稻田土壤真菌群落多样性和组成对麦秸还田的响应

在室内模拟试验下,采用常规分析和高通量测序技术,研究了淹水培养30 d后,不同量小麦秸秆(0、10、20和50 g/kg)施用下两种类型的稻田土壤(高砂土和黄泥土)真菌群落多样性和组成的演替规律及其驱动因子。结果表明:秸秆还田显著降低了高砂土真菌群落多样性并改变了高砂土真菌群落组成,但不同量秸秆还田下,高砂土真菌群落组成并无显著性差异;而秸秆还田对黄泥土真菌群落多样性并无显著影响,与未施用秸秆相比,低秸秆施用量(10和20 g/kg)并未显著改变黄泥土中真菌群落组成,而当秸秆施用量为50 g/kg时,黄泥土真菌群落组成明显迁移。进一步的典范相关分析(CCA)发现,pH、EC和有机质(SOM)是影响秸秆还田后高砂土真菌群落迁移的重要因子,而pH、EC、SOM和碳氮比(C/N)是影响秸秆还田后黄泥土真菌群落迁移的主要调控因子。综合分析认为,秸秆还田主要通过改变土壤性质来调控真菌群落结构,而不同类型土壤的真菌群落多样性和组成对秸秆还田的响应不同。     

Are decomposition and N release from organic mulches determined mainly by their chemical composition?

The influence of chemical composition on the decomposition and N release rates from samples of 11 organic mulches enclosed in nylon mesh bags was assessed under field conditions at the University of California, Riverside. Time was adjusted by temperature and the cumulative temperature-adjusted days (tad) were used to model the pattern of the decay and N release. The chemical composition of the mulches significantly affected their decay. In descending order of significance, the concentration of the polar extractable carbon fraction (C_P) and the acid insoluble fraction (C_AI) were significantly correlated with decomposition during the year of study. Correlation was positive with C_P and N and negative with C_AI (mostly lignin). The C_P was selected as the best predictor for mulch decomposition during the early and intermediate phases of this process (36 and 195 tad), but C_AI was selected as the best variable for predicting the fraction of the initial mulch mass remaining at the end of the study (397 tad). N was immobilized, as indicated by temporary increases in N masses in mulches above initial conditions, in shredded redwood, pine trimmings and in two of three compost mulches. Immobilization was most pronounced during the first 36 tad of the study, with a maximum rate that varied from 6 to 11.5% above the initial N concentrations. At the end of the study N releases ranged from 97% of initial N (grass clippings) to only 8% (one of the composts.) The C_P was selected as the best predictor for N remaining in the four sampling dates (397 tad) and explained from 52 to 68% of the variation in N release as a percentage of initial N content.     

不同美拉德反应底物溶液及其混合液添加对稻草腐解产物的影响

   稻草还田是黑土地保护的必然要求,但稻草富含木质素,单独腐解较难,能否借助美拉德（Maillard）反应底物对腐殖质形成的激发效应来加速稻草的腐解？   本研究采用室内培养法,以稻草为供试对象,加入适量MnO₂粉末,分别添加葡萄糖（Glucose,Glu）、邻苯二酚（Catechol,Cat）和甘氨酸（Glycine,Gly）的单一、两两组合（Glu-Cat、Glu-Gly和Cat-Gly）溶液及其混合液（Ms）,以添加等体积无菌水为对照,接种EM微生物菌剂,在28 ℃恒温条件下培养90 d,在0、30、60和90 d分别取样进行腐殖质组成分析。   ① 无论是否添加美拉德反应底物,稻草经腐解后水溶性物质碳含量（C_WSS）均有所上升,相比之下,3种美拉德反应底物混合液的添加更有利于C_WSS的提升,其次为Gly;添加美拉德反应底物更有利于胡敏素（Hu）的分解。② 添加不同美拉德反应底物溶液及其混合液的影响下,稻草腐解产物可提取腐殖酸碳含量（C_HE）的变化趋势不一。Glu-Cat处理对C_HE含量的提升作用最大,其次为Glu,而Gly和Glu-Gly处理则不利于可提取腐殖酸（HE）的形成;（3）稻草腐解过程胡敏酸（HA）分子结构先简单而后渐趋复杂,重新缩合的HA分子结构更加简单,Cat-Gly处理更有利于HA的分解,使其分子结构简单化,除此之外的其他处理,与CK相比,均可有效抑制HA分子的简单化,其中,添加葡萄糖的效果最佳,更有利于HA分子结构的稳定性,且可提升C_HA/C_FA,使腐殖质品质得以改善,而Cat不利于腐殖质品质提升、却更易促进Hu的分解。   添加美拉德反应底物更有利于稻草腐解产物C_WSS的提升以及Hu的分解,添加葡萄糖更有利于提升稻草腐解产物HA分子结构的稳定性,进而改善其腐殖质品质。     

