喀斯特地区三种人工林土壤微生物群落结构特征

为揭示不同人工植被修复模式对喀斯特土壤微生物群落的影响,采用氯仿熏蒸提取法和磷脂脂肪酸(phospholipid fatty acid, PLFA)法研究人工构建的降香黄檀(Dalbergia odorifera)纯林(PDOP)、顶果木(Acrocarpus fraxinifolius)纯林(PAFP)、顶果木×降香黄檀混交林(MADP)对土壤微生物生物量及土壤微生物群落结构的影响。结果表明:(1)PDOP的土壤微生物生物量碳(MBC)和微生物生物量氮(MBN)含量显著高于PAFP和MADP,PAFP显著高于MADP。(2)三种人工林土壤真菌、丛枝菌根真菌和总PLFA含量无显著差异,但PDOP土壤细菌、放线菌、丛枝菌根真菌和总PLFA含量均高于PAFP和MADP,PAFP高于MADP。PDOP的土壤细菌、革兰氏阳性菌、革兰氏阴性菌、放线菌的PLFA含量显著高于MADP。MADP的真菌细菌比显著高于PDOP,但与PAFP无显著差异。(3)冗余分析表明,土壤阳离子交换量、pH和C:N是影响土壤微生物群落组成的最主要影响因子。从三种人工林的土壤微生物生物量及微生物群落结构来看,在喀斯特地区MADP并未显示出酸性土地区混交林提高土壤微生物生物量、改善土壤微生物群落结构的优势,但混交林的真菌细菌比最高,更有利于提高土壤生态系统的稳定性。     

除草剂对桉树人工林下植物及土壤微生物群落的影响

除草剂在桉树人工林中的应用越来越普遍,但关于除草剂对桉树人工林林下植物和土壤微生物群落的影响知之甚少。通过桉树人工林低剂量高频率(LHF)、中剂量中频率(MMF)、高剂量低频率(HLF)除草剂喷施试验,并与人工除草(MT)为对照,比较分析不同剂量、不同频率除草剂施用对林下植物和土壤微生物群落的影响。结果表明,施用除草剂导致桉树人工林林下植物种类和功能群组成发生显著变化,但并未显著降低林下植物群落物种丰富度和多样性,随除草剂施用频率的降低及恢复时间的增加,物种丰富度及多样性指数呈恢复趋势。除草剂施用也导致土壤养分含量降低。除草剂通过对林下植物群落和土壤养分的负面影响间接影响土壤微生物群落。LHF显著降低藤本植物而显著提高蕨类植物功能群的重要值,从而显著降低了微生物群落、真菌和放线菌的磷脂脂肪酸(PLFA)含量。MMF显著降低木本和藤本植物而显著提高禾草植物功能群的重要值,导致土壤微生物群落和放线菌的PLFA含量显著降低。HLF未显著影响林下植物及土壤微生物群落,但土壤全磷含量显著降低,速效磷含量也大幅下降。施用除草剂显著降低了土壤微生物生物量碳、氮的含量。因此,生产上应减少除草剂的施用,...     

