Abundance Of Arbuscular Mycorrhizal Fungi Research Articles

Anaerobically mineralized nitrogen as a potential indicator of the activity and abundance of mycorrhizal fungi in Mollisols

Anaerobically mineralized nitrogen (AN) is a suitable soil health indicator. The AN is sensitive to soil use changes and is related to soil and particulate organic carbon and aggregate stability. This work aims to evaluate the relationship between AN and 1) easily extractable glomalin-related soil proteins; 2) abundance of arbuscular mycorrhizal fungi measured by the number of arbuscular mycorrhizal fungi spores, and 3) arbuscular mycorrhizal fungi activity (root colonization). Soil samples were taken at depths of 0-5 and 5-20 cm from cultivated and uncultivated plots throughout the southeastern province of Buenos Aires. Anaerobically mineralized nitrogen, soil organic carbon, particulate organic carbon, aggregate stability, easily extracted glomalin-related soil proteins and the logarithm of the number of arbuscular mycorrhizal fungi spores (log spores) at 0-5, 5-20 and 0-20 cm depths were determined. In wheat roots, the percentages of total infection and arbuscules at 0-20 cm were measured. At all depths, AN was positively correlated to easily extractable glomalin-related soil proteins (r=0.34-0.65), which is an indicator of arbuscular mycorrhizal fungi activity and abundance. Likewise, AN was positively related to log-spores (r=0.58-0.78), which is an indicator of arbuscular mycorrhizal fungi abundance. However, AN was not related to root colonization (the percentages of total infection and arbuscules) that manifests the activity of arbuscular mycorrhizal fungi at a specific moment. Thus, anaerobically mineralized nitrogen would be an indicator of mid- to long-term changes in arbuscular mycorrhizal fungi abundance and activity (easily extractable glomalin-related soil proteins and log-spores) resulting from soil use. Consequently, the AN would allow monitoring an important aspect of soil microbiological health associated with arbuscular mycorrhizal fungi. However, it is necessary to evaluate the relationships studied in this work in a wider range of soil situations.

Sex-specific phosphorus acquisition strategies and cycling in dioecious Populus euphratica forests along a natural water availability gradient.

Soil phosphorus (P) availability affects plant growth and distribution. However, it is still unknown how sex-specific variation in functional traits affects plants' P acquisition and soil P transformation. On wet sites, female poplars had a greater specific root length (SRL), and a higher diversity of arbuscular mycorrhizal fungi (AMF) and phosphate-solubilizing bacteria (PSB). Male poplars living on wet sites increased the abundance of AMF and PSB communities and enhanced moderately labile and highly resistant organic P mineralisation via increased phosphatase activity. In contrast, on the dry site, the abundance and diversity of AMF and PSB communities increased in females, enhancing moderately labile and highly resistant organic P mineralisation via elevating phosphatase activities. Males maintained greater SRL and promoted Ca-P mobilisation via the release of root carboxylic acids and rhizosphere acidification on the dry site. The AMF community diversity followed a similar pattern as that of the PSB community when altering the P availability of different-sex plants. Our results indicated that organic P and Ca-P are the major sources of plant-available P in natural P. euphratica forests. Seasonal shifts and geographic locations affected the share of organic and inorganic P pools, and AMF and PSB diversities, ultimately altering sex-specific P acquisition strategies of plants.

Prairie restoration promotes the abundance and diversity of mutualistic arbuscular mycorrhizal fungi.

