Arbuscular mycorrhizal fungi reduce decomposition of woody plant litter while increasing soil aggregation

The decomposition of plant organic matter and the stability of soil aggregates are important components of soil carbon cycling, and the relationship between decomposition rate and arbuscular mycorrhizal fungi (AMF) has recently received considerable attention. The interaction of AMF with their associated microorganisms and the consequences for litter decomposition and soil aggregation still remain fairly unclear. In a laboratory pot experiment we simultaneously tested the single and combined effects of one AMF species (Rhizophagus irregularis) and a natural non-AMF microbial community on the decomposition of small wooden sticks and on soil aggregation. To disentangle effects of hyphae and roots we placed mesh bags as root exclusion compartments in the soil. The decomposition of the wooden sticks in this compartment was significantly reduced in the presence of AMF, but not with the non-AMF microbial community only, compared to the control, while aggregation was increased in all treatments compared to the control. We suggest that AMF directly (via localized nutrient removal or altered moisture conditions) or indirectly (by providing an alternative carbon source) inhibited the activity of decomposers, leading to different levels of plant litter degradation under our experimental settings. Reduced decomposition of woody litter in presence of AMF can be important for nutrient cycling in AMF-dominated forests and in the case of woody plants and perennials that develop lignified roots in grasslands.     

烟草与丛枝菌根真菌的共生效应研究进展

丛枝菌根(Arbuscular mycorrhiza,AM)真菌是陆地生态系统中广泛存在的一类专性共生土壤微生物,是根系土壤区域中重要的功能菌群之一.AM真菌可侵染植物根系形成丛枝菌根共生体,改变植物根系形态和改善营养状况,从而提高宿主植物的生长发育、产量、质量和抗逆性.目前从烟草根系土壤分离报道的AM真菌已达13属5...     

Increased N availability in grassland soils modifies their microbial communities and decreases the abundance of arbuscular mycorrhizal fungi

Two complementary studies were performed to examine (1) the effect of 18 years of nitrogen (N) fertilization, and (2) the effects of N fertilization during one growing season on soil microbial community composition and soil resource availability in a grassland ecosystem. N was added at three different rates: 0, 5.44, and 27.2 g N m⁻² y⁻¹. In both studies, Schizachyrium scoparium was the dominant plant species before N treatments were applied. Soil microbial communities from each experiment were characterized using fatty acid methyl ester (FAME) analysis. Discriminant analysis of the FAMEs separated the three N fertilizer treatments in both experiments, indicating shifts in the composition of the microbial communities. In general, plots that received N fertilizer at low or high application rates for 18 years showed increased proportions of bacterial FAMEs and decreased fungal FAMEs. In particular, control plots contained a significantly higher proportion of fungal FAMEs C18:1(cis9) and C18:2(cis9,12) and of the arbuscular mycorrhizal fungal (AMF) FAME, C16:1(cis11), than both of the N addition treatment plots. A significant negative effect of N fertilization on the AMF FAME, C16:1(cis11), was measured in the short-term experiment. Our results indicate that high rates of anthropogenic N deposition can lead to significant changes in the composition of soil microbial communities over short periods and can even disrupt the relationship between AMF and plants.     

Global diversity and distribution of arbuscular mycorrhizal fungi

Arbuscular mycorrhizal (AM) fungi form associations with most land plants and can control carbon, nitrogen, and phosphorus cycling between above- and belowground components of ecosystems. Current estimates of AM fungal distributions are mainly inferred from the individual distributions of plant biomes, and climatic factors. However, dispersal limitation, local environmental conditions,and interactions among AM fungal taxa may also determine local diversity and global distributions. We assessed the relative importance of these potential controls by collecting 14,961 DNA sequences from 111 published studies and testing for relationships between AM fungal community composition and geography, environment, and plant biomes. Our results indicated that the global species richness of AM fungi was up to six times higher than previously estimated, largely owing to high beta diversity among sampling sites. Geographic distance, soil temperature and moisture, and plant community type were each significantly related to AM fungal community structure, but explained only a small amount of the observed variance. AM fungal species also tended to be phylogenetically clustered within sites, further suggesting that habitat filtering or dispersal limitation is a driver of AM fungal community assembly. Therefore, predicted shifts in climate and plant species distributions under global change may alter AM fungal communities.     