施磷对干旱胁迫下箭竹根际土壤养分及微生物群落的影响

以箭竹及其根际土壤作为研究对象,采用两因素随机区组实验,设置2种水分处理（正常浇水和干旱胁迫）和2种施磷量处理（施磷和不施磷）,探究施磷对干旱胁迫下箭竹根际土壤养分及微生物群落结构和多样性的影响。结果表明：（1）干旱胁迫显著降低了箭竹根际土壤中微生物量碳、可溶性有机氮和有效磷的含量,虽对箭竹根际土壤微生物群落的多样性无显著影响,但显著降低了箭竹根际土壤中总PLFA（phospholipid fatty acid contents）的含量和真菌、细菌、革兰氏阳性菌与革兰氏阴性菌的PLFA含量以及革兰氏阳性菌/革兰氏阴性菌的PLFA比值,显著改变了箭竹根际土壤微生物群落结构,结果显著降低了箭竹的生物量。（2）施磷显著增加了受旱箭竹根际土壤中微生物量碳和有效磷的含量,虽大体上对受旱箭竹根际土壤微生物群落的多样性无显著影响,但显著增加了受旱箭竹根际土壤中总PLFA和真菌PLFA的含量,并在一定程度上增加了细菌、革兰氏阳性菌、革兰氏阴性菌和放线菌的PLFA含量以及革兰氏阳性菌/革兰氏阴性菌和真菌/细菌的PLFA比值,也在一定程度上改善了受旱箭竹根际土壤微生物群落结构,从而改善受旱箭竹的生长。（3）主成分分析表明,干旱对箭竹根际土壤微生物群落结构的影响显著,而施磷的影响不明显。（4）相关分析发现,箭竹根际土壤微生物群落结构与箭竹根际土壤微生物量碳、可溶性有机氮及箭竹生物量呈显著正相关。综上,干旱降低了箭竹根际土壤养分含量和微生物生物量,改变了箭竹根际土壤微生物群落结构,抑制了箭竹的生长;施磷能增加受旱箭竹根际土壤养分含量和微生物生物量,改善受旱箭竹根际土壤微生物群落结构,进而改善受旱箭竹的生长。     

南亚热带3种人工林土壤微生物生物量和微生物群落结构特征

以我国南亚热带格木、红椎和马尾松人工林为对象,采用氯仿熏蒸浸提法和磷脂脂肪酸法(PLFA)分析了林地土壤微生物生物量和微生物群落结构组成.结果表明: 林分和季节因素均显著影响土壤微生物生物量、总PLFAs量、细菌PLFAs量和真菌PLFAs量,且干季林分下的土壤微生物生物量、总PLFAs量、单个PLFA量均大于雨季.红椎人工林土壤微生物生物量碳(MBC)和总PLFAs量最高,而格木人工林土壤微生物生物量氮(MBN)最高.土壤pH值对土壤丛枝菌根真菌(16:1ω5c)的影响达到极显著正相关水平.土壤总PLFAs量、革兰氏阳性菌(G⁺)以及腐生真菌(18:2ω6,9c)、革兰氏阳性菌/革兰氏阴性菌(G⁺/G^-)与土壤有机碳、全氮和全磷显著相关,表明土壤有机碳、全氮、全磷含量是影响该地区土壤微生物数量和种类的重要因素.外生菌根真菌(18:1ω9c)和丛枝菌根真菌与土壤碳氮比值呈极显著相关.     

Field assessment of soil biological and chemical quality in response to crop management practices

Soil microbiological and chemical aspects were evaluated to determine the effects of conservation tillage and crop rotation on soil fertility over a 16-year period. A field trial was established to compare two cropping systems (continuous soybean and maize/soybean, soybean/maize rotation). In addition, maize (Zea mays L.) and soybean (Glycine max L., Merr) were grown in two different tillage systems: no tillage and reduced tillage. Soil populations of Trichoderma spp., Gliocladium spp. and total fungi were more abundant when maize or soybean were under conservation tillage and in the maize/soybean and soybean/maize rotation, than in continuous soybean. Furthermore, higher levels of microbial respiration and fluorescein diacetate hydrolysis (FDA), were recorded under no tillage systems. However, soil counts of Actinomycetes and Pythium spp., and Pythium diversity together with soil microbial biomass were not affected by the field treatments. To establish a correlation with soil biological factors, soil chemical parameters, such as pH, organic matter content, total N, electrical conductivity, N–NO₃ ⁻ and P were also quantified, most of the correlations being significantly positive. Under no tillage there was a clear increase of the amount of crop residues and the C and N soil content due to the presence of residues. Also the distribution of crop residues in surface soil due to zero tillage and the quality of these residues, depending on the crop rotation employed, improved on soil biological and chemical characteristics. Crop yield was also enhanced by zero tillage through the management of residues. Although yield values were not directly associated with the development of microorganisms, both yield and microorganisms were influenced by crop management. These results suggest that measuring soil properties over a long period helps to define effective management strategies in order to preserve soil conditions.     