Predicting how biological communities assemble in restored ecosystems can assist in conservation efforts, but most research has focused on plants, with relatively little attention paid to soil microbial organisms that plants interact with. Arbuscular mycorrhizal (AM) fungi are an ecologically significant functional group of soil microbes that form mutualistic symbioses with plants and could therefore respond positively to plant community restoration. To evaluate the effects of plant community restoration on AM fungi, we compared AM fungal abundance, species richness, and community composition of five annually cultivated, conventionally managed agricultural fields with paired adjacent retired agricultural fields that had undergone prairie restoration 5-9 years prior to sampling. We hypothesized that restoration stimulates AM fungal abundance and species richness, particularly for disturbance-sensitive taxa, and that gains of new taxa would not displace AM fungal species present prior to restoration due to legacy effects. AM fungal abundance was quantified by measuring soil spore density and root colonization. AM fungal species richness and community composition were determined in soils and plant roots using DNA high-throughput sequencing. Soil spore density was 2.3 times higher in restored prairies compared to agricultural fields, but AM fungal root colonization did not differ between land use types. AM fungal species richness was 2.7 and 1.4 times higher in restored prairies versus agricultural fields for soil and roots, respectively. The abundance of Glomeraceae, a disturbance-tolerant family, decreased by 25% from agricultural to restored prairie soils but did not differ in plant roots. The abundance of Claroideoglomeraceae and Diversisporaceae, both disturbance-sensitive families, was 4.6 and 3.2 times higher in restored prairie versus agricultural soils, respectively. Species turnover was higher than expected relative to a null model, indicating that AM fungal species were gained by replacement. Our findings demonstrate that restoration can promote a relatively rapid increase in the abundance and diversity of soil microbial communities that had been degraded by decades of intensive land use, and community compositional change can be predicted by the disturbance tolerance of soil microbial taxonomic and functional groups.

Nutrients addition decreases soil fungal diversity and alters fungal guilds and co-occurrence networks in a semi-arid grassland in northern China

Anthropogenic eutrophication is known to impair the diversity and stability of aboveground community, but its effects on the diversity, composition and stability of belowground ecosystems are not yet fully understood. In this study, we conducted a 9-year nitrogen (N) and phosphorus (P) addition experiment in a semi-arid grassland of Northern China to elucidate the impacts of nutrients addition on soil fungal diversity, functional guilds, and co-occurrence networks. The results showed that N addition significantly decreased soil fungal diversity and altered fungal community composition, whereas P addition had no impact on them. The relative abundance of arbuscular mycorrhizal fungi and leaf_saprotroph were reduced by N and P addition, but P addition enhanced the abundance of saprotrophic fungi. Co-occurrence network analysis revealed that N addition destabilized fungal network complexity and stability, while P addition slightly increased the network complexity. Additionally, the network analysis of N × P interaction revealed that P addition mitigated negative effects of N addition on network complexity and stability. Structural equation modeling (SEM) results suggested that nutrients addition directly or indirectly influenced the fungal community structure through the loss of plant richness and the increase of perennial grass biomass. These findings indicate that in comparison to P addition, N addition exhibits a pronounced negative effect on soil fungal communities. Our findings also suggest that changes in plant functional groups under nutrients deposition are pivotal in shaping soil fungal community structure in semi-arid grassland and highlight the need for a better understanding of the belowground ecosystem dynamics.

Interactions between halotolerant nitrogen-fixing bacteria and arbuscular mycorrhizal fungi under saline stress.

Soil salinity negatively affects crop development. Halotolerant nitrogen-fixing bacteria (HNFB) and arbuscular mycorrhizal fungi (AMF) are essential microorganisms that enhance crop nutrient availability and salt tolerance in saline soils. Studying the impact of HNFB on AMF communities and using HNFB in biofertilizers can help in selecting the optimal HNFB-AMF combinations to improve crop productivity in saline soils. We established three experimental groups comprising apple plants treated with low-nitrogen (0 mg N/kg, N0), normal-nitrogen (200 mg N/kg, N1), and high-nitrogen (300 mg N/kg, N2) fertilizer under salt stress without bacteria (CK, with the addition of 1,500 mL sterile water +2 g sterile diatomite), or with bacteria [BIO, with the addition of 1,500 mL sterile water +2 g mixed bacterial preparation (including Bacillus subtilis HG-15 and Bacillus velezensis JC-K3)]. HNFB inoculation significantly increased microbial biomass and the relative abundance of beta-glucosidase-related genes in the rhizosphere soil under identical nitrogen application levels (p < 0.05). High-nitrogen treatment significantly reduced AMF diversity and the relative abundance of beta-glucosidase, acid phosphatase, and urea-related genes. A two-way analysis of variance showed that combined nitrogen application and HNFB treatment could significantly affect soil physicochemical properties and rhizosphere AMF abundance (p < 0.05). Specifically, HNFB application resulted in a significantly higher relative abundance of Glomus-MO-G17-VTX00114 compared to that in the CK group at equal nitrogen levels. The impact of HNFB on the AMF community in apple rhizospheres is influenced by soil nitrogen levels. The study reveals how varying nitrogen levels mediate the relationship between exogenous HNFB, soil properties, and rhizosphere microbes.

