Factors Affccting Change of Microbial Community During Plant Residue Decomposition: A Review

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.未来针对野外田问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.     

基于固态13C核磁共振波谱研究植物残体分解和转化机制的进展

植物残体在土壤中的分解和转化影响了其养分归还和有机质形成过程。由于缺乏高分辨率的分析方法,对不同气候、植被和土壤类型条件下植物残体在分解过程中化学结构组成的演变特征和机制仍不清楚。核磁共振波谱技术在解析自然有机物化学组成方面具有独特的优势,本文综述了基于固态~(13)C核磁共振波谱(solid-state ~(13)C-NMR spectroscopy)技术评价植物残体的基质质量、解析植物残体的分解速率及其官能团组成的变化特征、揭示土壤腐殖质特性等方面的主要进展。未来针对植物残体分解和有机质形成机制的研究,应该结合稳定性同位素质谱和扫描电镜分析方法,综合分析植物残体中的有机化合物组成和物理结构;从多时空尺度揭示不同类型植物残体中有机碳官能团的降解路径;结合高通量测序和基因芯片分析方法,深入研究土壤微生物群落与植物残体化学结构的协同演变机制,提出不同气候–土壤–植被类型区促进土壤有机质形成的调控措施。     

接种蚯蚓对加入不同植物残体土壤微生物特性的影响

通过室内试验,研究不同类型土壤和植物残体施用下接种蚯蚓对土壤微生物群落组成及活性的影响,为将蚯蚓引入农田及水土流失区提供理论依据。供试土壤为黏粒含量较低的灰潮土和黏粒含量较高的典型红壤,供试植物残体为高碳氮比的玉米秸秆和低碳氮比的三叶草,供试蚯蚓为体型较大的威廉腔环蚓(Metaphire guillelmi)。结果表明:接种蚯蚓对微生物量碳(MBC)无显著影响;不同土壤无论是否施用植物残体,接种蚯蚓均使土壤基础呼吸(BR)显著增大,尤其是不施用植物残体时;两种土壤中不施用植物残体和施用三叶草时,接种蚯蚓均使代谢熵(qCO2)增大,而施用玉米秸秆接种蚯蚓使qCO2有下降趋势。Biolog孔平均颜色变化(AWCD)在接种蚯蚓时均增大,基质利用丰富度(S)和多样性指数(H)也增大,且未施用秸秆时的变化较为明显;主成分分析(PCA)表明接种蚯蚓后土壤微生物群落组成与结构发生了明显变化。土壤微生物群落特性变化受蚯蚓、土壤及植物残体间交互作用的影响。     

森林次生演替过程中有机质层和矿质层土壤微生物残体的变化

微生物对土壤有机质(SOM)转化和形成具有重要作用,然而微生物残体对SOM贡献的评估仍是目前的热点。以长白山5个森林次生演替序列(20 a、80 a、120 a、200 a和≥300 a)和2个土壤深度(0～5 cm有机质层和5～15 cm矿质层)为对象,利用氨基糖和中红外光谱技术,探究森林次生演替过程中微生物残体变化及其对土壤有机碳(SOC)的贡献。森林次生演替序列80～200 a显著增加了有机质层和矿质层微生物残体含量及其对SOC的贡献,而在演替300 a均显著降低。森林演替80～200a有机质层和矿质层土壤芳香族碳组分/多糖较低,有利于微生物生物量碳(MBC)产生和微生物碳利用(高的MBC/SOC),促进微生物残体积累及其对SOC的贡献;而演替300 a芳香族碳组分/多糖较高,抑制MBC产生和微生物碳利用,导致微生物残体及其对SOC贡献的下降。SOC含量差异导致不同土壤深度微生物残体含量的变化,有机质层高的SOC产生高的MBC,进而刺激微生物残体积累;此外,有机质层难利用SOM组分高于矿质层,导致真菌残体对SOC的贡献比例下降,而细菌残体的贡献增加。     

土壤微生物多样性与地上植被类型关系的研究进展

土壤微生物是生态系统中重要的组成成分,土壤微生物多样性代表着微生物群落的稳定性,对植物的生长发育和群落结构的演替具有重要作用。同时地上植被也影响土壤微生物多样性,地上植被和地下微生物间具协同作用和正负反馈效应的互作机制。探讨植被和土壤微生物多样性之间的互作关系,为植物保护和生态系统的可持续发展研究提供参考。     

土壤微生物多样性与地上植被类型关系的研究进展

土壤微生物是生态系统中重要的组成成分,土壤微生物多样性代表着微生物群落的稳定性,对植物的生长发育和群落结构的演替具有重要作用。同时地上植被也影响土壤微生物多样性,地上植被和地下微生物间具协同作用和正负反馈效应的互作机制。探讨植被和土壤微生物多样性之间的互作关系,为植物保护和生态系统的可持续发展研究提供参考。     

土壤微生物多样性与地上植被类型关系的研究进展

土壤微生物是生态系统中重要的组成成分,土壤微生物多样性代表着微生物群落的稳定性,对植物的生长发育和群落结构的演替具有重要作用.同时地上植被也影响土壤微生物多样性,地上植被和地下微生物间具协同作用和正负反馈效应的互作机制.探讨植被和土壤微生物多样性之间的互作关系,为植物保护和生态系统的可持续发展研究提供参考.     

