Response of soil microbial community in Jiuduansha wetland to different successional stages and its implications for soil microbial respiration and carbon turnover

To clarify the variation in soil microbial respiration (SMR) in Jiuduansha wetland during different succession stages, the SMR of five typical zones was evaluated. The results showed that the SMR during different successional stages of vegetation varied significantly (P < 0.05), with the SMR of the Spartina alterniflora zone (0.43 mg CO₂ g⁻¹ d⁻¹) being the highest. These findings implied that S. alterniflora could enhance the SMR. Based on both the SMR and input of organic matter from plant decomposition, the Phragmites australis community likely possesses a higher organic carbon accumulation capability. In addition, the results of the present study implied that the difference in microbial characteristics among the wetland soils may be the primary reason for their different SMR. Path analysis indicated that the correlation between soil bacterial diversity and SMR was especially strong. Moreover, phylogenetic analysis showed that the bacterial community structure along the successional stages varied. Specifically, microbial species such as Acidobacteria, δ-Proteobacteria and Cytophaga belonging to Bacteroidetes, which have special heterotrophic metabolic capabilities or the ability to degrade cellulose, were the dominant soil bacterial flora in the S. alterniflora zone, which ultimately strengthened the SMR. Different elevations and vegetation types leading to a change in the wetland soil characteristics such as waterlogging time and inorganic nitrogen may be important factors resulting in the differences in soil microbial characteristics of different successional stages in Jiuduansha wetland.     

棉花连作对北疆土壤酶活性、致病菌及拮抗菌多样性的影响

本文通过测定土壤酶活性与微生物PCR-DGGE指纹图谱研究了北疆棉区5年棉花连作(CtN5)、10年棉花连作(CtN10)及15年棉花连作(CtN15)对土壤过氧化氢酶、蔗糖酶、芳基硫酸酯酶、脱氢酶和蛋白酶酶活性的影响,分析了土壤细菌、真菌、镰刀菌和枯草芽孢杆菌群落结构多样性对北疆棉田长期连作的响应。结果表明:过氧化氢酶、蔗糖酶、脱氢酶活性随棉花连作年限延长而下降。CtN15处理的过氧化氢酶、蔗糖酶和脱氢酶活性分别比CtN10处理下降15.0%、6.4%和12.0%,比CtN5处理下降16.8%、58.6%和49.5%(P0.05);芳基硫酸酯酶与蛋白酶活性随连作年限的增加呈先下降后升高的特点。土壤细菌、真菌多样性指数随连作年限的增加明显下降。CtN15的细菌条带数比CtN10下降7.41%,Ct N10比CtN5降低1.72%。CtN15真菌条带数和Shannon-Wiener多样性指数分别为78和3.22,比CtN5处理低17.02%和5.29%。土壤镰刀菌和枯草芽孢杆菌的条带数、多样性指数均表现为先下降后升高。CtN15枯草芽孢杆菌Shannon-Wiener和Simpson指数分别比CtN10处理高54.8%和14.5%。北疆长期连作棉田的土壤酶活性和土壤微生物群落多样性总体呈下降趋势,长期连作对棉田土壤生物性状有明显负面影响。     

