Arbuscular Mycorrhizal Fungi Richness Research Articles

The role of hedgerows in soil functioning within agricultural landscapes

Intensification of agriculture has led to major losses of hedgerows and field margins worldwide. Soil sample extraction, in situ time series of soil moisture, temperature and soil water quality analyses, annual earthworm sampling and arbuscular mycorrhizal (AM) fungi sampling enabled comparison of soil functions between typical hedgerows, grass field margins, pasture and arable (mainly winter wheat) fields in a temperate, lowland setting. Mean bulk density (upper 50 cm), surface compaction and soil moisture content were significantly lower while organic matter content and porewater dissolved organic carbon concentrations were significantly greater in hedgerow soils, than margins or fields. Mean nitrate and phosphate concentrations were three and ten times larger, respectively, in soil solutions under hedgerows than arable fields while ammonium concentrations were least in arable fields. Saturated hydraulic conductivity was significantly greater under hedgerows (median = 102 mm hr−1) where it took an average of one hour longer for soils to reach maximum moisture content following rainfall, than adjacent arable (median = 3 mm hr−1) or pasture fields and margins (median = 27 mm hr−1). Hedgerow soils had a greater proportion of flow through micropores and less macropore flow than other soils. The pasture and margin soils had the largest proportion of macropore flow (>85%) and more (and larger) anecic earthworm species, such as Lumbricus terrestris which produce vertical burrows. Earthworm density, biomass and diversity were greater in pasture and margin soils, followed by hedgerow soils, and tended to be lowest in arable soils. For both total and AM fungi, hedgerow soils hosted a distinct and heterogeneous soil community, margin and pasture communities were diverse but clustered together, and arable communities formed a distinct cluster, with low inter-sample variation and significantly lowest AM fungal richness. The findings demonstrate that soils under hedgerows, which should be conserved, can provide important functions on farmland including storing organic carbon, promoting infiltration and storing runoff, increasing earthworm diversity and hosting distinct AM communities.

Non-random association patterns in a plant-mycorrhizal fungal network reveal host-symbiont specificity.

Arbuscular mycorrhizal (AM) fungi are obligate plant symbionts that have important functions in most terrestrial ecosystems, but there remains an incomplete understanding of host-fungus specificity and the relationships between species and functional groups of plants and AM fungi. Here, we aimed to provide a comprehensive description of plant-AM fungal interactions in a biodiverse semi-natural grassland. We sampled all plant species in a 1,000-m2 homogeneous plot of dry calcareous grassland in two seasons (summer and autumn) and identified root-colonizing AM fungi by SSU rDNA sequencing. In the network of 33 plant and 100 AM fungal species, we found a significant effect of both host plant species and host plant functional group on AM fungal richness and community composition. Comparison with network null models revealed a larger-than-random degree of partner selectivity among plants. Grasses harboured a larger number of AM fungal partners and were more generalist in partner selection, compared with forbs. More generalist partner association and lower specialization were apparent among obligately, compared with facultatively, mycorrhizal plant species and among locally more abundant plant species. This study provides the most complete data set of co-occurring plant and AM fungal taxa to date, showing that at this particular site, the interaction network is assembled non-randomly, with moderate selectivity in associations between plant species and functional groups and their fungal symbionts.

Arbuscular mycorrhizal fungi associated with the babassu palm (Attalea speciosa) in the eastern periphery of Amazonia, Brazil

ABSTRACT Babassu, Attalea speciosa (Arecaceae) is a ruderal palm native to Amazonia, which turned dominant in frequently burned lands throughout the ‘arc of deforestation’ and other degraded lands, in extreme cases attaining complete dominance. This study investigated arbuscular mycorrhizal fungi (AMF) as one possible explanation for the outstanding ecological success of this exceptional palm. We explored the relationships between the babassu palm and native arbuscular mycorrhizal fungi and babassu effects on the AMF richness and mycorrhizal inoculum potential (MIP) in the eastern periphery of Amazonia. For this purpose, we sampled topsoil (0-20 cm) at the onset of the rainy season from a 5-year-old secondary forest regrowth (SEC) area with three levels of babassu dominance (sites with 10, 50 and 70% babassu biomass shares), and at three distances (0, 2.5 and 4 m) from isolated babassu patches within a degraded pasture (PAS), both with five replications per treatment. Glomerospore density varied from 100 to 302 per gram of soil, 56% higher in SEC than PAS. We identified a total of 16 AMF species, with dominance of Acaulospora (six species) followed by Glomus (three species). AMF richness increased with babassu dominance in SEC sites, and reduced with distance from babassu patches within the PAS. The colonization rate of babassu roots was higher in SEC than in PAS, whereas MIP was similar in both areas and without treatment differences. Our study points to strong mycorrhizal association of the babassu palm as a potential mechanism for its outstanding ecological success in degraded lands.

