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SSS4.1

EDI
Soil biodiversity and soil structure: an interdisciplinary view

Soil structure is essential for soil biota and soil functioning. But its study remains difficult because of its heterogeneity in space and time. To understand the interactions between soil structure and soil biodiversity, a strong interdisciplinary approach merging soil physics, soil ecology and soil chemistry is needed. Soil structure defines the myriad of microhabitats that host the unparalleled biodiversity observed in soils. The micro-gradients in oxygen, moisture, nutrients and organic compounds act as ecological filters for soil biota and define soil functioning. The soil structure is also highly variable in time, being constantly re-modelled by numerous factors such as the alternation of wet and dry cycles, the activity of the soil biota, especially plant roots and ecosystem engineers (e.g. microbes, notably filamentous fungi stabilizing aggregates, soil macrofauna, etc.), and the input of fresh organic matter.
In this session, we invite interdisciplinary contributions on: (i) the formation and spatiotemporal variability of the soil structure, and on (ii) the role of the soil microhabitat in determining soil biodiversity. Field, experimental and modeling approaches are welcome. The ultimate aim is to understand how soil structure, from micro-architecture to macropores, emerges from interactions within soil, and how it determines the outcome of soil processes (e.g mineralization) that have an important outreach for plants (e.g through mycorrhizae for example).

Convener: Amandine ErktanECSECS | Co-conveners: Claire Chenu, John Koestel, Edith Hammer, Naoise Nunan
Presentations
| Wed, 25 May, 10:20–11:50 (CEST)
 
Room -2.47/48

Wed, 25 May, 10:20–11:50

Chairpersons: Edith Hammer, John Koestel, Naoise Nunan

10:20–10:22
Introduction

10:22–10:32
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EGU22-1112
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solicited
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Highlight
Steffen Schlüter et al.

Organic farming aims at improving soil fertility in vineyard soils through a combination of farming practices. We studied the effect of organic management on community traits of free-living nematodes as well as bulk and microstructure properties of soil by comparing them to conventional management, both within vine rows and in interrows. The objectives of this study were to: 1) identify differences between management systems in terms of nematode abundance and molecularly measured community composition, and 2) to scrutinize, whether these changes can be explained by microstructural properties measured with X-ray computed tomography (X-ray CT) of individual soil aggregates. Nematode abundance was mainly  governed by habitat constraints, which was reflected in significant correlations with soil moisture and with porosity in the habitable size range of 20–220 μm obtained with X-ray CT. The lack of bioturbation by fine roots and the absence of irrigation reduced the abundance of water-filled, habitable pores, which resulted in the lowest nematode abundance in conventionally managed interrows without a grass cover. Community composition in terms of diversity and maturity, in turn, was not affected by habitat constraints but mainly governed by resource availability for the soil food web estimated by particulate and dissolved organic matter contents. The permanent grass cover and lack of tillage in interrows of the organic vineyard improved resource availability and promoted the build-up of omnivores and predators that are especially sensitive to disturbance. The organically managed interrows therefore had lower diversity and higher maturity than conventionally managed interrows. Differences between conventional and
organic management were in general greater in interrows than within vine rows.
These findings highlight the added value of pore structure investigations via X-ray CT in understanding trophic interactions of nematodes. At the same time, they stress the importance of exact sampling locations on nematode traits especially for perennial, woody crops.

How to cite: Schlüter, S., Gil, E., Doniger, T., Applebaum, I., and Steinberger, Y.: Abundance and community composition of free-living nematodes as a function of soil structure under different vineyard managements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1112, https://doi.org/10.5194/egusphere-egu22-1112, 2022.