Variations in microbial community composition through two soil depth profiles

Soil profiles are often many meters deep, but with the majority of studies in soil microbiology focusing exclusively on the soil surface, we know very little about the nature of the microbial communities inhabiting the deeper soil horizons. We used phospholipid fatty acid (PLFA) analysis to examine the vertical distribution of specific microbial groups and to identify the patterns of microbial abundance and community-level diversity within the soil profile. Samples were collected from the soil surface down to 2 m in depth from two unsaturated Mollisol profiles located near Santa Barbara, CA, USA. While the densities of microorganisms were generally one to two orders of magnitude lower in the deeper horizons of both profiles than at the soil surface, approximately 35% of the total quantity of microbial biomass found in the top 2 m of soil is found below a depth of 25 cm. Principal components analysis of the PLFA signatures indicates that the composition of the soil microbial communities changes significantly with soil depth. The differentiation of microbial communities within the two profiles coincides with an overall decline in microbial diversity. The number of individual PLFAs detected in soil samples decreased by about a third from the soil surface down to 2 m. The ratios of cyclopropyl/monoenoic precursors and total saturated/total monounsaturated fatty acids increased with soil depth, suggesting that the microbes inhabiting the deeper soil horizons are more carbon limited than surface-dwelling microbes. Using PLFAs as biomarkers, we show that Gram-positive bacteria and actinomycetes tended to increase in proportional abundance with increasing soil depth, while the abundances of Gram-negative bacteria, fungi, and protozoa were highest at the soil surface and substantially lower in the subsurface. The vertical distribution of these specific microbial groups can largely be attributed to the decline in carbon availability with soil depth.     

Changes of the functional diversity of soil microbial community during the colonization of abandoned grassland by a forest

The impact of secondary succession of grassland communities towards a Norway spruce forest on soil microbial community was studied on a belt transect established in the Pol’ana Mts., Central Europe. Data on understory vegetation, light availability, soil properties and microbial activity were collected on 147 plots distributed over regular grid. Moreover, distributions of functional groups of microorganisms were assessed using BIOLOG analysis on a subset of 27 plots. Mantel partial correlations between microbial community indicators and environmental variables showed that microbial activity generally decreased with increasing tree density and size, whereas it increased with increasing radiation at the soil surface, soil temperature, and cover and diversity of understory vegetation. Functional richness and diversity of microorganisms were positively correlated with solar radiation, but also with plant species richness and diversity. Abundance of several functional groups correlated closely with succession-related variables. Redundance analysis of microbial data provided slightly different outcomes. Forward selection yielded only two environmental variables significantly influencing the composition of the microbial community: tree influence potential and organic carbon content. Abundances of several functional microbial groups correlated with tree influence, documenting that microbial community changes are at least partially driven by the colonization of grassland by trees. Nevertheless, the relative importance of abiotic environment change and plant community succession on microbial community dynamics remains unresolved.     

转Bt基因棉叶对土壤微生物多样性的影响

应用Biolog方法研究了转Bt基因棉粉碎叶腐解对土壤微生物群落结构功能多样性的影响。取腐解10d、25d、40d、55d、70d土样分析土壤微生物群落多样性指数及土壤微生物对聚合物、胺类、氨基酸、糖、羧酸和其他类碳源利用情况。结果表明:在腐解过程中,转Bt基因棉粉碎叶土壤微生物群落丰富度下降,群落多样性显著降低,而群落优势集中性明显提高;转Bt基因棉粉碎叶影响了土壤微生物群落对碳源的利用程度,表现为可显著增加对糖类、胺类和氨基酸类碳源的利用,初期显著降低对羧酸类碳源的利用,对聚合物类和其他类碳源的利用率无显著影响;主成分分析表明转Bt基因棉粉碎叶对土壤微生物群落原有结构功能影响具有持续性。     