Relation between arbuscular mycorrhizal fungi, root-lesion nematodes and soil characteristics in maize agroecosystems

Native communities of arbuscular mycorrhizal fungi (AMF) and root inhabiting nematodes were examined in nine maize plots of conventional smallholders in Mexico differing in geographic location, soil properties and agricultural practices. Total species richness of AMF revealed 34 spore morphotypes, 27 of which were identified to species level and 7 to genus level. Only four AMF species were recovered from all nine maize plots: Paraglomus occultum, Funneliformis mosseae, Gigaspora albida and Acaulospora splendida. In the field, fine roots from all plots were colonized by AMF during the full crop cycle with highest colonization at flowering. AMF colonization responded to soil characteristics, mainly P, Ca and pH. Lowest AMF root colonization was found in maize plots with higher soil P levels. Eggs and adults of the endoparasitic root-lesion nematode (Pratylenchus spp.) were frequently observed with highest abundance at the vegetative plant growth phase. In addition, correlation analysis revealed complex interactions between nematode abundance and AMF root colonization depending on both maize growth phase and maize plots. The AMF from the field rhizosphere soil were propagated in pots under greenhouse conditions to produce AMF spores in better conditions and to corroborate their identity. When maize plants were grown in pots with a sterile phosphate-limiting substrate and supplemented with non-sterile soil from the plot sites harbouring native AMF communities, maize growth was strongly promoted allowing to reach flowering. This information will be useful to establish agricultural practices of maize cultivation that promote the use of native AMF.

Root colonizing and soil borne communities of arbuscular mycorrhizal fungi differ among soybean fields with contrasting historical land use

Arbuscular mycorrhizal fungi (AMF) are a key component of soil microbiota in natural and anthropogenic ecosystems. Even though soil type and climate conditioned land uses in the past, soybean cultivation has overrode such limitations and replaced the earlier diverse agro- and natural ecosystems in many countries of South America. We investigated whether actual diversity patterns of local AMF communities were determined by previous land uses and their intrinsic environmental conditions. We sequenced AMF DNA from root and soil samples collected from current soybean fields with three historical land use situations (HLU): agricultural fields, livestock farming and forest sites. We detected overall high AMF richness: 87 virtual taxa (VT) in soil and 69 VT in soybean roots. Mean number of VT per sample ranged from 8.1 to 19.2; it was not affected by HLU nor type of sample, but correlated with soil texture, pH, and plant density. Conversely, AMF community composition did significantly diverge among HLU and type of sample. A distinctive community composition was observed in roots of historical agricultural fields which differed from any other soil and root sample evaluated in this study. We attribute this finding to variations in the abundance pattern of predominant AMF taxa (Glomeraceae and Gigasporaceae). Our results indicate that soybean cultivation supports relatively high AMF diversity, with apparent legacies from earlier management and natural habitats in the composition of resident AMF communities.

The effect of slope aspect on the phylogenetic structure of arbuscular mycorrhizal fungal communities in an alpine ecosystem

Slope aspect not only modifies microclimate and soil-forming processes, but also significantly influences biogeographical patterns of species and multiple ecosystem functions across terrestrial landscapes. However, the effect of slope aspect on arbuscular mycorrhizal (AM) fungi, a group of functionally important root-associated microorganisms, remains poorly understood. In this study, we investigated AM fungal communities in an alpine ecosystem on a northwest-facing slope (NS) and a southeast-facing slope (SS) along a steep environmental gradient. Ecological processes structuring the fungal communities were inferred according to phylogenetic patterns and species abundance distributions. Thirty-two distinct AM fungal virtual taxa (VTs) were identified, predominantly belonging to the genus Glomus. The change of slope aspect from SS to NS recorded a significant decline in AM fungal richness, resulting in a marked loss of Glomus VTs and the dominance of Rhizophagus. Moreover, both taxonomic and phylogenetic composition of AM fungal communities significantly varied between the two slope aspects, this being largely driven by niche partitioning based on microclimate, soil pH and plant species composition. The influence of geographical distance was negligible. AM fungal communities were phylogenetically clustered on SS and random on NS, suggesting that the central process structuring communities shifted from a niche-dominated filter to the combination of competitive exclusion and a niche filter. Similarly, AM fungal species abundance distribution showed the best fit with the Lognormal model on SS and the Zipf-Mandelbrot model on NS, indicating that community dynamics on both slopes were also in accordance with niche-based mechanisms.

