The fungal prime habitat is soil, and fungi are a key organism group for shaping the soil environment and influencing its functions. Their polarized, network forming growth, their diverse ecological roles such as mutualistic interactions with plants, decomposition of organic residues, their importance as pathogens/predators of various organisms, their role in soil structure buildup and their unique suites of metabolic compounds make them important players for many soil ecosystem functions.
We welcome contributions to this session that study fungal influences on soil functions such as biogeochemical cycling, decomposition and carbon storage, sustainable soil fertility, heavy metal and organic pollutant remediation, soil physics including aggregation, biodiversity relationships and trophic interactions. Contributions may involve both biotrophic (including the mycorrhizal) and/or saprotrophic fungi.
Soil biota provides services that are beneficial to the productivity and sustainability of land use systems. This session aims to discuss how land use systems affect soil biodiversity and how soil biodiversity (i.e. the performance of functional groups) feeds back to soil functions and ecosystem services. Knowledge is mounting that a sustainable intensification of land use needs to include the conservation of processes and functions run by soil biota that are essential for self-preservation considering services provided by soil biota including soil biodiversity. The joined European agricultural policy including soil and biodiversity conservation is asking for surveys throughout Europe. The strong progress in developing methods for biodiversity determination in soil and the quantification of biota specific impacts should be mirrored by the contributions. Moreover, transversal interactions with socio-economical sciences should lead to the development of tools to assess soil management as a socio-ecological issue.
This session will focus on the role of soil biology in delivering soil functions in systems formed by a human, e.g. agricultural, forests or restored sites and the synergies and trade-offs that occur within the bundle of soil functions, crossing several spatial and temporal scales. Additionally we welcome contributions aiming at promotion of soil managing practices that aim to optimize the multi-functionality of soils.
vPICO presentations: Mon, 26 Apr
Temperate and boreal forest trees are dependent on soil microorganisms for the acquisition of limiting nutrients, including phosphorus. These include ectomycorrhizal fungi, which form a symbiotic association with the roots of the trees, and soil-dwelling bacteria. The exact roles of and mechanisms used by ectomycorrhizal fungi and soil bacteria in plant phosphorus nutrition and phosphorus cycling are unclear, as are the effects of fungal identity and nutrient availability on these processes.
We compared the effects of inoculation with two species from the ectomycorrhizal fungal genus Pisolithus on the amounts of phosphorus available to and present in Eucalyptus grandis seedlings, under different levels of nitrogen fertilisation and atmospheric CO2. We then further explored the phosphorus-solubilising abilities of the fungi and soil bacterial community using in vitro plate assays, soil enzymatic assays and qPCR analyses.
We show evidence of synergistic interactions between the ectomycorrhizal fungi and soil bacterial community to improve phosphorus nutrition in the soil – interactions that are impacted by both nitrogen and CO2 levels and the species of the fungus. Our findings expand the current understanding of how ectomycorrhizal fungi and soil bacteria contribute to forest tree phosphorus nutrition and reveal how this interaction has important implications for sustainable forest management practices and estimations of future climate impacts on forest ecosystems.
How to cite: Stuart, E., McDonald, C., Castañeda-Gómez, L., Wong-Bajracharya, J., Anderson, I., Carrillo, Y., Plett, J., and Plett, K.: Whodunnit? Solving the mysteries of soil phosphorus solubilisation in an ectomycorrhizal tripartite interaction, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10558, https://doi.org/10.5194/egusphere-egu21-10558, 2021.
Soil degradation is a major concern worldwide and tropical agriculture is a major contributor to CO2 release from soils. There is growing interest in stabilizing atmospheric CO2 abundance to reduce its direct effect on global warming, by focusing on the potential of soil to sequester carbon. Soil structure directly influences soil stability and carbon sequestration. Arbuscular mycorrhizal fungi (AMF) are one of the most important microbial soil components for soil aggregate formation and stabilization through physical and biochemical processes allowing the encapsulation of organic carbon. However, the contribution of AMF to soil aggregation remains to be demonstrated under field and farming conditions and has only been shown in pot experiments with sterilized non-mycorrhizal controls. Large differences in cassava (Manihot esculenta Cranz), yield when inoculated under field conditions with diverse isolates of the AMF species Rhizophagus irregularis, suggests that carbon directed belowground and more importantly carbon sequestered within soil aggregates after harvesting might be driven by differences among AMF inocula. Thus, we evaluated the effect of 11 different isolates of Rhizophagus irregularis on CO2 emissions to the atmosphere (soil respiration), soil aggregation and the amount of soil organic carbon stored in aggregates in soils under commercial cassava cropping. Soil respiration was measured in situ by infrared gas analyser (IRGA, Li-COR 8100A) means. Soil samples were taken in surface (10 cm) and subsoil (30 cm) were taken to determine water stable aggregates size distribution (6.3, 4, 2, 1 and 0.5 mm), total stable aggregates (TSA) and total organic carbon (TOC) per aggregate size. After just one-year, our results showed that carbon decomposition (as measured by soil respiration), soil aggregation and carbon storage (in soil aggregates) were significantly affected by inoculation with AMF. Soil respiration was strongly and differentially affected by R. irregularisisolates with a difference of up to 78% in CO2 release from the soil. In surface, we found differences in TSA of up to 20% among inoculation treatments driven principally by an increase up to 6.3% in macroaggregate sizes. In subsoil, the TSA differences were up to 40% between AMF lines and at 2 mm aggregate size differences were up to 9,22% compare with non-inoculated treatment. Interestingly in this experiment, TOC and soil aggregation were not correlated. Although TOC in macroaggregates was significatively different up 44% among AMF treatments. Soil aggregation is a soil property often thought as static. Moreover, changes in soil aggregation as the ones we have shown here had only been reported after long-term experiments (up to 30 years) with low intrusive tillage practices (non- or reduced-tillage). Our results clearly show the enormous potential of using AMF in field conditions as a primary tool to improve ecosystem services and soil health in short periods of time.
Keywords: Soil aggregation, AMF, Cassava, carbon storage, soil respiration
How to cite: Peña Quemba, D. C., Rodriguez, A., and Sanders, I.: Application of arbuscular mycorrhizal fungi alters soil respiration, soil aggregation and total organic carbon in tropical agriculture , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13823, https://doi.org/10.5194/egusphere-egu21-13823, 2021.
Fungal mycelia consist of an interconnected network of filamentous hyphae and represent the dominant phase of the lifecycle in all major fungal phyla, from basal to more recent clades. Indeed, the ecological success of fungi on land is partly due to such filamentous network growth. Nevertheless, fungal ecologists rarely use network features as functional traits. Given the widespread occurrence of this body type, we hypothesized that interspecific variation in network features may reflect both phylogenetic affiliation and distinct ecological strategies among species. We show first that there is high interspecific variation in network parameters of fungi, which partly correlates with taxonomy; and second that network parameters, related to predicted-mycelial transport mechanisms during the exploration phase, reveal the trait space in mycelium architecture across species. This space predicts a continuum of ecological strategies along two extremes: from highly connected mycelia with high resilience to damage but limited transport efficiency, to poorly connected mycelia with low resilience but high transport efficiency. We argue that mycelial networks are potentially a rich source of information to inform functional trait analysis in fungi, but we also note the challenges in establishing common principles and processing pipelines that are required to facilitate widespread use of network properties as functional traits in fungal ecology.
How to cite: Aguilar-Trigueros, C., Fricker, M., and Rillig, M.: Network properties as functional traits for fungi, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15518, https://doi.org/10.5194/egusphere-egu21-15518, 2021.
Copper-based fungicides are commonly applied in vineyards to control fungal diseases that can severely affect grapevine productivity. Continuous application of this type of fungicides contributes to Cu accumulation in surface horizons of the soil, which can generate toxicity problems in plants, regardless of being an essential nutrient. Several strategies have been proposed to immobilize or counteract the effect of soil contaminants, such as plant inoculation with arbuscular mycorrhizal fungi (AMF). However, depending on the element concentration, this may not be sufficient to avoid its excessive accumulation in belowground and/or aboveground organs. Since Fe is known to have an antagonistic interaction with Cu in plants, Fe application, as an amendment, in vineyard soils, could be a good strategy to avoid excessive Cu uptake by grapevines growing in Cu-contaminated soils. However, little information is available on the combined effects of both strategies.
In order to reveal the possible beneficial effects of plant mycorrhization and Fe application in Cu-contaminated soils on grapevine growth and nutrition, a mesocosm experiment was established under controlled conditions. Two-year-old plants, previously inoculated or not with two different AMF, were grown in pots filled with 6.5 kg of an Arenosol collected from a wine-growing region. These plants were subjected to three soil treatments: 1) soil contamination with Cu, where the grapevines were watered with a solution containing 5.89 mg/L CuSO4 to ensure that the soil in each container reached 300 mg Cu/kg; 2) soil contamination with Cu + Fe addition, where the plants were watered with a solution that contained the same amount of CuSO4 plus 0.38 mg/L of FeNaEDTA·3H2O to achieve 100 mg of Fe/kg soil; and 3) non-contaminated soil watered with deionized water. Four months later, at the end of the growing season, plant vegetative growth as well as leaf and root nutrient contents were analyzed.
