Evidence for ecological matching of whole AM fungal communities to the local plant-soil environment

The range of ecological roles exhibited by arbuscular mycorrhizal (AM) fungi depends on functional differences among naturally occurring local assemblages of AM species. While functional differences have been demonstrated among AM fungal species and among geographic isolates of the same species, almost nothing is known about functional differences among whole communities of naturally occurring AM fungi. In the greenhouse, we reciprocally transplanted whole AM fungal communities between plant-soil systems representing a serpentine grassland and a tallgrass prairie, using as hosts two grasses common to both systems. For Sorghastrum nutans, native fungi consistently enhanced plant growth more than fungi switched from the alternate system. For Schizachyrium scoparium, foreign and native fungi promoted plant growth similarly in both the serpentine and prairie systems. Thus, the use of foreign inoculum in restoration could change the relative performance, and potentially the competitive abilities, of co-occurring plant species. Moving AM fungal inocula into foreign environments also caused changes in the taxonomic composition of the resultant spore communities, demonstrating their response to environmental influences. These results provide strong evidence for functional differences among naturally occurring AM communities and suggest that a particular AM fungal community may be better matched ecologically to its local habitat than communities taken from other locations.     

沙田柚根围AM真菌的生境适宜性和季节变化性

以山地长寿沙田柚成年果树为对象,研究不同生境和季节对丛枝菌根(Arbuscular mycorrhiza,AM)真菌侵染以及根围土壤中AM真菌孢子密度的影响.试验结果表明,不同生境下,菌根侵染率和AM真菌孢子密度都是以梯田最高,坡地次之,洼地最低;在坡地和洼地生境下,生草区均高于清耕区.两块试验地AM真菌的菌丝侵染率均为夏季最高(16.8%±1.9%和16.0%±1.8%),秋季次之,冬季最低;丛枝和泡囊的形成也是夏/秋季较高,春/冬季较低;而根围土壤中AM真菌孢子密度则是秋季最高[(159±19)个/100 g和(167±17)个/100 g],夏季次之,冬季最低.总之,对于长寿沙田柚成年果树,AM真菌的菌根侵染率在夏季梯田最高,根围土壤中的AM真菌孢子密度在秋季梯田最高;在坡地和洼地生境中,生草处理均可显著提高菌根侵染率和AM真菌孢子密度.图4参27     

AM真菌对烟草砷吸收及根际pH的影响

采用矿区3种砷(As)含量土壤水提液的琼脂培养基变色试验,研究接种土著(Glomus spp.,Acaulospora spp.)与外源(Glomus caledonium)AM真菌对煳草(Nicotiana tabacum L.)As吸收以及根际pH的影响.结果表明,除无As水平下的烟草对照苗根际pH持续升高外,其它处理的烟草化苗根际pH都有先升高后降低的规律,而且菌根化苗根际pH的降低速度快于对照苗.烟草地上部分As含量在所有处理中没有表现出显著的差异.在无As水平下,烟草地下部分As含量依次为外源菌根化苗>土著菌根化苗>对照苗.在低As、中As、高As水平下,土著菌根化苗的地下部分As含量显著高于外源菌根化苗以及对照苗.可见,接种AM真菌可以降低烟草根际pH,从而影响烟草的As吸收,这也显示了AM真菌应用于烟草安全的可能性.此外,本研究表明土著AM真菌与外源AM真菌对培养基质中的同一As水平有着不同的响应.     