A Comparison of Soil Microbial Community Structure, Protozoa and Nematodes in Field Plots of Conventional and Genetically Modified Maize Expressing the Bacillus thuringiens is CryIAb Toxin

Field trials were established at three European sites (Denmark, Eastern France, South-West France) of genetically modified maize (Zea mays L.) expressing the CryIAb Bacillus thuringiensis toxin (Bt), the near-isogenic non-Bt cultivar, another conventional maize cultivar and grass. Soil from Denmark was sampled at sowing (May) and harvest (October) over two years (2002, 2003); from E France at harvest 2002, sowing and harvest 2003; and from SW France at sowing and harvest 2003. Samples were analysed for microbial community structure (2003 samples only) by community-level physiological-profiling (CLPP) and phospholipid fatty acid analysis (PLFA), and protozoa and nematodes in all samples. Individual differences within a site resulted from: greater nematode numbers under grass than maize on three occasions; different nematode populations under the conventional maize cultivars once; and two occasions when there was a reduced protozoan population under Bt maize compared to non-Bt maize. Microbial community structure within the sites only varied with grass compared to maize, with one occurrence of CLPP varying between maize cultivars (Bt versus a conventional cultivar). An overall comparison of Bt versus non-Bt maize across all three sites only revealed differences for nematodes, with a smaller population under the Bt maize. Nematode community structure was different at each site and the Bt effect was not confined to specific nematode taxa. The effect of the Bt maize was small and within the normal variation expected in these agricultural systems.     

Effect of Zero Tillage and Residues Conservation on Continuous Maize Cropping in a Subtropical Environment (Mexico)

The effects of zero tillage and residue conservation in continuous maize-cropping systems are poorly documented, especially in the tropics, and are expected to vary highly with climatic conditions and nitrogen availability. In the present study, maize was cultivated during the wet and dry seasons in central Mexico for three consecutive years, under different treatments combining tillage with residue management techniques and with nitrogen rates. In some treatments, maize was also intercropped with jackbean, Canavalia ensiformis L. (DC). Yield and yield components as well as physiological traits and soil characteristics were assessed during the wet and dry seasons for the third year of cultivation. During the wet season, zero tillage was associated with less biomass and grain yield. Leaf chlorophyll concentration was smaller under zero tillage, suggesting less nitrogen uptake. Both zero tillage and residue conservation reduced early growth and strongly increased ear rot. During the dry season, zero tillage was associated with greater root mass, as measured by electrical capacitance. Residue conservation decreased the anthesis-silking interval, suggesting better water uptake. There was, however, no significant effect of tillage or residue management practices on yield. Zero tillage was found to be associated with increased soil bulk density, nitrogen concentration and microbial biomass organic carbon. Residue conservation increased soil carbon concentration as well as microbial biomass organic carbon. Intercropping with jackbean and conservation of its residues in addition to maize residues increased soil nitrogen concentration. Further investigation may provide more information on the factors related to zero tillage and residue conservation that affect maize early growth, and determine to which extent the observed modifications of soil chemical and physical properties induced by conservation tillage will further affect maize yield.     

深松对乌拉尔甘草根际土壤养分以及微生物群落功能多样性的影响

通过大田试验和室内分析相结合,研究了深松对乌拉尔甘草根际土壤养分和微生物群落功能多样性的影响,以期为乌拉尔甘草人工种植地土壤耕作措施优化和土壤环境改良提供依据。结果表明,与未深松(常规耕作)处理相比,深松处理对乌拉尔甘草根际土壤0—20 cm耕层土壤养分含量无显著性影响,可显著提高乌拉尔甘草根际土壤20—40 cm耕层有机质、全氮、全磷和全钾的含量,分别提高了60.8%、65.3%、48.9%和86.8%;明显增加了0—20 cm和20—40 cm耕层细菌、真菌和放线菌的数量(P0.05),3种类型的微生物数量均呈现出上层大于下层,深松大于未深松的变化趋势。在156 h的微生物温育期内,深松处理下不同土层的平均颜色变化率(AWCD)均显著高于未深松处理,并显著提高了AWCD的利用率(72 h,P0.05),较未深松分别提高了35.5%和130.8%。与未深松处理相比,深松处理显著提高了土壤微生物的多样性指数(H、S、D)。主成分分析(PCA)表明,深松优化了乌拉尔甘草根际土壤微生物的群落组成;聚合物、羧酸类化合物、氨基酸和碳水化合物是深松处理下根际土壤微生物利用的主要碳源。总而言之,深松处理显著提高乌拉尔甘草根际土壤养分含量、微生物数量和微生物多样性指数,改变了微生物群落功能多样性,造成这种差异的主要原因可能是深松改变了土壤耕层结构,改善了微生物的生存环境。因此,深松对乌拉尔甘草人工种植地土壤质量的改良有积极作用。     