10:32–10:38
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EGU22-58
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ECS
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Virtual presentation
Jingzhong Lu and Stefan Scheu

Generalist species vary in resource use with environments. High intraspecific variation in resource use may hamper trophic niche differentiation and coexistence of microarthropod species. To better understand intraspecific niche variation, we quantified stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) within and between populations of 40 Oribatida species (Acari) that co-occur in litter (OL) and soil (0–5 cm, mainly OF/H, AH) of five forest types (native European beech, non-native Douglas fir, range-expanding Norway spruce, two beech–conifer mixed forests). Although stable isotope signature of bulk material differed between litter and soil, δ13C and δ15N values of Oribatida species were remarkably stable irrespective of soil depth. Furthermore, Oribatida were more enriched in 13C in European beech than in coniferous forests, but δ15N values of Oribatida were similar across forest types. We conclude that trophic position (δ15N values) of Oribatida species is highly consistent across forest type, and that Oribatida species occupy virtually identical trophic niches (δ13C and δ15N values) irrespective of the soil depth they colonize. Despite that stable isotope analysis cannot reveal what animals actually feed on, our results suggest that low intraspecific variability facilitates niche differentiation and coexistence of Oribatida species. Overall, the results indicate that generalist species of soil microarthropods may be highly consistent in their resource use irrespective of environments. 

How to cite: Lu, J. and Scheu, S.: High consistency of trophic niches in soil microarthropod species (Oribatida, Acari) across soil depth and forest type, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-58, https://doi.org/10.5194/egusphere-egu22-58, 2022.

10:38–10:44
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EGU22-2817
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ECS
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Virtual presentation
Amandine Erktan et al.

Soil is a complex habitat that host an important diversity of soil organisms. The latter process soil organic matter along trophic chains that play a key role in soil functioning. While important progress has been made to decipher complex trophic interactions in soils, the role of soil animal mobility within the pore space as a determinant of food accessibility, and thus trophic interactions, remains poorly studied. Collembolans are ubiquitous microarthropods playing a pivotal role in soil food webs. We expected that collembolans colonize soil pores of equivalent dimension to their body size (few hundred microns). In these pores, they may hide from predators and access food resources, notably microbes. However, experimental evidences of the range of soil pores accessible to Collembola, and how it affects their mobility are missing. We used self-designed 3D printed physical pore simulation models with pore cylinders of 0.5, 0.75, 1 and 3 mm diameter (and all 4 mm long) to test how the pore diameter affects the mobility of six collembolan species (Heteromurus nitidus, Sinella curviseta, Folsomia candida, Ceratophysella denticulata, Protaphorura fimata and Mesaphorura macrochaeta). For each species, 10 individuals were placed in the soil pore simulation model at moist and dark conditions, and their ability to pass through pores was assessed after 7.5 minutes of incubation. We observed that collembolan mobility increased with pore diameter (P < 0.001), but this varied among species (P < 0.001). Species with the largest body size, namely H. nitidus (body width 0.58 ± 0.29 mm) and C. denticulata (body width 0.50 ± 0.12 mm) were particularly restricted with less than 1% of the individuals passing through pore necks of 0.4 mm. As the pore neck diameter increased, passage increased more for C. denticulata than for H. nitidus. Only 46 ± 20 % of the individuals of H. nitidus passed through a pore neck of 1 mm, whereas for C. denticulata it was 76 ± 10 %. Across the different pore diameters, P. fimata (body width 0.36 ± 0.08 mm) was the least restricted species, with 76 ± 18 % of individuals passing through pores of 0.4 mm diameter. M. macrochaeta (body width 0.11 ± 0.07 mm), S. curviseta (body width 0.39 ± 0.26 mm) and F. candida (body width 0.31 ± 0.09 mm) showed intermediate restriction in mobility with 54 ± 28 %, 43 ± 19 % and 43 ± 28 % of the individuals passing through pore of 0.4 mm diameter, respectively. At a pore diameter of 1 mm, these proportions raised to 84 ± 20%, 79 ± 10% and 95 ± 5%, respectively. Overall, Collembolan species were able to enter pores 20 ± 37 - 171 ± 33 µm wider than their body width, suggesting different ability to enter narrow pores depending on species. We conclude that the dimension of the pore diameter is a main factor restricting the mobility of collembolans in soil and presumably functions as main determinant of food accessibility.

How to cite: Erktan, A., Winkler, R., Henning-Krogh, P., and Scheu, S.: Effect of pore diameter on the mobility of six collembolan species: an experimental approach using 3D printed soil pore simulation models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2817, https://doi.org/10.5194/egusphere-egu22-2817, 2022.