Grapevines inoculated with AMF demonstrated a good level of tolerance to high Cu concentrations in soil, as they presented significantly higher root biomass than non-inoculated plants and Cu was mainly accumulated in the roots avoiding its translocation to the aerial part. However, when the Cu-contaminated soil was amended with Fe, a significant decrease was observed in root biomass in all mycorrhizal inoculation treatments and Cu was accumulated in grapevine leaves. Contrastingly, Fe application helped to avoid the excessive increase of Mn concentrations in leaf and roots that is commonly induced in Cu contaminated soils, which can be detrimental for grapevine growth.
These results demonstrated that mycorrhizal inoculation is a suitable strategy to promote grapevine growth in Cu-contaminated soils. However, special attention needs to be taken when applying amendments to correct Cu contamination, as the mycorrhizal status of plants may alter the expected outcome.
How to cite: Nogales, A., S. Santos, E., Victorino, G., Viegas, W., and Abreu, M. M.: Mycorrhizal inoculation and application of Fe correction in the soil for ameliorating grapevine performance in a copper-contaminated soil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4254, https://doi.org/10.5194/egusphere-egu21-4254, 2021.
Hydraulic properties of mycorrhizal soils have rarely been reported and difficulties in directly assigning potential effects to hyphae of arbuscular mycorrhizal fungi (AMF) arise from other consequences of AMF being present, i.e. their influence on growth and water consumption rates of their host plants that both also influence soil hydraulic properties.
We assumed that the typical nylon meshes used for root-exclusion experiments in mycorrhizal research can provide a dynamic hydraulic barrier. It is expected that the uniform pore size of the rigid meshes causes a sudden hydraulic decoupling of the enmeshed inner volume from the surrounding soil as soon as the mesh pores become air-filled. Growing plants below the soil moisture threshold for hydraulic decoupling would minimize plant-size effects on root-exclusion compartments and allow for a more direct assignment of hyphal presence to modulations in soil hydraulic properties.
We carried out water retention and hydraulic conductivity measurements with two tensiometers introduced in two different heights in a cylindrical compartment (250 cm³) containing a loamy sand, either with or without the introduction of a 20 µm nylon mesh equidistantly between the tensiometers. Introduction of a mesh reduced hydraulic conductivity across the soil volumes by two orders of magnitude from 471 to 6 µm d-1 at 20% volumetric water content.
We grew maize plants inoculated or not with Rhizophagus irregularis in the same soil in pots that contained root-exclusion compartments while maintaining 20% volumetric water content. When hyphae were present in the compartments, water potential and unsaturated hydraulic conductivity increased for a given water content compared to compartments free of hyphae. These differences increased with progressive soil drying.
We conclude that water extractability from soils distant to roots can be facilitated under dry conditions when AMF hyphae are present.
How to cite: Bitterlich, M. and Pauwels, R.: Hyphal colonization of Rhizophagus irregularis increases unsaturated hydraulic conductivity of a loamy sand distant from roots, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4564, https://doi.org/10.5194/egusphere-egu21-4564, 2021.
Alkaline Fe ore tailings are by far one of the most challenging environmental issue facing the global mining industry, which is ranked 4th globally in terms of their discharge volumes in storage dams. These tailings possess poor physical structures and adverse chemical properties (e.g., alkaline pH and deficiencies of organic carbon and nutrients) and it is hard for sustainable colonization of plants and microbial communities. Eco-engineering tailings into soil-like substrate in situ is a promising technology to achieve sustainable rehabilitation of tailing landscape. The formation of water stable aggregates (WSA) in tailings primed with eco-engineering inpiuts (e.g., plant biomass organic matter and fertilisers) is indicative of the first milestone of soil formaiton, resulting from bio-geochemically driven mineral weathering and cementation. WSAs are basic physical units underpinning soil structure and functions, such as the porosity and hydraulic conductivity, gas exchange and water retention, biological activities of microbes and roots. The further development and evolution may be enhanced by Arbuscular mycorrhizal (AM) fungi associated with plants colonising infertile soil (such as tailing-soil), because of their role in generating organic cements and organo-mineral interactions. Our previous study found that AM fungi were present in the Fe ore mine tailing site, associated with colonising native plants. In the present study, we have investigated the role of AM symbiosis (Glomus spp. in association with Sorghum spp.) in aggregate formation and organic matter sequestration in Fe ore tailings eco-engineered with organic matter amendment and pioneer plant colonization. The results showed that AM fungi formed symbiotic association with Sorghum spp. plant roots (with mycorrhizal colonization intensity above 80%) in the eco-engineered tailings. Quantitatively, AM symbiosis enhanced the formation of micro-aggregates (53~250 um) rather than macro-aggregate aggregates (250 um~2000 um) formation, which may be partially due to the direct role of extra-radical mycelium as revealed by FE-SEM analysis. Qualitatively, AM symbiosis increased the amount of organic carbon and nitrogen associated with mineral particles in the macro-aggregates. Those organic carbon associated with minerals was found to be rich in carboxyl C and alkyl C, as revealed by synchrotron based C 1s X-ray absorption near edge structure (NEXAFS, conducted in Australia Synchrotron) and the Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra. Overall, the study revealed the role of AM fungi in advancing the formation of microaggregates and increasing the sequestration of organic C and N in macroaggregates in the eco-engineered Fe ore tailings. These suggest that AM fungi inoculum be added to pioneer plants to not only enhance plant growth via improved nutrient and water acquisition, but also to advance aggregate formation and quality via increased organic C and N sequestration with impacted mineral particles.
How to cite: Li, Z., Wu, S., and Huang, L.: Arbuscular Mycorrhizal symbiosis enhances aggregate formation and organic matter sequestration in alkaline Fe ore tailings, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4658, https://doi.org/10.5194/egusphere-egu21-4658, 2021.
Soil pH is consistently recorded as the single most important variable explaining bacterial richness and community composition locally as globally. Bacterial richness responds to soil pH in a bell-shaped pattern, highest in soils with near-neutral pH, while lower diversity is found in soil with pH >8 and <4.5. Also, community turnover is strongly determined by pH for bacteria. In contrast, pH effects on fungi is apparently less pronounced though also much less studied compared to bacteria. Still, pH appears to be a significant determinant for fungal communities but typically not the most important. Rarely are bacterial and fungal communities co-analyzed from the same field samples taken across pH gradients. Here we analyze the community responses of fungi and bacteria in parallel over an extreme pH gradient ranging from pH 4 to 8 established by applying strongly alkaline wood ash to replicated plots in a Picea abies plantation. Bacterial and fungal community composition were assessed by amplicon-based meta-barcoding. Bacterial richness were not significantly affected by pH, while fungal richness and a-diversity were stimulated with higher pH. We found that both, bacterial and fungal communities increasingly deviated from the untreated plots with increasing amount of wood ash though fungal communities were more resistant to changes than bacterial. Soil NH4, NO3 and pH significantly correlated with the NMDS pattern for both bacterial and fungal communities. In the presentation we will discuss resistance versus sensitivity of different fungal functional guilds towards higher pH as well as the underlying factors explaining the community changes.
How to cite: Kjoller, R. and Cruz-Paredes, C.: Do fungi and bacteria respond similar across a steep local pH gradient?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5720, https://doi.org/10.5194/egusphere-egu21-5720, 2021.
Since industrialization, the global average temperature increases with far reaching consequences for the world climate. One phenomenon is the current occurrence of more heavy and long droughts in Middle Europe, which lead to extensive tree die-off and shows that we need a better understanding of the forest-soil ecosystem in times of climate change.
Within the interdisciplinary Kranzberg Roof Experiment, we study the drought resistance and drought recovery of mature Norway spruce (Picea abies) and European beech (Fagus sylvatica). The trees experienced a rainfall exclusion for five years during the vegetation period and were rewetted by drip irrigation in summer 2019. Our interest focuses in the functional role of ectomycorrhizal and overall fungal communities on tree drought resistance and recovery. Particularly, we hypothesized the rewetting event will lead to a shift in community structure because of steeply rising water and nutrient availabilities.
To get insights to the development of the fungal communities right after the rewetting period, we sequenced the fungal ITS2 region of fine root DNA extracts. The roots were taken from soil cores before and at several time-points after irrigation.
We found that the fungal communities stayed quite similar to each other during the time-frame of recovery we investigated (84 days), while the amount of new root tips strongly increased directly after the rewetting. Surprisingly, the organic material which had accumulated as it was not degraded during the years of drought, did not lead to a shift in community composition. In particular, there were no changes in the relative amounts of saprotroph fungi in the phase after the rewetting.
Therefore, root fungal communities – the interface between trees and soil – seemingly did not experience a strong pressure to adapt their composition to the new condition, which matches their resistant behavior during the long drought phase before (cf. abstract 2937).