Lithology and niche habitat have significant effect on arbuscular mycorrhizal fungal abundance and their interspecific interactions

The chemical properties of bedrock play a crucial role in shaping the communities of soil and root-associated arbuscular mycorrhizal fungi (AMF). We investigate AMF community composition and diversity in bulk soil, rhizosphere soil, and roots in karst and non-karst forests. Chemical properties of bedrock of the calcium oxide (CaO) and ratio of calcium oxide and magnesium oxide (Ca/Mg), soil pH, and exchangeable Ca2+ were higher in karst carbonate rocks compared to non-karst clastic rocks. Conversely, bedrock phosphorus content (P-rock), silicon dioxide (SiO2) content, and tree diversity exhibited an opposing trend. AMF abundance was higher in non-karst clastic rocks than in karst carbonate rocks. Stronger interspecific interactions among AMF taxa occurred in the bulk soil and rhizosphere soil of non-karst clastic rocks compared to karst carbonate rocks. AMF abundance and diversity were higher in rhizosphere soil and roots, attributed to increasing nutrient availability when compared to the bulk soil. A more complex network within AMF taxa was observed in rhizosphere soil and roots compared to bulk soil due to an increase in AMF abundance and diversity in rhizosphere soil and roots. Comparing non-karst clastic rocks, karst carbonate rocks increased soil nitrogen (N) and P levels, which can be attributed to the elevated content of soil Ca2+ and Mg2+ content, facilitated by the high CaO content and Ca/Mg ratio in the bedrock of karst forests. However, the thicker soil layer exhibited higher soil nutrient storage, resulting in greater tree diversity in non-karst forests. These findings suggest that high tree richness may increase root biomass and secretion of root exudates in non-karst regions, thereby enhancing the abundance of AMF and their interspecies interactions. Consequently, the diverse bedrock properties that drive variations in soil properties, nutrients, and plant diversity can impact AMF communities, ultimately promoting plant growth and contributing to vegetation recovery.

Facultative mycorrhization in a fern (Struthiopteris spicant L. Weiss) is bound to light intensity

BackgroundThe establishment of mycorrhizal relationships between a fungus and a plant typically enhances nutrient and water uptake for the latter while securing a carbon source for the fungus. However, under a particular set of environmental conditions, such as low availability of light and abundant nutrients in the soil, the resources invested in the maintenance of the fungi surpass the benefits obtained by the host. In those cases, facultative mycorrhizal plants are capable of surviving without symbiosis. Facultative mycorrhization in ferns has been overlooked until now. The present study measured the response of Struthiopteris spicant L. Weiss, and its root-associated fungi to different levels of light and nutrient availability in terms of growth, mycorrhizal presence, and leaf nutrient content. This fern species exhibits a great tolerance to variable light, nutrient, and pH conditions, and it has been found with and without mycorrhizae. We conducted a greenhouse experiment with 80 specimens of S. spicant and three factors (Light, Phosphorus, and Nitrogen) resulting in eight treatments.ResultsWe found a significant influence of the factor light on fungal community composition, plant biomass, and nutrient accumulation. Departing from a lack of colonization at the initial stage, plants showed a remarkable increment of more than 80% in the arbuscular mycorrhizal fungi (AMF) richness and abundance in their roots when grown under high light conditions, compared with the ones in low light. We also observed an upward trend of C:P and C:N ratios and the above- and belowground biomass production when AMF abundance increased. Furthermore, the compositional analysis of the whole fungal communities associated with S. spicant roots revealed clear differences among low-light and high-light treatments.ConclusionsThis study is the first to investigate the importance of light and nutrient availability in determining fern-AMF relationships. We confirmed that Struthiopteris spicant is a facultative mycorrhizal plant. The composition and diversity of AMF found in the roots of this fern are strongly influenced by light and less by nutrient conditions. Our study shows that ferns respond very sensitively to changes in environmental factors, leading to shifts in the associated mycorrhizal communities.