氯甲基吡啶对滴灌棉田土壤微生物群落功能多样性的影响

已知硝化抑制剂氯甲基吡啶能有效抑制土壤硝化,减少氮的淋洗和硝化-反硝化损失,促进作物对氮素的吸收,但是其对干旱区滴灌条件下土壤微生物群落功能多样性的影响尚不明确。本试验研究了尿素添加氯甲基吡啶(Nitrapyrin)分次随水滴施对干旱区滴灌棉田土壤微生物碳代谢和群落功能多样性的影响。试验采用随机区组设计,设置不施氮肥[CK,0 kg(N)·hm~(-2)]、单施尿素[Urea,225 kg(N)·hm~(-2)]和尿素添加氯甲基吡啶[Urea+nitrapyrin,225 kg(N)·hm~(-2)+2.25 kg(nitrapyrin)·hm~(-2)]3个处理,重复4次,采用Biolog-ECO法进行土壤微生物碳代谢和功能多样性研究。结果表明:与不施氮肥(CK)相比,施用尿素和尿素添加氯甲基吡啶均能显著提高土壤微生物对31种碳源的代谢能力(AWCD)和代谢强度(S)(P0.05),增加土壤微生物多样性和丰富度(Shannon指数、Simpson指数、Mc Intosh指数和Richness指数)以及对各类碳源的利用能力。尿素添加氯甲基吡啶随水滴施后,土壤微生物AWCD值、碳代谢强度、Shannon指数、Simpson指数、Mc Intosh指数以及Richness指数均大于单施尿素处理,且较单施尿素处理分别提高13.83%、9.33%、1.29%、1.34%、11.26%、11.79%(P0.05),均匀度指数则低于单施尿素处理(P0.05)。PCA和聚类分析结果表明,施用尿素和尿素添加氯甲基吡啶对土壤微生物群落功能多样性均产生了显著影响,但尿素添加氯甲基吡啶与单施尿素处理差异不显著;氯甲基吡啶的添加提高了土壤微生物对聚合物、酚酸、羧酸、氨基酸以及胺类的利用,降低了对碳水化合物的利用(P0.05)。上述研究结果得出,在干旱区滴灌棉田,尿素添加氯甲基吡啶分次随水滴施可调控土壤的微生态环境,在一定程度上提高土壤微生物的代谢能力,增加微生物群落功能多样性,缓解因长期施用无机氮肥导致的土壤微生物活性的降低。     

麦地土壤线虫群落结构对有机肥和秸秆还田的响应

通过猪粪有机肥的施用和秸秆还田,研究其对农田土壤线虫数量、属的种类及群落结构的影响。田间试验处理为CK(不施肥对照)、HF(施化肥)、ZH(猪粪堆肥 化肥)、JHB(秸秆 化肥 秸秆伴侣)、ZHJ(猪粪堆肥 化肥 秸秆)、ZDH(猪粪堆肥有机无机复合肥 化肥)6个处理。结果表明：在6个施肥处理中共鉴定出4目11科22属线虫,其中食细菌线虫9属,食真菌线虫5属,植食线虫4属,杂食-捕食线虫4属。JHB、ZHJ和ZDH处理的土壤线虫数量显著高于CK和HF处理,而HF与CK处理之间没有显著差异;化肥、有机肥和秸秆配施可以增加食细菌线虫的丰度,抑制植食线虫垫刃属和螺旋属的繁殖;除了ZDH外,其他4个处理的植食线虫丰度明显低于CK。 JHB、ZHJ和ZDH的线虫通路比值(NCR)显著高于CK,表明有机管理的农田土壤腐屑食物网的分解途径主要依靠细菌分解途径。CK、JHB、ZHJ和ZDH的的成熟指数(MI)显著高于HF,表明单施化肥对土壤环境干扰较大。多样性指数(H′)、优势度指数(λ)、均匀度指数(J) 和瓦斯乐斯卡指数(WI)在6个处理中均没有显著差异。在6个施肥处理中,均以c-p 2类群的土壤线虫比例最高,其次是c-p 3-5,c-p 1类群比例最低。通过线虫营养类群、群落结构及生态指数综合分析得出,JHB和ZHJ为最佳施肥方式。     

多菌灵重复施药对其持久性及土壤微生物群落功能多样性的影响

选择浙江大学华家池校区大棚蔬菜试验田,研究了多菌灵(以active ingredient,a.i.计)0.94、1.88和4.70 kg hm-2三种剂量重复施药对其持久性及土壤微生物功能多样性的影响。结果表明,第1次施药后,多菌灵在土壤中的降解速率分别为0.11、0.25、0.74 mg kg-1d-1;第4次施药后,多菌灵在土壤中的降解速率分别达到0.18、0.39、1.00 mg kg-1d-1。随着施药次数的增加,多菌灵的降解速率逐渐增大。初次施药后,土壤微生物群落AWCD值明显低于对照,土壤微生物群落的Shannon、Simpson和McIntosh指数也均低于对照水平。第4次施药后,三个处理土壤微生物群落的AWCD值、Shannon、Simpson和McIntosh指数均恢复到对照水平。     