How to cite: Danzberger, J., Werner, R., Weikl, F., and Pritsch, K.: Unperturbed root fungal communities in a temperate forest recovering from five years of reoccurring droughts , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6334, https://doi.org/10.5194/egusphere-egu21-6334, 2021.
Restoring natural plant communities on abandoned agricultural fields can be challenging due to a degraded soil community and a fertilizer legacy. We discovered that fungi are the initiators of a tighter connected soil food web which restores the closed carbon and nutrients cycles in soils, thereby accommodating species-rich plant communities in grasslands. Boosting the fungal channel as a bottom-up approach could thus be used as a next-generation restoration measure. We show data of soil inoculation experiments and trace the progression of change in the fungal community via sequencing and functioning via community response profiles. We assessed the top-down foraging of predators and consumers on the microbiome by analysing gut contents of consumers and predators from different restoration stages. We will be able to show preliminary data on the effect of fungi and their higher trophic levels in stimulating species-rich plant communities as well as give a prospect on the wider applications for microbiome engineering.
How to cite: Morriën, E., Quist, C., Cuk, S., Koppen, J., Varkevisser, E., and Hannula, E.: Fungi play a key role in the restoration of species-rich grasslands: trace-labelling carbon through the food chain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12568, https://doi.org/10.5194/egusphere-egu21-12568, 2021.
Ectomycorrhizal fungi use both extracellular enzymes and hydroxyl radicals to decompose soil organic matter (SOM) in a way that is similar to that of their saprotrophic wood decomposing ancestors. Although it are ultimately the individual hyphae that decompose SOM, it has remained unclear if it is also the local environmental conditions experienced by individual hyphae that control the decomposition activity of these hyphae or if it is the overall physiological status of the mycelium these hyphae are connected to that drives decomposition activity of hyphae. We set up an experimental system in which the decomposition activity of individual hyphae could be imaged using infrared (IR) microspectroscopy. Colonies of the ectomycorrhizal fungus Paxillus involutus were grown on solid, sterile lignin films which were amended with ferrihydrite minerals or not. The decomposition activity of individual hyphae was subsequently related to the local environmental conditions experienced by subsets of hyphae (presence or absence of ferrihydrite in lignin substrates) of a mycelial colony and the overall physiological status of the mycelium (difference in hydroxyl radical producing capacity of the mycelium and organic versus inorganic nitrogen nutrition). Using this experimental set-up, we have shown that the local conditions experienced by individual hyphae plays a key role in determining the decomposition activity of these hyphae, but the overall decomposition activity of the mycelium these hyphae were connected to also played a clear role. We also showed that hyphae which more actively oxidized the lignin substrate, also secreted more extracellular matrix materials, suggesting a functional involvement of fungal extracellular matrices in this decomposition process. We conclude that phenotypic heterogeneity occurring between genetically identical hyphal tips may be an important strategy for filamentous fungi to cope with heterogeneous and constantly changing soil environments.
How to cite: Op De Beeck, M., Troein, C., Siregar, S., Gentile, L., Abbondanza, G., Peterson, C., Persson, P., and Tunlid, A.: Regulation of fungal decomposition at single-cell level, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8198, https://doi.org/10.5194/egusphere-egu21-8198, 2021.
Plant roots are usually colonized by various arbuscular mycorrhizal (AM) fungal species, which vary in morphological, physiological, and genetic traits. This colonization constitutes the mycorrhizal nutrient uptake pathway (MP) and supplements the pathway through roots. Simultaneously, the extraradical hyphae of each AM fungus is associated with a community of bacteria. However, whether the community structure and function of the microbiome on the extraradical hyphae differ between AM fungal species remains unknown. In order to understand the community structure and the predicted functions of the microbiome associated with different AM fungal species, a splitroot compartmented rhizobox cultivation system, which allowed us to inoculate two AM fungal species separately in two root compartments, was used. We inoculated two separate AM fungal species combinations, (i) Funneliformis mosseae and Gigaspora margarita and (ii) Rhizophagus intraradices and G. margarita, on a single root system of cotton. The hyphal exudate-fed, active microbiome was measured by combining 13C-DNA stable isotope probing with MiSeq sequencing. We found that different AM fungal species, which were simultaneously colonizing a single root system, hosted active microbiomes that were distinct from one another. Moreover, the predicted potential functions of the different microbiomes were distinct. We conclude that the arbuscular mycorrhizal fungal component of the system is responsible for the recruitment of distinct microbiomes in the hyphosphere. We found that arbuscular mycorrhizal fungi cocolonizing on single plant roots recruit their own specific microbiomes, which should be considered in evaluating plant microbiome form and function. Our findings demonstrate the importance of understanding trophic interactions in order to gain insight into the plant-AM fungus-bacterium symbiosis
How to cite: Zhou, J., Chai, X., Zhang, L., George, T., Wang, F., and Feng, G.: Different Arbuscular Mycorrhizal Fungi Cocolonizing on a Single Plant Root System Recruit Distinct Microbiomes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9524, https://doi.org/10.5194/egusphere-egu21-9524, 2021.
Soil organic matter (SOM) is any material produced by living organisms at various stages of decomposition. SOM enhances soil fertility and quality and influences soil’s ability to fight against soil-borne diseases. Atmospheric CO2 sequestration into SOM through improved agricultural management practices has been suggested to be a cost effective way to mitigate climate change.
The build-up of SOM is largely regulated by soil microbial activity. Soil microbes use most plant-derived C and either produce CO2 or incorporate C into their biomass and after death microbial necromass may contribute to stable SOM. Arbuscular mycorrhizal (AM) fungi are one of the root colonizing soil microbes important in nutrient cycling, plant nutrition, growth and composition and maybe soil aggregation. The benefits of microbes including AM fungi should be thus utilized for climate friendly agriculture by magnifying their benefits via better agricultural management.
Cover crops use is one of the climate friendly agricultural practices. Cover crops if managed right, can provide several benefits e.g. enhanced soil C sequestration, reduced emissions from fertilizer production, weed suppression, better soil moisture retention and microbial activity. Moreover, use of diverse cover crops may favor higher soil biodiversity leading to high SOM content. In this project, plant diversity impacts on soil and root fungal community composition and microbial activity related to soil C sequestration were studied in a field experiment. In addition, special attention was given to AM fungi.
The field experiment was started in May, 2019 in Viikki Research farm, University of Helsinki. The experiment consists of seven treatments comparing four different levels of biodiversity to conventional monoculture treatments and bare fallow. Eight different species of cover crops representing four functional traits were sown under barley: 1) nitrogen (N2)-fixing + shallow rooting , 2) deep rooting, 3) N2-fixing +deep rooting and 4) no N2-fixing and shallow rooting. Barley and cover crop root samples and soil samples were collected from two growing seasons 2019 and 2020. Root samples were analyzed for AM fungal colonization %. Soil samples were analyzed for soil microbial biomass and microbial respiration in different seasons. Preliminary results showed no significant cover crop diversity effect on AM fungal colonization % in barley root in 2019. Soil microbial biomass and soil microbial respiration showed seasonal variations but not significant cover crop diversity effect. Therefore, fungal communities in soil and root will be examined using Illumina (MiSeq) sequencing targeting the fungal internal transcribed spacer (ITS) region. Soil enzyme activities and carbon use efficiency will be performed to gain insight into microbial activity. Obtained results will show if microbial community and activity is affected by either plant family composition or plant diversity.
How to cite: Shrestha, R., Huusko, K., Salonen, A.-R., and Heinonsalo, J.: Climate-smart agriculture: microbiological impacts of plant diversity to soil carbon (C) sequestration., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13588, https://doi.org/10.5194/egusphere-egu21-13588, 2021.
Arbuscular mycorrhiza (AM) is ancient and widespread inter-kingdom symbiotic relationship being established by a majority of terrestrial plant species and specialized fungi, which interconnect plant roots with surrounding soil. By doing so, this symbiosis can greatly increase acquisition of multiple mineral nutrients such as phosphorus, nitrogen (N), and copper by the plants from the soil, in exchange for reduced carbon supplied by the plant host. Supposedly, this is mainly due to extending the soil volume accessible for nutrient acquisition by the fungal hyphae compared to roots alone. Both the plants and the AM fungi require N for construction of their bodies. This can potentially result in different effects of AM symbiosis establishment on plant N nutrition ranging from positive to negative. Yet, the demand for and efficiency of mineral N uptake from the soil by a mycorrhizal plant is usually higher than that of a nonmycorrhizal plant. This may exert important feedbacks of AM symbiosis on soil processes in general and N cycling in particular. Here we asked what role does the symbiosis play in acquisition of N by a model plant, Andropogon gerardii, from an organic source (i.e., plant litter labeled with 15N) supplied in a soil zone beyond the direct reach of roots. Further, we tested whether this process of N acquisition by plant from the soil via mycorrhizal hyphae could be affected by supplying various synthetic nitrification inhibitors (DCD, nitrapyrin, or DMPP) along with the litter. We observed efficient acquisition of N to mycorrhizal plants via mycorrhizal pathway irrespective of the nitrification inhibitor supplied or not along with the plant litter. These results were strongly contrasting with 15N uptake (but not total N content of the plants or the plant biomass) of the nonmycorrhizal plants, which generally received much less 15N than the mycorrhizal plants, and this was further suppressed by nitrapyrin or DMPP supplementation of the organic N source as compared to DCD or the control (i.e., no inhibitor) treatment. Quantitative real-time PCR analyses of the microbial communities indicated that microbes involved in the rate-limiting step of nitrification, i.e., the ammonia oxidizers, were suppressed similarly by AM fungi as they were by nitrapyrin or DMPP amendments. These results suggest that mycorrhizal fungi successfully outcompeted the prokaryotic ammonia oxidizers, and this was most likely by accessing and efficiently utilizing/removing free ammonia ion pool in/from the soil via their extensive hyphal networks.