Mycorrhizal benefit differs among the sexes in a gynodioecious species

Both plant sex and arbuscular mycorrhizal (AM) symbiosis influence resource acquisition and allocation in plants, but the interaction between these two components is not well established. As the different plant sexes differ in their resource needs and allocation patterns, it is logical to presume that they might differ in their relationship with AM as well. We investigate whether the association with AM symbiosis is different according to the host plant sex in the gynodioecious Geranium sylvaticum, of which, besides female and hermaphrodite plants, intermediate plants are also recognized. Specifically, we examine the effects of two different AM fungi in plant mass allocation and phosphorus acquisition using a factorial greenhouse/common garden experiment. Cloned G. sylvaticum material was grown in symbiosis with AM fungi or in non-mycorrhizal condition. We evaluated both the symbiotic plant benefit in terms of plant mass and plant P content and the fungal benefit in terms of AM colonization intensity in the plant roots and spore production. Our results suggest that G. sylvaticum plants benefit from the symbiosis with both AM fungal species tested but that the benefits gained from the symbiosis depend on the sex of the plant and on the trait investigated. Hermaphrodites suffered most from the lack of AM symbiosis as the proportion of flowering plants was dramatically reduced by the absence of AM fungi. However, females and intermediates benefited from the symbiosis relatively more than hermaphrodites in terms of higher P acquisition. The two AM fungal species differed in the amount of resources accumulated, and the fungal benefit was also dependent on the sex of the host plant. This study provides the first evidence of sex-specific benefits from mycorrhizal symbiosis in a gynodioecious plant species.     

Distinct mycorrhizal communities on new and established hosts in a transitional tropical plant community

The extent to which interspecific plants share mycorrhizal fungal communities depends on the specificity of the symbiosis. For tropical forest tree seedlings, colonization by mycorrhizal fungi associated with established vegetation could have important consequences for survival and growth. I used a novel molecular technique to assess the potential for sharing of mycorrhizas in forest and pasture in southern Costa Rica, by identifying arbuscular mycorrhizal (AM) fungi in roots of the forest canopy tree species Terminalia amazonia, pasture grasses Urochloa ruziziensis and U. decumbens, and seedlings of T. amazonia planted into experimental reforestation plots. I tested the hypotheses that experimental seedlings were colonized either by the AM fungal community of the forest T. amazonia (suggesting host specificity) or of Urochloa (suggesting absence of specificity/importance of local environment). After two years, pasture-grown T. amazonia seedlings were colonized by neither community, but rather by a species of Glomus that was rarely observed on the other plants. These results suggest that conspecific seedlings planted into existing vegetation generate a distinct mycorrhizal community that may influence competitive interactions and the relative costs and benefits of the AM fungal symbiosis at early stages in the life cycle of tropical trees.     

Effects of two different intercropping systems on arbuscular mycorrhizal fungal colonization and polychlorinated biphenyl (PCB) dissipation北大核心CSCD

Polychlorinated biphenyls (PCBs) are typical organic contaminants in the environment. It is indicated that plants and soil microorganisms have a positive synergistic effect on the remediation of PCB-contaminated soil. To investigate the effect of intercropping on arbuscular mycorrhizal (AM) fungal colonization and PCB remediation, a pot-cultivation experiment with two intercropping treatments, corn (Zea mays L.) / ryegrass (Lolium perenne L.) and corn/alfalfa (Medicago sativa L.), and a corn monoculture was conducted in a greenhouse. All treatments were inoculated with Funneliformis mosseae M47V. Plant biomass, root mycorrhizal colonization rate, concentration of PCBs and their homologs in soil, 16S rDNA gene abundance, and community composition measured by Terminal Restriction Fragment Length Polymorphism (T-RFLP) were determined after harvesting the plants. Intercropping significantly increased the root mycorrhizal colonization rate and plant biomass of corn (P < 0.05), as well as the available N content of the soil. A significant difference of the bacterial community composition was found among different treatments (P < 0.05). Compared with corn monoculture, corn/alfalfa intercropping significantly increased soil bacteria abundance (P < 0.05). The dissipation rates of total PCBs, as well as that of penta-chloro biphenyls were significantly increased in the intercropping treatments, when compared to the corn monoculture treatment. Moreover, corn/ryegrass intercropping has a significantly positive effect on the dissipation of tri-chloro biphenyls. Non-metric multidimensional scaling (NMDS) analysis indicated that the PCBs homologues composition were significantly correlated with the relative abundance of 128 bp and 148 bp T-RFs. Corn intercropping with ryegrass or alfalfa has a positive effect on root mycorrhizal colonization rate and plant biomass of corn. Inoculation of AM fungi in intercropping treatments significantly improved the efficiency of PCB remediation by promoting bacterial abundance and shifting the bacterial community composition. In conclusion, intercropping combined with AM fungi have positive synergistic effects on the remediation of PCB-contaminated soils. © 2018 Science Press. All rights reserved.     

