#Microorganisms & Fungi #BEF #Soil Ecology #2023 – 2026 #2020 – 2023 #Land use #Species communities #Soil organisms #Fertilisation #Interaction #Mycorrhiza fungi #Soil microorganisms #Carbon cycle #Functional diversity #Temporal scale #Enzymes #Food source #Grassland #Root #Microbial community #Plant - fungus interaction #Nitrogen cycle #Stable isotopes #Soil #Mineralisation #Nutrients #Litter

SCALEMIC (Contributing project)

The function of the hyphosphere in carbon and nutrient partitioning between plants and microorganisms in grassland soils under different land-use intensities

Cost-neutral extension 2023-2026

Picture: The photo shows a hand in a turquoise glove lifting a piece of soil between meadow grass. The thickness of the piece of soil is estimated at ten to fifteen centimetres.

Background

Reduction in land-use intensity may favour plant-symbiont interactions, modifying nutrient acquisition strategies of plants and microbes at different scales. At the rhizosphere scale, for example, a narrow region of soil directly influenced by root secretions and associated soil microorganisms, the root-soil interface is characterised by gradients of nutrients, protons, carbon resources, and living microorganisms. The hyphosphere is defined as a sphere where symbiotic and non-symbiotic fungi are present in the soil environment; it is characterised by intense fungal-bacterial-soil. These distinct zones are often difficult to separate experimentally from each other.

Goals

The aim of our study is to unveil how fungal-bacterial interactions in the hyphosphere contribute to plant nutrition, as well as how the carbon supply from plants affect bacteria via the symbiotic interactions with fungi.

In the next three years, we will test the following hypotheses:

Both symbiotic fungi (mycorrhizal fungi) and free-living saprotrophic fungi dominate initial microbial carbon uptake from the plant by rapid processing and channelling of rhizodeposits into the hyphosphere, wherefore this can function as a ‘carbon bridge’ between plants and bacteria; bacteria profit as secondary consumers.
Plants rely on nutrient transport via the hyphosphere to a greater extent in low as compared to high land-use intensity (LUI) grassland soils.
Experimental de-intensification of grassland land use will modify abundance and function of soil microorganisms either by reducing nutrient supply (reduced fertilisation, direct response of soil microorganisms) or by reducing mowing intensity (changing plant input into soils, indirect response of soil microorganisms).

Methods

In order to test our hypotheses, we will need a complete separation between the rhizosphere and the hyphosphere. We will use newly developed HYPHOboxes that experimentally separate the hyphosphere from the rhizosphere and the surrounding bulk soil (Fig. 1).

Fig. 1. HYPHObox compartments. a. HYPHObox schema, b. HYPHObox compartments with different meshes and c. HYPHObox as seen from the side of the rhizosphere compartment.

Experiments 1 and 2: Carbon flow from plants to the hyphosphere and nutrient flow from the hyphosphere to the plants and back

The goals of these experiments are to understand (i) which fungi benefit most from plant-derived carbon in grassland ecosystems and which fungi are responsible for the ‘long-distance’ transport (>15 mm) of carbon, thereby providing resources for bacteria as secondary consumers (Fig. 2a), and (ii) which fungi are responsible for the transport ¹³C and ¹⁵N from the detritusphere through the hyphosphere to the rhizosphere (Fig. 2b). We will use a ¹³CO₂pulse labelling approach to quantify the carbon flux of plant-fixed C into fungi and their associated bacteria, and a ¹³C and ¹⁵N labelling in the detritusphere compartment will allow us to measure long-term ¹³C and ¹⁵N incorporation in the microbial biomass as well as its transfer to the plant biomass.

Fig. 2. Experimental design of the first and second experiments: a) 13CO2 labelling of plants and 15N labelling in the detritusphere compartment will allow us to measure short-term 13C incorporation in the microbial biomass as well as 15N incorporation in the plant biomass; b) 13C and 15N labelling in the detritusphere compartment will allow us to measure long-term 13C and 15N incorporation in the microbial biomass as well as its transfer to the plant biomass.