10:44–10:50
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EGU22-1418
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ECS
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Virtual presentation
Andrey Zuev

In-growth mesh bag technique is widely used for assessing production and turnover of the fungal mycelium in soil, but remains poorly standardized. Various filling materials are used mainly quartz sand with particle size range of 0.4–2.0 mm or 0.5–1.5 mm. Substrate particle size plays a crucial role in soil pore formation: larger pore space may increase the growth of mycelium that spreads along cracks and other air-filled pores In contrast, the volume of soil explored by fungi can increase with greater bulk density while mycelium allocation shifts from a few large pores to more evenly distributed small pores. This research was aimed at testing the use of quartz sand of different particle size, as a filling for in-growth mesh bags, in order to obtain a maximum amount of fungal mycelium. Mesh bags were incubated in a Norway spruce forest in Central Russia. Mycelial biomass was higher in sand of coarse (> 0.5 mm) particle size and reached maximum (up to 798 μg of mycelium dry weight g−1 sand).

How to cite: Zuev, A.: Fungal mycelium growth: effects of the sand particle size, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1418, https://doi.org/10.5194/egusphere-egu22-1418, 2022.

10:50–10:56
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EGU22-9836
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ECS
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Highlight
Hanbang Zou et al.

A better understanding of soil carbon sequestration is important as the rapid elevation of carbon emission has significantly impacted our climate. The soil carbon dynamic process is strongly associated with trophic interactions in the soil communities. However, direct investigation of microbes and trophic interactions at microscale has been a major challenge due to the opacity of soil and the exceedingly complex pore spaces that limit direct in situ observation of trophic interactions and their variations with soil structure. As such, we decide to use microfluidic technique to create a two dimensional heterogeneous porous microenvironment containing nutrient patches of different quantity and quality to mimic the complex soil pore network and its heterogenous distribution of resources. This allows us to directly visualize and investigate the ability of organisms to access spaces starting from an initial ecophysiological precondition to changes of spatial accessibility mediated by interactions with the microbial community.

Microfluidics is a multidisciplinary platform that integrates micro fabrication, physical chemistry analysis, automation and microscopy. It has been widely used in life science and chemistry as it allows precise liquid manipulation, rapid measurements, real-time visualization at microscale, which is especially of interest and benefit to microbial studies. We created a complex pore network mimicking different soil environments – earlier considered impossible to achieve experimentally. The microfluidic channel contains a random distribution of cylindrical pillars of different sizes so as to mimic the pore space variations found in real soil. The randomness in the design creates various spatial availability for microbes. The nutrient patches within the pore space are achieved via capillary force trapping or UV curing hydrogel. In the former method, the patches are created by trapping nutrients in the predesign pore space due to interfacial tension between air and nutrient liquid. However, displacement instability during air injection makes it hard to control the formation of the patches. The latter enables better and more precise patches size and location manipulation but hydrogel biocompatibility with various fungal species remains a major challenge and hydrogel curing requires special facilities. The microfluidic nutrient patches provide spatial heterogeneities of resource distribution, which allows us to have a better understanding of the influence of spatial accessibility on the microbial community. The chip has five different nutrient distribution levels, ranging from centralized – a single large nutrient patch-  to increasingly dispersed nutrient distributions - sets of up to 49 loosely distributed nutrient patches of equal total volume. The experiments will be carried out using sterile cultures of fluorescent bacteria and fungi, synthetic communities of combinations of these, or a whole soil community inoculum. We will quantify the consumption of organic matter from the different areas via fluorescent substrates, and measure the bio- and necromass produced. We hypothesise that denser distribution will increase the net decomposition of organic matter as a centralized nutrient location increases the interactions within the microbial communities and individuals present in that area, which induces higher competition stress in the different communities.

How to cite: Zou, H., Ohlsson, P., and Hammer, E.: Two-dimensional microfluidic nutrient patches for direct visualization of microbial resource cycling , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9836, https://doi.org/10.5194/egusphere-egu22-9836, 2022.

10:56–11:02
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EGU22-3447
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ECS
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Julia Horak et al.