Molecular diversity of arbuscular mycorrhizal fungi associated with an Mn hyperaccumulator—Phytolacca americana,in Mn mining area

Arbuscular mycorrhizal fungi (AMF) have great potential for assisting metal-hyperaccumulating plants in the remediation of contaminated soils. However, little information is available about the symbiosis and community composition of AMF associated with manganese (Mn) hyperaccumulator, such as Phytolacca americana, growing on Mn-contaminated soils under natural conditions. Therefore, the objective of this study was to analyze AMF diversity and community composition in P. americana roots growing at an Mn mining site. Molecular techniques were used to analyze AMF community composition and phylogenetic relationship in P. americana roots sampled from three Mn mine spoils and one adjacent reference areas. Results obtained showed that mycorrhizal symbionts successfully established even in the most heavily Mn-polluted sites. Root colonization and AMF diversity were significantly negatively correlated with total and extractable Mn concentrations. Principal component analysis (PCA) revealed that Mn contamination impacted AMF diversity, and shaped AMF community structure. Phylogenetic analyses demonstrated that all species were affiliated with Glomus, suggesting that Glomus was the dominant genus in this AMF community. Some unique sequences that occurred exclusively in heavily polluted sites associated with P. americana may belong to symbiotic fungi with great potential for improving the phytoremediation efficiency of Mn-contaminated soils.     

Arbuscular mycorrhizal colonization of selected herbaceous plants under arid protected area in Tunisia

Arbuscular mycorrhizal fungi (AMF) play an important role in plants growth and soils dynamic in all most ecosystems. The main objective of the present study was to evaluate the plant-AMF interactions on soil functions under arid protected area ‘Zarat-Gabès’ in Tunisia.

AMF colonization was evaluated by visual observation of AMF in fine roots of eight herbaceous plants. The level of mycorrhizal colonization varied between plants. Astragalus corrugatus and Hippocrepis areolata showed the highest mycorrhizal performance. The relative spore number was significantly different across rhizosphere soils. Statistical analysis showed a clearly positive correlation between the number of spores and plant-mycorrhizal intensity.

For microbiological parameters, our results showed that mycorrhizal plants improved significantly the various microbiological parameters. Rhizosphere soils of Astragalus corrugatus and Hippocrepis areolata presented the necessary microbial densities and microorganisms more stable compared to unplanted soil. This study allowed obtaining a new result that challenges us about the need for efficient management of natural resources in the objective of nature conservation.     

大豆/玉米间作体系中接种AM真菌和根瘤菌对氮素吸收的促进作用

利用大豆和玉米之间根系不同分隔方式的盆栽试验,研究了在玉米/大豆间作体系中接种大豆根瘤菌、AM真菌Glomus mosseae和双接种对间作体系氮素吸收的促进作用。结果表明,双接种处理显著提高了大豆及与其间作玉米的生物量、氮含量,双接种大豆/玉米间作体系总吸氮量比单接AM菌根、根瘤菌和不接种对照平均分别增加22.6%、24.0%和54.9%。大豆促进了与其间作玉米对氮素的吸收作用,在接种AM真菌和双接种条件,间作玉米的AM真菌侵染率提高,大豆根瘤数增加; 接种AM真菌处理,不分隔和尼龙网分隔比完全分隔玉米吸氮量的净增加量是未接种对照的1.8、2.6倍,双接种处理分别是对照的1.3和1.7倍。说明在间作体系中进行有效的根瘤菌和AM真菌接种,发挥两者的协同作用对提高间作体系土壤养分利用效率,进一步提高间作体系的生产力有重要的意义。     