How to cite: Jansa, J., Kotianová, M., Gančarčíková, K., Rozmoš, M., Hršelová, H., Bukovská, P., and Dudáš, M.: Arbuscular mycorrhiza and nitrification: Competition for free ammonium ions?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9975, https://doi.org/10.5194/egusphere-egu21-9975, 2021.
Ectomycorrhizal fungi (EMF) play a key role in the cycling of nitrogen (N) and carbon (C) in boreal forests. Trees receive growth-limiting N in exchange for allocating C to their mycorrhizal symbionts, but supplying the fungi with C can also cause N immobilization, which hampers tree growth. We present results from field and greenhouse experiments combined with mathematical modelling, showing that these are not conflicting outcomes.
Under N limitation, which is the general case in boreal forests, the plant host has been observed to continue supplying its ectomycorrhizal partner with C, and even increasing this C investment, while the fungus reduces mobilization of N to its host (Corrêa et al. 2008, 2010). N is thus withheld under conditions of limiting availability, and the host tree cannot unlock it by supplying the EMF with more C, because such an investment results in further diminishing N returns. Critical to this question is the observation that more than one fungus can form mycorrhiza on a given tree and that several trees can be connected to a given fungal individual (Southworth et al. 2005).
We hypothesize that plants sharing common ectomycorrhizal symbionts compete with each other for N by exporting C to the EMF network, and vice versa for a fungus. The fungi making up the EMF network export N to hosts if it is absorbed in excess of their own growth demand, which is limited by C; Exporting more than this would reduce their growth, exporting less would reduce their competitiveness for plant C (Näsholm 2013, Franklin 2014). This hypothesis has specific and predictable implications for relationship between plant C export to EMF and N uptake: At the community level, increasing plant C supply to EMF would increase both fungal N uptake and N use, but as soil N availability gradually becomes limiting, uptake should saturate while EMF N use continued to increase, leading to declining N export to plants.
We conducted two experiments, one in potted mesocosms and the other in a boreal forest setting. Belowground C flux was reduced by shading and/or stem strangling, which is a treatment whereby the flow of C to the root system is physically restricted by blocking transport through the phloem in the stem (Björkman 1944; Henriksson et al. 2015). Strangling a subset of seedlings growing in the same pot accomplishes two things: 1) the total belowground C flux is decreased, and 2) each seedling’s relative contribution to that flux is altered.
Based on measurements and mathematical modelling, we conclude that belowground C allocation by trees can indeed fuel N immobilization, reducing the amount of N to be distributed among the trees. But we also found that individual trees received nutritional benefits in proportion to their C contribution to the fungal network. We illustrate the evolutionary underpinnings of this situation by drawing on the analogous tragedy of the commons (Hardin 1968), where the shared mycorrhizal network is the commons, and explain how rising atmospheric CO2 may lead to greater nitrogen immobilization in the future.
How to cite: Henriksson, N., Franklin, O., Tarvainen, L., Marshall, J., Lundberg-Felten, J., Eilertsen, L., and Näsholm, T.: The mycorrhizal tragedy of the commons, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15571, https://doi.org/10.5194/egusphere-egu21-15571, 2021.
The anthropogenic impact on soil microbiota in polar climate remains overlooked and the comparison between microbiota in urban and natural soils in polar regions are highly interesting. Fungi are the key components of soil microbiota, responsible for improtant functions and ecsystem services and highly senstive to direct (e.g., pollution) and indirect (e.g., urban heat island) anthropogenic effects. Urban soils of Murmanks (68.967 N, 33.083 E) – the biggest polar city in the world – were studied in comparison to Podzols of the natural forest-tundra area. Soil fungi in urban and natural soils were analyzed by luminescence microscopy and PCR real time.
The fungal biomass in the upper horizon of Technosol varied from 0.50 to 0.75 mg/g of soil, which was 1.5-2 times less than in Podzol. Different profile distribution of fungal biomass was shown for urban and natural soils. In natural Podzol, the highest fungal biomass was observed in the upper organic O horizon, then decreased in the topsoil mineral elluvial E horizon, and then slightly increased in the subsoil mineral illuvial Bs horizon. In urban soils, the second maximum of number of fungi in the soil profile was not found. The biomass of fungi decreased exponentially in the soil profile.
The number of ITS ribosomal gene copies of fungi in the topsoil organic horizon of natural Podzol reached 1010gene copies/g of soil. In urban soils, there was a decrease in their number by 6 or more times. The number of fungal gene copies decreased sharply down the soil profile in both urban and natural soils. So, if the number of fungi in topsoil horizons was about 108-1010 gene copies /g of soil, in subsoil horizons it was 106-107 gene copies/g of soil. First of all, this may be due to the mycorrhizal mycobiota, which has the largest extent of mycelium in the topsoil horizons of soil. In forest soil, the number of gene copies in horizon E was 37 times less than in the topsoil horizon; in urban soil, the content of gene copies in the subsoil BC horizon is 10 times less than in the topsoil horizon.
The proportion of fungal mycelium varied from 28 to 80%. A minimum of mycelium was found in the subsoil horizons, while the topsoil horizons were abundant with fungal hyphae, the length of which in them reached more than 160 m/g of soil. The maximum amount of mycelium (581.72 m/g of soil) was observed in natural Podzol. The number of single-celled fungal propagules (spores and yeasts) was 104-105 cells/g of soil. Most of the propagules are represented by small-sized forms (2-3 microns), the proportion of which increased from the topsoil horizons (68-93%) to the deep ones (up to 100%). This trend was observed for both urban and background soils. Large propagules with a diameter of 5-7 microns were found exclusively in the topsoil horizons, and their number is no more than 103 cells/g of soil.
Acknowledgements This research was supported by state task AAAA-A18-118021490070-5 and Russian Foundation for Basic Research project № 19-29-05187.
How to cite: Korneykova, M., Nikitin, D., Dolgikh, A., and Vasenev, V.: Biomass and number of gene copies of fungi in the polar urban soils, Murmansk, Russia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10864, https://doi.org/10.5194/egusphere-egu21-10864, 2021.
Our knowledge about the role of microbial organisms as drivers of soil biogeochemical cycles is mainly based on soil analyses, and the physiological information that exists for few microbial model organisms. In soil, measurements of process rates and element contents can be related to the apparent activity of the microbial community, though conclusions are often indirect - actual microbial physiology and diversity remains hidden. By contrast, analyses of microbial physiology under controlled conditions are hardly representative of the vast diversity of microorganisms in soil, and a transfer of these findings to complex soil systems is challenging. Thus, we argue that a better exchange among these ecological disciplines will lead to a valuable transfer of relevant questions, knowledge and improved understanding of the role of microbes in soil and its responses to environmental change.
Here, we provide examples of an evaluation of microbial parameters relevant in soil biogeochemical cycles, analysing traits in a collection of 31 saprobic fungi in response to varying substrate conditions. The large dataset allowed to test several assumptions and conclusions derived from soil system analyses exemplarily for soil fungi. Specifically, we (1) evaluated the optimum C:N:P (carbon:nitrogen:phosphorus) substrate ratio for fungal growth and activity, (2) assessed the responses in carbon-use efficiency and enzyme activity to N deficiency, (3) analyzed the relevance of C versus N supply for fungal growth and activity under varying substrate conditions and (4) tested the assumption of microbial stoichiometric homeostasis, that represents a basic principle in soil ecological stoichiometry.
Fungal responses to changes in N and C availability were partly consistent with expectations, e.g. regarding general nutrient demands, though as often discussed C availability appeared more relevant for growth especially in complex substrates. Enzymatic activity and respiration also positively correlated with N availability, resulting in decreased carbon-use efficiency at high N supply. These findings, for example, contradict certain conclusions in soil analyses, namely that N limitations will result in “N mining” (high enzymatic activity), while the excess of C causes “overflow respiration” and reduced CUE. Regarding fungal C:N:P ratios, those were only related to nutrient demands when growing in simple media, while in soil substrate such relations seem more complex. Contradicting the assumption of microbial homeostasis in soil, fungal individuals showed more flexible C:N:P ratios than expected, though the degree of flexibility varied among isolates. In general, the results also reveal a large trait variation among different isolates, with several traits showing a phylogenetic signal, indicating variations in microbial activity depending on community composition.