Linking soil functions to microbial community structure is arguably one of the greatest challenges in soil ecology, presumably due to the structural complexity and heterogeneity of soil across scales and time, as well as the large number of microbial taxa present. To overcome these impediments, we here introduce a model soil ecosystem - the “Synthetic Soil” - which allows soil structure and microbial community composition to be varied separately, to disentangle the complex relationship. The Synthetic Soil consists of a mixture of sterilized primary and secondary soil minerals and organic matter of plant and microbial origin, which together constitute the artificial soil matrix. This abiotic soil matrix is then inoculated with an in-silico designed, minimal microbial community, composed of 12 selected soil bacteria and fungi.

We demonstrate the applicability of the approach, by incubating the Synthetic Soil in a sterile environment for five weeks. During this period, an actively growing soil community established, indicated by stable respiration rates, increasing DNA- and ammonium concentrations, depletion of dissolved organic carbon, and by changes in relative abundances of the community members. Additionally, the minimal community was actively decomposing soil organic matter by the production of extracellular enzymes. In conclusion, the Synthetic Soil approach developed in this study, allows the construction of powerful and modifiable model ecosystems, which will make it possible to link soil functions to microbial community structure and thus to address fundamental questions of soil ecology.  

How to cite: Horak, J., Schmidt, H., Hadziabdic, L., Kits, K. D., and Richter, A.: A synthetic soil approach to link microbial community composition to soil functions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3447, https://doi.org/10.5194/egusphere-egu22-3447, 2022.

11:02–11:08
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EGU22-1063
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ECS
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On-site presentation
Frederic Leuther et al.

Soil structure is a dynamic property of soils which undergoes continuous changes due to various abiotic and biotic drivers. At the same time, the spatial arrangement of pores, organic matter and minerals influences soil functions, such as storage and filtering of water, nutrient cycling, or habitat for soil organisms and plants. In terms of carbon storage and matter turnover, the rearrangement of soil structure and herewith the change in accessibility of soil carbon for microbial decomposition is highly relevant. However, the turnover of soil structure and its constituents is difficult to quantify. In this study, a new method of structure labelling with inert garnet-particles in combination with X-ray µCT was used to determine the turnover rate of macro-aggregates and their drivers in two field experiments. Trials were conducted in topsoils of a Chernozem and a Luvisol under grassland, both with a silty loam texture but under different climatic conditions (Chernozem = 480 mm precipitation, Luvisol 886 mm). Over the course of 4 years, soil structure was regularly determined by X-ray µCT at two resolutions, 60 µm and 15 µm, to track soil structure development with time and in response to seasons. By excluding roots and soil fauna > 30 µm in half of the samples, it was possible to estimate the contribution of abiotic and biotic drivers. The distribution of garnet particles was determined in order to quantify the rate of soil structure turnover as related to potential biotic drivers. It is shown that soil structure turnover by natural processes is slow and that both abiotic and biotic drivers affect soil structure. Turnover under dry climatic condition was significantly slower due to lower biological activity. When soil is mixed by fauna > 30 µm activity, the distribution of garnet particles originally located at the surfaces of macro-aggregates became increasingly randomised, indicating rearrangement of soil structure and establishment of new pore−soil matrix interfaces.

How to cite: Leuther, F., Mikutta, R., Wolff, M., Kaiser, K., and Schlüter, S.: Soil structure turnover under grassland is mainly driven by biotic drivers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1063, https://doi.org/10.5194/egusphere-egu22-1063, 2022.

11:08–11:14
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EGU22-3431
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ECS
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Virtual presentation
Mohanned Abdalla and Mutez Ahmed

