异显著;而高肥力紫潮泥SMBN和SDOC峰值差异不显著．前7d,SMBC／SMBN〈10;14d后,同一时刻单施硫铵处理SMBC／SMBN〉稻草．硫铵配施．不同处理的SDOC!SDON3d时最大．28d时最小．     

Soil microbial biomass influence on strontium availability in mine soil

Abstract

The main aim of our work was to assess whether strontium (Sr) affects soil microbial biomass size and activity, and the involvement of said biomass in the availability process of the metal. In addition, information concerning the distribution and mobility of the stable element within ecosystems may allow the prediction of the behaviour of its radioisotope counterpart, ⁹⁰Sr. Samples were collected in the surroundings of a strontium mine and characterised for total and diethylene triamine pentaacetic acid (DTPA)-extractable Sr, total organic C (TOC), microbial biomass C (MBC), MBC/TOC ratio and metabolic quotient (qCO₂). Moreover, MBC and DTPA-extractable Sr were measured during a 45-day incubation experiment of samples soils amended with maize. Overall, increased levels of total Sr had a negative effect on both TOC and MBC. DTPA-extractable Sr was significantly correlated to MBC/TOC suggesting a possible role of soil microbial biomass in the mobilisation of the element. The synthesis of new microbial biomass after soil amendment was negatively affected by the initial content of DTPA-extractable Sr. Conversely, there was a linear positive relationship between newly formed MBC and DTPA-extractable Sr during the incubation, indicating that soil microbial biomass may promote the mobilisation of Sr. These findings indicate that soil amendment with easily degradable organic substrate significantly increases Sr mobility and availability.     

C:N:P stoichiometry in soil: is there a “Redfield ratio” for the microbial biomass?

Well-constrained carbon:nitrogen:phosphorus (C:N:P) ratios in planktonic biomass, and their importance in advancing our understanding of biological processes and nutrient cycling in marine ecosystems, has motivated ecologists to search for similar patterns in terrestrial ecosystems. Recent analyses indicate the existence of “Redfield-like” ratios in plants, and such data may provide insight into the nature of nutrient limitation in terrestrial ecosystems. We searched for analogous patterns in the soil and the soil microbial biomass by conducting a review of the literature. Although soil is characterized by high biological diversity, structural complexity and spatial heterogeneity, we found remarkably consistent C:N:P ratios in both total soil pools and the soil microbial biomass. Our analysis indicates that, similar to marine phytoplankton, element concentrations of individual phylogenetic groups within the soil microbial community may vary, but on average, atomic C:N:P ratios in both the soil (186:13:1) and the soil microbial biomass (60:7:1) are well-constrained at the global scale. We did see significant variation in soil and microbial element ratios between vegetation types (i.e., forest versus grassland), but in most cases, the similarities in soil and microbial element ratios among sites and across large scales were more apparent than the differences. Consistent microbial biomass element ratios, combined with data linking specific patterns of microbial element stoichiometry with direct evidence of microbial nutrient limitation, suggest that measuring the proportions of C, N and P in the microbial biomass may represent another useful tool for assessing nutrient limitation of ecosystem processes in terrestrial ecosystems.     

The role of environmental, root, and microbial biomass characteristics in soil respiration in temperate secondary forests of Northeast China