微生物残体在土壤中的积累转化过程与稳定机理研究进展

近年来,关于微生物残体在土壤有机质积累和转化过程中的作用越来越受到研究者的关注。土壤有机质中微生物残体的数量和组成比例变化与土壤有机质的形成、容量大小及周转特征密切相关。对目前土壤微生物残体研究方面的相关进展进行了梳理和总结,在明确土壤微生物残体的来源及其重要性的基础上,介绍了土壤微生物残体定量和转化的表征方法,阐述了微生物残体在土壤有机质积累转化过程中的作用及其主要影响因素,探讨了微生物残体在土壤中的稳定机制,提出了微生物通过同化代谢作用驱动细胞残体积累进而促进土壤有机质积累和稳定过程中亟待探讨的科学问题。期望为进一步探究陆地生态系统土壤有机质周转与微生物过程的相互作用机理提供一定的思考。     

改变凋落物和根系输入对米槠天然林土壤微生物群落的影响

伴随气候变化下亚热带地区米槠天然林净初级生产力变化,凋落物以及植物根系输入亦会发生改变,这将显著影响土壤微生物群落。于2019年7月在设置7年的米槠天然林植物残体添加和去除试验（the detritus input and removal treatments,DIRT）样地采集不同处理（对照、去除地上凋落物、去除地下根系、无凋落物输入、添加双倍地上凋落物）的2个土层土壤（0—10,10—20 cm）,测定微生物磷脂脂肪酸（phospholipid fatty acid,PLFA）含量,计算各微生物群落比值以及多样性,进一步揭示凋落物和植物根系输入对亚热带米槠天然林土壤微生物群落组成和多样性的影响。结果表明：（1）不同处理下0—10 cm土层微生物磷脂脂肪酸含量约为10—20 cm土层的2倍;（2）地上凋落物变化均使得革兰氏阳性菌、阴性菌及放线菌等细菌含量出现不同程度的下降,但不会对丛枝菌根等真菌含量产生影响,而去除根系处理显著降低丛枝菌根真菌含量;（3）微生物群落Shannon-wiener、Simpson多样性指数不受凋落物输入的影响,凋落物去除降低表层土壤微生物群落的Margalef丰富度,提高Pielou均匀度,表明0—10 cm土层微生物群落含量与分布状况受凋落物输入变化影响较大;（4）地下植物根系存在可提高真菌（如丛枝菌根真菌）含量,而地上凋落物输入主要改变细菌丰度以及群落结构。可溶性有机碳以及矿质氮是影响不同处理土壤微生物群落组成和多样性的主要因素。可见,凋落物和根系输入通过土壤理化性质的变化而影响了微生物群落,研究结果可为全面认识植物、土壤与微生物间的相互作用对森林生产力的影响提供科学依据。     

营养动力学为基础的生物残体分解的数学模型研究

生物残体是由活的生物(包括动物和植物)死亡后形成,如森林砍伐后遗留的树桩,温带森林中每年一度集中产生的枯枝落叶,森林和草原中大型动物死亡遗留的尸体,这些生物残体一般都独自形成一个实体,不与土壤进行均匀的混合,它们的分解,一般主要不是依靠贮积在土壤中的酶或微生物的作用,它们的分解要经过一个在残体内重新滋长微生物的过程,使残体逐渐腐烂变质,进行分解。因此,生物残体的分解,与其说是分解过程,还不如说是一个微生物的培养过程,或者说是这两个过程相互交错,一方面是微生物种群的增长,另一方面是残体中有机物质被微生物分解、转化、利用和复合成新的有机体,对于这样一个复杂的过程,通常适用于土壤有机质分解过程的Stanford-Smith方程^[2]就不适用了,而建立在营养动力学基础上的单种群模型(崔-Lawson方程^[3-5])却可加以转化用来描述这个过程。     

Soil microbial community patterns related to the history and intensity of grazing in sub-montane ecosystems