Recent studies have identified soil drying as a dominant driver of transpiration reduction at the global scale. Although Arbuscular Mycorrhiza Fungi (AMF) are assumed to play a pivotal role in plant response to soil drying, studies investigating the impact of AMF on plant water status and soil-plant hydraulic conductance are lacking. Thus, the main objective of this study was to investigate the influence of AMF on soil-plant conductance and plant water status of tomato under drought. We hypothesized that AMF limit the drop in matric potential across the rhizosphere, especially in drying soil. The underlying mechanism is that AMF extend the effective root radius and hence reduce the water fluxes at the root-soil interface. The follow-up hypothesis is that AMF enhance soil-plant hydraulic conductance and plant water status during soil drying. To test these hypotheses, we measured the relation between transpiration, soil and leaf water potential of tomato with reduced mycorrhiza colonization (RMC) and the corresponding wild-type (WT). We inoculated the soil of the WT with Rhizophagus irregularis spores to potentially upsurge symbiosis initiation. During soil drying, leaf water potential of the WT did not drop below -0.8 MPa during the first six days after withholding irrigation, while leaf water potential of RMC dropped below -1 MPa already after four days. Furthermore, AMF enhanced the soil-plant hydraulic conductance of the WT during soil drying. In contrast, soil-plant hydraulic conductance of the RMC declined more abruptly as soil dried. We conclude that AMF maintained the hydraulic continuity between root and soil in drying soils, hereby reducing the drop in matric potential at the root-soil interface and enhancing soil-plant hydraulic conductance of tomato under edaphic stress. Future studies will investigate the role of AMF on soil-plant hydraulic conductance and plant water status among diverse plant species growing in contrasting soil textures.

How to cite: Abdalla, M. and Ahmed, M.: Arbuscular mycorrhiza symbiosis improves plant water status and soil-root hydraulic conductance under drought , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3431, https://doi.org/10.5194/egusphere-egu22-3431, 2022.

11:14–11:20
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EGU22-7814
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ECS
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On-site presentation
Maximilian Wolff et al.

Application of farmyard manure (FYM) is common practice to improve physical and chemical properties of arable soil and crop yields. However, studies on effects of FYM application mainly focussed on topsoils, those in subsoils have been rarely been addressed so far. We, therefore, investigated the effects of a 36-year application of different FYM rates (0, 50, 100, 200 Mg ha−1 a−1) on organic carbon (OC) contents of a Chernozem in 0−30 cm (topsoil) and 35−45 cm (subsoil) depth, and its effects on soil structure and hydraulic properties in subsoil. X-ray computer tomography was used to analyse the response of macropore system (≥ 19 µm) and the distribution of particulate organic matter (POM) to different FYM applications. Based on morphological characteristics, POM was subdivided into a fresh and aged fraction. Image-derived POM volumes were related to contents in total OC (TOC) and water-extractable OC (WEOC) in order to differentiate between possible input sources of soil OC below the plough horizon. We show that manure application of up to 50 Mg ha−1 a−1 caused increases in TOC and WEOC contents only in the topsoil, whereas rates of ≥ 100 Mg ha−1 a−1 resulted in TOC enrichment also at deeper depth. In subsoil, the increase in POM (aged and fresh) and WEOC was more marked than that in TOC, indicating that POM and soluble OC may have facilitated the subsoil TOC enrichment. The subdivision of TOC into different OC sources shows that most of the increase was due to fresh POM, likely by roots. The increase in subsoil TOC went along with increases in macroporosity and macropore connectivity, possibly due to the stimulation of bioturbation. We neither observed increases in plant-available water capacity nor in unsaturated hydraulic conductivity. Our study shows that only very high applications of FYM over long periods can increase OC stocks of arable subsoil, but this increase is largely based on fresh, easily degradable POM and accompanied by high C losses.

How to cite: Wolff, M., Leuther, F., Kaiser, K., Schumann, L., Merbach, I., Mikutta, R., and Schlüter, S.: Responses of subsoil organic matter contents and physical properties to long-term application of increasing amounts of manure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7814, https://doi.org/10.5194/egusphere-egu22-7814, 2022.

11:20–11:26
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EGU22-9895
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ECS
Aymard Kouakou et al.

Abstract

After a Rubber plantation cycle (25 to 40 years), the greatest risk of soil degradation occurred during the replanting period which extends from the clear cutting of an old plantation to the planting of young rubber trees. During this period, the soil is subject to numerous disturbances mainly related to (1) the opening up of the environment following clear cutting (2) the export of organic matter with machines and (3) the practice of deep subsoiling by heavy machinery. These practices may affect directly or indirectly biodiversity and the delivery of soil functions (Missanjo and Kamanga-Thole 2014).