An island biogeography approach for understanding changes in compositional similarity at present scenario of biotic homogenization

Local extinction of native species and colonization of non-native species are commonly invoked as responsible for changes in species similarity among biotas of different regions. In this study we used a model of species similarity between islands to assess the emergent, and unexplored, effects of changes in colonization by native species, extinction of non-native species, and propagule pressure on species similarity among insular communities. The model predicts that extinction probability of endemic species has a positive but asymptotic effect on species similarity, which is exacerbated by increasing colonization and reducing extinction of non-native species. Species similarity tends to increase with increasing colonization probability by non-native species, however this effect may be reduced, or even reverted, when the islands are exposed to an elevated number of non-native species that are prone to extinction, high levels of endemic species loss, and an initially large number of native species shared between islands. Species similarity was positively affected by the propagule pressure rate of non-native species only when their colonization and extinction probabilities were large and small enough, respectively. A negative effect of propagule pressure rate can be caused by an increase in the pool size of non-native species, which involves the introduction of different species into different islands, promoting biotic differentiation between islands. Our results indicate that the interactions between colonization, extinction and species pool lead to nonlinear responses and unexpected scenarios of biotic change. In order to validate model predictions, future research programs should focus on understanding the dynamics on such complex meta-communities where coexist native, non-native and endemic species.     

Spatial and temporal patterns of seed dispersal: an important determinant of grassland invasion.

We measured spatial and temporal patterns of seed dispersal and seedling recruitment for 58 species in a grassland community to test whether seed dispersal could predict patterns of invasion after disturbance. For the 12 most abundant grasses, recruitment of native species was dependent on the propagule supply of both native and exotic species. Variability in seed rain on small spatial (1-10 m) and temporal (within season) scales led to qualitative differences in the outcome of disturbance colonization such that native species dominated disturbances when exotic seed supply was low but failed to establish when exotic seed supply was high. Local dispersal and spatial heterogeneity in species composition promoted coexistence of native and exotic species by creating refuges from high exotic seed supply within native dominated patches. Despite this, copious exotic seed production strongly limited recruitment of native species in exotic dominated patches. Most grasslands in California are presently dominated by exotic species, suggesting that competition at the seedling stage is a major barrier to native species restoration.     

The impact of tillage practices on arbuscular mycorrhizal fungal diversity in subtropical crops.

Arbuscular mycorrhizal fungi (AMF) are a main component of soil microbiota in most agrosystems. As obligately mutualistic symbionts, they colonize the roots of the majority of plants, including crop plants. We used molecular techniques to investigate how different tillage systems (moldboard, shred-bedding, subsoil-bedding, and no tillage) can influence the AM fungal community colonizing maize, bean, and sorghum roots in an experimental site located in northern Tamaulipas, Mexico. Roots from 36 plants were analyzed using AM fungal-specific primers to partially amplify the small subunit (SSU) of the ribosomal DNA genes. More than 880 clones were screened for restriction fragment length polymorphism (RFLP) variation, and 173 of these were sequenced. Ten AM fungal types were identified and clustered into three AM fungal families: Gigasporaceae, Glomaceae, and Paraglomaceae. Glomus was the dominating taxon in all the samples. Four of the 10 identified types were distinct from any previously published sequences and could correspond to either known unsequenced species or unknown species. The fungal diversity was low in the four agriculture management systems, but the multidimensional scaling (MDS) analysis and log-linear-saturated model indicated that the composition of the AMF community was significantly affected by the tillage system. In conclusion, since some fungal types were treatment specific, agricultural practices could directly or indirectly influence AM biodiversity.     