For secondary forests, the major forest resources in China (accounting for more than 50% of the national total), soil respiration (R _S) and the relationship between R _S and various biotic/abiotic factors are poorly understood. The objectives of the present study were to examine seasonal variations in soil respiration during the growing season, and to explore the factors affecting the variation in soil respiration rates for three forest types (Mongolian oak, Manchurian walnut and mixed forests) of temperate secondary forest in Northeast China. The results showed that (1) the maximum total R _S rate occurred in July, following a bell-shaped curve with season, (2) for all forest types, the total R _S was significantly influenced by soil temperature (P < 0.01), and did not significantly correlate with soil moisture, (3) compared with fine root biomass, coarse root biomass was more closely related with the root respiration in mixed forest (R ² = 0.711, P = 0.017) and in Manchurian walnut forest (R ² = 0.768, P = 0.010), and (4) microbial biomass carbon (MBC) and nitrogen were significantly correlated with heterotrophic R _S in Mongolian oak forest (R ² = 0.664, P = 0.026; R ² = 0.784, P = 0.008, respectively) and in mixed forest (R ² = 0.918, P = 0.001; R ² = 0.967, P = 0.001, respectively). We can conclude that in temperate secondary forests: (1) the R _S rate and the relationships between R _S and abiotic/biotic factors change greatly with forest types, and (2) R _S is strongly influenced by soil temperature, MBC, microbial biomass nitrogen and coarse root biomass in temperate secondary forests.     

红壤微生物量在土壤—黑麦草系统中的肥力意义

研究了红壤微生物量与土壤养分循环及植物生长的内在联系．结果表明,红壤微生物量不仅与土壤有机碳、全氮、有效氮等显著相关,而且与植物干物质产量及吸Ｎ 量也存在着良好的相关性,可作为指示红壤肥力水平和作物产量的重要指标．试验测得的红壤微生物量Ｎ 周转期较短,每年通过微生物周转的Ｎ 素达到微生物量氮含量的１ ．５ 倍到数倍．     

天台山七子花群落下土壤微生物生物量的季节动态

研究天台山七子花群落下土壤微生物生物量的季节变化规律及生态特性。根据实测数据分别对根际、根围微生物生物量碳、氮与土壤环境因子之间进行相关性分析,并建立了土壤微生物指标与环境因素之间的回归方程,以此为基础对天台山七子花群落下土壤微生物生物量的季节变化进行预测。回归分析表明：土壤温度、水分对微生物生物量的影响大于土壤pH值对微生物生物量的影响,而且土壤温度、水分对微生物生物量氮的影响大于对微生物生物量碳的影响。土壤温度对微生物生物量碳、氮的影响最大。     

Application of the chloroform fumigation-incubation method to the estimation of soil microbial biomass in burned and unburned Japanese red pine forests

Abstract Estimation of soil microbial biomass in burned and unburned Japanese red pine forests was attempted using the chloroform fumigation-incubation method. As the amount of CO₂-C evolved from the fumigated soil for 10–20 days after fumigation (designated as F') was always lower than that from the unfumigated soil during the same period (UF'), the formula, microbial biomass-C(M) = the amount of CO₂-C evolved from the fumigated soil for 0–10 days after fumigation, F) − F'/ k _c, was proposed instead of Jenkinson's conventional formula, M = (F − UF')/ k _c. The k _c value was also determined as 0.30 using 3 fungal and 3 bacterial cultured species as internal standards. Microbial biomass-C calculated by (F − F')/0.30 decreased with soil depth at both the burned (Nenoura, 3.5 years after fire) and unburned (Ato) sites, showing the significant correlation with the decrease of soil respiration and organic C content along soil depth. Microbial biomass-C in the 0–2 cm soil layer at the burned site at Nenoura was 130 mg/100 g dry soil and those in the HF horizon and 0–2 cm soil layer at the unburned site at Ato were 686 and 146 mg/100 g dry soil, respectively.     

The influence of stress treatments on the microbial biomass and the rate of decomposition of humified matter in soils containing different amoutns of clay