To mitigate soil degradation after one or more plantation cycles, some agricultural practices are commonly used, such as the implementation of a cover crop in the inter-rows at planting (Gao et al. 2017; Liu et al. 2018). Another alternative to restore soil functions is to leave the logging residues (i.e. trunk, branches, leaves and roots of the logged plantation) on the plot, given the high amount of carbon and nutrients accumulated in the tree at the clear-cut stage (Perron et al. 2021). The positive impact of crop residues has been demonstrated on soil fauna resilience (Lassauce et al. 2012; Carron et al. 2015), soil organic carbon and nutrients (Alam et al. 2018). However, so far, this agroecological practice has never been tested in rubber plantations and the effect of the restitution of logging residues on soil functioning has never been addressed.

We set up a field experiment after logging of the previous old RP in two industrial rubber plantations in Ivory Coast with contrasting soil types. In each RP, different type of logging residues and legume were added after clear cutting to determine their respective impact on the resilience of soil biodiversity. We hypothesized that (i) the input of logging residues and legumes after a clear-cutting will promote the resilience of soil biodiversity (microbial, nematode and macrofauna) (ii) soil types will affect the level of resistance and resilience of the soil biodiversity.

In both sites, we observed a significant loss of soil biodiversity, 6 months after clear-cutting and land preparation. The negative impact of mechanical disturbance on the dynamics of soil biodiversity has been revealed by lower abundance, richness, beta diversity, ecological indexes and co-occurrence networks. For example, soil macrofauna density significantly dropped by 36.04 and 93.65% at sandy and clay site respectively. Macrofauna diversity decreased significantly by 60.6% at sandy site and 91.39% at clay site. Practices with logging residues contributed to higher resilience of macrofauna density (~ 360% in clay site and 300% in sandy site) and diversity (134–154% in clay site and 58-73% in sandy site) than practice without residues (75–97% in clay site and 35-38% in sandy site). The application of logging residues and legume was the most efficient practice to promote soil biodiversity and to mitigate the negative impact of clear-cutting in rubber monocultures after a 40 years’ rotation.

Key words: Soil biodiversity, Rubber plantation, Restoration, Logging residues

How to cite: Kouakou, A., Yéo, K., Trap, J., Perron, T., Diakhaté, S., Gay, F., and Brauman, A.: Resistance and resilience of soil biodiversity after tree logging: case studies in rubber plantation in Ivory Coast, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9895, https://doi.org/10.5194/egusphere-egu22-9895, 2022.

11:26–11:32
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EGU22-10476
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On-site presentation
Erik Hobbie et al.

∙ To assess how belowground mycorrhizal networks may share resources, we used δ13C, δ15N, and C/N measurements to calculate spatial and temporal dynamics of carbohydrate and amino acid movement through ectomycorrhizal networks of mature trees.

∙ Canopies of 14 deciduous trees were continuously labeled with 13C-depleted CO2 from 2001-2005 (Swiss Forest FACE) and the 13C label traced into ectomycorrhizal sporocarps.

∙ Sporocarps derived 69±5%, 30±6%, and 16±7% of their carbon from labeled trees in the elevated (beneath labeled trees), 0-6 m, and 6-12 m distances, respectively. Sporocarp δ13C correlated positively with C/N under elevated CO2 and negatively elsewhere, reflecting that high-δ13C carbohydrates from surrounding trees contributed to sporocarps under elevated CO2 and low-δ13C carbohydrates from elevated CO2 trees contributed to sporocarps elsewhere. Sporocarp δ15N increased in Cortinarius with decreasing δ13C, suggesting that greater hyphal growth with elevated CO2 sequestered 15N-depleted N from sporocarp formation. Sporocarp loge C/N decreased during the 2004 growing season and the contribution of 13C-depleted carbon from elevated CO2 plants decreased at the 0-6 m and 6-12 m distances, suggesting decreased carbohydrate availability and network transport that year. In contrast, sporocarp loge C/N increased during the 2005 growing season and the contribution of 13C-depleted carbon from elevated CO2 plants increased at the 0-6 m distance, suggesting increased carbohydrate availability and network transport that year. Relative to other taxa, elevated CO2 reduced C/N by 15% and ambient CO2 increased C/N by 5% in taxa exclusively associated with deciduous trees, suggesting increased carbohydrate sharing by the deciduous-associated taxa.