菌根类型对森林树木净初级生产力的影响

菌根是土壤真菌与植物根系形成的共生体,存在于绝大多数植物（90%）的根系和生境中。菌根共有7种类型,在生态系统的过程和功能方面都扮演着十分重要的角色。为了增强对菌根在森林生态系统中重要功能的理解,文章基于全球森林数据库,在全球尺度上研究了不同菌根类型对森林树木净初级生产力（NPP）的影响。结果表明,森林树木NPP随菌根类型的不同而不同,AM类型菌根森林的NPP[679.49 g.m-2.a-1（以C计）]要显著高于含ECM类型菌根的森林[479.00 g.m-2.a-1（以C计）];菌根类型的不同对森林树木地上和地下及其各组分NPP的影响和贡献也存在着显著的不同,AM类型菌根对地下NPP的贡献要高于ECM菌根,而ECM菌根对地上NPP的贡献则较大。菌根类型对地上、地下NPP组分的影响分析则表明,AM类型的菌根对树叶和细根NPP的贡献较大,而ECM类型菌根则对树木主干和枝NPP的贡献较大。可见,森林树木总体NPP及其各组分NPP都随着菌根类型的不同而存在显著的差异。     

污泥堆肥利用中AM对稗草生长及Cu、Pb吸收的影响

在滨海盐渍土中分别混加质量分数为0%、20%、40%和60%的污泥堆肥,作为盆栽基质,研究摩西球囊霉（Glomusmosseae）和根内球囊霉（Glomus intraradices）2种AM真菌对稗草（Echinochloa crusgalli）生长及其吸收Cu、Pb的影响,分别以不接种AM真菌的处理为各自的对照。结果显示：添加污泥堆肥处理中稗草接种苗菌根侵染率均显著高于纯盐泽土处理。同时,随着盐渍土中污泥堆肥含量增加稗草生物量上升,其中在含有40%和60%污泥堆肥处理中接种AM真菌稗草的地上及地下部生物量显著高于未接种苗。接种AM真菌显著提高了稗草Cu、Pb富集总量;接种AM真菌显著提高了稗草地下部Cu富集量,却降低了地下部Pb累积量,提高了Pb向地上部的转运,增加了地上部Pb累积量。这些结果表明污泥堆肥中接种AM真菌可以促进稗草的生长和提高对重金属Cu、Pb的富集能力。     

Tree species and mycorrhizal associations influence the magnitude of rhizosphere effects

Previous research on the effects of tree species on soil processes has focused primarily on the role of leaf litter inputs. We quantified the extent to which arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) tree species influence soil microbial activity and nutrient availability through rhizosphere effects. Rhizosphere soil, bulk soil, and fine roots were collected from 12 monospecifc plots (six AM and six ECM tree species) planted on a common soil at the Turkey Hill Plantations in Dryden, New York. Rhizosphere effects were estimated by the percentage difference between rhizosphere and bulk soil samples for several assays. Rhizosphere effects on soil microbes and their activities were significant for ECM species but in only a few cases for AM species. In AM tree species, microbial biomass, net N mineralization, and phosphatase enzyme activity in the rhizosphere were 10-12% greater than in bulk soil. In ECM tree species, rhizosphere effects for microbial biomass, C mineralization rates, net N mineralization, and phosphatase activity were 25-30% greater than bulk soil, and significantly greater than AM rhizosphere effects. The magnitude of rhizosphere effects was negatively correlated with the degree of mycorrhizal colonization in AM tree species (r = -0.83) and with fine root biomass (r = -0.88) in ECM tree species, suggesting that different factors influence rhizosphere effects in tree species forming different mycorrhizal associations. Rhizosphere effects on net N mineralization and phosphatase activity were also much greater in soils with pH < 4.3 for both AM and ECM tree species, suggesting that soil pH and its relation to nutrient availability may also influence the magnitude of rhizosphere effects. Our results support the idea that tree roots stimulate nutrient availability in the rhizosphere, and that systematic differences between AM and ECM may result in distinctive rhizosphere effects for C, N, and P cycling between AM and ECM tree species.     