丛枝菌根真菌在湿地生境中的分布及其在人工湿地中的应用研究进展

Over the last three decades, the presence and functional roles of arbuscular mycorrhizal (AM) fungi in wetland habitats have received increasing attention. This review summarized the mycorrhizal status in wetlands and the effect of flooding on AM fungal colonization. Plants of 99 families living in 31 different habitats have been found to be associated with AM fungi, even including submerged aquatic plants and several plant species that were thought to be nonmycorrhizal (Cyperaceae, Chenopodiaceae, and Plumbaginaceae). The functions of AM fungi in wetland ecological systems could be concluded as their influences on the composition, succession, and diversity of the wetland plant community, and the growth and nutrition of wetland plants. Affecting the composition, succession, and diversity of the wetland plant community, AM fungi have positive, negative, or neutral effects on the performance of different wetland species under different conditions. The factors that affect the application effect of AM fungi in constructed wetland (CW) include flooding, phosphorus, plant species, aerenchyma, salinity, CW types, operation modes of CW, and wastewater quality. The generalist AM fungi strains can be established spontaneously, rapidly, and extensively in wastewater bioremediation technical installations; therefore, AM fungi can be considered ideal inhabitants of technical installations for the plant-based bioremediation of groundwater contaminated by organic pollutants or other contaminants. In the future, roles of AM fungi and factors that affect the purifying capacity of AM-CW system must be understood to optimize CW ecosystem.     

Arbuscular mycorrhizal fungi pre-inoculant identity determines community composition in roots

Pre-inoculation of seedlings with commercial, typically non-indigenous, AMF inoculants is common practice in horticultural and land reclamation industries. How these practices influence AMF community composition in pre-inoculated seedlings after they are planted in soil containing a resident AMF community is almost completely unknown. However, there may be important implications regarding success of horticultural practices, as well as unexpected ecological consequences. In this study we exposed Leucanthemum vulgare seedlings to five different AMF treatments (pre-inoculation with a representative of Glomus group A and Glomus group B, one of two Gigaspora spp., or no AMF) prior to exposure to a whole-soil, mixed-AMF community inoculum. After a growth period of 75 additional for 28 days, AMF community composition within the roots was analyzed using an approach combining LSU rDNA sequencing and T-RFLP analysis. Our results indicate that the AMF communities that assemble within roots were strongly influenced by AMF pre-inoculant identity. Pre-inoculation with either Glomus spp., unlike what was found for Gigaspora, greatly restricted numbers of other AMF ribotypes able to subsequently colonize roots after exposure to our Glomeraceae-dominated field soil; this suggested that phylogenetic relatedness and life history strategies may play a role in AMF community assembly. Our results further revealed concurrent changes in AMF community functions, as indicated by differences in plant biomass and foliar nutrients. These results serve to highlight the importance of considering life history differences when designing AMF inoculants and may have important implications regarding the introduction of non-indigenous AMF.     

蚕豆任米问作接种AM真菌与根瘤菌对其吸磷量的影响

盆栽试验研究不同根系分隔方式蚕豆/玉米间作接种AM真菌和根瘤菌对其吸收有机磷影响结果表明,接种AM真菌均显著促进玉米和蚕豆吸收有机磷,与对照相比吸P量分别增加138.1%和82.3%;接种AM真菌和根瘤菌对蚕豆吸收有机磷有协同促进作用,蚕豆根瘤数、根瘤重和菌根侵染率显著增加,并改善与其间作玉米的营养状况,明显促进玉米生长。     

AM 真菌对花生与甘薯产量的影响

在大田条件下试验研究了丛枝菌根(Arbuscular mycorrhiza,AM)真菌Glomus versiforme Berch及混合菌种[Glomus mosseae Nicolson&Gedermann+Sclerocystis smuosa(Gerd.Bakshi)Almeida ＆ Schenck]对花生与甘薯生长及产量的影响结果表明,供试AM真菌能显著促进花生植株生长健壮,增加单株果数,单位面积产量比对照增加21.3%.接种Glomus versiforme处理的甘薯植株高度和茎叶质量均低于对照,未增加植株生长量和产量;混合菌种处理则提高甘薯的生长量和增加单株薯块数,其单株产量、单位面积产量分别为对照的1.6和1.4倍,表明大田应用时不同作物应采用不同AM真菌.     