苹果园蜘蛛群落组成及其生态位研究初报

对山西省晋中苹果园蜘蛛群落组成及其生态位研究结果表明,所采集的4447头蜘蛛隶属15科41属68种;并应用Berger-Parker优势度指数分析得出不同时期果园蜘蛛群落优势类群及优势种,根据二维生态位重叠值与物种间相似性指标进行模糊聚类分析,以λ=0.89为聚类阈值,可将8种果园优势种蜘蛛划分为2个明显竞争群及3个分离种。     

基于文献计量分析的土壤微生物残体研究态势

土壤微生物残体是当前的热点研究领域,本研究在系统描述1991 ~ 2022年期间土壤微生物残体领域的研究现状及研究热点的基础上,分析了该领域尚存的一些有待解决的问题,有助于相关学者加深对该研究领域的理解,对进一步聚焦土壤微生物残体领域的研究方向具有重要参考价值。采用文献计量方法,对1991 ~ 2022年期间WOS（Web of Science）核心合集数据库收录的该研究领域论文的数量、被引频次、作者、国家（地区）、研究机构、期刊以及关键词进行统计。基于VOSviewer可视化软件分析贡献居前的作者、国家（地区）、研究机构、期刊以及重要关键词。①在1991 ~ 2022年间,中国学者在本研究领域共发表论文179篇,排名世界第一,占该领域全部文章总数的54.41%。②根据年度发文量,该领域的研究历程大体可分为三个阶段,分别为萌芽期（1991 ~ 2003年）、波动发展期（2004 ~ 2015年）和指数增长期（2016 ~ 2022年）。③何红波、梁超、张旭东以及丁雪丽是本研究领域的核心作者。④中国科学院是核心研究机构。⑤Soil Biology & Biochemistry为WOS数据库文献的主要来源期刊。⑥本领域关键词共现图表明当前研究多集中于土壤微生物残体对土壤有机质的贡献及其对气候变化的响应。土壤微生物残体领域研究正处于指数增长阶段,国内学者为该领域的发展做出了不可或缺的巨大贡献。微生物残体标识物的扩展、微生物残体与植物木质素在不同生态系统中的积累机制、微生物残体在氮、磷等养分循环中可能起到的重要作用,以及微生物残体含量在不同土壤深度以及更加广泛的地理格局中所展现出的差异等方面可能是今后土壤微生物残体领域的研究热点。     

Synergistic effects of regional climate patterns and local water management on freshwater mussel communities

Human alterations to aquatic ecosystems are leading to decreases in species richness and biomass and subsequent changes in community composition. In many cases species losses are non-random: species with traits poorly adapted to the new environmental conditions suffer greater losses. We used long-term data from a southern US river, the Kiamichi River, to evaluate the synergistic effects of regional climate patterns coupled with water management practices on freshwater mussel communities. Mussel communities in the river changed over the 15 year period of this study, with overall densities and species richness decreasing and community structure shifting from assemblages dominated by thermally sensitive to thermally tolerant species. These changes corresponded with a period of very low flows in the river caused by a combination of climate patterns (a regional drought) and local water management practices (decreased reservoir releases). These low flows, coupled with high summer air temperatures, changed the river in many locations from a continuously flowing river to a series of shallow, isolated pools where water temperatures sometimes exceeded 40 °C. Altered conditions led to higher mortality rates of thermally sensitive compared to tolerant species. We predict future shifts in river ecosystem function as mussel communities change in response to changing climate and water management.     

土壤线虫群落对过量施用农用化学品的响应

为研究施用过量的农用化学品对土壤线虫群落组成及多样性的影响,采用定点试验的方法,在哈尔滨市呼兰区选择典型农田生态系统进行试验,对比研究土壤线虫群落对施用过量的氮肥、磷肥、钾肥、除草剂及杀虫剂的响应。在试验田中共鉴定出土壤线虫27科45属,其中Cephalobus和Aphelenchus为优势属。施用不同浓度的各类农用化学品对土壤线虫群落组成、多样性均产生一定影响。线虫总数及食细菌线虫、食真菌线虫、植物寄生线虫数量在不同处理间均存在显著差异(P<0.05);其中,植物寄生线虫的相对丰度随化肥施用量的升高呈增加趋势。从土壤线虫的生态指数来看,除PPI(植物寄生线虫成熟指数)外,其他生态指数[MI(成熟度指数)、F/B(食真菌线虫与食细菌线虫数量比值)、Evenness(均匀度指数)、SR(丰富度指数)、H’(多样性指数)]在施用不同农用化学品处理之间也存在显著差异,并且,MI随着施用钾肥、氮肥浓度的增加而降低。土壤线虫可以作为揭示施用农用化学品过程中土壤质量变化的生物学指标,其群落及多样性的变化表明土壤线虫群落对农用化学品的过量施用产生了响应,过量施用农用化学品会增加土壤生态系统的干扰,对土壤环境造成威胁。     