Improving apple orchard health: The role of arbuscular mycorrhizal fungi in alleviating replant disease and strengthening soil microbial communities

The occurrence of apple replant disease (ARD) is inevitable during the renewal and transformation of aging orchards. This disease seriously threatens the healthy and sustainable development of the apple industry. Arbuscular mycorrhizal fungi (AMF) have shown great potential in promoting plant growth, resisting soil-pathogen infection and improving soil quality. However, there is relatively little information available about the application of AMF in the prevention and control of ARD. In this study, we conducted a pot and field experiment were conducted with inoculation of AMF (Paraglomus sp. SW1) on apple rootstock (Malus hupehensis Rehd. in the pot experiment and M9T337 in the field experiment) to explore the biocontrol effect of AMF on ARD by comparing the changes in fungal and AMF communities after AMF inoculation on apples under replanting conditions. AMF-inoculated apple was used as the treatment, while non-inoculated apple was used as the control. The results showed that AMF-inoculated plants not only promoted the growth of M. hupehensis Rehd., but also stimulated the branch elongation growth of young apple trees, compared to the control. After inoculation with AMF, the community structure of soil fungi and arbuscular mycorrhizal fungi changed significantly, with an increase in the abundance of fungi and AMF in soil, and a significant reduction in the abundance of Fusarium spp., especially Fusarium moniliforme, Fusarium solani, and Fusarium proliferatum. Additionally, the soil enzyme activity increased significantly. Furthermore, the levels of ammonium nitrogen (NH4+), nitrate nitrogen (NO3−), available phosphorus (AP), available potassium (AK), organic matter (SOM), and pH in the rhizosphere soil were significantly related to the changes in the community structure of fungi and AMF. The AP, NH4+ and NO3− was found to drive the fungal communities, while NH4+ and NO3− drove the AM fungal communities in replanting soil. In conclusion, apple-arbuscular mycorrhizal symbionts can effectively alleviate ARD by promoting plant growth and optimizing the structure of soil microbial communities. Future research, should test other gardening plants following AMF inoculation to prepare for a wider application in controlling replant disease.

Drought reduces productivity and anti-herbivore defences, but not mycorrhizal associations, of perennial prairie forbs.

During drought, plants allocate resources to aboveground biomass production and belowground carbohydrate reserves, often at the expense of production of defence traits. Additionally, drought has been shown to alter floral resources, with potential implications for plant-pollinator interactions. Although soil symbionts, such as arbuscular mycorrhizal (AM) fungi, can alleviate drought stress in plants, certain levels of drought may negatively impact this relationship, with potential cascading effects. Because of their importance to plant and animal community diversity, we examined effects of drought on biomass production, physical defence properties, nectar production, and associated AM fungal abundance of five common prairie forb species in a greenhouse study. Reduced soil moisture decreased vegetative biomass production. Production of trichomes and latex decreased under drought, relative to well-watered conditions. Ruellia humilis flowers produced less nectar under drought, relative to well-watered conditions. Intra-radical AM fungal colonization was not significantly affected by drought, although extra-radical AM fungal biomass associated with S. azurea decreased following drought. Overall, grassland forb productivity, defence, and nectar production were negatively impacted by moderate drought, with possible negative implications for biotic interactions. Reduced flower and nectar production may lead to fewer pollinator visitors, which may contribute to seed limitation in forb species. Reduced physical defences increase the likelihood of herbivory, further decreasing the ability to store energy for essential functions, such as reproduction. Together, these results suggest drought can potentially impact biotic interactions between plants and herbivores, pollinators, and soil symbionts, and highlights the need for direct assessments of these relationships under climate change scenarios.