Soil disturbance changes arbuscular mycorrhizal fungi richness and composition in a fescue grassland in Alberta Canada

Native grasslands are endangered by non-native plant invasion worldwide, including foothills fescue grasslands in North America. Large populations of non-native plant species have established in these disturbed fescue grasslands, forming dense monocultures and spreading into undisturbed areas. Soil disturbance and plant invasion can alter the arbuscular mycorrhizal fungi (AMF) community, an important symbiotic partner of most land plants, which could negatively affect native plant reestablishment. The objective of this study was to assess whether AMF communities on a fescue grassland shifted in response to disturbances by landfill storage and gravel quarrying and with invasion of non-native plant species relative to undisturbed grassland.Soil and root-AMF samples were procured from disturbed and undisturbed areas at three sites. Plant canopy cover and species richness were assessed. Soils were analyzed for pH; electrical conductivity; total nitrogen, carbon and phosphorus; and available nutrients. For relative AMF taxa abundance assessment, NS31 and AMF specific primer AML2 were used to amplify a central fragment of the V3 and V4 region of the 18S rRNA gene. AMF were characterized using 454 pyrosequencing and multiplexed barcoded samples amplified from genomic DNA isolated from roots.There were 92 AMF, including 15 potentially novel taxa detected. AMF communities in disturbed and undisturbed sampling locations were distinct except for one site, and indicator AMF virtual taxa (VT) for undisturbed grassland and disturbed sites were identified. AMF richness was higher in undisturbed (72 VT) than disturbed (64 VT) sites and AMF richness was positively correlated with plant species richness, diversity and native plant cover, and negatively correlated with non-native plant cover. There were 43 AMF VT on undisturbed and disturbed sites, 62% with higher relative abundance on disturbed sites. Site disturbance shifted AMF communities relative to undisturbed native fescue grassland; thus restoration success with native plants might be highly dependent on reintroducing native AMF.

Diversity of arbuscular mycorrhizal fungi in pasture areas in the Serra do Itajaí National Park

As obligate biotrophs, arbuscular mycorrhizal fungi (AMF) (Phylum Glomeromycota) may be directly affected by deforestation. The present study evaluated the effect of forest conversion into pastures on AMF diversity within the Serra do Itajai National Park (Santa Catarina, Brazil). Soil samples were collected during two seasons (spring and autumn) from four areas: nati­ve forest (NF); two pastures undergoing recovery through application of brushwood (PB) and perch (PP) techniques, respectively; and an untreated pasture (UP). AMF spores were extracted from soil through wet sieving and decanting. Species were identified based on the morphology of the spores. In total, 33 AMF species were observed, distributed into six families and 11 genera. The best-represented genera were Acaulospora and Glomus, with 14 and 8 species, respectively. Conversion of forests into pastures did not affect mean species richness of AMF between the areas, nor between the seasons. However, the total number of species was higher in the native forest, indicating the negative effect of deforestation on AMF community diversity in the evaluated pasture areas. AMF species diversity was also greater during autumn.

Vinasse irrigation: effects on soil fertility and arbuscular mycorrhizal fungi population