The impacts of forest clearance on lizard, small mammal and bird communities in the arid spiny forest, southern Madagascar

Madagascar is a global biodiversity hotspot threatened by forest loss, degradation and fragmentation, all of which are detrimental to the future survival of forest-dwelling organisms. For conservation purposes it is essential to determine how species respond to habitat disturbance, specifically deforestation. In this study we investigated the impacts of deforestation on three vertebrate communities, lizards, small mammals and birds, in an area of spiny forest subjected to anthropogenic forest clearance. Spiny forest has high levels of endemism, but conservation in this unique ecosystem is hindered by the lack of research. We undertook standardised trapping, time-constrained and timed species searches to assess species richness, species abundance and community composition of lizards, small mammals and birds in six areas of ‘forest’ and six ‘cleared’ areas. From surveys and opportunistic sightings we recorded a total of 70 species of birds, 14 species of mammals and 38 species of reptiles and amphibians. We found forest clearing to have a negative effect on species richness and community structure of all groups and identified loss of canopy cover as a driving factor behind this. However, the response and sensitivity to clearing varied between groups and species. Lizards (50%) and small mammals (40%) had the greatest decline in species richness in response to clearing as compared to birds (26%), although birds showed the greatest shift in community structure. The community in cleared areas contained more generalist and introduced species that have wider geographic ranges and habitat preferences, than those unique to the spiny forest. We found the first suite of species to suffer from forest clearance were those of high conservation priority due to their restricted geographic range. Our findings are discussed in relation to future spiny forest conservation and management.     

Community composition of ammonia-oxidizing bacteria in the rhizosphere of intercropped wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.), maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.), and faba bean (<Emphasis Type="Italic">Vicia faba</Emphasis> L.)

Cereal/cereal and cereal/legume intercropping systems are popular in the north, northwest, and southwest of China and often result in yield increases compared to monocropping. Rhizosphere interactions may play a significant role in the yield increases, particularly with respect to nutrient availability. The aim of this study was to investigate the effects of intercropping on N availability and community composition of ammonia-oxidizing bacteria in the rhizosphere of wheat, maize, and faba bean at different growth stages. Denaturing gradient gel electrophoresis (DGGE) based on 16S rRNA genes was used to analyze the community composition of bacterial ammonia oxidizers belonging to β-proteobacteria. The results showed that intercropping with faba bean significantly increased nitrate concentrations in the rhizosphere of wheat and maize at the second sampling time (20 June) compared to monocropping or intercropping between maize and wheat. Intercropping significantly affected the community composition of ammonia-oxidizing bacteria in the rhizosphere compared to monocropping, and the effects were most pronounced in the maize/faba bean and wheat/maize intercropping systems when faba bean and wheat were at anthesis and maize was in seedling stage. In wheat/faba bean intercropping, the effects of intercropping on community composition of ammonia-oxidizing bacteria were less pronounced at the seedling stage of the two species but were significant at anthesis.     

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。     

东北黑土区中小型土壤节肢动物群落对不同有机肥施用量的响应

为明晰等量无机肥料施入条件下不同有机肥施用量对耕作黑土区中小型土壤节肢动物群落的影响,于2018-2019年的6-9月在内蒙古兴安盟扎赉特旗农业科技示范园区种植基地设置4种不同施肥量处理(不施肥对照、低量有机肥15 000 kg/hm²、中量有机肥30 000 kg/hm²、高量有机肥45 000 kg/hm²)进行定点试验。结果表明：①共捕获中小型土壤节肢动物509 786头,隶属于12目66科,矮蒲螨科(Pygmephoridae)和等节䖴科(Isotomidae)均为4种施肥量下的优势物种,分别占总个体数的45.90% ~ 59.52% 和12.36% ~ 21.66%;②中小型土壤节肢动物个体数在水平及垂直方向上对有机肥料施入量响应一致,个体数在各土层随有机肥料施入量与施肥年限的增加而增加,随土层增大而减少,且主要在高量有机肥处理中显著增加,表明高量有机肥处理是促进中小型土壤节肢动物群落发展的最佳施肥量;③月动态分析表明,7-8月良好的水热条件与有机肥料施用对土壤动物具有正向复合作用,其中矮蒲螨科、等节䖴科、植绥螨科(Phytoseiidae)可以作为考察2年有机肥料施用对中小型土壤节肢动物群落积极效应的特征指标,隐翅甲科(Staphylinidae)和四奥甲螨科(Quadroppiidae)可作为消极效应的特征指标;④冗余分析结果显示,2018年影响土壤动物群落组成的主要因子是有机质、容重及速效钾,2019年为有效磷和容重。总体而言,施用有机肥可以提高黑土区土壤质量,高量有机肥可以改善中小型土壤节肢动物群落组成,为中小型土壤节肢动物提供适宜的生存环境。     