The influence of a soil amendment on the abundance and interaction of arbuscular mycorrhizal fungi with arable soils and host winter wheat.

Arbuscular mycorrhizal (AM) fungi have been shown to be associated with an estimated 70 % of vascular terrestrial plants. Such relationships have been shown to be sensitive to soil disturbance, for example, tillage in the preparation of a seed bed. From the application of arable soil management, AM fungal populations have been shown to be negatively impacted in abundance and diversity, reducing plant growth and development. The present study aims to utilise two sources (multipurpose compost and a commercial inocula) of mycorrhizal fungi for the amendment of arable soils supporting Zulu winter wheat under controlled conditions and quantify plant growth responses. A total of nine fields across three participating farms were sampled, each farm practicing either conventional, reduced, or zero tillage soil management exclusively. Soil textures were assessed for each sampled soil. Via the employment of AM fungal symbiosis quantification methods, AM fungi were compared between soil amendments and their effects on crop growth and development. The present study was able to quantify a mean 6 cm increase to crop height (P<0.001), 10 cm reduction to root length corresponding with a 2.45-fold increase in AM fungal arbuscular structures (P<0.001), a 1.15-fold increase in soil glomalin concentration corresponding to a 1.26-fold increase in soil carbon, and a 1.32-fold increase in the relative abundance of molecular identified AM fungal sequences for compost amended soils compared to control samples. Mycorrhizal inocula, however, saw no change to crop height or root length, AM fungal arbuscules were reduced by 1.43-fold, soil glomalin was additionally reduced by 1.55-fold corresponding to a reduction in soil carbon by 1.31-fold, and a reduction to relative AM fungal species abundance by 1.26-fold. The present study can conclude the addition of compost as an arable soil amendment is more beneficial for the restoration of AM fungi beneficial to wheat production and soil carbon compared to the addition of a commercial mycorrhizal inocula.

Soil Physico-Chemical Properties and Different Altitudes Affect Arbuscular Mycorrhizal Fungi Abundance and Colonization in Cacao Plantations of Cameroon

Soil Physico-Chemical Properties and Different Altitudes Affect Arbuscular Mycorrhizal Fungi Abundance and Colonization in Cacao Plantations of Cameroon

Mycorrhizal effects on crop yield and soil ecosystem functions in a long-term tillage and fertilization experiment.

It is well understood that agricultural management influences arbuscular mycorrhizal (AM) fungi, but there is controversy about whether farmers should manage for AM symbiosis. We assessed AM fungal communities colonizing wheat roots for three consecutive years in a long-term (> 14 yr) tillage and fertilization experiment. Relationships among mycorrhizas, crop performance, and soil ecosystem functions were quantified. Tillage, fertilizers and continuous monoculture all reduced AM fungal richness and shifted community composition toward dominance of a few ruderal taxa. Rhizophagus and Dominikia were depressed by tillage and/or fertilization, and their abundances as well as AM fungal richness correlated positively with soil aggregate stability and nutrient cycling functions across all or no-tilled samples. In the field, wheat yield was unrelated to AM fungal abundance and correlated negatively with AM fungal richness. In a complementary glasshouse study, wheat biomass was enhanced by soil inoculum from unfertilized, no-till plots while neutral to depressed growth was observed in wheat inoculated with soils from fertilized and conventionally tilled plots. This study demonstrates contrasting impacts of low-input and conventional agricultural practices on AM symbiosis and highlights the importance of considering both crop yield and soil ecosystem functions when managing mycorrhizas for more sustainable agroecosystems.