Finally, we want to raise and discuss several emerging questions: How relevant is a deeper understanding of microbial physiology to understand soil biogeochemical processes? How do we include the variability of traits in diverse soil communities – are average values informative, or can we proceed with useful categories? And how can methods in soil science and microbial ecology be merged best to allow fruitful knowledge transfer?
How to cite: Camenzind, T., Lehmann, J., Lehmann, A., Aguilar-Trigueros, C. A., and Rillig, M. C.: How relevant are microbial traits to understand soil biogeochemical cycles? , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11186, https://doi.org/10.5194/egusphere-egu21-11186, 2021.
Soils are characterized by their largely varying microhabitats that determine their microbial communities and functions such as nutrient cycling. Microbes, and especially fungi, do not only react to those microhabitats but also contribute to shaping them.
We used transparent, microstructured chips simulating the internal pore space of soils, to microscopically study fungal mycelia at the hyphal scale. We investigated the variety of fungal morphologies in maze structures, and hyphal interactions with their biotic and abiotic microenvironments. We studied both a variety of laboratory strains including an arbuscular mycorrhizal fungus and natural soil inocula, and we quantified their growth strategies in different microstructures and their interactions with bacteria, protists and soil mineral particles.
We could observe how the rigid hyphae of fungi opened up passages through chip- or soil solids and aggregates, increasing the spatial availability of the pore space. They, on the other hand, also filled up pores and pore necks with their biomass, creatingbarriers for both organisms, flow of water and sedimentation of matter, and thus changing the pore size distribution and -connectivity. Hyphae also increased the wettability of pores, which led to a higher connectivity of water films across air pockets and thus benefiting the dispersal of water-dwelling microorganisms, a phenomenon earlier termed “fungal highways”. We found the abundance of both bacteria and protists strongly increased in pore spaces containing hyphae in comparison to those without, dispersal events via fungal hyphae that happened frequently and were quantifiable in the high internal replication of our chip’s pore space channels. This allowed us to conclude on a high relevance of this mode of dispersal in soils with intermediate moisture. Fungal hyphae had thus a strong and obvious effect on their surrounding microenvironments and organisms.
We consider the study of microbial behaviour and interactions at the cellular scale in microhabitats to be essential for a better understanding of soil functions, and to gain mechanistic insight into phenomena observable at macroscale.
How to cite: Hammer, E., Mafla Endara, M. P., Arellano Caicedo, C. G., Pucetaite, M., Aleklett Kadish, K., and Ohlsson, P.: Fungi as Ecosystem Engineers in the Soil Pore Space, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13098, https://doi.org/10.5194/egusphere-egu21-13098, 2021.
Ecological stoichiometry provides a valuable framework to understand functional variation among organisms, particularly with respect to responses to stress. Trophic dynamics are an important element of this framework, although symbiotic interactions are poorly integrated. Here, we assessed concentrations and ratios of carbon ([C]), nitrogen ([N]) and phosphorus ([P]) in tissues of lucerne (Medicago sativa) and their associated arbuscular mycorrhizal (AM) fungi growing under ambient or extreme (high temperature and/or low soil moisture) environmental conditions. In general, the AM fungal mycelium was depleted in [C] by 50% and [N] by 46% but enriched in [P] by more than six times when compared to plant shoots and roots. Warming and moisture limitation resulted in further increases in [P] and reduced C:P and N:P ratios in all tissues, while AM fungal [N] and C:N responses were muted and decoupled from those in plant tissues. Using high-throughput DNA sequencing and joint species distribution modelling, we were also able to link compositional shifts in AM fungal communities in roots and soil to variation in hyphal chemistry. As such, this work provides insight into the ecological strategies of AM fungi associated with an important pasture legume (among many other species); some potential consequences for carbon and nutrient exchange between soil, fungal and plant pools; and how these interactions are impacted by climate extremes.
How to cite: Zhang, H., Churchilll, A., Anderson, I., Igwenagu, C., Power, S., Plett, J., Macdonald, C., Pendall, E., Carrillo, Y., and Powell, J.: Ecological stoichiometry reveals variation in phosphorus and nitrogen responses to warming and drought across mycorrhizal partners , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14036, https://doi.org/10.5194/egusphere-egu21-14036, 2021.
Ectomycorrhizal fungi are central members of the forest fungal community, forming symbiosis with most trees in temperate and boreal forests, enhancing plant access to limiting soil nutrients. Decades of greenhouse studies have shown that specific mycorrhizal fungi enhance tree seedlings growth and nutrient uptake rates, and that these effects are sustained when seedlings are out-planted into regenerating forests. Whether these relationships scale up to affect the growth of mature trees and entire forests harboring diverse fungal communities remains unknown. In this study, we combined a continental set of European forest inventory data from the ICP forest network with molecular ectomycorrhizal fungal community surveys to identify features of the mycorrhizal mycobiome linked to forest productivity. We found that ectomycorrhizal fungal community composition was a key predictor of tree growth, and this effect was robust to statistically accounting for climate, nitrogen deposition, soil inorganic nitrogen availability, soil pH, and forest stand characteristics. Furthermore, ectomycorrhizal fungi with greater genomic investment in energy production and inorganic nitrogen metabolism, but lower investment in organic nitrogen acquisition, were linked to faster tree growth. Lastly, we sampled soils from fast and slow growing forests and introduced their microbiomes into a sterilized growth medium to experimentally isolate microbiome effects on tree development. Consistent with our observational analysis, tree seedling growth was accelerated when inoculated with microbiomes from fast vs. slow growing forests. By linking molecular community surveys and long-term forest inventory data in the field, and then pairing this with a microbiome manipulation study under controlled conditions, this work demonstrates an emerging link between the forest microbiome and dominant European tree growth rates.
How to cite: Anthony, M., Crowther, T., van der Linde, S., Suz, L., Bidartondo, M., Cox, F., Schaub, M., Rautio, P., Ferretti, M., Vesterdal, L., Devos, B., and Averill, C.: Ectomycorrhizal fungal composition and function predict tree growth across Europe , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7875, https://doi.org/10.5194/egusphere-egu21-7875, 2021.
Altered temperature and precipitation regimes particularly prolonged drought periods when combined with heat strongly affect forests in the last decades. However, neither did all trees die nor even stop growing at all sites. We are interested in the question if below ground interaction with ectomycorrhizal fungi could be partly mediating strong soil drought. For this purpose, we established sampling sites with Fagus sylvatica, Picea abies or Pinus sylvestris along a natural precipitation gradient of 400 km length in Bavaria (Germany). We hypothesized root associated fungal communities to reflect long-term adaptation to local edaphic and climate conditions and that the resulting tree-fungal partnerships have distinct compositional patterns.
How to cite: Pritsch, K., Roth, M., and Weikl, F.: Ectomycorrhizal communities along a precipitation gradient in Bavaria (Germany), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6176, https://doi.org/10.5194/egusphere-egu21-6176, 2021.
Microbial communities are major players in carbon and nitrogen cycling globally and are of particular importance for plant communities in the nutrient poor soils of boreal forests. Especially relevant are the fungal communities in the soil that interact with the plants in multiple ways, indirectly through their pivotal role in the breakdown of organic matter and, more directly, through mycorrhizal symbiosis with plant roots. Large-scale disturbances of these complex microbial communities can lead to shifts in soil carbon storage with unknown and global-scale long-term consequences. To understand the dynamics of these communities and their relationship to associated plants in response to climate change and anthropogenic influence, we need a better understanding of how modern “omics” methods can help us to understand compositional and functional shifts of these microbiomes. Microbial gene expression and functional activity can be assayed with RNA sequencing (RNA-Seq) data from environmental samples. In contrast, currently phylogenetic marker gene amplicon sequencing data is generally used to assess taxonomic composition and community structure of the microbiome. Few studies have considered how much of this structural and taxonomic information is included in RNA-Seq transcriptomic data from matched samples. Here we describe fungal communities using both RNA-Seq and fungal ITS1 DNA amplicon sequencing to compare the outcomes between the methods. We used a panel of root and needle samples from mature stands of the coniferous tree species Picea abies (Norway spruce) growing in untreated (nutrient deficient) and nutrient enriched plots at the Flakaliden forest research site in boreal northern Sweden. We created an assembly-based, reproducible and hardware agnostic workflow to taxonomically and functionally annotate fungal RNA-Seq data obtained from Norway spruce roots, which we compared to matching ITS amplicon sequencing data. We show that the community structure indicated by the fungal transcriptome is in agreement with that generated by the ITS data, while also identifying limitations imposed by current database coverage. Furthermore, we show examples to demonstrate how metatranscriptomics data additionally provides biologically informative functional insight at the community and individual species level. These findings highlight the potential of metatranscriptomics to advance our understanding of interaction, response and effect both between host plants and their associated microbial communities, and among the members of microbial communities in environmental samples in general.