Aquatic plant community invasibility and scale-dependent patterns in native and invasive species richness

Invasive species richness often is negatively correlated with native species richness at the small spatial scale of sampling plots, but positively correlated in larger areas. The pattern at small scales has been interpreted as evidence that native plants can competitively exclude invasive species. Large-scale patterns have been understood to result from environmental heterogeneity, among other causes. We investigated species richness patterns among submerged and floating-leaved aquatic plants (87 native species and eight invasives) in 103 temperate lakes in Connecticut (northeastern USA) and found neither a consistently negative relationship at small (3-m2) scales, nor a positive relationship at large scales. Native species richness at sampling locations was uncorrelated with invasive species richness in 37 of the 60 lakes where invasive plants occurred; richness was negatively correlated in 16 lakes and positively correlated in seven. No correlation between native and invasive species richness was found at larger spatial scales (whole lakes and counties). Increases in richness with area were uncorrelated with abiotic heterogeneity. Logistic regression showed that the probability of occurrence of five invasive species increased in sampling locations (3 m2, n = 2980 samples) where native plants occurred, indicating that native plant species richness provided no resistance against invasion. However, the probability of three invasive species' occurrence declined as native plant density increased, indicating that density, if not species richness, provided some resistance with these species. Density had no effect on occurrence of three other invasive species. Based on these results, native species may resist invasion at small spatial scales only in communities where density is high (i.e., in communities where competition among individuals contributes to community structure). Most hydrophyte communities, however, appear to be maintained in a nonequilibrial condition by stress and/or disturbance. Therefore, most aquatic plant communities in temperate lakes are likely to be vulnerable to invasion.     

Mycorrhizal species differentially alter plant growth and response to herbivory

Plants simultaneously interact with multiple organisms which can both positively and negatively affect their growth. Herbivores can reduce plant growth through loss of plant biomass and photosynthetic area, while plant mutualists, such as mycorrhizal fungi, can increase plant growth through uptake of essential nutrients. This is the first study examining whether species-specific associations with mycorrhizal fungi alter plant tolerance to herbivory. We grew Plantago lanceolata plants with three species of mycorrhizal fungi previously shown to have differential impacts on plant growth and subjected them to herbivory by the specialist lepidopteran herbivore, Junonia coenia. Association with mycorrhizal fungus Glomus white provided the greatest growth benefit but did not alter plant response to herbivory. Alternatively, association with Archaeospora trappei provided less growth promotion but did lead to tolerance to herbivory in the form of an increased growth rate. Finally, an association with the fungus Scutellospora calospora led to neither plant growth promotion nor tolerance to herbivory. In fact, an association with S. calospora appeared to reduce plant tolerance to herbivory. An association with all three species of mycorrhizae resulted in a pattern of growth similar to that of plants grown only with Glomus white, suggesting that growth promotion by multiple mycorrhizal species is driven by the inclusion of a "super fungus," in this case, Glomus white. This work illustrates that plant response to herbivory depends upon the mycorrhizal fungal mutualist with which a plant is associated.     