氮素添加对贝加尔针茅草原土壤团聚体微生物群落的影响

大气氮沉降增加作为全球气候变化的重要因素,其对土壤生态系统影响的研究受到了生态学家的广泛关注。土壤微生物是有机物分解和养分循环的主要参与者,在维持土壤的功能多样性和可持续发展方面发挥着重要的作用。氮沉降的激增会引起土壤微生物群落结构和功能的改变。土壤中营养物质在不同团聚体组分中分布的不均匀,为微生物提供了空间异质微生境。为揭示草原土壤不同粒径团聚体中微生物群落分布及其对氮素添加响应特征。自2010年起,在内蒙古贝加尔针茅草原典型地段设置N₀（0 kg hm^-2 a^-1）、N₁₅（15 kg hm^-2 a^-1）、N₃₀（30 kg hm^-2 a^-1）、N₅₀（50 kg hm^-2 a^-1）、N₁₀₀（100 kg hm^-2 a^-1）、N₁₅₀（150 kg hm^-2 a^-1）6个氮素添加处理模拟氮沉降野外控制试验。采用磷脂脂肪酸（phospholipid fatty acid,PLFA）法测定>2 mm、0.25-2 mm和<0.25 mm 3个粒径土壤团聚体中微生物PLFA含量,探讨氮素添加对土壤团聚体微生物群落结构的影响。结果表明：氮素添加提高了土壤碳、氮含量,降低了土壤pH。氮素添加显著提高了0.25-2 mm土壤团聚体微生物群落磷脂脂肪酸总量、真菌磷脂脂肪酸含量和真菌/细菌（Fungi/bacteria,F/B）、革兰氏阳性菌/革兰氏阴性菌（Gram-positive bacteria/gram-negative bacteria,G⁺/G^-）的比值（P<0.05）,降低了土壤团聚体微生物Margalef丰富度指数（P<0.05）。相关性分析表明,土壤团聚体微生物总PLFAs、真菌PLFAs含量、G⁺/G^-、F/B与土壤有机碳、全氮含量呈显著正相关关系,与C/N值负相关。综合研究表明,连续8年氮素添加显著提高了土壤有机碳和全氮含量、降低了土壤pH;提高了0.25-2 mm土壤团聚体真菌群落,土壤有机碳、全氮的固持与真菌群落的增加有关。     

肉苁蓉寄主梭梭根际土壤微生物种类及群落结构特征

为探索梭梭根际土壤微生物结构特征及其与肉苁蓉寄生的关系,应用磷脂脂肪酸(PLFA)法分析了5—8月份梭梭生长季节的根际土壤微生物种类及群落结构特征,采用湿筛倾注-蔗糖离心法对其根际土壤AM真菌进行了初步分离和鉴定,并分析了肉苁蓉寄生与梭梭根际微生物及环境因子间的相关性。结果表明,5—7月3个月份的梭梭根际土壤微生物磷脂脂肪酸种类及含量均显著高于8月份,总磷脂脂肪酸和AM真菌磷脂脂肪酸以6月份含量最高。梭梭根际土壤共鉴定出AM真菌4属35种,它们分别为球囊霉属(Glomus)22种、无梗囊霉属(Acaulospora)7种、多孢囊霉属(Diversispora)3种和巨孢囊霉属(Gigaspora)3种。其中以黑球囊霉(Glomus melanosporum)和双网无梗囊霉(Acaulospora bireticulata)为优势种群,并且发现了与寄生有关的巨孢囊霉属AM真菌。6月份和8月份的AM真菌孢子数量最多,而5月份的AM真菌孢子数量最低。6月份梭梭根际土壤提取液得到的肉苁蓉种子萌发率(65.94%)和田间接种寄生率(59.19%)均为最高值,而5月份土壤提取液测试得到的肉苁蓉种子萌发率最低。因此,推测梭梭根际AM真菌可能参与了肉苁蓉的寄生过程。相关分析表明梭梭根际土壤微生物种类和数量主要与土壤温湿度和土壤理化性质相关性较大,其中可能与寄生有关的真菌数量与土壤温度呈显著正相关;肉苁蓉寄生率与土壤温度及土壤养分呈显著负相关。研究为解析梭梭根际土壤微生物在肉苁蓉寄生过程中的作用以及指导肉苁蓉人工种植提供参考。     