Arbuscular mycorrhizal fungi in degraded typical steppe of inner Mongolia

Arbuscular mycorrhizal (AM) fungi may have some potential use in the restoration of degraded grassland through beneficial effects on plant growth and soil quality. A field investigation was conducted in three grassland sites of typical steppe in Inner Mongolia. The three plant communities, one of which was undegraded, one moderately degraded and the third severely degraded, were studied by collecting soil samples and samples of four plant species that occurred in all three sites. The percentage of root length colonized by AM fungi was estimated and the species composition and diversity of AM fungus spores recovered from the soil were determined using spore morphological characteristics. Although differences between the sites may have been due partly to other factors, it is likely that the degree of degradation was an important factor. No decline was found in the AM colonization of the roots of the indicator plant species in the moderately or severely degraded plant communities, and two plant species showed higher colonization status in the two degraded areas. Glomus geosporum and Scutellospora calospora were the dominant AM fungi in the undegraded steppe, while G. geosporum and Glomus aggregatum dominated the two degraded sites which also had low spore densities, species richness and diversity indices. However, different AM species showed different distributions among the three plant communities and the results indicate that both biotic and abiotic factors were important in determining the AMF communities, with biotic factors possibly the more important. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of agricultural management practices on arbuscular mycorrhizal fungal abundance in low-input cropping systems of southern Africa: a case study from Zimbabwe

Previous research, mostly in temperate agricultural systems, has shown that management practices such as fallow period, tillage, crop rotation, and phosphorus (P) fertilizer applications can influence the abundance of arbuscular mycorrhizal fungi (AMF), but relatively little is known about their effect in smallholder farmers’ fields in sub-Saharan Africa. In this study, we evaluated the effect of four subsistence crops that form associations with AMF, moderate P fertilization, tillage, and fallow period on the subsequent AMF abundance on three contrasting low fertility soils in south-western Zimbabwe. Arbuscular mycorrhizal fungal abundance was estimated based on early mycorrhizal colonization of maize (Zea mays L.) or lablab (Lablab purpureus L.) following the various treatments. The previously grown crop significantly affected AMF abundance (p < 0.001). It was highest after lablab followed by pigeonpea (Cajanus cajan L.), maize, and groundnut (Arachis hypogaea L.), and there were significant positive correlations between AMF abundance and aboveground biomass of pigeonpea, lablab, and maize. Contrary to much previous research, P fertilization, fallowing, and tillage did not significantly decrease AMF abundance. In smallholder farmers’ fields in the semi-arid tropics of sub-Saharan Africa, therefore, growing vigorous mycorrhizal plants prior to the dry season could be more important than minimizing P fertilizer applications, fallow periods, and tillage to maintain or increase AMF abundance.     

丛枝菌根真菌对棉花耐盐性的影响研究

盆栽灭菌试验研究丛枝(AM)真菌对棉花耐盐性的影响结果表明,自然盐渍化土壤和人工模拟盐渍条件下接种AM真菌处理的生物产量显著高于不接种处理,相同土壤下菌根真菌对棉花植株生长的促进作用随盐水平的提高而增大,表明AM真菌与植株建立的共生关系有利于棉花在盐渍土壤中生长。盐胁迫下棉花植株对P的需要量增加,接种AM真菌可提高植株含P量,促进植株生长,提高棉花的耐盐性。     

