病原菌及菌根菌维持森林植物多样性机制的研究进展

森林植物物种与土壤微生物之间的相互作用决定森林生物多样性。尤其是土壤中的病原菌、菌根菌等微生物在森林物种多样性保护中起到重要作用。Janzen-Connell假说和植物-土壤反馈模型是利用植物与土壤微生物之间的相互作用关系解释森林物种多样性机制的重要模型。本文针对土壤真菌解释森林物种多样性机制进行了综合评述，介绍了病原菌和菌根菌各自在森林实生苗更新的作用机制，探讨病原菌及其菌根菌两者对森林物种多样性的相对重要性，森林实生苗与土壤微生物之间相互作用的变化规律，总结了近年来国际森林物种多样性机制的研究。提出了病原菌和菌根菌两者共同在生态系统中的作用，并探讨未来的研究方向。     

特殊生境中丛枝菌根真菌多样性

丛枝菌根真菌(AMF)是生态系统的重要组分之一,不仅具有丰富的遗传、物种和功能多样性,而且还具有生态系统多样性,即该真菌的分布与栖息生境复杂多样.AMF侵染植物根系形成菌根,营专性活体共生营养,生态适应性强,除了森林、草原和农田生态系统外,还广泛分布于保护地、盐碱地、矿区污染地、石化与农药污染地、荒漠地、干旱地、湿地、沼泽地、火山地、高原、低温与极地等植物多样性匮乏的特殊生境,形成独特的群落结构,发挥着不可替代的生理生态功能.本文总结了上述生境中AMF物种多样性与菌根发育特点,旨在为进一步开展这些特殊生境和极端环境下的AMF研究提供基本信息.     

外生菌根真菌生物地理学研究进展

外生菌根真菌对植物矿质营养、生态系统物质循环、物种演化进程等具有十分重要的作用,但其生物地理学研究长期滞后于动植物。扩散和隔离是解释外生菌根真菌生物地理分布格局的重要理论。古地质、古气候和宿主植物是外生菌根真菌地理分布格局形成的重要推动因子。基因组学、生物信息学技术与生物地理学方法相互结合和补充,可以用来研究一些复杂的真菌生物地理学问题。文中详细阐述了外生菌根真菌生物地理学研究的重要过程和现状,如真菌物种界定、常用数据分析方法、起源和演化规律及其在生物多样性保护方面的应用等,并初步探讨了其未来的发展方向。     

丛枝菌根真菌物种多样性研究进展

丛枝菌根(arbuscular mycorrhiza, AM)真菌是生态系统中生物多样性的重要组分之一,具有十分丰富的物种多样性、遗传多样性和功能多样性.该真菌分类地位不断提高已上升至门,下设1个纲、4个目、13个科,19个属,现已报道214种.丛枝菌根对保持生态平衡、稳定和提高生态系统可持续生产力具有重要作用.本文分析了世界范围内丛枝菌根真菌物种多样性研究现状、不同生态系统中影响丛枝菌根真菌物种多样性的关键因子及其调控途径;认为分子生物学技术是今后丛枝菌根真菌物种多样性研究的主要方法.     

中国AM真菌的生物多样性

菌根是真菌与植物根系所建立的互惠共生体 ,其中以丛枝菌根在自然界中分布最广。AM真菌遍布各生态系统 ,不仅大量分布于农田和森林土壤 ,而且还广泛存在于多种逆境环境中。绝大多数的植物包括苔鲜、蕨类、裸子植物、被子植物都能被AM真菌侵染。我国的AM真菌研究始于 2 0世纪 80年代 ,迄今为止 ,已经对多种生态环境中多种寄主植物根围的AM真菌进行了调查研究 ,共报道了 7个属的 99种AM真菌。本文从物种多样性、生境多样性和寄主多样性等三个方面概括介绍了 2 0年来我国在AM真菌生物多样性研究中取得的进展 ,并探讨了未来的研究动向。     

红壤坡地杂草群落VA菌根真菌的宿主物种调查

本研究调查了红壤坡地幼龄果园杂草群落的物种多样性以及主要物种被VA菌根真菌的侵染率和侵染强度,分析了VA菌根真菌侵染与根际土壤磷系水平的关系。研究区域幼龄果园杂草群落共有杂草96种,分属27科。对17个科的39个物种的调查发现,所调查的物种均不同程度上被VA真菌所侵染,但科与科之间存在显著差异,同一科的不同种之间也差异明显。相关分析表明,VA菌根真菌对不同毁草种 的侵染率和侵染强度与土壤磷素水平关系不甚密切,VA菌根真菌强度可能主要决定于宿主植物特性和VA菌根真菌的选择。因此,在不影响农业生产的前提下,尽可能保持杂草的多样性将有利于VA菌根真菌的生存。     