Crop rotation and tillage systems as a proactive strategy in the control of peanut fungal soilborne diseases

Soil management practices can affect the population dynamics of soil microbial communities. Cultural practices can be adequately combined to benefit natural populations of microorganisms that may have a role in biological control (actinomycetes, Trichoderma spp., and Gliocladium spp.), thus contributing to the management of peanut fungal soilborne diseases in a sustainable manner within ecological boundaries. During six agricultural cycles, rhizosphere soil samples were taken from a field subjected to crop rotation (soybean, peanut, and maize), peanut being under two tillage systems (no till, reduced tillage) with the aim of quantifying populations of soil microorganisms. The incidence of diseases caused by soilborne fungi in peanut was determined at harvest. The highest amount of actinomycetes, Trichoderma spp., and Gliocladium spp. were recorded when maize was the preceding crop. Regarding tillage systems, the populations of the three groups of microorganisms were higher in peanut under no tillage than under reduced tillage. Under these conditions, the lowest incidence of peanut blight (Sclerotinia minor) and root rot (strains of Fusarium solani) was observed, suggesting a possible natural control of peanut soilborne pathogens. The quantification of actinomycetes, Trichoderma spp., and Gliocladium spp. was used as a tool to explore the impacts of different management systems on microbial groups that may be involved in the biological control of soilborne diseases, with the aim of combining those practices that improve native populations of possible beneficial microorganisms. This manipulation can provide sustainable management strategies in the control of soilborne diseases, avoiding the use of artificial inoculations of microorganisms, and reducing agrochemical application.     

Long-Term Phosphorus Fertilization Impacts Soil Fungal and Bacterial Diversity but not AM Fungal Community in Alfalfa

Soil function may be affected by cropping practices impacting the soil microbial community. The effect of different phosphorus (P) fertilization rates (0, 20, or 40 kg P₂O₅ ha⁻¹) on soil microbial diversity was studied in 8-year-old alfalfa monocultures. The hypothesis that P fertilization modifies soil microbial community was tested using denaturing gradient gel electrophoresis and phospholipids fatty acid (PLFA) profiling to describe soil bacteria, fungi, and arbuscular mycorrhizal (AM) fungi diversity. Soil parameters related to fertility (soil phosphate flux, soluble P, moisture, phosphatase and dehydrogenase assays, and carbon and nitrogen content of the light fraction of soil organic matter) were also monitored and related to soil microbial ribotype profiles. Change in soil P fertility with the application of fertilizer had no effect on crop yield in 8 years, but on the year of this study was associated with shifts in the composition of fungal and bacterial communities without affecting their richness, as evidenced by the absence of effect on the average number of ribotypes detected. However, variation in soil P level created by a history of differential fertilization did not significantly influence AM fungi ribotype assemblages nor AM fungi biomass measured with the PLFA 16:1ω5. Fertilization increased P flux and soil soluble P level but reduced soil moisture and soil microbial activity, as revealed by dehydrogenase assay. Results suggest that soil P fertility management could influence soil processes involving soil microorganisms. Seasonal variations were also recorded in microbial activity, soil soluble P level as well as in the abundance of specific bacterial and fungal PLFA indicators of soil microbial biomass.     