Limits to the bioindication potential of Collembola in environmental impact analysis: a case study of forest soil-liming and fertilization

We tested the suitability of the collembolan community as a bioindicator for assessing the effects of forest soil-liming and fertilization on the belowground decomposer community. Our investigation was based on a 5-year survey that took place in a German oak-hornbeam and spruce forest in which amelioration measures took place in 1988, 1994 and 1995, with chemical parameters and Collembola being sampled between 1993 and 1997. To address these questions, we applied new methods which have not yet, to our knowledge, been used in biomonitoring studies on forest soils. We used a time-lag analysis for the detection of directional change and a regression-tree induction to show the relationship between Collembola and soil factors. Soil parameters changed considerably after the onset of liming and fertilization. However, no change was detected in community composition over time, nor was there a relationship between Collembola and soil parameters that would make possible the development of a model with at least a moderate predictive success. Taking into account the effort invested in this study (5-year sampling period, identification of 35,000 Collembola, 99 species, 1,170 chemical analyses), we question the suitability of collembolan communities as a bioindicator for forest disturbance.     

Microbial succession in litter decomposition in the semi-arid Chaco woodland

Microbial succession associated with litter decomposition was studied in the semi-arid western Chaco woodland of Cordoba province, Argentina. Annual rainfall in the area averages 450 mm, concentrated during the summer (October-March). We placed 200 g of freshly shed litter in metallic cages covered with 1 mm mesh divided in four equal size sectors, for 1 year. Cages were sampled at 3-month intervals from the starting date. On each sampling date, we collected the content of one sector from each cage for analysis. Microbial functional groups (ammonifiers, nitrifiers, N-fixing, cellulolytic, and sugar fungi) and litter chemical composition (carbon, nitrogen, insoluble fibre, and phenol concentration) were analysed in the initial litter and litter samples collected at the end of each sampling period. Litter mass remained constant during the dry season (winter and spring), decreasing abruptly in the wet season (summer and autumn). Nitrogen content increased significantly until summer (from 1.52 to 2.18%), whereas phenols and C/N ratio decreased (from 2.48 to 0.67 and from 40 to 20%, respectively). Sugar fungi and ammonifiers increased rapidly since the initial stages and remained stable throughout the year (from log 5.0 to log 6.2 and from log 5.4 to log 20.0, respectively). Cellulolytic bacteria and fungi as well as nitrifiers decreased markedly during winter and spring, peaking in summer. Nitrogen-fixing bacteria increased during the study period (from log 1.6 to log 4.8), showing a significant correlation with ammonifiers, C/N ratio, and N content (r²=0.801, 0.573 and 0.513, respectively). Our results show that microbial successions in litter decomposition are strongly influenced by synergic interaction among functional groups and litter chemical composition. Moreover, they also suggest that biological nitrogen fixation may have an important role in improving the C/N ratio, and therefore favours a higher decomposition rate.     

金线莲根部内生菌多样性宏基因组的分析

金线莲(Anoectochilus roxburghii(Wall.)Lindl)是中国传统中药,具有重要的药用价值,现代医学用来治疗糖尿病和癌症。金线莲作为兰科植物,与内生菌在长期的生长过程中建立起和谐的共生关系,内生菌产生多种次生代谢产物,帮助宿主植物抗菌防虫。现有实验条件下,环境中绝大多数的微生物不能培养,而宏基因组学是认识环境中不可培养微生物的重要手段。本研究对福建金线莲根部内生菌富集进行探索,提取混合内生菌样品宏基因组DNA,并对宏基因组DNA纯化,PCR扩增微生物16S r DNA片段,克隆至大肠杆菌(Escherichia coli)并测序。根据16S r DNA信息初步对富集的内生菌群落分析,内生菌主要是不可培养细菌(uncultured bacterium)、不可培养堆肥细菌(uncultured compost bacterium)、肠杆菌科(enterobacteriaceae)、类芽胞杆菌属(Paenibacillus sp.)、芽胞杆菌属(Bacillus sp.)和短芽胞杆菌属(Brevibacillus sp.)的微生物。本研究为挖掘金线莲内生菌资源提供基础资料。