How to cite: Schneider, A., Sundh, J., Sundström, G., Richau, K., Delhomme, N., Grabherr, M., Hurry, V., and Street, N.: Comparative fungal community analyses using metatranscriptomics and ITS-amplicon sequencing from Norway spruce, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7249, https://doi.org/10.5194/egusphere-egu21-7249, 2021.
Mycorrhizae are a symbiosis between fungi and plants. We have learned about the complexity of mechanisms of interaction and interactions between the mycorrhizae and the local environment from over a century of laboratory observations experiments. Point observations and laboratory studies identify processes, but cannot delineate activity. Our goal is to use an in situ system to study mycorrhizal roots and fungi during hot moments, daily shifts, and seasonal change.
We integrated continuous in situ observation-sensor measurements using our Soil Ecosystem Observatories. As turnover rate estimates are related to sample frequency, individual scans using manual minirhizotrons (Bartz and Rhizosystems) and Rhizosystems Automated Minirhizotrons (32,000-3.01mm x 2.26mm 307,200 pixel images). Automated scans were collected up to 4x daily. Manual scans across multiple tubes in campaigns provided spatial variation. Images were organized into mosaics using RootView software, and roots and hyphae identified and length, width and biovolume determined using RootDetector <http://www.rhizosystems.com/>. Individual roots and hyphae were tracked using RootFly <https://cecas.clemson.edu/~stb/rootfly/>. Lifespans were determined using Mark-Recapture modeling and turnover calculated. With each minirhizotron tube, sensors were placed at 3 or 4 depths for temperature, moisture, CO2 and O2 at 5minute intervals.
Mycorrhizal fungi (MF) explore soil for nutrients and requiring C. Most C to the hyphae is respired (with a 14C signal of autotrophic respiration), with the remaining divided into decomposing (heterotrophic respiration) and sequestered C pools.
Our first site is a mature neotropical rainforest, the La Selva Biological Station, Costa Rica. Trees predominantly form arbuscular mycorrhizae (AM). AMF fungi comprise 50% of total fungal mass (PLFA). Aboveground NPP-C was 750g/m2. Root standing crop C was 120g/m2, average lifespan 60days, =6 generations/y, = root NPP of 720g/m2/y. The AMF hyphal standing crop C was 12.5g/m2, average lifespan of 25 days, =14.7 generations/y, = AMF NPP of 183g/m2/y. With an NPP of 1,650g/m2/y, then AMF comprises 11% of NPP.
Soil respiration provides CO2, converting in water to HCO3-, altering soil pH (Henry's Law). AMF respiration thereby increases P availability. If 10% of the AM fungal hyphae are live, then the hyphal respiration is 438g/m2/y of C, =38% of total soil respiration and 16% of site respiration.
Our second site is a mature California mixed forest, USA. Ectomycorrhizal (EM) trees predominate. Annual NPP-C was 200g/m2, and root NPP was 200g/m2. EMF NPP was 162.6g/m2, or 27% of the NPP. N, water, and temperature limit NPP. The seasonal signal was very high in this ecosystem. Peak standing crop of extramatrical EM hyphae was 19gC/m2 in April. Total soil respiration in April was 0.26g/h, and extramatrical hyphae 0.029g/h, or 11% of the total soil respiration. Since P is less limiting, but N and water are, hyphae likely play a greater role in enzymatic activity and exploratory surface area.
In summary, different mycorrhizal fungi play different roles depending on ecosystem limiting factors. With global change, our challenge is to determine how an ecosystem will change and the extent and rapidity of mycorrhizal fungal change.
How to cite: Allen, M., Taggart, M., Rothbart, G., and Harmon, T.: Comparative mycorrhizal fungal production and respiration of a neotropical rainforest versus a California mixed forest, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11982, https://doi.org/10.5194/egusphere-egu21-11982, 2021.
Middle Europe’s forests face an increasing risk of recurring summer droughts. To explore the impact of such conditions, trees in a mature spruce-beech forest were exposed to five successive years of extreme summer drought during the Kranzberg Roof Experiment located in Bavaria (Grams et al. 2021, DOI: 10.1002/ecs2.3399).
Those trees (Picea abies and Fagus sylvatica) heavily depend on their ectomycorrhizal fungal symbiosis partners (ECMf) belowground. Thus, we set out to identify modes of compositional and functional adaptation in these communities.
We monitored ECMf communities via metabarcoding and analysed the functionality of morphotyped ectomycorrhizae via testing their enzyme activities.
To our surprise, most effects were quantitative throughout the whole period. Total enzyme activities strongly declined alongside the numbers of vital root tips of drought treated trees, while enzyme activities per surviving root tip remained remarkably similar to controls. Likewise, ECMf communities only experienced minor shifts that only slightly increased during the years, although different capacities for drought tolerance in ECMf have previously been hypothesised.
Summed up: Along with most tree individuals, their fungal partners showed a strong ability to resist the applied extreme drought scenario, at the cost of severely diminished capacities at the ecosystems level.
Speculatively, individual root tips could be seen as surviving insulae whose fungal communities only experienced indirect and moderated drought effects. Therefore, the ECM system may rather show an inherent resistance to drought, with observable qualitative adaptation requiring a still longer time-frame.
How to cite: Weikl, F. and Pritsch, K.: Are ectomycorrhizal fungi actually adapting to 5 years of extreme summer drought in Middle European forests?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2937, https://doi.org/10.5194/egusphere-egu21-2937, 2021.
Fungal community in the soil plays a central role in natural systems and agroecosystems, therefore it attracted much research interests. However, the fungal microbiota of aromatic plants, such as Salvia sclarea L., especially in trace-element (TE) polluted conditions and within the framework of phytomanagement approaches, remains unexplored. The presence of high concentrations of TE in the soil is likely to negatively affect not only microbial diversity and community structures, but also plant establishment and growth. The objective of this study is to investigate the soil fungal and arbuscular mycorrhizal fungi (AMF) community structure and their changes over time in TE-polluted soils in the vicinity of a former lead smelter and under the cultivation of clary sage. We used Illumina MiSeq amplicon sequencing to evaluate the effects of in situ clary sage cultivation during two successive years, combined or not with an exogenous AMF inoculation, on the rhizospheric soil and root fungal communities. We obtained 1239 and 569 fungal amplicon sequence variants (ASV) respectively in the rhizospheric soil and roots of S. sclarea in TE-polluted conditions. Remarkably, 69 AMF species were detected in our experimental site, belonging to 12 AMF genera. Besides, the inoculation treatment significantly shaped the fungal communities in soil, and increased the number of AMF ASVs in clary sage roots. In addition, successive years of clary sage cultivation also significantly shaped both fungal and AMF communities in the soil and root biotopes. Our data provide new insights on fungal and AMF communities in the rhizospheric soil and roots of clary sage grown in TE-polluted agricultural soil.
Keywords: Trace Elements-polluted soils, fungal microbiota, Salvia sclarea, arbuscular mycorrhizal fungi
How to cite: Raveau, R., Fontaine, J., Hijri, M., and Lounès Hadj-Sahraoui, A.: Clary sage cultivation and mycorrhizal inoculation influence rhizosphere fungal community structure over time in a trace-element polluted site, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12862, https://doi.org/10.5194/egusphere-egu21-12862, 2021.
Arbuscular mycorrhiza (AM) fungi are associated with almost all land plants and provide soil nutrients and other benefits to their plant hosts in exchange for photosynthetic products. While fertilization regimes in managed grasslands or agricultural systems are tailored for increasing plant biomass, their potential effects on AM fungi are rarely taken into account. Nutrient-driven changes in abundance and community composition of AM fungi, however, may feedback on ecosystem performance in the long term. Therefore, it is necessary to get a better understanding on how AM fungal communities respond to changes and imbalances in soil nutrient availabilities.
Here, we evaluated how long-term nutrient deficiency of phosphorus (P), nitrogen (N) and potassium (K) affects the abundance and community composition of AM fungi in a mountainous grassland. In addition, we investigated how the responses of AM fungi to those deficiencies were modulated by liming and the type of fertilizer addition (inorganic versus organic).
Our study was carried out on a long-term nutrient deficiency experimental grassland site in Admont (Styria, Austria), established in 1946. Different fertilization treatments were applied for more than 70 years in a randomized block design, including numerous combinations of inorganic (P, N, K with/without lime) and organic (solid manure and liquid slurry) fertilizers. The hay meadow at the site is cut three times per year and biomass is not returned to the system. Therefore, biomass and nutrients have been continuously removed for decades, leading to different types of soil nutrient deficiency. In this study, we collected both root and soil samples in July 2019 and quantified AM fungi and other microbial groups by measuring neutral fatty acid (NLFA) and phospholipid fatty acid (PLFA) biomarkers, respectively. Additionally, we applied DNA and RNA-based amplicon sequencing of the 18S rRNA gene to identify AM fungal community composition.