Changes in Communities of Fusarium and Arbuscular Mycorrhizal Fungi as Related to Different Asparagus Cultural Factors

Asparagus (Asparagus officinalis) is a high-value perennial vegetable crop that has shown a marked decline in productivity after many years of continuous harvesting. This decline is caused by an increase in both abiotic (autotoxicity, harvesting pressure) and biotic stresses [fungal infections, mainly Fusarium crown and root rot (FCRR)]. To gain insight into disease development and possible mitigation strategies, we studied the effects of harvesting, time in the growing season, and field age on FCRR development, Fusarium species composition, and arbuscular mycorrhizal fungi (AMF) communities in both a controlled field experiment and an ecological survey of commercial fields. In one experiment, a 3-year-old asparagus field was subdivided into plots that were harvested or not and sampled throughout the growing season to assess short-term dominant Fusarium species shifts. In addition, diseased and healthy asparagus plants sampled from six commercial fields in the same geographical region were used to assess Fusarium and AMF communities in relation to different parameters. Fusarium and AMF communities were described by using a polymerase chain reaction (PCR)–denaturing gradient gel electrophoresis (DGGE) approach, and results were analyzed by mainly correspondence analysis and canonical correspondence analysis. Results showed that dominant Fusarium taxa assemblages changed throughout the growing season. Harvested plots had significantly more FCRR symptomatic plants at the end of the growing season, but this effect was not related with any trend in Fusarium community structure. Sampling site and plant age significantly influenced AMF community structure, whereas only sampling site consistently influenced the Fusarium community. Diseased and healthy plants harbored similar Fusarium and AMF communities. Shifts in Fusarium community might not be responsible for different disease incidence because they are ubiquitous regardless of plant health status or harvesting regime. The different incidence noted might rather be related to plant physiology, antagonist microbial communities, or soil parameters.     

川西亚高山不同林龄云杉人工林土壤微生物群落结构

以川西亚高山云杉人工林林地土壤为对象,采用磷脂脂肪酸(PLFA)法研究了4种不同林龄(50、38、27和20年)的人工林土壤微生物多样性和群落结构特征.结果表明: 随着林龄的增加,土壤有机碳和全氮含量逐步增加;土壤微生物Shannon多样性和Pielou均匀度指数则呈现先增后减的趋势.土壤微生物总PLFAs量、细菌PLFAs量、真菌PLFAs量、放线菌PLFAs量以及丛枝菌根真菌PLFAs量均表现为随林龄的增加而增加.主成分分析(PCA)表明,不同林龄人工林的土壤微生物群落结构之间存在显著差异,其中,第1主成分(PC1)和第2主成分(PC2)共同解释了土壤微生物群落结构总变异的66.8%.冗余分析(RDA)表明,对土壤微生物群落结构产生显著影响的环境因子分别为土壤有机碳、全氮、全钾以及细根生物量.随着人工造林时间的延长,土壤肥力和微生物生物量增加,森林生态系统的恢复进程稳定.     

长期养分添加对贝加尔针茅草原土壤微生物群落的影响

土壤微生物是土壤生态系统的重要组成部分,是土壤生态系统物质循环和能量流动的主要参与者,在维持土壤生态系统过程和功能方面发挥着关键作用。以内蒙古贝加尔针茅草原为研究对象,采用磷脂脂肪酸(PLFA)技术,探讨连续12年氮(N)、磷(P)、钾(K)养分单一添加和复合添加条件下草地土壤理化性质、微生物群落结构特征的变化及其主要影响因素。结果表明,长期养分添加条件下,土壤有机碳和全氮均无显著变化,但磷(P、NP、PK、NPK)和钾(K、NK、PK、NPK)添加处理分别显著提高了土壤速效磷和速效钾含量(P < 0.05)。单一氮添加显著增加了土壤硝态氮和铵态氮含量,并显著降低了土壤pH值(P < 0.05)。单一磷和钾添加均提高了土壤细菌、真菌、放线菌和总PLFA含量,而单一氮添加和复合养分添加(NP、NK、PK、NPK)均显著降低了以上指标的含量(P < 0.05)。此外,各养分添加处理均未显著改变革兰氏阳性细菌与革兰氏阴性细菌比(G⁺/G^-),但含氮的复合添加处理(NP、NK、NPK)均显著降低了真菌与细菌比 (F/B) (P < 0.05)。相关性分析结果表明,多种微生物PLFA含量与速效磷和铵态氮显著负相关,与土壤pH值显著正相关。基于冗余分析和随机森林模型分析发现土壤pH值和土壤磷含量是影响土壤微生物群落特征的主要驱动因素。综上,长期养分添加显著改变了土壤速效养分含量和土壤pH值,并显著影响了土壤微生物群落结构。     