Long-term variations in the frequency and intensity of sheep (Ovis aries) grazing have led to the development of ubiquitous plant successional transitions in sub-montane regions of the UK. In this study, we measured a range of soil microbial properties across these successional transitions in three biogeographic regions of the UK, to establish how gradients of grazing-influence (in terms of the history and intensity of sheep grazing) alter the biomass, activity, and structure of soil microbial communities. We also measured soil physicochemical variables to relate changes in soil microbial community arrangement along these grazing-related successional transitions to key soil properties. Our results from three locations show that microbial communities of soils display some consistent and ‘broad-scale’ trends along successional transitions that are related to the history and intensity of grazing. We show that microbial biomass of soil is maximal at low-to-intermediate levels of grazing influence and that the phenotypic evenness (a component of diversity) of the microbial community declines as the intensity of grazing increases. We also provide evidence that soil microbial communities of heavily grazed sites are dominated by bacterial-based energy channels of decomposition, whereas in systems that are less intensively grazed, or completely unmanaged, fungi have a proportionally greater role. Further studies are needed to establish the significance of these changes in relation to soil-level ecosystem processes of decomposition and nutrient cycling. The data show that human disturbances can have profound effects on the biomass and structure of the soil communities that regulate soil processes in these ecosystems and that these effects are consistent across sites.     

Soil microbial dynamics and genetic diversity in soil under monoculture wheat grown in different long-term management systems

Organic matter incorporation into soil can increase nutrient availability to plants but it can affect soil microbial communities. These in turn influence soil fertility and plant growth. Soil biochemical and microbiological properties are indicators of soil quality, but there is still no consensus as to how these should be used. Recent developments in molecular biology have provided new tools to obtain a view of the whole microbial community. The long-term impact of crop residue management on the microbial biomass, and on the activity and community structure of soil bacteria was evaluated in a clay soil of Southern Italy, where a monoculture of durum wheat (Triticum durum Desf.) was grown in semiarid conditions, and burning or incorporation of post harvest plant residues were typical practices. The role of N-mineral fertilization, simultaneously with the ploughing in of crop residues and during the plant growth cycle was also investigated. Total bacterial counts of viable cells, biomass C, ATP content of soil microorganisms, genetic fingerprinting of the total eubacterial community and of ammonia oxidizers were evaluated. Burning and incorporation did not affect microbial biomass C, ATP content, and total bacterial counts of viable cells although statistically relevant changes were detected among rhizosphere and bulk soil samples regardless of the crop residue management used. Molecular fingerprinting confirmed that: no significant change in the composition and diversity of total bacteria, as well as of ammonia oxidizers was induced by the crop residue managements; that soil bacteria were more sensitive to N fertilizer application during the plant growth cycle; and that rhizosphere soil samples were significantly different from those of the bulk soil. As microbiological and genetic factors related to soil fertility were not affected significantly, the long-term incorporation of crop residues, under the field conditions investigated, is a sustainable practice to manage post-harvest residues.     

Residue chemistry and microbial community structure during decomposition of eucalypt, wheat and vetch residues

Previous studies have shown that residue chemistry and microbial community structure change during decomposition, however little is known about the relationship between C-chemistry and microbial community structure. To address this knowledge gap, we studied C-chemistry and microbial community structure during the decomposition of eucalypt, wheat and vetch residues with and without additional inorganic N. Bags containing ground residues of eucalypt, wheat, and vetch were buried in sand microcosms after inoculation with a diverse microbial community. Respiration was measured over an incubation period of 150 days. At different times during incubation, total C and N of the residues were analysed and residue carbon chemistry was determined by ¹³C-NMR (nuclear magnetic resonance) spectroscopy. Microbial communities were assessed by phospholipid fatty acid (PLFA) analyses.Results indicated that during decomposition, residue C-chemistry and microbial community composition changed over time and differed between residue types. Changes in microbial community structure were associated with changes in residue C-chemistry, mainly the relative content of aryl-C and O-alkyl-C. Addition of N increased cumulative respiration, altered C-chemistry during decomposition, particularly in high C/N residues (wheat and eucalypt), and changed microbial succession leading to an earlier establishment of a stable microbial community structure. N addition to eucalypt and wheat reduced the decomposition of aryl-C compounds.     

A microcosm experiment to evaluate the influence of location and quality of plant residues on residue decomposition and genetic structure of soil microbial communities