The aim of this research was to determine the vinasse irrigation effects on the arbuscular mycorrhizal fungi (AMF) population (total spore abundance (TSA), richness, relative abundance, and diversity indices) and soil parameters and nutrients at high doses. The irrigation of soil with vinasses derived from sugarcane, beet, or alcohol production is a common practice around the world. Little is known about how this affects the AMF community and soil nutrients. The spider plant (Chlorophytum comosum, (Thunb.) Jacques), a mycorrhizable plant, was used to investigate the effect of 4 months of frequent vinasse irrigation (0, 25, 50, 75, and 100% vinasse concentration) on AMF and soil characteristics, e.g., electrical conductivity (EC), pH, mineral N, available P, Na+, K+, Ca2+, and Mg2+. The vinasse irrigation decreased the TSA, AMF richness and diversity after 4 months, regardless of vinasse concentration. The vinasse irrigation did not acidify the soil, but the EC, mineral N and available P increased. The biomass of C. comosum decreased (77–81%) after vinasse irrigation for 4 months. Frequent irrigation with vinasse at concentrations ≥50% increases EC, K+, Na+, Mg2+, Ca2+ and available P in the soil, and decreases the amount of AMF spores, richness and diversity, which is not desirable in agricultural soils.

Chronic fertilization of 37\xa0years alters the phylogenetic structure of soil arbuscular mycorrhizal fungi in Chinese Mollisols

Arbuscular mycorrhizal fungi (AMF) play vital roles in sustaining soil productivity and plant communities. However, adaption and differentiation of AMF in response to commonly used fertilization remain poorly understood. In this study, we showed that the AMF community composition was primarily driven by soil physiochemical changes associated with chronic inorganic and organic fertilization of 37 years in Mollisols. High-throughput sequencing indicated that inorganic fertilizer negatively affected AMF diversity and richness, implying a reduction of mutualism in plant–AMF symbiosis; however, a reverse trend was observed for the application of inorganic fertilizer combined with manure. With regards to AMF community composition, order Glomerales was dominant, but varied significantly among different fertilization treatments. All fertilization treatments decreased family Glomeraceae and genus Funneliformis, while Rhizophagus abundance increased. Plant-growth-promoting-microorganisms of family Claroideoglomeraceae and genus Claroideoglomus were stimulated by manure application, and likely benefited pathogen suppression and phosphorus (P) acquisition. Family Gigasporaceae and genus Gigaspora were negatively correlated with available P in soil. Additionally, redundancy analysis further suggested that soil available P, organic matter and pH were the most important factors in shaping AMF community composition. These results provide strong evidence for niche differentiation of phylogenetically distinct AMF populations under different fertilization regimes. Manure likely contributes to restoration and maintenance of plant–AMF symbiosis, and the balanced fertilization would favor the growth of beneficial AMF communities as one optimized management in support of sustainable agriculture in Mollisols.

Biodiversity of arbuscular mycorrhizal fungi and ecosystem function.

Contents Summary 1059 I. Introduction: pathways of influence and pervasiveness of effects 1060 II. AM fungal richness effects on ecosystem functions 1062 III. Other dimensions of biodiversity 1062 IV. Back to basics - primary axes of niche differentiation by AM fungi 1066 V. Functional diversity of AM fungi - a role for biological stoichiometry? 1067 VI. Past, novel and future ecosystems 1068 VII. Opportunities and the way forward 1071 Acknowledgements 1072 References 1072 SUMMARY: Arbuscular mycorrhizal (AM) fungi play important functional roles in ecosystems, including the uptake and transfer of nutrients, modification of the physical soil environment and alteration of plant interactions with other biota. Several studies have demonstrated the potential for variation in AM fungal diversity to also affect ecosystem functioning, mainly via effects on primary productivity. Diversity in these studies is usually characterized in terms of the number of species, unique evolutionary lineages or complementary mycorrhizal traits, as well as the ability of plants to discriminate among AM fungi in space and time. However, the emergent outcomes of these relationships are usually indirect, and thus context dependent, and difficult to predict with certainty. Here, we advocate a fungal-centric view of AM fungal biodiversity-ecosystem function relationships that focuses on the direct and specific links between AM fungal fitness and consequences for their roles in ecosystems, especially highlighting functional diversity in hyphal resource economics. We conclude by arguing that an understanding of AM fungal functional diversity is fundamental to determine whether AM fungi have a role in the exploitation of marginal/novel environments (whether past, present or future) and highlight avenues for future research.