硬化地表对不同树种土壤微生物群落结构和功能的影响

城市硬化地表可减少土壤有机物输入,并改变土壤理化性质,由此可能影响土壤微生物群落结构和功能,但目前国内外相关研究较少。为研究不同树种下土壤微生物群落对硬化地表的响应,设置透水硬化地表(Pervious pavement, P)、不透水硬化地表(Impervious pavement, IP)和自然地表(Control, C)3个处理水平的地表类型,并栽种北方常见的常绿针叶树油松(pine,Pinus tabulaeformis)和落叶阔叶树白蜡(ash,Fraxinus chinensis)。采用氯仿熏蒸浸提法、磷脂脂肪酸法(PLFA)及BIOLOG培养法分别测定了土壤微生物量、群落结构和功能多样性。结果表明:(1)与自然地表(C)相比,硬化地表下土壤微生物生物量碳、氮含量显著降低(P0.05),土壤微生物群落组成和群落功能多样性发生了改变。透水和不透水硬化地表下土壤微生物细菌、真菌数量降低,真菌/细菌(fungi/bacteria, F/B)、cy/pre(环丙基脂肪酸/前体结构cyclopropyl fatty acid/monoenoic precursors)和sat/mono(一般饱和脂肪酸/单不饱和脂肪酸normal saturated fatty acid/monounsaturated fatty acid)等环境压力指标均显著升高(P0.05),且土壤微生物cy/pre值在不透水硬化地表下显著高于透水硬化地表下,表明不透水硬化地表下土壤环境压力更大;不透水硬化地表下土壤微生物对糖类、氨基酸类、羧酸类、胺类和聚合物的利用显著降低(P0.05),微生物群落功能丰富度及多样性指数显著降低(P0.05)。(2)土壤微生物群落结构和功能多样性在不同树种间存在一定差异。油松树下土壤微生物真菌、丛枝菌根真菌(arbuscular mycorrhizal fungi, AMF)和F/B值在透水和不透水硬化地表下均显著降低(P0.05),而白蜡树下只在透水硬化地表下显著降低(P0.05);硬化地表使土壤微生物对糖类、氨基酸类和聚合物的利用强度在油松和白蜡树下表现出显著差异。硬化地表对土壤微生物的影响将进一步影响城市绿地的养分循环、树木生境和生态系统服务功能。     

Microbial communities in different soil types do not converge after diesel contamination

AIMS: To study the comparative effect of diesel addition and simulated bioremediation on the microbial community in three different soil types.METHODS AND RESULTS: Three different soils were amended with diesel and bioremediation treatment simulated by addition of nutrients. The progress of bioremediation, and the effect on the indigenous microbial communities, was monitored using microbiological techniques. These included basal respiration, sole carbon source utilization patterns using both a commercially-available substrate set and a set designed to highlight changes in hydrocarbon-utilizing bacteria, and phospholipid fatty acid (PLFA) profiling. The development of active hydrocarbon-degrading communities was indicated by the disappearance of diesel, increases in soil respiration and biomass, and large changes in the sole carbon source utilization patterns and PLFA profiles compared with control soils. However, comparison of the relative community structure of the three soils using PLFA profiling showed that there was no tendency for the community structure of the three different soil types to converge as a result of contamination. In fact, they became more dissimilar as a result. Changes in the sole carbon source utilization patterns using the commercially-available set of carbon sources indicated the same result as shown by PLFA profiling. The specially selected set of carbon sources yielded no additional information compared with the commercially-available set.CONCLUSIONS: Diesel contamination does not result in the development of similar community profiles in different soil types.SIGNIFICANCE AND IMPACT OF THE STUDY: The results suggest that different soils have different inherent microbial potential to degrade hydrocarbons, a finding that should be taken into account in impact and risk assessments. Following the development of the microbial community and its recovery is a useful and sensitive way of monitoring the impact and recovery of oil-contaminated soils.     