Responses of the arbuscular mycorrhizal fungi community to warming coupled with increased drought in an arid desert region

Warming coupled with precipitation changes induced by climate change profoundly affect desert ecosystem functions in global drylands. Arbuscular mycorrhizal fungi (AMF) play a crucial role in such ecosystems by regulating energy and nutrient exchange. However, little is known about how AMF communities respond to warming coupled with reduced precipitation (W + RP). We evaluated the impacts of 0.5 °C and 1.5 °C increase in temperature coupled with 5 % and 8 % reductions in total annual precipitation (0.5 °C W + 5 % RP, 1.5 °C W + 8 % RP) on AMF communities and the main ecological processes structuring AMF community assemblies in the rhizosphere soil of typical winter annual plants in the Tengger Desert, northwest China. The results showed that warming coupled with reduced precipitation could significantly alter the composition, abundance, and diversity of AMF communities. Both AMF biomass and AMF diversity increased in the 0.5 °C W + 5 % RP treatment but decreased in the 1.5 °C W + 8 % RP treatment. The 1.5 °C W + 8 % RP treatment significantly reduced root biomass and the AMF colonization rate but increased the specific root length, indicating a trade-off between fine roots and their symbiotic AMF. The AMF community was phylogenetically random in the 0.5 °C W + 5 % RP treatment but appeared clustered in the 1.5 °C W + 8 % RP treatment, implying that more pronounced warming coupled with reduced precipitation can promote the deterministic assembly of the AMF community. We provide a conceptual framework for comprehending the mechanisms underlying the effects of warming coupled with reduced precipitation on AMF communities, incorporating biological and geochemical processes. Overall, the findings of this study suggest that AMF abundance and diversity and the main ecological processes driving AMF assemblages respond differently to more pronounced compared to less intensive warming coupled with reduced precipitation. Importantly, higher warming coupled with a reduction in precipitation reduced plant dependence on AMF and resulted in stronger environmental filtration by significantly reducing soil water content.

Arbuscular mycorrhizal fungal community association determines the production of flavonoids and chlorogenic acid in Acer truncatum Bunge

Arbuscular mycorrhizal (AM) fungi can affect plant secondary metabolic pathways, but how the composition and function of AM fungal communities affect the secondary metabolite content of Acer truncatum Bunge remains unknown. Ten typical A. truncatum plantations were used in southern Shaanxi province. The entropy weight method was applied to construct two grades of A. truncatum tree plantations (ordinary and superior). The interaction between AM fungi and trees in the different grades of plantations was compared. The effects of AM fungal community, soil fertility, climatic factors, and plant nutrients on the contents of flavonoids and chlorogenic acid in leaves were studied. There were no differences in the α and β diversity of AM fungal associations among different grades of trees, but the hyphal colonization rate and co-occurrence network characteristics were different. There were no differences in plant height and diameter at breast height (DBH), but higher flavonoid and chlorogenic acid contents were found in the leaves of superior trees compared to ordinary trees, and this difference was attributed to variations in their AM fungal communities. For A. truncatum trees of similar growth (same height and DBH), the abundance of AM fungi was positively correlated with leaf flavonoids and chlorogenic acid contents in superior tree grade stands, but negatively correlated in ordinary tree stands. The positive correlation between leaf flavonoid content and soil fertility in superior tree grade was mediated by the β diversity of AM fungi recruited in this environment. The relative abundance of VTX00069 and VTX00156 was positively correlated with leaf flavonoid and chlorogenic acid contents, which provides direction for the selection of AM fungi that promote flavonoids and chlorogenic acid production in A. truncatum leaves. Overall, the effect of specific AM fungal communities in the rhizosphere soil of A. truncatum on its flavonoids and chlorogenic acid contents is direct and important. This study provides new insights into enhancing the production of secondary metabolites in A. truncatum.

Impacts of Lithology and Slope Position on Arbuscular Mycorrhizal Fungi Communities in a Karst Forest Soil.