Our data shows that deficiencies of one or more elements had a major impact on both AM fungal biomass and community composition. AM fungal biomass was higher in plots that received no fertilizers compared to inorganically fertilized plots, but lower in plots which were deficient only in certain single or multiple elements, specifically in plots fertilized with inorganic N only (i.e., deficient in P and K). Conversely, liming and organic fertilizer amendments increased AM fungal biomass compared to plots containing inorganic fertilizers without lime. Across all treatments, AM fungal biomass was positively correlated with pH and soil water content, and negatively with dissolved N compounds, indicating indirect effects via responses of other soil parameters to nutrient deficiency. Long-term nutrient deficiency also altered plant community composition, which may also have indirectly affected AM fungal communities.
We conclude that long-term nutrient deficiency, and in particular the stoichiometry of available nutrients, strongly affects the abundance and community composition of AM fungi in grassland soil. This response may be linked to changes in plant community composition or soil chemistry both as a result and as a cause, emphasizing the complexity of feedbacks determining the response of grassland ecosystems to changing nutrient conditions.
How to cite: Jenab, K., Gorka, S., Darcy, S., Fuchslueger, L., Canarini, A., Martin, V., Wiesenbauer, J., Spiegel, F., Imai, B., Schmidt, H., Hage-Ahmed, K., Pötsch, E. M., Richter, A., Jansa, J., and Kaiser, C.: The effect of long-term nutrient deficiency on the abundance and community composition of arbuscular mycorrhizal fungi in a mountainous grassland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12688, https://doi.org/10.5194/egusphere-egu21-12688, 2021.
The main driver of the Carpathian landscape is the process of natural forest succession, which causes the overgrowing of the unique semi-natural meadows. Land-use changes influence the balance of organic carbon in the soil, simultaneously may cause carbon sequestration or CO2 emission. Whereas, there is still a lack of knowledge covering the impact of natural forest succession on organic carbon cycling. The purpose of this study was to investigate the dynamics of organic carbon in the different land-use soils. The selected properties showing the rate of mineralization process as well as soil biological activity were taken into account.
This study was located in three selected Carpathians’ national parks. Soil samples were taken from 0-10 cm and 10-20 cm soil layers of ten transects each consisting three different land use: semi-natural meadow, succession (30-75 aged trees), and old-growth forest (more than 150 years). Measurements of microbial biomass carbon (MBC), dissolved organic carbon (DOC), dehydrogenase (DHA) and invertase (INW) activity and microbial respiration were made on fresh soil samples. Based on the first-order kinetic model of microbial respiration the cumulative respiration was calculated. Additionally, the metabolic quotient (qCO2), the microbial quotient (qMIC), and the mineralization quotient (qM) were calculated.
The mean Corg content ranged from 17.6 g kg-1 in the 10-20 cm layer of succession to 41.5 g kg-1 in the 0-10 cm layer of forest. Considering the individual land use variants in the 0-10 cm layer meadow characterised the highest MBC, DHA and qM, and the lowest qCO2 values. In the succession, the highest cumulative respiration and qCO2 and the lowest MBC and INW were noted. Whereas the forest characterised the highest INW and the lowest cumulative respiration, DHA, qMIC and qM. Similarity, in the 10-20 cm layer meadow the highest MBC and DHA as well as qMIC were found. The succession characterised the highest cumulative respiration, qCO2 and qM and the lowest qMIC. However, in the forest the highest INW and the lowest qCO2, qMIC and qM were noticed.
Overall, for all investigated soils the positive correlations between Corg and MBC, DHA and negative correlations Corg with qMIC, qCO2 and DOC were shown. Whereas, when we take into consideration the individuals land use variants and depths can be stated that the content of organic carbon was shaped by different properties. In the 0-10 cm content of Corg in meadow and forest positive correlated with cumulative respiration and DHA, and negative with qM. Additionally, in forest negative correlations Corg with DOC, INW and qCO2 were found. While in succession the positive correlations Corg with MBC and INW and negative correlations Corg with DHA, qMIC and DOC were noted. In the 10-20 cm layers of meadow and succession Corg positive correlated with MBC, INW, qCO2 and negative with qM and DOC. Additionally, the qMIC positive correlation with Corg in meadow and negative correlation in succession was found. Whereas, in forest Corg positive correlated with qM and MBC, while negative correlations between Corg and qMIC, DOC and qCO2 were noticed.
How to cite: Józefowska, A., Sokołowska, J., and Zaleski, T.: Dynamics of soil organic carbon during natural forest succession in the Polish Carpathian Mountains, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11093, https://doi.org/10.5194/egusphere-egu21-11093, 2021.
Millipedes are among the largest and most important invertebrates, with over 12,000 identified and 80,000 expected species worldwide. Millipedes are detritivores living on leaf litter, deadwood, or soil. Because of the poor nature of their diets, millipedes compensate through high food consumption. Thanks to this, they are keystone species in many terrestrial ecosystems. In fact, in tropical and temperate zones, they rank the third most essential macrodetritivores after termites and earthworms and consume 10-36% of the annual litter. Thus, they contribute to soil formation and are essential forest ecosystem engineers. Despite their ecological importance, it remains unclear what role does their microbiome play in their diet.
We studied the gut microbiota of 11 millipede species and measured key physicochemical conditions (redox, pH and O2 levels). We found that the bacterial and archaeal communities were phylogenetically conserved while the fungi matched the diet. Methanogenic millipedes had a distinct community dominated by fermenting and syntrophic microorganisms. Follow-up experiments on the methanogenic and non-methanogenic species Epibolus pulchripes and Glomeris connexa, respectively, showed that both could survive prolonged antibiotic treatment, although with some disruption of their digestion. Antibiotics treatment significantly reduced the faecal bacterial colony counts after seven days in both species. Additionally, methane production dropped by 74% in the group treated with antibiotics and 52%, in the group that received sterile feed without antibiotics.
Microbiome analysis of these groups showed major shifts of the community composition in response to antibiotics, but less so with sterile feed. Apart from the presence of methanogens, high methane production correlated with a high relative abundance of Bacteroidia, while Gammaproteobacteria dominated the guts of millipedes with low, or no, methane production.
By supplementing the millipedes' diet with BES, methane production could be suppressed entirely within 21 days. Microscopic analysis of the faeces (using CARD-FISH) revealed methanogens from the orders Methanobacteriales and Methanomassiliicoccales associated with ciliates. These methanogens persisted even in the absence of methane production.
Our results indicate a significant gut microbiome activity in cellulolytic, fermentative and methanogenic litter decomposition processes, however, unlike in ruminants and termites with a limited nutritional contribution to the host.
How to cite: Angel, R., Šustr, V., Eyiuche Nweze, J., Gupta, S., Horváthová, T., M. Ardestani, M., Petrová, E., and Faktorová, L.: Millipedes cluster into distinct ecophysiological guilds based on their microbiome, with clear ecosystem implications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12016, https://doi.org/10.5194/egusphere-egu21-12016, 2021.
Peatlands are globally valued for the ecosystem services they deliver, including water quality regulation and carbon sequestration. In the UK, blanket bogs are the main peatland habitat and previous work has linked blanket bog management, especially rotational burning of heather vegetation on grousemoors, to impacts on these ecosystem services. However, we still lack a mechanistic, process-level understanding of how peatland management and habitat status is linked to ecosystem service provision, which is mostly driven by soil microbial processes.
Here we examine bacterial and fungal communities across a spectrum of “intact” to degraded UK blanket bogs and under different vegetation management strategies. Sites included grousemoors under burnt and alternative mown or uncut management along with further locations including 'near intact', degraded and restored sites across a UK climatic gradient ranging from Exmoor (South UK), the Peak District (Mid) to the Flow Country (North). Moreover, an experiment was setup at the University of York with peat mesocosms taken from all sites and management/habitat conditions to allow a comparison between field and controlled conditions and assessing root-mediated processes. Using a structural equation model, we linked grousemoor management to specific fungal/bacterial functional groups, and have started to relate this to changes in water quality provision and carbon cycle aspects. This represents a significant step in the effort to use microbial communities as indicators of peatland habitat condition in UK upland blanket bogs.
How to cite: Burn, W., Heinemeyer, A., Helgason, T., Glaves, D., and Morecroft, M.: The Hidden Half: Linking microbial communities to habitat condition and vegetation management in UK blanket bogs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11861, https://doi.org/10.5194/egusphere-egu21-11861, 2021.