菌根真菌多样性与植物多样性的相互作用研究进展

菌根共生双方多样性影响着生态系统的过程与功能。菌根真菌-寄主植物之间的共生组合存在偏好性或特异性,这导致菌根真菌对寄主植物的效益差异和寄主植物对菌根真菌的利益差别：两者在互利共生过程中不仅相互选择,还存在相互促进与制约的关系(如互补与选择效应、竞争),从而在一定程度上决定生态系统的演化与发展。本文概述了植物多样性与菌根真菌多样性的相互影响,探讨了两者互作可能存在的调控因素与机制,对存在的问题和争议进行了总结,并提出了进一步研究的方向。深入阐明植物多样性与菌根真菌多样性之间的互作关系,将丰富生物共生学理论,增强菌根应用潜力及生物多样性的维持。     

菌根生物技术在退化草地生态系统中的意义

综述了草地生态系统退化的现状、原因及其恢复途径;综述了菌根在草地生态系统中的功能和作用的研究进展,表明菌根是草地生态系统中不可忽视的重要组成部分。菌根对草原生态系统的作用是多样的,重点讨论的是菌根对生物多样性的影响,提出维持草原生态系统的生物多样性是防止草地进一步退化的关键,菌根与植物的共生是是草场健康发展的关键。菌根生物技术在我国草地保护和草场恢复上具有重要的位置。     

四川黄龙沟优势兰科植物菌根真菌多样性及其季节变化

在自然条件下,兰科菌根真菌对兰花的种子萌发和植株生长都是必不可少的。为了解高原兰科植物菌根真菌的多样性状况及其季节性变化规律,选取了四川黄龙沟的两种生境中生长的8种优势兰科植物,分别于植株的萌芽期(4月份)、生长期(7月份)和果期(9月份)采集营养根进行菌根真菌的多样性研究。其中,黄花杓兰(Cypripedium flavum)、少花鹤顶兰(Phaiusdelavayi)、二叶匍茎兰(Galearis diantha)和广布小蝶兰(Ponerorchis chusua)分布在开阔生境;筒距兰(Tipularia szechuanica)、小花舌唇兰(Platanthera minutiflora)、珊瑚兰(Corallorhiza trifida)和尖唇鸟巢兰(Neottia acuminate)则分布在密林生境。通过对分离所得的50个菌株进行形态观察和ITS序列测定相结合的鉴定,共获得菌根真菌41种。对担子菌和子囊菌分别进行的系统发育树构建结果显示,子囊菌为优势种类(35种),以柔膜菌目(Helotiales)、炭角菌目(Xylariales)和肉座菌目(Hypocreales)内的种类为主,担子菌则以胶膜菌(Tulasnellaceaesp.)为主。在8种兰科植物中,二叶匐茎兰表现出极高的专一性,其菌根真菌均属于Hypocrea。其余兰科植物的菌根真菌分别属于不同的科,专一性相对较低。物种丰富度和Simpson多样性指数分析结果表明,密林生境的兰科植物的菌根真菌多样性在各生长季节基本高于开阔生境。此外,两种生境的优势兰科植物的菌根真菌物种多样性随生长季节转变所呈现的变化规律是相似的:萌发期和生长期的多样性均较高,峰值出现在生长期,到果期时则大幅下降。这与高原兰科植物的生长特性及营养供求规律基本相符。     

兰科菌根的生态学研究进展

兰科植物(Orchidaceae)是典型的菌根植物,自然条件下其种子的成功萌发和生长的早期阶段对菌根真菌有绝对的依赖性,在有些成年兰科植物中菌根真菌仍起着重要的作用。目前大部分兰科植物已为濒危物种,鉴于兰科植物天然的菌根共生关系,开展兰科植物和菌根真菌互作的生态学研究不仅具有极高的科研价值,更有助于兰科植物的物种保护和野生种群的生态恢复。近年研究表明,兰科植物对真菌的选择和二者共生关系的建立与菌根真菌的空间分布和丰度密切相关,然而当前对自然环境中兰科菌根真菌的实际分布还了解甚少,因此文章从生态学角度系统分析兰科植物与菌根真菌的关系,探讨该领域的研究热点,旨在为兰科菌根的生态学研究提供参考。     

The mycorrhizal dependence of subordinates determines the effect of arbuscular mycorrhizal fungi on plant diversity

It is widely recognized that arbuscular mycorrhizal fungi (AMF) influence plant community structure. Several studies in the past few years have focused on the effect of AMF on plant diversity, showing contradictory results. On the basis of studies carried out in grasslands, it has been proposed that these results may not be in conflict but rather depend on mycorrhizal dependence of dominant and subordinate species in the plant community. Here, we propose a simple conceptual model to explain the effect of AMF on plant diversity and dominance hierarchy. Our model suggests that the effect of AMF on plant diversity can be explained mainly by mycorrhizal dependence of subordinates. It also gives predictions for a wider range of community types, and helps in identifying the systems in which empirical data are most critically needed.     