The effects of location (soil surface vs. incorporated in soil) and nature of plant residues on degradation processes and indigenous microbial communities were studied by means of soil microcosms incubation in which the different soil zones influenced by decomposition i.e. residues, soil adjacent to residues (detritusphere) and distant soil unaffected by decomposition (bulk soil) were considered. Plant material decomposition, organic carbon assimilation by the soil microbial biomass and soil inorganic N dynamics were studied with ¹³C labelled wheat straw and young rye. The genetic structure of the community in each soil zone were compared between residue locations and type by applying B- and F-ARISA (for bacterial- and fungal-automated ribosomal intergenic spacer analysis) directly to DNA extracts from these different zones at 50% decomposition of each residue. Both location and biochemical quality affected residue decomposition in soil: 21% of incorporated ¹³C wheat straw and 23% left at the soil surface remained undecomposed at the end of incubation, the corresponding values for ¹³C rye being 1% and 8%. Residue decomposition induced a gradient of microbial activity with more labelled C incorporated into the microbial biomass of the detritusphere. The sphere of influence of the decomposing residues on the dynamics of soluble organic C and inorganic N in the different soil zones showed particular patterns which were influenced by both residue location and quality. Residue degradation stimulated particular genetic structure of microbial community with a gradient from residue to bulk soil, and more pronounced spatial heterogeneity for fungal than for bacterial communities. The initial residue quality strongly affected the resulting spatial heterogeneity of bacteria, with a significance between-zone discrimination for rye but weak discrimination between the detritusphere and bulk soil, for wheat straw. Comparison of the different detrituspheres and residue zones (corresponding to different residue type and location), indicated that the genetic structure of the bacterial and fungal communities were specific to a residue type for detritusphere and to its location for residue, leading to conclude that the detritusphere and residue corresponded to distinct trophic and functional niches for microorganisms.     

Microbial community structure and residue chemistry during decomposition of shoots and roots of young and mature wheat (Triticum aestivum L.) in sand

There is limited understanding of the relationship between carbon (C) chemistry and microbial community structure during decomposition of shoot and root residues and how plant age affects this. In this study, residues of young wheat shoots and roots, mature wheat shoots and roots or a 1:1 mix of mature shoot + root (MSR) were added to sand inoculated with a diverse microbial community. Respiration was measured over 60 days. On days 0, 15, 30 and 60, total C and nitrogen were measured, residue C chemistry was determined by ¹³C‐NMR (nuclear magnetic resonance) spectroscopy and microbial community structure was assessed by phospholipid fatty acid (PLFA) analyses. Cumulative respiration was least in young roots and did not differ among the other residue types. In MSR, decomposition was similar to that of shoots and roots alone; shoot material appeared to be preferentially decomposed. The decomposition rate of all residues combined was not related to C chemistry. However, mineralized C (C_min) was negatively correlated with the percentage of (aryl + O‐aryl)‐C in mature but not in young residues. Mineralized C of roots was positively correlated with the percentage of (di‐O‐alkyl + O‐alkyl)‐C, whereas this was not the case for shoots. Microbial community structure was influenced by time, plant organ and plant age. There was no general relationship between microbial community structure and C chemistry of the residues.     

不同植物秸秆腐解特性与土壤微生物功能多样性研究

采用网袋法探讨不同秸秆在3个长期试验地的腐解特征,结合Biolog微平板技术,对不同长期试验地土壤微生物群落多样性进行了研究。结果表明,随着腐解时间的增加,秸秆腐解的变化趋势为烘干秸秆新鲜秸秆。葡萄园土壤微生物活性高,稳定性好,其次为桃园和农田。农田土壤微生物活性低、稳定性差,不同处理的秸秆在腐解过程中残留率变化较大,而果园土壤微生物活性相对较高、稳定性好,不同处理的秸秆在腐解过程中残留率变化较小。土壤碱解氮、速效磷和土壤温度与土壤微生物群落的三大指数呈极显著相关,且不同秸秆处理的腐解残留率与土壤微生物群落的优势度呈显著负相关,微生物群落在一定程度上影响了秸秆分解的速率。     

Fate of nitrogen from crop residues as affected by biochemical quality and the microbial biomass

Net mineralization of N from a range of shoot and root materials was determined over a period of 6 months following incorporation into a sandy-loam soil under controlled environment conditions. Biochemical “quality” components of the materials showed better correlation with net N mineralization than did gross measures of the respiration and N content of the soil microbial community during decomposition. The quality components controlling net N mineralization changed during decomposition, with water-soluble phenolic content significantly correlated with net N mineralization at early stages, and water-soluble N, followed by cellulose at later stages. C-to-N and total N were correlated with net N mineralization towards the end of the incubation only. Cumulative microbial respiration during the early stages of decomposition was correlated with net N mineralization measured after 2 months, at which time maximum net N mineralization was recorded for most residues. However, there was no relationship between microbial-N and net N mineralization. Biochemical quality factors controlling the C and N content of the residue remaining at the end of the incubation as light fraction organic matter (LFOM) were also investigated. Both C and N content of LFOM derived from the residues were correlated with residue cellulose content, and the chemical characteristics of LFOM were highly correlated with those of the original plant material. Incorporation of low cellulose, high water-soluble N-containing shoot residues resulted in more N becoming mineralized than had been added in the residues, demonstrating that net mineralization of native soil organic matter had occurred. Large amounts of N were lost from the mineral-N pool during the incubation, which could not be accounted for by microbial immobilization.     

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.     

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.