∙ These patterns indicated that 1) carbohydrates (high C/N), not amino acids (low C/N), were preferentially transferred between regions differing in source δ13C, 2) sporocarp C/N reflected yearly plant productivity, 3) network transport was influenced by climate, and 4) taxonomy influenced transport dynamics belowground.

How to cite: Hobbie, E., Keel, S., Steinmann, K., Wilhelm, M., Saurer, M., Siegwolf, R., and Körner, C.: The Spatial Extent of Carbohydrate Sharing in the Wood-Wide Web Varies with Climate and with Taxonomy of Ectomycorrhizal Fungi : Insights from the Swiss Forest FACE, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10476, https://doi.org/10.5194/egusphere-egu22-10476, 2022.

11:32–11:38
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EGU22-9671
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On-site presentation
Gry Lyngsie

It has been established that brown-rot (BR) [1] and some ectomycorrhizal (ECM) [2] fungi use a non-enzymatic Fenton reaction (Fe2+ + H2O2 à Fe3+ + ∙OH) to decompose carbon. This Fenton reaction is driven by secondary metabolites, namely hydroquinones (H2Q), and to date studies of H2Q with redox reactive minerals have primarily been conducted under anoxic conditions and in batch setups. This approach introduces two shortcomings: Firstly, oxic iron(III) (oxyhydr)oxide (FeOOH) transformation and vertical translocation in the soil is ignored. Secondly, as the redox potential (EH) of FeOOH decrease as a function of increasing Fe2+ concentration in solution, the reductive dissolution stops when the EH of Q/H2Q is higher than EH of FeOOH/Fe2+[3]. It follows that in order to investigate the full potential of H2Q driven Fe mobilization an experimental setup, in which the solution is removed from the interface of the reaction, is needed. Consequently, this study will investigate the Fe mobilization potential of 2,6-dimethoxhydroquinone (DMHQ, a stable analogue to a common secondary metabolites produced by BR fungi) in a flow setup with continuous application of H2Q and removal of Fe2+ under oxic and natural relevant concentrations. A low-tech column set-up with synthesized ferrihydrite coated sand (1-0.5 mm) were supplied with 100 mL 20 µM DMHQ bi-daily over a three months period (50 times in all) and pH and Fe2+ concentration was monitored in the outlet. Before and after DMHQ application the coated ferrihydrite’s crystallinity was investigated with dithionite-citrate-bicarbonate and ammonium oxalate extractions. Results will be presented showing that DMHQ can reduce ferrihydrite and mobilize Fe2+ under oxic conditions and further that the ferrihydrite becomes increasingly crystalline, thus less reactive, after exposure to 100 µmol of 2,6-DMHQ. In light of the wide distribution of the Fenton reaction, with BR fungi dominating C sequestration in the boreal forest and ECM fungi being abundant in the boreal forest, eucalyptus forest and heathlands, these findings have interesting implications. Moreover, the results support that podsolization, i.e. the translocation of sesquioxides and soil organic matter associated with the above mentioned ecosystems, is linked to reductive dissolution of FeOOH by fungal secondary metabolites as previously suggested [4].

[1]             E. V Ier, K.E. Hammel, A.N. Kapich, K. a J. Jr, Z.C. Ryan, K. a Jensen, Reactive oxygen species as agents of wood decay by fungi, Enzyme Microb. Technol. 30 (2002) 445–453. doi:10.1016/S0141-0229(02)00011-X.

[2]             L. Qu, K. Makoto, D.S. Choi, A.M. Quoreshi, T. Koike, The Role of Ectomycorrhiza in Boreal Forest Ecosystem BT  - Permafrost Ecosystems: Siberian Larch Forests, in: A. Osawa, O.A. Zyryanova, Y. Matsuura, T. Kajimoto, R.W. Wein (Eds.), Springer Netherlands, Dordrecht, 2010: pp. 413–425. doi:10.1007/978-1-4020-9693-8_21.