Impact of sulfadiazine and chlorotetracycline on soil bacterial community structure and respiratory activity

Veterinary medicines enter agricultural soils by the use of animal excrements as fertilizers. To study their impact on soil bacterial communities, microcosms containing orthic luvisol soil were spiked with the antimicrobial agents sulfadiazine (SDZ) and chlorotetracycline (CTC) at three different concentrations (1, 10, 50 mg kg⁻¹ soil) and incubated for 48 days at 20 °C. The impact on the microbial respiratory activity was measured continuously in a respirometer (Sapromat). Changes in bacterial community structure were visualized by means of PCR-denaturing gradient gel electrophoresis (DGGE) of 16S rDNA derived from soil samples after 1, 7, 11 and 48 days. Additionally, growth inhibitory effects of SDZ and CTC on bacteria previously isolated from the same soil were tested in agar diffusion tests. In microcosms with soil and antibiotics only, no effects could be observed, either on respiratory activity or on bacterial population structure. Therefore, further incubations were conducted in the presence of an additional assimilable carbon source (5 g glucose kg⁻¹ soil). In the presence of glucose, SDZ affected soil respiration as well as the bacterial community structure: Additional bands appeared and some bands already visible at the beginning of incubations increased in intensity. A clear relationship between SDZ concentrations and changes in DGGE patterns became visible. During 48 days of incubation, changes in DGGE patterns were minimal in microcosms with 50 mg SDZ kg⁻¹soil indicating an inhibition of strains, which were capable of growing on glucose in the presence of lower SDZ concentrations. Only a few soil bacterial isolates (5 out of 47 strains tested) were weakly inhibited by SDZ in agar diffusion disk tests. Contrastingly, CTC inhibited growth of 12 soil bacterial isolates significantly in disk tests, but no effects on soil respiration and bacterial community structure could be observed. In the presence of the soil matrix the growth inhibitory potential of CTC decreased due to adsorption or complexation. This was confirmed in growth inhibition experiments with soil suspensions and time-dependent sampling.     

不同秸秆还田方式对和田风沙土土壤微生物 多样性的影响

秸秆还田是有效利用秸秆资源的重要途径,能够提高土壤养分含量、调节土壤微生物的群落结构和多样性,但目前还缺乏不同秸秆还田方式对新疆沙化土壤肥力和微生物多样性影响的系统报道。为探索新疆沙化土壤肥力可持续提升模式,于2010—2012年在和田风沙土土壤上设置秸秆直接还田(NPKS)、过腹还田(NPKM,15.0 t×hm~(-2))和炭化还田(NPKB1,2.5 t×hm~(-2);NPKB2,15.0 t×hm~(-2))定位试验,研究不同秸秆还田处理对和田风沙土土壤养分、微生物数量、土壤酶活性和Biolog碳源利用的影响。结果表明:1)与单施化肥(NPK)相比,不同秸秆还田方式均能显著提高风沙土土壤养分含量,其中NPKM处理效果最好,其次是NPKB2处理,NPKS和NPKB1处理分别为第3和第4。2)不同秸秆还田方式对土壤微生物数量影响差异显著,均增加了土壤中细菌、放线菌和生理菌群的数量,与NPK处理相比,细菌数量NPKB2处理最高,放线菌数量NPKM处理最高,分别显著提高了413.16%和574.19%。但NPKB1和NPKB2处理对生理菌群数量的提升效果好于NPKS处理和NPKM处理。土壤酶活性,不同秸秆还田方式总体好于NPK处理,NPKM处理的提升效果最好。3)Biolog碳源利用分析表明不同秸秆还田方式均能提高风沙土土壤微生物活性和丰富度指数。主成分分析表明,不同秸秆还田方式土壤微生物群落明显不同,起分异作用的碳源主要为羧酸类和糖类。聚类分析显示NPKB2和NPKM处理之间、NPKB1和NPKS处理之间土壤微生物功能相似。由此可以看出,不同秸秆还田方式均能显著提高和田沙化土壤微生物活性和功能多样性,但不同方式的增效不同。从3年定位试验结果看,秸秆过腹还田和炭化还田的效果较好,秸秆直接粉碎还田有增加土传病害的风险。该结果将为南疆沙化土壤肥力可持续提升提供一定的理论指导。     