The influence of lithology and slope position on arbuscular mycorrhizal fungi (AMF) communities has been explored in various ecosystems, but there is a limited understanding of these mechanisms in karst regions. This study focused on typical karst hills with contrasting lithologies, specifically dolomite and limestone. Additionally, three slope positions (upper, middle, and lower) were investigated within each hill in karst forest ecosystems. Total phosphorus (TP) content in the soil was higher in dolomite compared to limestone. Conversely, exchangeable calcium (Ca) was lower in dolomite than in limestone. Notably, the lithology, rather than the slope position, exerted a significant impact on AMF diversity and abundance and the presence of specific AMF taxa. Dolomite exhibited greater AMF richness and a higher Shannon index in comparison to limestone when not accounting for slope position. The AMF community composition differed between dolomite and limestone. For instance, without considering slope position, the relative abundance of Acaulospora, Diversispora, and Paraglomus was higher in dolomite than in limestone, while the relative abundance of Claroideoglomus displayed an opposing trend. Furthermore, a more complex interaction among AMF taxa was observed in dolomite as compared to limestone, as evidenced by an increase in the number of nodes and edges in the co-occurrence networks within the dolomite. The genera Glomus, Claroideoglomus, and Diversispora exhibited a higher number of links with each other and with other AMF taxa. The study identified TP and Ca as the primary factors determining variations in AMF diversity between dolomite and limestone. Consequently, it is imperative to consider the underlying lithology and soil conditions when addressing the restoration of degraded karst hilly areas.

Effects of field-aging on the impact of biochar on herbicide fate and microbial community structure in the soil environment

Biochar can enhance organic carbon storage and mitigate the adverse effects of pesticides in the soil. However, the mechanisms by which field-aging affects the impacts of biochar on herbicide behavior and the composition of microbial communities in the soil remain unclear. This study aimed to investigate the influences of aged and fresh biochar on herbicide behavior and microbial community structure in the soil. Herein, with 14C-labeled technology, aged treatment (soil amended with field-aged biochar), fresh treatment (soil amended with fresh biochar), and control (soil without biochar) were installed to evaluate their treatment capacities. The results showed that the average leaching out and mineralization of simazine in the aged treatment were significantly higher by 4.8% and 1.66% (P < 0.05) compared with the fresh treatment. Relative to the control, the pesticide was significantly adsorbed (P < 0.05) in the aged treatment. The abundance of arbuscular mycorrhizal fungi (AMF) significantly increased by 1.03 and 1.16-fold, whereas fungi increased dramatically by 1.02-fold and decreased by 1.21-fold in the aged and fresh treatments, respectively (P < 0.05). In addition, eukaryotes were effectively reduced by 1.02 and 1.14-fold in these treatments, respectively (P < 0.05). This study suggests that field aging can undermine the impacts of biochar on pesticides and modify the microbial community structure in the soil environment.

Cover crop identity determines root fungal community and arbuscular mycorrhiza colonization in following main crops

AbstractCover crops (CC) can promote nutrient retention and recycling for main crops yet may also promote soilborne pathogens or suppress beneficial root symbionts such as arbuscular mycorrhizal fungi (AMF). We investigated how root fungal communities of main crop are affected by preceding CC monocultures and mixtures and by main crop identity. We expected that AMF abundance and diversity in main crops are promoted by AM‐host CC, and suppressed by non‐AM‐host CC, and that mixtures of CC species can promote beneficial and suppress pathogenic root fungi. Our full‐factorial field experiment comprised crop rotation in sand soil with different CC treatments (monocultures of radish [AM non‐host], ryegrass, clover, vetch [AM hosts], mixtures of radish + vetch, ryegrass + clover and fallow) and two main crops (oat and endive). At peak crop growth, we investigated the root fungal communities in the main crops using microscopy and high throughput sequencing (Illumina MiSeq). Cover crop identity was of prime importance and CC legacy overruled main crop identity in determining root fungal communities in main crops. Compared with fallow, CC with ryegrass increased AMF colonization and richness in both main crops and of non‐AMF in oat. Legacies of ryegrass, ryegrass + clover and vetch resulted in distinct root fungal communities in the main crops, while the legacy of CC with radish were similar to the legacy of fallow. Root fungal community in crops after clover had highest abundance of representative fungal pathogens in contrast with the other CC treatments that resulted in fungal communities where pathogens were scarce. Oppositely to expected, CC mixtures did not enhance fungal symbionts or suppressed pathogens. Overall, fungal communities in roots of the main crops in our field experiment were determined by the preceding CC species in monoculture, rather than by the CC AMF preference or functional group. This research highlights that the choice of CC determines the root fungal community in main crop which may influence crop quality.