Biological invasions increase the richness of arbuscular mycorrhizal fungi from a Hawaiian subtropical ecosystem

Biological invasions can have various impacts on the diversity of important microbial mutualists such as mycorrhizal fungi, but few studies have tested whether the effects of invasions on mycorrhizal diversity are consistent across spatial gradients. Furthermore, few of these studies have taken place in tropical ecosystems that experience an inordinate rate of invasions into native habitats. Here, we examined the effects of plant invasions dominated by non-native tree species on the diversity of arbuscular mycorrhizal (AM) fungi in Hawaii. To test the hypothesis that invasions result in consistent changes in AM fungal diversity across spatial gradients relative to native forest habitats, we sampled soil in paired native and invaded sites from three watersheds and used amplicon sequencing to characterize AM fungal communities. Whether our analyses considered phylogenetic relatedness or not, we found that invasions consistently increased the richness of AM fungi. However, AM fungal species composition was not related to invasion status of the vegetation nor local environment, but stratified by watershed. Our results suggest that while invasions can lead to an overall increase in the diversity of microbial mutualists, the effects of plant host identity or geographic structuring potentially outweigh those of invasive species in determining the community membership of AM fungi. Thus, host specificity and spatial factors such as dispersal need to be taken into consideration when examining the effects of biological invasions on symbiotic microbes.

Experimentally altered rainfall regimes and host root traits affect grassland arbuscular mycorrhizal fungal communities.

Future climate scenarios predict changes in rainfall regimes. These changes are expected to affect plants via effects on the expression of root traits associated with water and nutrient uptake. Associated microorganisms may also respond to these new precipitation regimes, either directly in response to changes in the soil environment or indirectly in response to altered root trait expression. We characterized arbuscular mycorrhizal (AM) fungal communities in an Australian grassland exposed to experimentally altered rainfall regimes. We used Illumina sequencing to assess the responses of AM fungal communities associated with four plant species sampled in different watering treatments and evaluated the extent to which shifts were associated with changes in root traits. We observed that altered rainfall regimes affected the composition but not the richness of the AM fungal communities, and we found distinctive communities in the increased rainfall treatment. We found no evidence of altered rainfall regime effects via changes in host physiology because none of the studied traits were affected by changes in rainfall. However, specific root length was observed to correlate with AM fungal richness, while concentrations of phosphorus and calcium in root tissue and the proportion of root length allocated to fine roots were correlated to community composition. Our study provides evidence that climate change and its effects on rainfall may influence AM fungal community assembly, as do plant traits related to plant nutrition and water uptake. We did not find evidence that host responses to altered rainfall drive AM fungal community assembly in this grassland ecosystem.

Compost Addition Enhanced Hyphal Growth and Sporulation of Arbuscular Mycorrhizal Fungi without Affecting Their Community Composition in the Soil.

Arbuscular mycorrhizal (AM) fungi form symbiotic associations with most crop plant species in agricultural ecosystems, and are conspicuously influenced by various agricultural practices. To understand the impact of compost addition on AM fungi, we examined effect of four compost rates (0, 11.25, 22.5, and 45 Mg/ha) on the abundance and community composition of AM fungi in seedling, flowering, and mature stage of soybean in a 1-year compost addition experiment system in Northeast China. Soybean [Glycine max (L.) Merrill] was used as test plant. Moderate (22.5 Mg/ha) and high (45 Mg/ha) levels of compost addition significantly increased AM root colonization and extraradical hyphal (ERH) density compared with control, whereas low (11.5 Mg/ha) level of compost addition did not cause significant increase in AM root colonization and ERH density. AM fungal spore density was significantly enhanced by all the compost rates compared with control. The temporal variations analysis revealed that, AM root colonization in seedling stage was significantly lower than in flowering and mature stage. Although AM fungal operational taxonomic unit richness and community composition was unaffected by compost addition, some abundant AM fungal species showed significantly different response to compost addition. In mature stage, Rhizophagus fasciculatum showed increasing trend along with compost addition gradient, whereas the opposite was observed with Paraglomus sp. In addition, AM fungal community composition exhibited significant temporal variation during growing season. Further analysis indicated that the temporal variation in AM fungal community only occurred in control treatment, but not in low, moderate, and high level of compost addition treatments. Our findings highlighted the significant effects of compost addition on AM growth and sporulation, and emphasized that growth stage is a stronger determinant than 1-year compost addition in shaping AM fungal community in black soil of Northeast China.

Effects of land use on arbuscular mycorrhizal fungal communities in Estonia.