植物残体分解过程中微生物群落变化影响因素研究进展

植物残体是土壤有机质的重要来源,研究分解植物残体的微生物群落结构及其演替规律日益受到重视。本文综述了影响植物残体分解过程中微生物群落结构和功能变化的3个主要因素:植物残体的性质、土壤和气候环境因素、农艺措施,这些因素通过影响微生物本身的活性和植物残体分解过程中化学组成的变化从而导致微生物群落的变化,同时植物残体腐解过程中微生物群落存在明显的演替现象。以上因素的影响并不是孤立的,而是相互联系和制约的。未来针对野外田间条件下植物残体的分解过程,仍需深入研究关键微生物群落的演替规律以及不同影响因素的交互作用机制。     

Rapid effects of plant species diversity and identity on soil microbial communities in experimental grassland ecosystems

Changes in plant community structure, including the loss of plant diversity may affect soil microbial communities. To test this hypothesis, plant diversity and composition were experimentally varied in grassland plots cultivated with monocultures or mixtures of 2, 3 or 4 species. We tested the effects of monocultures versus mixtures and of plant species composition on culturable soil bacterial activity, number of substrates used and catabolic diversity, microbial biomass N, microbial respiration, and root biomass. These properties were all measured 10 months after seeding the experiment. Soil bacterial activity, number of substrates used and catabolic diversity were measured in the different plant communities using BIOLOG GN and GP microplates, which are redox-based tests measuring capacity of soil culturable bacteria to use a variety of organic substrates. Microbial biomass N, microbial respiration, and root biomass were insensitive to plant diversity. Culturable soil microbial activity, substrates used and diversity declined with declining plant diversity. Their activity, number of substrates used and diversity were significantly higher in plots with 3 and 4 plant species than in monocultures and in plots with 2 species. There was also an effect of plant species composition. Culturable soil microbial activity and diversity was higher in the four-species plant community than in any of the plant monocultures suggesting that the effect of plant diversity could not be explained by the presence of a particular plant species. Our results showed that changes in plant diversity and composition in grassland ecosystems lead to a rapid response of bacterial activity and diversity.     

Effects of soil frost on growth, composition and respiration of the soil microbial decomposer community

Most climate change scenarios predict that the variability of weather conditions will increase in coming decades. Hence, the frequency and intensity of freeze-thaw cycles in high-latitude regions are likely to increase, with concomitant effect on soil carbon biogeochemistry and associated microbial processes. To address this issue we sampled riparian soil from a Swedish boreal forest and applied treatments with variations in four factors related to soil freezing (temperature, treatment duration, soil water content and frequency of freeze-thaw cycles), at three levels in a laboratory experiment, using a Central Composite Face-centred (CCF) experimental design. We then measured bacterial (leucine incorporation) and fungal (acetate in ergosterol incorporation) growth, basal respiration, soil microbial phospholipid fatty acid (PLFA) composition, and concentration of dissolved organic carbon (DOC). Fungal growth was higher in soil exposed to freeze-thawing perturbations and freezing temperatures of −6 °C and −12 °C, than under more constant conditions (steady 0 °C). The opposite pattern was found for bacteria, resulting in an increasing fungal-to-bacterial growth ratio following more intensive winter conditions. Soil respiration increased with water content, decreased with treatment duration and appeared to mainly be driven by treatment-induced changes in the DOC concentration. There was a clear shift in the PLFA composition at 0 °C, compared with the two lower temperatures, with PLFA markers associated with fungi as well as a number of unsaturated PLFAs being relatively more common at 0 °C. Shifts in the PLFA pattern were consistent with those expected for phenotypic plasticity of the cell membrane to low temperatures. There were small declines in PLFA concentrations after freeze-thawing and with longer durations. However, the number of freeze-thaw events had no effect on the microbiological variables. The findings suggest that the higher frequency of freeze-thaw events predicted to follow the global warming will likely have a limited impact on soil microorganisms.     