Novel weapons: invasive plant suppresses fungal mutualists in America but not in its native Europe

Why some invasive plant species transmogrify from weak competitors at home to strong competitors abroad remains one of the most elusive questions in ecology. Some evidence suggests that disproportionately high densities of some invaders are due to the release of biochemicals that are novel, and therefore harmful, to naive organisms in their new range. So far, such evidence has been restricted to the direct phytotoxic effects of plants on other plants. Here we found that one of North America's most aggressive invaders of undisturbed forest understories, Alliaria petiolata (garlic mustard) and a plant that inhibits mycorrhizal fungal mutualists of North American native plants, has far stronger inhibitory effects on mycorrhizas in invaded North American soils than on mycorrhizas in European soils where A. petiolata is native. This antifungal effect appears to be due to specific flavonoid fractions in A. petiolata extracts. Furthermore, we found that suppression of North American mycorrhizal fungi by A. petiolata corresponds with severe inhibition of North American plant species that rely on these fungi, whereas congeneric European plants are weakly affected. These results indicate that phytochemicals, benign to resistant mycorrhizal symbionts in the home range, may be lethal to na?ve native mutualists in the introduced range and indirectly suppress the plants that rely on them.     

Insects mediate the effects of propagule supply and resource availability on a plant invasion

Invasive species are a global threat to biodiversity and the functioning of natural ecosystems. Here, we report on a two-year experiment aimed at elucidating the combined and relative effects of three key controls on plant invasions: propagule supply, soil nitrogen (N) availability, and herbivory by native insects. We focus on the exotic species Lespedeza cuneata, a Rank 1 invasive species. Propagule supply and soil N-availability interacted to control the density and foliar cover of L. cuneata. In low N plots, density and foliar cover of L. cuneata were higher in the propagule addition plots than in the plots to which propagules were not added. Surprisingly, this interaction was significant only when the abundance of herbivores was experimentally reduced. This experiment provides evidence that native insect herbivores mediate the interactive effects of propagule supply and resources on invasion by a widespread invasive plant species.     

Influences of global environmental changes on arbuscular mycorrhizal fungal communities: a review北大核心CSCD

丛枝菌根(arbuscular mycorrhizal, AM)真菌是生态系统地上地下部的重要连接体,对其群落结构特征的研究有助于菌种资源的发掘和生态系统的可持续发展.人类生产生活活动对全球环境带来了一系列的改变,如二氧化碳和臭氧浓度升高、氮沉降、增温及降水减少/增多等,全球环境变化对AM真菌群落结构的影响也引起了广泛关注.针对二氧化碳和臭氧浓度升高、增温、氮沉降和降水减少/增多等全球环境变化因子,总结其对AM真菌群落结构影响的国内外研究进展,探讨全球环境变化对AM真菌群落的可能作用途径.已有模拟全球环境变化实验研究主要集中于北半球的草原、农田和森林系统.大多研究发现二氧化碳和臭氧浓度升高未对AM真菌多样性产生不利影响,但使AM真菌群落结构显著分异.氮沉降和增温对AM真菌多样性的影响表现为降低、无显著影响和增加等多种情况,对AM真菌群落结构的影响也表现为未显著和显著分异,主要与模拟实验处理方式、增加幅度、土壤养分水平和生态系统类型等因素有关.降水减少未显著影响AM真菌群落结构和多样性,而降水增加使AM真菌群落结构发生显著分异.这些研究主要注重AM真菌群落结构和多样性如何改变等生态现象而潜在机理探索以及热带和南半球不同生态系统下的研究尚不足.另外,鉴于全球变化因子间的关联性,复合因子对AM真菌群落结构的影响值得重视.(图1表4参113)     

Plant winners and losers during grassland N-eutrophication differ in biomass allocation and mycorrhizas