Arbuscular mycorrhizal (AM) fungal communities vary across habitat types, as well as across different land use types. Most relevant research, however, has focused on agricultural or other severely human-impacted ecosystems. Here, we compared AM fungal communities across six habitat types: calcareous grassland, overgrown ungrazed calcareous grassland, wooded meadow, farmyard lawn, boreonemoral forest, and boreonemoral forest clear-cut, exhibiting contrasting modes of land use. AM fungi in the roots of a single host plant species, Prunella vulgaris, and in its rhizosphere soil were identified using 454-sequencing from a total of 103 samples from 12 sites in Estonia. Mean AM fungal taxon richness per sample did not differ among habitats. AM fungal community composition, however, was significantly different among habitat types. Both abandonment and land use intensification (clearcutting; trampling combined with frequent mowing) changed AM fungal community composition. The AM fungal communities in different habitat types were most similar in the roots of the single host plant species and most distinct in soil samples, suggesting a non-random pattern in host-fungal taxon interactions. The results show that AM fungal taxon composition is driven by habitat type and land use intensity, while the plant host may act as an additional filter between the available and realized AM fungal species pool.

The effects of road building on arbuscular mycorrhizal fungal diversity in Huangshan Scenic Area.

Arbuscular mycorrhizal (AM) fungi are vital soil microbes that connect many individual plants into a large functional organism via a vast mycelial network under the ground. In this study, the changes of soil AM fungal community in response to road-building disturbance caused by tourism development in Huangshan (Yellow Mountain) Scenic Area are assessed. Road building have brought negative effects on AM fungal community, inducing lower diversity parameters, including species number, spore density and diversity indices. However, the dominant genus and species of AM fungi which play key roles in the AM fungal community composition are quite similar before and after road building. Moreover, there are no significant differences in species richness of AM fungi associated with plants, suggesting the tolerance of AM fungal community to the disturbance of road building.

Colonization and Spore Richness of Arbuscular Mycorrhizal Fungi in Araucaria Nursery Seedlings in Curitiba, Brazil

Araucaria or Paraná pine [Araucaria angustifolia (Bertol.) Kuntze, 1898] is an endangered timber tree species of Atlantic Forest that naturally forms symbiosis with arbuscular mycorrhizal fungi (AMF). The objective of this experiment was to evaluate AMF colonization and spore AMF richness in araucaria seedlings produced in nursery at the metropolitan region of Curitiba, Brazil, with the interest of identifying a taxonomical AMF group. For that, soil and fine roots of 6-month-, 1-year-, 2-year-, 3-year-, and 5-year-old araucaria seedlings were sampled and evaluated. Evaluations indicated that araucaria seedlings were well colonized by AMF (with rates varying from almost 50 to over 85%) and produced an abundant number of mycorrhizal spores (from 344 to 676 spores per seedling). Samples contained spores of the species Acaulospora scrobiculata, Dentiscutata heterogama, and Glomus spinuliferum and unidentified species of genera Gigaspora and Glomus. The Glomus genus was the most abundant kind of AMF spores found under nursery conditions. Therefore, the experiment evidenced that Glomus is a promising genus candidate for being used as AMF inoculant in production of araucaria seedlings.

Arbuscular Mycorrhizal Fungal Communities in Organic and Conventional Onion Crops in the Columbia Basin of the Pacific Northwest United States

Onions are highly responsive to arbuscular mycorrhizal fungi (AMF), but little is known about AMF communities in onion crops (∼10,000 ha) in the semiarid, irrigated region of the Columbia Basin of Washington and Oregon. AMF communities and root colonization were compared in organic and conventional onion fields, and between paired conventional fields that were fumigated or not with metam sodium. AMF were detected in all fields at all sampling times, with no differences in root colonization of onions used to bait soil from organic versus conventional and fumigated versus nonfumigated fields. However, AMF colonization of roots of onion plants sampled midsummer was greater in organic versus conventional fields (67 versus 51%) and less in fumigated versus nonfumigated conventional fields (45 versus 67%). Pyrosequencing identified four AMF genera (Glomus, Claroideoglomus, Paraglomus, and Diversispora) and four dominant operational taxonomic units (OTUs) (Glomus mosseae (Funneliformis mosseae), Glomus Whitfield type 17, Claroideoglomus lamellosum, and Glomus MO_G17). AMF community structure in roots of onion plants collected from crops midsummer was different in organic versus conventional crops, with greater AMF diversity and richness in organic than conventional crops. There was no effect of organic versus conventional crops on dominant OTUs, but several low-abundance OTUs in organic fields were not detected in conventional fields. There was no consistent effect of metam sodium chemigation on AMF communities in onion crops. Overall, cropping practices in organic versus conventional onion production, and the use of metam sodium soil fumigation by center-pivot chemigation do not appear to be major drivers of AMF communities.