Functional resilience of soil microbial communities depends on both soil structure and microbial community composition

The effects of soil structure and microbial community composition on microbial resistance and resilience to stress were found to be interrelated in a series of experiments. The initial ability of Pseudomonas fluorescens to decompose added plant residues immediately after a copper or heat stress (resistance) depended significantly on which of 26 sterile soils it was inoculated into. Subsequent studies showed that both the resistance and subsequent recovery in the ability of P. fluorescens to decompose added plant residues over 28 days after stress (resilience) varied significantly between a sandy and a clay-loam soil. Sterile, sandy and clay-loam soil was then inoculated with a complex microbial community extracted from either of the soils. The resulting microbial community structure depended on soil type rather than the source of inoculum, whilst the resistance and resilience of decomposition was similarly governed by the soil and not the inoculum source. Resilience of the clay-loam soil to heat stress did not depend on the water content of the soil at the time of stress, although the physical condition of the soil when decomposition was measured did affect the outcome. We propose that soil functional resilience is governed by the physico-chemical structure of the soil through its effect on microbial community composition and microbial physiology.     

Shifts in bacterial community structure associated with inputs of low molecular weight carbon compounds to soil

Low molecular weight carbon (C) substrates are major drivers of bacterial activity and diversity in the soil environment. However, it is not well understood how specific low molecular weight C compounds, which are frequently found in root exudates and litter leachates, influence bacterial community structure or if there are specific groups of soil bacteria that preferentially respond to these C inputs. To address these knowledge gaps, we added three simple C substrates representative of common root exudate compounds (glucose, glycine, and citric acid) to microcosms containing three distinct soils from a grassland, hardwood forest, and coniferous forest. CO₂ production was assessed over a 24 h incubation period and, at the end of the incubation, DNA was extracted from the samples for assessment of bacterial community structure via bar-coded pyrosequencing of the 16S rRNA gene. All three C substrates significantly increased CO₂ production in all soils; however, there was no relationship between the magnitude of the increase in CO₂ production and the shift in bacterial community composition. All three substrates had significant effects on overall community structure with the changes primarily driven by relative increases in β-Proteobacteria, γ-Proteobacteria, and Actinobacteria. Citric acid additions had a particularly strong influence on bacterial communities, producing a 2-5-fold increase in the relative abundance of the β-Proteobacteria subphylum. These results suggest that although community-level responses to substrate additions vary depending on the substrate and soil in question, there are specific bacterial taxa that preferentially respond to the substrate additions across soil types.     

Effects of tree identity dominate over tree diversity on the soil microbial community structure