Summary ¹⁴C-labelled substrates (glucose, hemicellulose, cellulose, maize straw, and barley straw) were incubated in 4 soils with clay contents of, 6, 12, 16 and 34%. After 2 years an average of 20% of the labelled C remained in the soils; 10% of this residual C was in biomass as determined by fumigation with CHCl₃.Air-drying, C addition (unlabelled glucose), heating (80°C), and grinding of the soils accelerated the evolution of labelled CO₂. Grinding and heating had the largest effect, increasing CO₂ evolution during the first 10 days by a factor of 15 to 22 relative to untreated soil. Air-drying had the least effect; it increased the CO₂ evolution 7 to 9 times. The accelerating effect was still measurable, during the third month of incubation when the CO₂ evolution was 1.2 to 1.9 times that from untreated soil.The treatments also affected the labelled biomass; air-drying had the least effect, and grinding the most. Three months after these two treatments the biomass was 3/4 and 1/4, respectively, of the amount at the start.On the average the treatments in all four soils had the greatest affect on humified material originating from glucose, hemicellulose, and cellulose; the least effect was on material originating from straw.The addition of unlabelled glucose accelerated the evolution of labelled CO₂–C in all four soils. The size of the effect on CO₂ evolution and on the biomass was similar to that of air-drying.Grinding killed a larger percentage of the biomass in the sandy soil than in the soils with a high content of clay. The effect of the other treatments was largely the same in all four soils.The effect of the treatments towards the native biomass and humic matter was largely parallel to that on the labelled biomass.The observations are consistent with the view that the biomass as determined by fumigation with CHCl₃ mainly consists of dormant organisms. CO₂ production — the biological activity — was related to the amount of available organic material and not the size of the biomass.     

Comparative assessment of soil microbial biomass determined by the methods of direct microscopy and substrate-induced respiration

The content of microbial biomass (MB) was determined in samples of gray forest, chestnut, and tundra soils with different physicochemical properties (0.4–22.7% C_org; 8.4–26.8% silt particles; pH 4.3–8.4) by the methods of substrate-induced respiration (MB_SIR) and direct microscopy (MB_M). The samples of two upper soil layers, 0–5 and 5–10 cm (without plant litter), from different ecosystems (forest, forest shelter belt, meadow, fallow, and arable) and elements of relief of interfluvial tundra (block/upper land plateau, depression between blocks) have been analyzed. The content of microbial biomass in the 0–5-cm soil layer was 216–8134 and 348–7513 μg C/g soil as measured by the methods of substrate-induced respiration and direct microscopy, respectively. The MB_SIR and MB_M values closely correlated with each other: r = 0.90 and 0.74 for 0–5 and 5–10 cm, respectively. The average MB_SIR/MB_M ratio was 90 and 60% for 0–5 and 5–10 cm, respectively. The portion of microbial carbon in total organic soil carbon was, on average, 4 and 3% (SIR) and 5 and 7% (direct microscopy) for 0–5 and 5–10 cm, respectively. Possible reasons for the differences between MB_SIR and MB_M values in the soils under study are discussed.     

油松-辽东栎混交林地表凋落物与氮添加对土壤微生物生物量碳、氮及其活性的影响

2010年9月-2011年10月,在山西省灵空山油松和辽东栎混交林样地采取随机区组设计,研究了地表凋落物和氮添加处理对土壤微生物生物量碳、氮和微生物活性的影响.凋落物处理包括:剔除凋落物(N)、叶凋落物加倍(L)、枝果凋落物加倍(B)和混合凋落物加倍(LB);氮添加量分别为0(N0)、5 g· m-2·a-1(N1)和10 g·m-2·a-1(N2).结果表明:剔除地表凋落物且无氮添加时,油松和辽东栎混交林地的土壤有机碳(SOC)含量显著降低,其他试验处理间对SOC的影响无显著差异.土壤微生物生物量碳(MBC)、氮(MBN)及其活性(MR)的变化范围依次为:262.42 ～ 873.16 mg·kg-1、73.55 ～ 173.85 mg·kg-1和2.38～3.68mg·kg-1·d-1.MBC、MBN和MR两两间呈极显著正相关.氮添加对MBC、MBN和MR均无显著影响;凋落物处理对MR影响显著,表现为混合凋落物加倍处理的MR最高,叶凋落物加倍处理次之,剔除凋落物处理最低,而对MBC和MBN无显著影响.凋落物和氮添加处理在整个试验过程中未表现出交互作用.短期的氮添加处理和森林地表凋落物变化对土壤微生物过程的影响有限.