玉米||大豆间作对AMF时空变化的影响

为探究农田生态系统中不同种植模式下丛枝菌根真菌(AMF)生长发育及产生孢子和球囊霉素状况,本试验设置两种结构的间作模式(6M6S:6行玉米与6行大豆间作; 3M3S:3行玉米与3行大豆间作)以及单作玉米(CKM)和单作大豆(CKS)4个处理,分析不同种植模式对AMF生长时空变化的影响。结果表明:菌根侵染率、侵染密度和菌丝密度随着AMF与作物共生期延长逐渐增加,丛枝丰度呈现先增加后减少的趋势。两年试验中,玉米乳熟期(大豆鼓粒期), 3M3S处理的菌根侵染率、侵染密度和丛枝丰度,土壤孢子密度、易提取球囊霉素含量和总球囊霉素含量均显著高于单作。在作物生育期内, AMF的孢子密度从269.40个·(100g)~(-1)增加至1 484.20个·(100g)~(-1),易提取球囊霉素含量从430.88μg·g~(-1)增加至600.78μg·g~(-1),总球囊霉素含量从942.59μg·g~(-1)增加至1 304.03μg·g~(-1)。玉米乳熟期,间作边行玉米的菌丝密度、孢子密度、易提取球囊霉素和总球囊霉素含量最高;大豆鼓粒期,间作边行大豆的菌丝密度和易提取球囊霉素含量最高,孢子密度最低。相关性分析表明,总球囊霉素和易提取球囊霉素与菌丝密度呈极显著正相关,相关系数分别达0.71和0.73;孢子密度和菌丝密度与侵染率呈极显著正相关,相关系数分别达0.72和0.75。因此,农田生境中AMF能与根系建立良好的共生关系,并随着季节变化和作物生长呈现周期性变化。间作促进了AMF的侵染,增加了球囊霉素和孢子的产量,间作处理中AMF与各行作物共生表现出边际效应。3M3S处理是最有利于AMF生长的种植模式。     

蚯蚓与丛枝菌根真菌的相互作用及其对植物的影响

蚯蚓和丛枝菌根(Arbuscular mycorrhiza,AM)真菌都是有益的土壤生物,对提高土壤养分有效性和植物吸收利用营养元素具有重要影响。本文综述了蚯蚓对AM真菌取食、传播和侵染的影响、蚯蚓与AM真菌相互作用的效应和机制方面的最新研究进展,以及AM真菌与蚯蚓互作改善植物营养和生长以及协同修复土壤重金属方面的作用,以期为今后研究发展提供依据。     

Changes in soil organic carbon,total nitrogen,and abundance of arbuscular mycorrhizal fungi along a large-scale aridity gradient

Changes in soil organic carbon, total nitrogen, pH, and the abundance of arbuscular mycorrhizal fungi are examined along a large-scale aridity gradient from southeast to northwest in China. Soil organic carbon and total nitrogen decreased but pH increased with increased aridity. Aboveground plant biomass, spore abundance, and colonization of roots by arbuscular mycorrhizal fungi also declined as the aridity increased. Soil organic carbon and total nitrogen were positively correlated with aboveground plant biomass, and arbuscular mycorrhizal fungal spore number and root colonization were positively correlated with soil organic carbon, total nitrogen, and aboveground plant biomass but were negatively correlated with soil pH. A structural equation model suggested that aridity affected soil organic carbon and total nitrogen by limiting aboveground plant biomass. Aridity exerted a large direct effect and smaller indirect effects (via changes in aboveground plant biomass) on the abundance of arbuscular mycorrhizal fungi. Soil pH also directly influenced arbuscular mycorrhizal fungal abundance. These results suggest that aboveground plant biomass could be a key factor driving the changes of soil organic carbon, total nitrogen, and arbuscular mycorrhizal fungal abundance along this aridity gradient in China.     

N,P Contribution and soil adaptability of four arbuscular mycorrhizal fungi

Abstract

A glasshouse study was conducted to investigate the symbiotic efficiency and soil adaptability of four AMF using glass-bead cultivation systems. The results showed that efficiency and adaptability of four fungi varied among three soils. Particularly, efficiency of BEG167 shifted from positive in Beijing soil to negative in Guangdong soil. Furthermore, BEG167 had high adaptability in all three soils. Intraspecific differences of BRG168 and BEG221 were found in efficiency and adaptability in three soils. Taking efficiency and adaptabilty into consideration, it was concluded that BEG167, BEG168 and BEG221 in Beijing soil, BEG151 in Hubei soil, and BEG151 and BEG168 in Guangdong soil were effective AMF for maize.     