This study investigated the possible effects of tree species diversity and identity on the soil microbial community in a species-rich temperate broad-leaved forest. For the first time, we separated the effects of tree identity and tree species diversity on the link between above and belowground communities in a near-natural forest. We established 100 tree clusters consisting of each three tree individuals represented by beech (Fagus sylvatica L.), ash (Fraxinus excelsior L.), hornbeam (Carpinus betulus L.), maple (Acer pseudoplatanus L.), or lime (Tilia spec.) at two different sites in the Hainich National Park (Thuringia, Germany). The tree clusters included one, two or three species forming a diversity gradient. We investigated the microbial community structure, using phospholipid fatty acid (PLFA) profiles, in mineral soil samples (0–10 cm) collected in the centre of each cluster.The lowest total PLFA amounts were found in the pure beech clusters (79.0 ± 23.5 nmol g⁻¹ soil dw), the highest PLFA amounts existed in the pure ash clusters (287.3 ± 211.3 nmol g⁻¹ soil dw). Using principle components analyses (PCA) and redundancy analyses (RDA), we found only for the variables ‘relative proportion of beech trees’ and ‘living lime fine root tips associated with ectomycorrhiza’ a significant effect on the PLFA composition. The microbial community structure was mainly determined by abiotic environmental parameters such as soil pH or clay content. The different species richness levels in the clusters did not significantly differ in their total PLFA amounts and their PLFA composition. We observed a tendency that the PLFA profiles of the microbial communities in more tree species-rich clusters were less influenced by individual PLFAs (more homogenous) than those from species-poor clusters.We concluded that tree species identity and site conditions were more important factors determining the soil microbial community structure than tree species diversity per se.     

广谱抗真菌蛋白转基因水稻秸秆模拟还田对土壤真菌群落结构的影响

为探讨广谱抗真菌蛋白转基因水稻秸秆降解对土壤真菌群落结构的影响,本文在室温条件下进行田间秸秆还田模拟试验,设不添加秸秆(S)、添加转基因水稻‘转品1’秸秆(S-Z1)、添加转基因水稻‘转品8’秸秆(S-Z8)、添加非转基因水稻‘七丝软粘’秸秆(S-CK)4个土壤处理,采用传统的平板计数法和变性梯度凝胶电泳(denatured gradient gel electrophoresis,DGGE)技术,分析广谱抗真菌蛋白转基因水稻秸秆模拟还田过程中土壤可培养真菌数和土壤真菌群落的变化情况。平板计数结果表明,在秸秆降解的第40 d,转基因水稻秸秆处理(S-Z1、S-Z8)与非转基因水稻秸秆处理(S-CK)土壤之间的可培养真菌数差异显著,但秸秆降解中后期(50~90 d),S-Z1、S-Z8和S-CK之间土壤可培养真菌数的差异均不显著。真菌18S r RNA的PCR-DGGE图谱显示,S-Z1、S-Z8和S-CK在秸秆降解过程中没有显著不同的条带出现,仅有个别条带在亮度上存在差异。DGGE图谱条带多样性分析结果表明,在秸秆降解的个别时间段,S-Z1、S-Z8和S-CK之间在丰富度和Shannon-Wiener多样性指数上存在显著差异,而在秸秆降解的整个过程均匀度指数差异均不显著。对DGGE主要条带和差异性条带进行克隆测序后发现,子囊菌占最大比重,其次为担子菌、壶菌,而在转基因和非转基因土壤处理间亮度上存在差异的条带属于子囊菌。以上研究结果表明,广谱抗真菌蛋白转基因水稻秸秆降解对土壤真菌群落结构的影响是短暂的、不持续的。     

转Bt基因棉对土壤无脊椎动物群落结构的影响

采用干、湿漏斗分离法,运用群落生态学方法,研究了转Bt基因棉"GK12"和"新棉33B"对棉田0～15 cm土层土壤无脊椎动物群落结构的影响.结果表明,线虫和螨类为棉田土壤无脊椎动物优势类群,其频度分别为54%以上和18%以上,与亲本常规棉"泗棉3号"相比,"GK12"提高了土壤线蚓数量,但降低了某些土壤无脊椎动物类群(如同翅目、目和双翅目)的数量;两种Bt棉田中,"新棉33B"棉田的同翅目昆虫数量显著高于"GK12",蜘蛛目数量显著低于"GK12"棉田,其他土壤无脊椎动物类群的数量则基本上无显著差异."GK12"显著降低了土壤无脊椎动物类群的丰富度、多样性和均匀度;两种Bt棉中,"新棉33B"棉田土壤无脊椎动物类群的丰富度、多样性和均匀度较高.Renyi多样性指数曲线也表明,"GK12"棉田各土层土壤无脊椎动物群落的多样性均显著低于"泗棉3号"棉田;"新棉33B"棉田各土层土壤无脊椎动物群落的多样性高于"GK12",但10～15 cm土层常见类群和优势类群的多样性较低.在各土层中,土壤无脊椎动物数量、多样性指数和均匀度指数动态在不同类型棉田趋势基本相同.7～11月期间,10月是土壤无脊椎动物数量的高峰期,此时在"泗棉3号"棉田土壤无脊椎动物在0～5 cm的表层和10～15 cm的深层土壤均较多,在"GK12"和"新棉33B"棉田则集中于10～15 cm的深层土壤.11月, "泗棉3号"土壤无脊椎动物类群的多样性和均匀度呈下降趋势,"GK12"则呈上升趋势.可见,种植Bt棉"GK12"可改变某些土壤无脊椎动物类群的数量,降低类群的丰富度、多样性和均匀度;两种Bt棉田的土壤无脊椎动物群落结构也有一定的差异,"新棉33B"棉田土壤无脊椎动物群落的多样性高于"GK12".     