Experiment 3: De-intensification of grassland sites – Direct versus indirect effects on soil microorganisms (multi-grassland land-use experiments)

De-intensification of land use may drive changes in microbial communities and in the soil functions they regulate. The newly established multi-grassland land-use experiments (Fig. 3) will make it possible to identify the direct and indirect mechanisms that may contribute to changes in microbial abundance and function.

Background

Picture: The collage contains a drawing and two photos. The drawing shows the schematic of a so-called hypho-box, which is placed in the soil during the experiment and separates the hypho-sphere from the rizo-sphere. The box consists of five vertically arranged ten millimetre thick compartments, i.e. areas separated by membranes. The two outer areas are accessible for the rizo-sphere, the two areas behind it for the hypo-sphere. In the area in the middle there is a marking compartment. Photo 1 shows the five compartments with gauzes in different mesh sizes. The outer compartments are black, the middle one with the labelling area is white. Photo 2 shows a close-up of the rizo-sphere compartment — Fig. 1. HYPHObox compartments. a. Schematic HYPHObox, b. HYPHObox compartments with gauzes with different mesh sizes and c. HYPHObox seen from the side of the rhizosphere compartment

Picture: The diagram in parts A and B shows information on two experiments. Part A, viewed from the side, shows the diagram of a hypho-box buried in the ground, in which the hypho-sphere is separated from the rizo-sphere. The box consists of five vertically arranged ten millimetre wide compartments, i.e. areas separated by membranes. The two outer areas are accessible as the rizo-sphere, the two areas behind it as the hypo-sphere. In the area in the middle is a nutrient compartment. A plant is shown at the top of the earth's surface above the hypo box. An arrow leads from the nutrient compartment of the box upwards to the plant, which is labelled with the sign for heavy, stable isotopes of nitrogen. Leading from the plant to the hydro box are two arrows labelled with the sign for heavy, stable isotopes of carbon. One of the arrowheads ends in the hydro-sphere, one in the rhizo-sphere.
Part B of the diagram shows the following differences from part A: Instead of a nutrient compartment, there is a litter compartment in the box. Four arrows with nitrogen signs lead out of the compartment. One of the arrowheads is directed towards the plant, another into the surrounding soil and the last two into the area of the hydro-sphere and the rhizo-sphere inside the box. Also leading out of the nutrient compartment into the surrounding soil and the two spheres are arrows with carbon signs. — Fig. 2. experimental setup of the first and second experiments: a. 13CO2 labeling of plants and 15N labeling in the detritus sphere compartment allow us to determine both short-term 13C incorporation into microbial biomass and 15N incorporation into plant biomass. b. 13C and 15N labeling in the detritus sphere compartment allow us to determine long-term 13C and 15N incorporation into microbial biomass and their transfer to plant biomass

Picture: The photo shows a fenced plot with a meadow on which the grass is half green and half brown. To the right behind the meadow is a group of trees consisting of deciduous and coniferous trees. To the left behind are hills with more meadows and groups of trees as well as individual trees. — Fig. 3 Newly established trial on mowing and grazing reduction in the Swabian Alb. Image taken in August 2020 by A. Abrahão

Publications

Increasing plant species richness by seeding has marginal effects on ecosystem functioning in agricultural grasslands

Freitag M., Hölzel N., Neuenkamp L., van der Plas F., Manning P., Abrahão A., Bergmann J., Boeddinghaus R., Bolliger R., Hamer U., Kandeler E., Kleinebecker T., Knorr K.-H., Marhan S., Neyret M., Prati D., Le Provost G., Saiz H., van Kleunen M., Schäfer M., Klaus V. H. (2023): Increasing plant species richness by seeding has marginal effects on ecosystem functioning in agricultural grasslands. Journal of Ecology 111 (9), 1968-1984. doi: 10.1111/1365-2745.14154

Microbial drivers of plant richness and productivity in a grassland restoration experiment along a gradient of land use intensity

Abrahão A., Marhan S., Boeddinghaus R. S., Nawaz A., Wubet T., Hölzel N., Klaus V. H., Kleinebecker T., Freitag M., Hamer U., Oliveira R. S., Lambers H., Kandeler E. (2022): Microbial drivers of plant richness and productivity in a grassland restoration experiment along a gradient of land use intensity. New Phytologist 236 (5), 1936-1950. doi: 10.1111/nph.18503

Linear mixed models and geostatistics for designed experiments in soil science ‐ two entirely different methods or two sides of the same coin?