[3]             C.A. Gorski, R. Edwards, M. Sander, T.B. Hofstetter, S.M. Stewart, Thermodynamic Characterization of Iron Oxide–Aqueous Fe 2+ Redox Couples, Environ. Sci. Technol. 50 (2016) 8538–8547. doi:10.1021/acs.est.6b02661.

[4]             N. van Breemen, U.S. Lundström, A.G. Jongmans, Do plants drive podzolization via rock-eating mycorrhizal fungi?, Geoderma. 94 (2000) 163–171. doi:10.1016/S0016-7061(99)00050-6.

How to cite: Lyngsie, G.: Oxic transformation and translocation of ferrihydrite by fungal secondary metabolites, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9671, https://doi.org/10.5194/egusphere-egu22-9671, 2022.

11:38–11:44
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EGU22-2385
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ECS
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Highlight
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Virtual presentation
Olivia Azevedo et al.

Ectomycorrhizae (EcM) are evolved mutualistic associations between soil fungi and plant roots. It has been shown that there can be species-specific differences in the ability to colonise roots. Colo­nised roots have increased longevity, greater resistance to pathogens, toxic elements in the soil and extreme con­ditions of temperature, acidity and moisture.

EcM inocula are an essential resource in forest management. Nevertheless, measures being implemented worldwide to promote forest cover recovery to reduce atmospheric CO2 levels can cause ecological shifts. Shifts to ecological communities take place as species become more or less abundant, are wiped out or colonise new habitats. However, these changes may not be captured by metrics focusing on species richness alone.

The lack of direct evidence of large-scale EcM temporal change in fungal community structure or function over time - commonly used in animal and plant research - is a basic, structural knowledge gap. Understanding temporal changes in community composition, whether via species losses and gains, or alterations to relative abundance and dominance is therefore essential to fathom the performance of terrestrial ecosystems, in particular the soil environment and its functions.

This study will characterise EcM fungi in woodland sites of varying ages. This study uses a space-for-time approach, benefiting from a collection of sites part of a wider study on the biodiversity responses to woodland planting.

How to cite: Azevedo, O., van der Linde, S., Park, K., Ashwood, F., Fuentes-Montemayor, E., Wilson, C., Watts, K., and Vanguelova, E.: Belowground networking: Biogeography of EcM fungi and species variation at different woodland ages, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2385, https://doi.org/10.5194/egusphere-egu22-2385, 2022.

11:44–11:50
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EGU22-13545
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Stefano Mocali et al.

The production, formulation and use on agricultural soils of biofertiliser or biostimulant mixtures containing several species of microorganisms is becoming increasingly common. The study of the interactions between the biological components of such products is less frequent. Often the marketed mixtures combine a high microbial load, in the form of both spores and propagules of fungi and bacteria whose positive or negative synergies are tested only to a limited extent, mainly because of the costs involved in field trials. The in vitro study of interactions between fungi or between fungi and bacteria is very important for understanding what can be expected in vivo, i.e. once microorganisms are released in large quantities into soils that already have local microbial communities.  The use of innovative techniques such as digital qPCR and phenotype microarrays now makes it possible to rapidly test thousands of interactions between two or more microorganisms. In this work, a method is proposed to evaluate the positive or negative effects of co-inoculums of different microorganisms on some main biological functions, and in particular the use of defined nutritive sources. The proposed protocol combines the application of commercial BiologR microplates with the quantification of the biomass of the individual co-inoculated strains by means of molecular tracing techniques and digital qPCR analysis. In vitro analysis of the effects of interactions is crucial because competition or commensalism can give rise to new compounds (i.e. enzymes, antibiotics, allopathic molecules) or behaviours (production of resistant structures, cellular apoptosis, changes in life cycle as perfect state inhibition or stimulation, etc.), which in turn can have definite effects on both the efficacy of the product and the variability of its properties.

How to cite: Mocali, S., Canfora, L., and Pinzari, F.: Qualitative-quantitative protocol for studying the interaction between fungi and between fungi and bacteria to produce bio-fertilising co-inoculants , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13545, https://doi.org/10.5194/egusphere-egu22-13545, 2022.