Enhanced bioremediation of PAH-contaminated soil by wheat bran and microbial community response

ABSTRACT

Microcosms were set up containing a PAH polluted soil to investigate biostimulation (addition of wheat bran and fertilizer) and bioaugmentation (inoculation with Pseudomonas sp. SB). After 60 d the fertilizer + wheat bran gave the highest PAH degradation. The degradation rate was 42.2%, significantly higher than the 18.7% in the fertilizer only treatment. Principal coordinate analysis (PCoA) indicates that wheat bran treatment can significantly alter soil bacterial and fungal communities. In addition, wheat bran promoted the enrichment of some soil bacteria such as Bacillaceae, Xanthomonadaceae, Streptomycetaceae, and Chitinophagaceae, and the fungi Talaromyces, Humicola, unclassified_Chaetomiaceae and Mortierella. These results highlight the potential of wheat bran application to reduce the PAHs detected in soil.     

秸秆还田方式对农田土壤结构及冬小麦产量的影响

为探索一种能够充分发挥秸秆改良土壤结构和提高作物产量作用的秸秆还田措施, 通过2 a小区试验, 以传统的秸秆还田方式[长秸秆(50 mm)覆盖或翻压还田, CK1、CK2]作为对照, 对比研究了粉碎、氨化秸秆以及与无机土壤改良剂(硫酸钙)混合翻压施用措施对农田土壤结构及冬小麦产量的影响。结果表明, 粉碎并氨化秸秆施入土壤后, 能显著(P<0.05)降低耕层(0~15 cm)土壤的容重, 增加土壤孔隙度, 但对耕层以下土壤容重及孔隙度改善效果不明显; 氨化秸秆施入土壤后较未氨化秸秆能显著(P<0.05)增加0~15 cm土壤中>0.25 mm土壤团聚体含量, 粉碎并氨化秸秆能显著(P<0.05)降低土壤团聚体分形维数, 提高0~15 cm土壤平均重量直径和几何平均直径各项评价指标。此外, 冬小麦穗粒数、1 m2有效穗数、千粒重和地上部总干物质量与籽粒产量的相关系数分别为0.30(P>0.05)、0.76(P<0.01)、 0.89(P<0.01)和0.88(P<0.01), 提高冬小麦有效穗数或地上部总干物质量可能是增加作物产量的主要途径。粉碎并氨化秸秆还田较秸秆覆盖能显著(P<0.05)提高冬小麦有效穗数; 粉碎并氨化秸秆与无机土壤改良剂(硫酸钙)混合施用措施提高冬小麦产量效果最为显著, 在冬小麦2个生长季比长秸秆覆盖还田(CK1)分别增产11.12%和17.84%, 比长秸秆翻压还田(CK2)分别增产7.39%和16.58%, 是本试验最佳秸秆还田方式。该研究成果可为干旱、半干旱地区改良秸秆还田措施、提高作物产量提供理论依据。