Soil microorganisms are an essential component of forest ecosystems being directly involved in the decomposition of organic matter and the mineralization of nutrients. Anthropogenic disturbances such as logging and livestock modify the structure and composition of forests and also the structure and diversity of soil microbial communities changing critical biogeochemical processes in the soil. In this research we evaluated the effect of anthropic disturbance on the soil in a degradation gradient of Andean temperate forest. This gradient comprises mature forest stands dominated by Nothofagus dombeyii, secondary forests dominated by Nothofagus alpina with medium degradation, a highly degraded forests dominated by Nothofagus obliqua and a highly degraded grassland. We evaluate the reservoir of the main soil nutrients (TC, TN, NO3-, NH4+) and the structure, diversity and functions of the soil microbial community (bacteria and fungi) via NGS-Illumina sequencing and metagenomic análisis with DADA2 pipeline in R-project. The results show a higher amount of TC, TN, NO3- and C:N ratio in the most degraded condition (degraded grassland). There are no significant differences in the amount of TC, TN and NH4+ along the forest degradation gradient. This reflects a C:N:P stoichiometry that tends to decrease as forest degradation increases. The soil bacteria community was mainly dominated by Phyla Proteobacteria (45.35%), Acidobacteria (20.73%), Actinobacteria (12.59%) and Bacteroidetes (7.32%). At genus level there are significant differences, Bradyrhizobium has a higher relative abundance in the condition of mature forest which tends to decrease along the gradient of degradation forest. The soil fungi community was dominated by the Phyla Ascomycota (42.11%), Mortierellomycota (28.74%), Basidiomycota (24.61%) and Mucoromycota (2.06%). At genus level the condition of degraded grassland has significantly lower relative abundance of the genera Mortierella and Cortinarius. The degraded grassland soil microbial community is significantly less diverse in terms of bacteria (D' = 0.47±0.04) however it is significantly more diverse in terms of fungi (H' = 5.11±0.33).
How to cite: Atenas, A., Aburto, F., Hasbun, R., and Merino, C.: Effects of anthropogenic degradation of an Andean temperate forest on the soil nutrients and on the diversity and function of the soil microbial community, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14004, https://doi.org/10.5194/egusphere-egu21-14004, 2021.
Forest parks play an important role in the sustainable functioning of urban ecosystems. In contrast to natural forests, urban forests are under continuous anthropogenic pressure, affecting the soil microbial community functioning and its capacity to provide many ecosystem services. Moreover, another significant factor determining such functioning is bioclimatic conditions, i.e., city geographic location. Our study aims to examine the effect of urbanization on soil microbial biomass and functional diversity along a latitudinal gradient of European Russia. Urban forest parks (UFP) were chosen in Moscow, Tula, and Belgorod cities located in mixed coniferous-broadleaved forests, deciduous forests, and forest-steppe biomes of European Russia, respectively (17 sites). Outside of the cities the reference suburban forests (SUF) were selected (12 sites). When selecting sites, we considered the following criteria: i) same soil reference group within the biome (Retisols, Luvisols, Phaeozems in mixed coniferous-broadleaved forests, deciduous forests, and forest-steppe, respectively), ii) loam parent materials, and iii) forest aged ≥60 years. In each UFP and SUF, five spatially distributed plots were chosen, in which soil samples were taken from the upper 10 cm layer without litter (totally 85 and 60 for UFP and SUF). For freshly collected soil samples, microbial biomass carbon content (MBC, substrate-induced respiration method) and basal respiration (BR; rate of CO2 release) were measured, then the ratio BR / MBC = qCO2 was calculated. The community level physiological profile of soil microorganisms (CLPP, MicroRespTM technique) indicating the microbial ability to utilize different organic substrates (carbohydrates, acids: amino, carboxylic, phenolic, 14 totally) was tested. CLPP data were used to calculate the Shannon–Wiener diversity index (HCLPP).
It was found that soil BR decreased on average from SUF to USP in all studied biomes, while the MBC content did not change significantly. A significant increase of MBC in USP and SUF soils was observed from north to south (from mixed coniferous-broadleaved forests to forest-steppe), and for qCO2 – decreasing. The CLPP of the studied soils were dominated by microorganisms consuming carboxylic acids (ascorbic and citric) and carbohydrates (glucose, fructose, galactose). Cluster analysis identified two groups that differed by soil CLPP: i) mixed coniferous-broadleaved forests and deciduous forests (Moscow, Tula) and ii) forest-steppe (Belgorod). Soil HCLPP index didn’t significantly differ between SUF and UFP in all studied biomes. Two-way ANOVA showed that soil MBC, qCO2, and HCLPP changes were more associated with bioclimatic conditions (18-47% of explained variance, P <0.05) than urbanization (P> 0.05). On contrary, soil BR was more sensitive to urbanization (4% of explained variance, P <0.05) than to the change of bioclimatic conditions (P> 0.05). Notably, driving factors of spatial variation for the studied soil microbial properties within each city (53-92% unexplained variance) have yet to be identified.
This study was supported by the Russian Foundation for Basic Research, project No. 20-04-00148.
How to cite: Ananyeva, N., Khatit, R., Sushko, S., Buyvolova, A., Dolgikh, A., Zhuravleva, A., Selezneva, A., Vasenev, V., and Ivashchenko, K.: Soil microbial biomass and functional diversity in urban forest parks and suburban forests of various biomes in European Russia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14784, https://doi.org/10.5194/egusphere-egu21-14784, 2021.
Large-scale microbiome studies are currently facing challenges to overcome the lack of knowledge in relation to the interactions occurring among microbial communities and their surrounding environment. As a result, the study of associations through co-occurrence network analysis may lead to a better understanding for the aggregation or exclusion interactions in microbial studies and it offers a mapping of how information flows among the members of the microbiome system. By using 16S and ITS high-throughput sequencing, we studied the associations of bacterial and fungal communities in different olive compartments (fruit, phyllosphere, stem, xylem sap and roots) and the surrounding soil (bulk and rhizosphere) from three olive genotypes (‘Picual’, ‘Arbequina’ and ‘Frantoio’) growing at three olive orchards (Úbeda, Baena and Antequera) which differ in physicochemical soil characteristics and climate, in Andalusia, Southern Spain. Results based on the analysis of amplicon sequence variant (ASVs) displayed distinct microbial association network behaviors according to plant or soil compartments. Thus, plant compartment showed a positive association between Actinobacteria and Proteobacteria whereas some negative associations were exhibited by fungal communities, mainly from phyla Ascomycota and Basidiomycota. On the other hand, the negative associations of fungi were more noticeable in the soil compartments and the bacterial phylum Firmicutes played a different role in the soil than in the plant compartments. Furthermore, members of the bacterial phyla Deinococcota and Armatimonadota were unique in plant compartments while the phylum Verrucomicrobiota was only detected in the soil compartment. Overall, 14 keystone species with positive and negative associations in aboveground and belowground compartments were predicted based on the network parameters of high closeness and degree, and a low betweenness centrality. Interestingly, Bradyrhizobium and Pseudonocardia were positioned as two common keystone species among the positive associations in both compartments. This powerful analysis can reveal new knowledge regarding specific microbial associations on soil and plant microbiomes and it can propose a possible road map to investigate potential microbial source migration from soil to olive compartments.
Study supported by Projects XF-ACTORS 727987 (EU-H2020) and AGL2016-75606-R (MICINN Spain and FEDER-EU). MA-M acknowledged the predoctoral contract for the Training of Personal Investigator (FPI- MICINN) with reference BES-2017-082361 and COST Action CA16107 EuroXanth.
How to cite: Anguita-Maeso, M., Estudillo-Cazorla, C., León-Ropero, G., Navas-Cortés, J. A., de Menezes, A., and Landa, B. B.: Co-occurrence network inference analysis allows identification of keystone microbial species associated to soil compartments and environments in cultivated olive, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2893, https://doi.org/10.5194/egusphere-egu21-2893, 2021.
Soil enzymes catalyse the hydrolysis of various soil compounds leading to an increase in the availability of nutrients for plants and microorganisms, but the increase in mobility might also lead to losses by leaching. Sources of extracellular soil enzymes in soil include release by soil microorganisms such as bacteria and fungi and plant roots but also microbial necromass. Irrespective of their source, the released enzymes can accumulate in the soil by becoming stabilized on mineral and organic surfaces. It is generally assumed that 40 to 60% of measured enzyme activity originate from stabilized enzymes. As such they directly affect the ability of a soil to fulfil its numerous functions, including the provision of nutrients to plants, the cleaning of percolating water and climate regulation.
Although measurements of soil enzyme activity are increasingly recognised as sensitive indicators of soil health, variations and inconsistencies between existing methods make it difficult to compare the results of different studies. Most commonly, soil enzyme activities are assessed using destructive biochemical laboratory incubations, thus altering the natural soil conditions.
Therefore, based on the principle of soil zymography, a membrane based method to map the heterogeneity of enzymatic activity on exposed soil surfaces, we developed a portative, hand-held sensor allowing rapid measurement of the soil enzymatic activity in-situ (Digit Soil; https://www.digit-soil.com/). In this presentation, we will compare the performance of our sensor to laboratory incubations for the application on various types of soils differing in basic properties such as pH, texture and soil organic matter content at different moisture conditions.
Based on the results, we will discuss the prospects this new sensor offers for rapid in-situ evaluation of soil health in the framework of precision agriculture and sustainability labels.
How to cite: Iven, H., Meller, S., Luster, J., and Frossard, E.: A novel in-situ soil enzymatic activity sensor- expanding soil precision measurements to indicator of soil health., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10708, https://doi.org/10.5194/egusphere-egu21-10708, 2021.
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