Lineare gemischte Modelle und Geostatistik für geplante Experimente in den Bodenwissenschaften – zwei unversöhnliche Methoden oder zwei Seiten derselben Medaille

Slaets J., Boeddinghaus R. S., Piepho H.-P. (2021): Linear mixed models and geostatistics for designed experiments in soil science ‐ two entirely different methods or two sides of the same coin? European Journal of Soil Science 72 (1), 47-68. doi: 10.1111/ejss.12976

The Mineralosphere – Interactive zone for microbial colonization and carbon use in grassland soils

Boeddinghaus R. S., Marhan S., Gebala A., Haslwimmer H., Vieira S., Sikorski J., Overmann J., Soares M., Rousk J., Rennert T., Kandeler E. (2021): The Mineralosphere – Interactive zone for microbial colonization and carbon use in grassland soils. Biology and Fertility of Soils 57, 587–601. doi: 10.1007/s00374-021-01551-7

Unraveling spatiotemporal variability of arbuscular mycorrhizal fungi in a temperate grassland plot

Goldmann K., Boeddinghaus R. S., Klemmer S., Regan K. M., Heintz-Buschart A., Fischer M., Prati D., Piepho H.-P., Berner D., Marhan S., Kandeler E., Buscot F., Wubet T. (2020): Unraveling spatio‐temporal variability of arbuscular mycorrhiza fungi in a temperate grassland plot. Environmental Microbiology 22 (3), 873-888. doi: 10.1111/1462-2920.14653

Bacterial colonization of minerals in grassland soils is selective and highly dynamic

Nach welchen Regeln besiedeln Bakterien den Boden?

Vieira S., Sikorski J., Gebala A., Boeddinghaus R. S., Marhan S., Rennert T., Kandeler E., Overmann J. (2020): Bacterial colonization of minerals in grassland soils is selective and highly dynamic. Environmental Microbiology 22 (3), 917-933. doi: 10.1111/1462-2920.14751

Stochastic dispersal rather than deterministic selection explains the spatio-temporal distribution of soil bacteria in a temperate grassland

Richter-Heitmann T., Hofner B., Krah F.-S., Sikorski J., Wüst P. K., Bunk B., Huang S., Regan K., Berner D., Boeddinghaus R. S., Marhan S., Prati D., Kandeler E., Overmann J., Friedrich M. W. (2020): Stochastic dispersal rather than deterministic selection explains the spatio-temporal distribution of soil bacteria in a temperate grassland. Frontiers in Microbiology 11: 1391. doi: 10.3389/fmicb.2020.01391

Recovery of ecosystem functions after experimental disturbance in 73 grasslands differing in land‐use intensity, plant species richness and community composition

Erholung von Ökosystemfunktionen nach experimenteller Störung in 73 Grünlandflächen mit unterschiedlicher Landnutzungsintensität, Artenvielfalt und Zusammensetzung der Pflanzengesellschaft

Schäfer D., Klaus V. H., Kleinebecker T., Boeddinghaus R. S., Hinderling J., Kandeler E., Marhan S., Nowak S., Sonnemann I., Wurst S., Fischer M., Hölzel N., Hamer U., Prati D. (2019): Recovery of ecosystem functions after experimental disturbance in 73 grasslands differing in land‐use intensity, plant species richness and community composition. Journal of Ecology 107 (6), 2635-2649. doi: 10.1111/1365-2745.13211

Plant functional trait shifts explain concurrent changes in the structure and function of grassland soil microbial communities