Patterns and regulation of mycorrhizal plant and fungal diversity

The diversity of mycorrhizal fungi does not follow patterns of plant diversity, and the type of mycorrhiza may regulate plant species diversity. For instance, coniferous forests of northern latitudes may have more than 1000 species of ectomycorrhizal (EM) fungi where only a few ectomycorrhizal plant species dominate, but there are fewer than 25 species of arbuscular mycorrhizal (AM) fungi in tropical deciduous forest in Mexico with 1000 plant species. AM and EM fungi are distributed according to biome, with AM fungi predominant in arid and semiarid biomes, and EM fungi predominant in mesic biomes. In addition, AM fungi tend to be more abundant in soils of low organic matter, perhaps explaining their predominance in moist tropical forest, and EM fungi generally occur in soils with higher surface organic matter.EM fungi are relatively selective of host plant species, while AM tend to be generalists. Similar morphotypes of AM fungi collected from different sites confer different physiological benefits to the same plant species. While the EM fungi have taxonomic diversity, the AM fungi must have physiological diversity for individual species to be so widespread, as supported by existing studies. The environmental adaptations of mycorrhizal fungi are often thought to be determined by their host plant, but we suggest that the physiology and genetics of the fungi themselves, along with their responses to the plant and the environment, regulates their diversity. We observed that one AM plant species,Artemisia tridentata, was associated with different fungal species across its range, indicating that the fungi can respond to the environment directly and must not do so indirectly via the host. Different species of fungi were also active during different times of the growing season on the same host, again suggesting a direct response to the environment.These patterns suggest that even within a single functional group of microorganisms, mycorrhizal fungi, considerable diversity exists. A number of researchers have expressed the concept of functional redundancy within functional groups of microorganisms, implying that the loss of a few species would not be detectable in ecosystem functioning. However, there may be high functional diversity of AM fungi within and across habitats, and high species diversity as well for EM fungi. If one species of mycorrhizal fungus becomes extinct in a habitat, field experimental data on AM fungi suggest there may be significant shifts in how plants acquire resources and grown in that habitat.     

Beech carbon productivity as driver of ectomycorrhizal abundance and diversity

We tested the hypothesis that carbon productivity of beech ( Fagus sylvatica ) controls ectomycorrhizal colonization, diversity and community structures. Carbon productivity was limited by long-term shading or by girdling. The trees were grown in compost soil to avoid nutrient deficiencies. Despite severe limitation in photosynthesis and biomass production by shading, the concentrations of carbohydrates in roots were unaffected by the light level. Shade-acclimated plants were only 10% and sun-acclimated plants were 74% colonized by ectomycorrhiza. EM diversity was higher on roots with high than at roots with low mycorrhizal colonization. Evenness was unaffected by any treatment. Low mycorrhizal colonization had no negative effects on plant mineral nutrition. In girdled plants mycorrhizal colonization and diversity were retained although ¹⁴C-leaf feeding showed almost complete disruption of carbon transport from leaves to roots. Carbohydrate storage pools in roots decreased upon girdling. Our results show that plant carbon productivity was the reason for and not the result of high ectomycorrhizal diversity. We suggest that ectomycorrhiza can be supplied by two carbon routes: recent photosynthate and stored carbohydrates. Storage pools may be important for ectomycorrhizal survival when photoassimilates were unavailable, probably feeding preferentially less carbon demanding EM species as shifts in community composition were found.     

Genetic diversity and host plant preferences revealed by simple sequence repeat and mitochondrial markers in a population of the arbuscular mycorrhizal fungus Glomus intraradices

Arbuscular mycorrhizal fungi (AMF) are important symbionts of plants that improve plant nutrient acquisition and promote plant diversity. Although within-species genetic differences among AMF have been shown to differentially affect plant growth, very little is actually known about the degree of genetic diversity in AMF populations. This is largely because of difficulties in isolation and cultivation of the fungi in a clean system allowing reliable genotyping to be performed. A population of the arbuscular mycorrhizal fungus Glomus intraradices growing in an in vitro cultivation system was studied using newly developed simple sequence repeat (SSR), nuclear gene intron and mitochondrial ribosomal gene intron markers. The markers revealed a strong differentiation at the nuclear and mitochondrial level among isolates. Genotypes were nonrandomly distributed among four plots showing genetic subdivisions in the field. Meanwhile, identical genotypes were found in geographically distant locations. AMF genotypes showed significant preferences to different host plant species (Glycine max, Helianthus annuus and Allium porrum) used before the fungal in vitro culture establishment. Host plants in a field could provide a heterogeneous environment favouring certain genotypes. Such preferences may partly explain within-population patterns of genetic diversity.     