AM菌对三叶草吸收、累积重金属的影响

采用4室根箱培养系统,探讨了Cu、Zn、Pb、Cd 4种重金属复合污染土壤中,丛枝菌根菌对三叶草生长及吸收、累积重金属的作用,结果表明:重金属Cu 100mg/kg、Zn 600mg/kg、Pb 300mg/kg、Cd 10mg/kg的复合污染对三叶草生物量影响较小,但土壤重金属处理使丛枝菌根菌Glomus intraradices和Glomus caledonium对三叶草的侵染率分别降低53%和56%,菌种G.intraradice的菌丝密度降低73%;接种菌根真菌能明显减少重金属复合污染土壤中三叶草对Cu、Cd和Pb的吸收,并强化根系在限制重金属Pb和Cd向地上部运输中的作用,地上部Pb和Cd含量分别下降24.2%~55.3%和65%~97.9%,使三叶草地上部Cd和Pb含量均低于我国牧草重金属安全含量,提高了三叶草可食部分的质量;不同菌根真菌对三叶草吸收、累积及分配重金属的影响有明显差异,Glomus intraradices对减少三叶草对重金属的吸收及其在地上部可食部分的累积的作用大于Glomus caledonium。丛枝菌根菌对于强化三叶草根系对重金属的固持作用,调节生态系统中重金属的生物循环,减轻重金属对食物链的污染风险方面起着重要作用。     

长期保护性耕作对丛枝菌根真菌多样性的影响

为了明确我国北方干旱地区长期保护性耕作以及深松对丛枝菌根真菌(AMF)多样性的影响,笔者于2014年在山西省临汾市连续22年实施保护性耕作的长期定位试验基地,针对免耕覆盖(NTS)、深松免耕覆盖(SNTS)及传统耕作(TT)3种处理方式,进行了不同耕作条件下土壤AMF物种丰度、孢子密度、Shannon多样性指数以及AMF侵染率等因素的比较研究。结果显示,长期保护性耕作(NTS和SNTS)共分离鉴定出AMF 7属9种,其中根孢囊霉属(Rhizophagus)和斗管囊霉属(Funneliformis)各2种,球囊霉属(Glomus)、近明球囊霉属(Claroideoglomus)、无梗囊霉属(Acaulospora)、硬囊霉属(Sclerocystis)和隔球囊霉属(Septoglomus)各1种;而传统耕作(TT)共分离鉴定出AMF 6属8种,没有检测到无梗囊霉属。NTS、SNTS和TT处理在不同土层的AMF优势种基本一致,0~40 cm土层为摩西斗管囊霉(Fu.mosseae)和变形球囊霉(G.versiforme),40~80 cm土层为摩西斗管囊霉、变形球囊霉和聚丛根孢囊霉(Rh.aggregatum),80~120 cm土层为聚丛根孢囊霉,120 cm土层以下只有NTS和SNTS处理中存在聚丛根孢囊霉,说明保护性耕作措施促进了AMF向土壤深层发展。NTS和SNTS处理在同一土层的AMF物种丰度、孢子密度和Shannon多样性指数均高于TT处理,SNTS处理高于NTS处理。同一耕作措施不同土层的AMF物种丰度、孢子密度和Shannon多样性指数均随土层加深而逐渐降低;NTS和SNTS处理在小麦各生育期的丛枝侵染率和孢子密度均高于TT处理;各处理在小麦拔节期的AMF侵染率最高,分别为14.9%、16.1%和10.6%,而在收获期的土壤孢子密度最高,分别为111.7个·(100g)~(-1)、125.0个·(100g)~(-1)和90.3个·(100g)~(-1)。研究认为,长期免耕覆盖、尤其深松免耕覆盖,提高了AMF多样性。该研究结果可为中国北方旱作农田生态系统中AMF自然潜力的充分发挥,以及保护性耕作技术的合理应用提供科学依据。