黄顶菊对不同入侵地植物群落及土壤微生物群落的影响

为明确不同入侵地植物群落和土壤生态对黄顶菊入侵的反馈机制,选取天津静海(JH)、河北沧州(CZ)、河北衡水(HS)及河南安阳(AY)4个黄顶菊入侵典型区域,研究黄顶菊对不同入侵地植物群落多样性、土壤理化及土壤微生物群落结构的影响,并进一步揭示植物群落、土壤养分和土壤微生物之间的相关关系。结果表明,黄顶菊入侵显著降低了JH、CZ和HS的植物群落多样性指数(P0.05),改变了四个地区的土壤理化性质,显著升高了不同入侵地真菌PLFA的含量、总PLFA的含量、真菌/细菌和革兰氏阴性菌/革兰氏阳性菌(P0.05),降低了土壤微生物的Margalef丰富度指数(P0.05),但均存在地区间差异;RDA和相关分析的结果表明,硝态氮、全氮的含量对植物群落的影响较大,而铵态氮的含量对土壤微生物群落结构的影响较大,除丰富度指数外,植物群落与土壤微生物群落的多样性指数之间存在显著的负相关关系(P0.05)。总之,黄顶菊改变了入侵地植物群落多样性,并且对入侵地土壤理化性质和土壤微生物群落结构产生了显著影响,且存在地区差异。本研究将为更好的理解外来植物的入侵机制及制定相应的防控策略提供理论依据。     

高寒半湿润沙地植物与土壤微生物多样性对植被恢复的响应

为探究植被恢复对高寒半湿润沙化脆弱生态系统的恢复效应,明确植物群落与土壤微生物多样性对恢复的响应,为高寒沙化植被恢复提供科学支撑。以青藏高原东南缘沙化地为对象,通过连续种植老芒麦(Elymus sibiricus)进行植被恢复,分析连续3年恢复后,植物群落物种组成与多样性的变化,土壤微生物群落不同季节数量与多样性的变化,探讨植物与土壤微生物多样性对植被恢复的响应特征。结果表明:老芒麦作为建群种促进植被恢复过程,3年后植物群落物种数量相较对照增加了13种,而物种种类相较对照新增14种,川甘亚菊(Ajania potaninii)从群落中消失,总体表现为短命植物和对水分需求较高的植物种类增加,植物群落物种多样性增加;土壤中微生物群落和微生物数量季节性变化剧烈,在非生长季节后期(4月),土壤细菌含量相较对照组增加了1.2倍(0-15 cm)与1.8倍(15-30 cm),真菌含量相较对照组增加了0.5倍(0-15 cm)和5.1倍(15-30 cm),放线菌相较对照组增加了1.5(0-15 cm)倍和4倍(15-30 cm);土壤微生物多样性显著增加。种植老芒麦恢复高寒半湿润沙化脆弱生态系统,促进了植物群落物种多样性与土壤微生物群落多样性恢复,这将有助于高寒沙化生态系统恢复过程。     

保护性耕作对土壤微生物群落及其介导的碳循环功能的影响

农田生态系统耕作方式显著影响土壤微生物群落结构和功能,进而影响土壤微生物介导的土壤碳循环过程。以免耕结合作物秸秆还田为核心的保护性耕作是提升土壤碳汇功能和肥力的重要措施,其中土壤微生物发挥了关键作用。尽管有较多关于保护性耕作下微生物群落结构与功能的研究,但由于土壤系统的复杂性、环境因素以及微生物群落评价方法的差异性,尚未形成对保护性耕作下土壤微生物群落响应规律的系统认知。此外,研究多关注土壤微生物作为分解者的作用以及植物源碳对土壤碳库形成的贡献,而忽略了微生物源碳对土壤碳库形成和稳定的贡献。本文在归纳土壤有机质形成和稳定理论体系演变的基础上,梳理了土壤微生物研究方法的进展,重点阐述了保护性耕作对土壤微生物生物量、群落多样性和组成、碳代谢活性以及微生物源有机碳截获的影响,并对未来该领域的研究方向进行展望,以期为探索农田生态系统土壤微生物群落响应规律及其介导的土壤碳循环功能提供参考。