AM真菌物种多样性:生态功能、影响因素及维持机制

AM真菌物种多样性是土壤生态系统生物多样性的重要组分之一。尽管对AM真菌多样性已有多年研究,但是,已有研究绝大多数仅停留在对AM真菌群落种属解析层面上,对AM真菌物种多样性生态功能及维持机制方面的认识较浅。从生态功能、影响因素及维持机制3个方面系统地综述了近年来AM真菌多样性领域的研究进展。认为AM真菌多样性对植物群落生产力的调控机制及结合理论与实践解析AM真菌多样性维持机制是该领域未来的重点研究方向。     

Mycorrhizal features and leaf traits covary at the community level during primary succession

The mycorrhizal association between fungi and plants is thought to be an important component of the functional diversity of plant communities, although evidence is weak. We explored community-level changes to mycorrhizal features and leaf traits along a primary successional gradient on a sedimentation coast. We found that community weighted mean values of mycorrhizal features and leaf traits varied systematically along the successional series, representing a transition from communities dominated by more stress-tolerant plant species (less mycorrhizal colonization and lower specific leaf area) to less stress-tolerant plant species (higher mycorrhizal colonization and specific leaf area). Despite the co-variation in leaf traits and mycorrhizal features at the community level, only mycorrhizal features showed an increasing functional diversity with successional age. These results suggest that mycorrhizal fungi should not be forgotten in trait-based plant community ecology.     

丛枝菌根真菌种群的孢子季相动态研究

以草坪为研究对象,研究草坪土壤中丛枝菌根真菌种群的孢子组成、孢子密度、物种丰富度、多样性及其季相变化规律。结果表明,丛枝菌根真菌孢子密度、物种丰富度和多样性指数在一年内随季节变化表现出一定的季相变化规律,三者均在冬季达到最高,在时间节律上与植物群落季相变化不同步;同时分析了气候因素(平均温度、降雨量和日照时间等)对丛枝菌根真菌的影响。结果表明,气候因素对孢子密度、物种丰富度和多样性指数均有显著影响。     

Resistance of soil biota and plant growth to disturbance increases with plant diversity

Plant diversity is critical to the functioning of ecosystems, potentially mediated in part by interactions with soil biota. Here, we characterised multiple groups of soil biota across a plant diversity gradient in a long‐term experiment. We then subjected soil samples taken along this gradient to drought, freezing and a mechanical disturbance to test how plant diversity affects the responses of soil biota and growth of a focal plant to these disturbances. High plant diversity resulted in soils that were dominated by fungi and associated soil biota, including increased arbuscular mycorrhizal fungi and reduced plant‐feeding nematodes. Disturbance effects on the soil biota were reduced when plant diversity was high, resulting in higher growth of the focal plant in all but the frozen soils. These results highlight the importance of plant diversity for soil communities and their resistance to disturbance, with potential feedback effects on plant productivity.     

Native soil microbial amendments generate trade‐offs in plant productivity,diversity, and soil stability in coastal dune restorations

Given the important role that soil microbes play in structuring plant communities and mediating ecosystem functions, there is growing interest in harnessing microbial communities to restore degraded ecosystems. Dune restorations, in particular, may benefit from native soil amendments because microbial diversity and abundance are very low in unvegetated areas. In an outdoor mesocosm experiment simulating Texas Gulf Coast dune restorations, we tested how native soil microbial amendments and restored diversity of foundational grasses influenced three key restoration responses: plant performance, plant diversity (including the colonization of native forbs), and soil stability. We found that native microbial amendments increased plant diversity and have the potential to increase soil stability, but this came at the cost of decreased plant biomass. Our results suggest that soil enemies in the native microbial amendments increased plant diversity by decreasing the performance of the dominant grass species and that arbuscular mycorrhizal fungi in the native microbial amendments increased the density of fungal hyphae in the soil, which can increase soil stability. Depending on the goals of the restoration, native soil microbial amendments may be a simple and inexpensive method to provide restoration benefits.