Human activities release tremendous amounts of nitrogenous compounds into the atmosphere. Wet and dry deposition distributes this airborne nitrogen (N) on otherwise pristine ecosystems. This eutrophication process significantly alters the species composition of native grasslands; generally a few nitrophilic plant species become dominant while many other species disappear. The functional equilibrium model predicts that, compared to species that decline in response to N enrichment, nitrophilic grass species should respond to N enrichment with greater biomass allocation aboveground and reduced allocation to roots and mycorrhizas. The mycorrhizal feedback hypothesis states that the composition of mycorrhizal fungal communities may influence the composition of plant communities, and it predicts that N enrichment may generate reciprocal shifts in the species composition of mycorrhizal fungi and plants. We tested these hypotheses with experiments that compared biomass allocation and mycorrhizal function of four grass ecotypes (three species), two that gained and two that lost biomass and cover in response to long-term N enrichment experiments at Cedar Creek and Konza Long-Term Ecological Research grasslands. Local grass ecotypes were grown in soil from their respective sites and inoculated with whole-soil inoculum collected from either fertilized (FERT) or unfertilized (UNFERT) plots. Our results strongly support the functional equilibrium model. In both grassland systems the nitrophilic grass species grew taller, allocated more biomass to shoots than to roots, and formed fewer mycorrhizas compared to the grass species that it replaced. Our results did not fully support the hypothesis that N-induced changes in the mycorrhizal fungal community were drivers of the plant community shifts that accompany N eutrophication. The FERT and UNFERT soil inoculum influenced the growth of the grasses differently, but this varied with site and grass ecotype in both expected and unexpected ways suggesting that ambient soil fertility or other factors may be interacting with mycorrhizal feedbacks.     

The role of chitin in the decomposition of ectomycorrhizal fungal litter

Ectomycorrhizal fungal tissues comprise a significant forest-litter pool. Ectomycorrhizal (EM) fungi may also influence the decomposition of other forest-litter components via competitive interactions with decomposer fungi and by ensheathing fine roots. Because of these direct and indirect effects of ectomycorrhizal fungi, the factors that control the decomposition of EM fungi will strongly control forest-litter decomposition as a whole and, thus, ecosystem nutrient and carbon cycling. Some have suggested that chitin, a component of fungal cell walls, reduces fungal tissue decomposition because it is relatively recalcitrant. We therefore examined the change in chitin concentrations of EM fungal tissues during decomposition. Our results show that chitin is not recalcitrant relative to other compounds in fungal tissues and that its concentration is positively related to the decomposition of fungal tissues. Variation existing among EM fungal isolates in chitin concentration suggests that EM fungal community structure influences C and nutrient cycling.     

菌根真菌对土壤呼吸的影响

土壤是陆地生态系统的重要组成部分,是地球最大的碳库之一。土壤呼吸是陆地生态系统向大气释放CO2的主要途径之一,其微小的变化将导致大气CO2浓度的较大波动。菌根是土壤真菌与植物根系形成的共生体,存在于绝大多数植物(90%)的根系和生境中。菌根共有7种类型,其中,在自然界中以丛枝菌根和外生菌根为主。众多研究表明,菌根对土壤呼吸有着至关重要的影响,是预测土壤CO2释放速率必须考虑,但却是难以估算的因素。文章总结了有关菌根(包括丛枝菌根和外生菌根)对土壤呼吸影响的研究进展,对目前所得到的研究结果进行了分析,表明菌根真菌侵染植物根系形成菌根后,能提高土壤呼吸的速率,其可能的途径有3条:(1)增强了根系的呼吸,(2)菌根真菌自身呼吸的组分,(3)根外菌丝促进了非根际区土体的呼吸。但是,菌根侵染对根系呼吸敏感性(Q10)影响的研究,大多数则表现为不显著。同时,菌根对土壤呼吸的影响受到各种因素的制约。通过对不同温度下菌根真菌呼吸速率的分析,表明菌根真菌对温度的升高具有适应性。从目前已发表的报道来看,目前关于菌根对土壤呼吸影响的研究还非常少,但可喜的是,近年来,越来越多的研究已经意识到了菌根在土壤呼吸中的重要作用。准确评估菌根在土壤呼吸中的贡献,将有助于预测未来在气候变化下,土壤CO2的排放量。