Does Over-Dominance of Bambusa bambos alter the Abundance and Composition of Arbuscular Mycorrhizal Fungal Community?

Plants have the potential to modify soil biological properties through root exudates and litter inputs. Bambusa bambos (L) Voss., a native bamboo, has been expanding its range in Intermediate and dry zone forests in Sri Lanka. With synchronised flowering and death cycles, bamboos have shown the potential to modify forest dynamics. No study has been attempted so far to evaluate its impacts on biological properties of forest soils. The current study assessed the impacts of population expansion of B. bambos on arbuscular mycorrhizal fungi (AMF) by conducting a comparative study with the help of bamboo-dominated (BD) and non-bamboo (NB) forest patches in the Intermediate Zone, Sri Lanka. The study sites are located in Moragahakanda in the Central Province of Sri Lanka. Two sites (located 4 km apart from each other) were selected; one dominated by bamboo (BD) and the other with no bamboo (NB). Eight composite soil samples (from a depth of 0-20 cm) were analysed for soil moisture content (%) and microbial biomass Carbon (MBC %). Wet sieving and decanting method was used to quantify the AMF spores. Different morphotypes were identified using spore wall characteristics. The results revealed significantly higher soil moisture in BD than in NB while MBC% showed no significant difference. A relatively higher total spore count (2,923) was reported in BD compared to NB (2,776). BD forests also demonstrated significantly higher mean spore abundance (≈ 500/100g soil) compared to that in NB forests (≈100/100g soil), with higher relative contribution from largest spores (125 μm). The AMF richness was relatively low in BD forest (15) than in NB (18), with 14 morphotypes present in both forest types. Shannon-Wiener index and evenness were relatively higher in NB (2.38 and 0.3) in comparison to BD (2.24 and 0.28). B. bambos has shown the potential to increase the AMF abundance with no impact on its richness and composition. Higher AMF abundance may possibly due to favourable micro-habitat conditions at BD compared to NB. Identification of such changes is crucial to introduce measures for conservation and restoration of these sensitive forests.Keywords: Native bamboos, AMF, Rapid spread, Bambusa bambos, Sri Lanka

Tropical‐temperate comparison of landscape‐scale arbuscular mycorrhizal fungal species distributions

AbstractAimMycorrhizas are among the most common symbioses on Earth, impacting plant community structure and ecosystem functioning, yet little landscape‐scale data linking mycorrhizal fungal diversity to biotic and abiotic properties exist to inform conservation. We examined arbuscular mycorrhizal (AM) fungal diversity in tropical and temperate locations and identified potential drivers of species distributions and diversity for use as proxy indicators in biodiversity conservation.LocationAM fungal communities were documented at 60 sites in the Colorado Plateau in south‐western United States and La Gran Sabana in south‐eastern Venezuela.MethodsCommunities of plants and AM fungi and abiotic variables were measured along 50‐m transects in three vegetation types (shrublands, forests, and traditional agricultural fields). Model selection and multivariate analyses were used to evaluate environmental predictors of AM fungal diversity and community structure.ResultsAM fungal species richness (α diversity) and community structure, but not among‐site turnover (β diversity), differed between tropical and temperate locations; only 15% of taxa were present in both locations. In unmanaged sites, AM fungal richness was not correlated with plant richness, but instead predicted by soil pH and temperature (temperate) or precipitation and latitude (tropics). The structure of AM fungal communities was influenced by plant identity but not plant diversity in both locations. Traditional, sedentary Hopi agriculture influenced AM fungal communities on the Colorado Plateau, but Pemón shifting slash‐and‐burn agriculture did not alter AM fungal communities at La Gran Sabana. At both locations, AM fungal community structure was linked to soil texture and nitrogen.Main conclusionsOur study demonstrates similarity between tropical and temperate regions in the biotic and abiotic drivers of landscape‐scale AM fungal species distributions. Soil and climate as well as habitat heterogeneity may serve as proxy indicators of AM fungal communities for use in conservation planning to preserve the ecosystem functions and services of mycorrhizas.