Evaluation of the relation between soil biomass of arbuscular mycorrhizal fungi and glomalin-related soil protein in conservation agriculture

Arbuscular mycorrhizal fungi (AMF) are indicators of soil health and are associated with various soil benefits, primarily linked to glomalin accumulation from hyphal turnover. However, the direct connection between glomalin-related soil protein (GRSP) and AMF has been questioned. The study aimed to investigate the correlation between different fractions of GRSP and fatty acid fractions in soil, as well as the impact of conservation agriculture practices on AMF biomass and GRSP content. Findings revealed a positive correlation between easily extractable (EE) GRSP and phospholipid fatty acid (PLFA) 16:1ω5, while no significant correlations were found for difficultly extractable (DE) or total GRSP fractions. These results highlight the complexity of GRSP dynamics and the need for further research on different fractions and their relation to AMF biomass. Additionally, the study demonstrated that mechanical soil management had a greater impact on AMF hyphal biomass and EE-GRSP compared to residue management. Direct seeding, a reduced tillage approach, led to higher hyphal biomass and EE-GRSP, indicating AMF sensitivity to tillage intensity. This suggests that tillage practices exert a stronger influence on AMF abundance and GRSP content than residue management.

Can cardiolipins be used as a biomarker for arbuscular mycorrhizal fungi?

Specific biomarker molecules are increasingly being used for detection and quantification in plant and soil samples of arbuscular mycorrhizal (AM) fungi, an important and widespread microbial guild heavily implicated in transfers of nutrients and carbon between plants and soils and in the maintenance of soil physico-chemical properties. Yet, concerns have previously been raised as to the validity of a range of previously used approaches (e.g., microscopy, AM-specific fatty acids, sterols, glomalin-like molecules, ribosomal DNA sequences), justifying further research into novel biomarkers for AM fungal abundance and/or functioning. Here, we focused on complex polar lipids contained in pure biomass of Rhizophagus irregularis and in nonmycorrhizal and mycorrhizal roots of chicory (Cichorium intybus), leek (Allium porrum), and big bluestem (Andropogon gerardii). The lipids were analyzed by shotgun lipidomics using a high-resolution hybrid mass spectrometer. Size range between 1350 and 1550Da was chosen for the detection of potential biomarkers among cardiolipins (1,3-bis(sn-3'-phosphatidyl)-sn-glycerols), a specific class of phospholipids. The analysis revealed a variety of molecular species, including cardiolipins containing one or two polyunsaturated fatty acids with 20 carbon atoms each, i.e., arachidonic and/or eicosapentaenoic acids, some of them apparently specific for the mycorrhizal samples. Although further verification using a greater variety of AM fungal species and samples from various soils/ecosystems/environmental conditions is needed, current results suggest the possibility to identify novel biochemical signatures specific for AM fungi within mycorrhizal roots. Whether they could be used for quantification of both root and soil colonization by the AM fungi merits further scrutiny.

Impact of ecological stages on the soil microbiota and soil abiotic factors in tropical and subtropical Brazilian regions.

Our aim was to test if ecological stages may influence the arbuscular mycorrhizal fungi (AMF), nematodes, and the soil chemical properties in agroforestry systems (AF), unassisted forest restoration (UFR), and natural ecosystem (Ne) located in the Brazilian Tropical and Subtropical regions. We collected soil samples to determine AMF, nematodes, soil pH, P, and soil organic carbon (SOC). AMF and nematode richness in the AF and Ne were similar in the tropical region. The redundancy analysis (RDA) indicated that the abundance of AMF and soil nematodes was mainly affected by soil pH, P, and SOC. Differences were associated with (1) ecological stages, as we found differences in AMF and nematode abundance as affected by habitat simplification, and (2) changes in soil pH, SOC, and P. Our work increases the understanding of the AMF and soil nematode community in the rhizosphere of AF and Ne in tropical and subtropical regions.