Veränderungen von funktionellen Pflanzeneigenschaften erklären parallele Veränderungen in der Struktur und Funktion mikrobieller Gemeinschaften in Grünlandböden

Boeddinghaus R. S., Marhan S., Berner D., Boch S., Fischer M., Hölzel N., Kattge J., Klaus V. H., Kleinebecker T., Oelmann Y., Prati D., Schäfer D., Schöning I., Schrumpf M., Sorkau E., Kandeler E., Manning P. (2019): Plant functional trait shifts explain concurrent changes in the structure and function of grassland soil microbial communities. Journal of Ecology 107 (5), 2197-2210. doi: 10.1111/1365-2745.13182

Functional Traits and Spatio-Temporal Structure of a Major Group of Soil Protists (Rhizaria: Cercozoa) in a Temperate Grassland

Fiore-Donno A. M., Richter-Heitmann T., Degrune F., Dumack K., Regan K. M., Mahran S., Boeddinghaus R. S., Rillig M. C., Friedrich M. W., Kandeler E., Bonkowski M. (2019): Functional Traits and Spatio-Temporal Structure of a Major Group of Soil Protists (Rhizaria: Cercozoa) in a Temperate Grassland. Frontiers in Microbiology 10:1654. doi: 10.3389/fmicb.2019.01654

The mineralosphere – Succession and physiology of bacteria and fungi colonising pristine minerals in grassland soils under different land-use intensities

Die Mineralosphäre – Sukzession und Physiologie von Bakterien und Pilzen während der Besiedlung reiner Minerale in Grünlandböden mit unterschiedlicher Landnutzungsintensität

Kandeler E., Gebala A., Boeddinghaus R. S., Müller K., Rennert T., Soares M., Rousk J., Marhan S. (2019): The mineralosphere – Succession and physiology of bacteria and fungi colonising pristine minerals in grassland soils under different land-use intensities. Soil Biology and Biochemistry 136: 107534. doi: 10.1016/j.soilbio.2019.107534

Spatial and temporal variations of microorganisms in grassland soils – influences of land-use intensity, plants and soil properties

Räumliche und zeitliche Variationen von Mikroorganismen in Grünlandböden - Einflüsse von Landnutzungsintensität, Pflanzen und Bodeneigenschaften

Boeddinghaus R. S. (2019): Spatial and temporal variations of microorganisms in grassland soils - influences of land-use intensity, plants and soil properties. Dissertation, University Hohenheim

Einfluss der Landnutzungsintensität auf die mikrobielle Bio-masse von Grünlandböden

Bauer C. (2018): Einfluss der Landnutzungsintensität auf die mikrobielle Bio-masse von Grünlandböden. Bachelor thesis, University Hohenheim

Long-term effects of disturbance and seed addition on soil microbial biomass in grassland with high and low land-use intensity

Langzeit Effect von Störung und Ansaat auf die mikrobielle Biomasse in Grünlandböden mit hoher und niedriger Landnutzungsintensität

Lang K. (2018): Long-term effects of disturbance and seed addition on soil microbial biomass in grassland with high and low land-use intensity. Bachelor thesis, University Hohenheim

Spatial and temporal dynamics of nitrogen fixing, nitrifying and denitrifying microbes in an unfertilized grassland soil

Regan K., Stempfhuber B., Schloter M., Rasche F., Prati D., Philippot L., Boeddinghaus R. S., Kandeler E., Marhan S. (2017): Spatial and temporal dynamics of nitrogen fixing, nitrifying and denitrifying microbes in an unfertilized grassland soil. Soil Biology and Biochemistry 109, 214–226. doi: 10.1016/j.soilbio.2016.11.011

Die potentielle Methan-Oxidation des Bodens in Abhängigkeit von der Landnutzungsintensität am Beispiel von Grünland und Wald

Rohrbach K. (2017): Die potentielle Methan-Oxidation des Bodens in Abhängigkeit von der Landnutzungsintensität am Beispiel von Grünland und Wald. Bachelor thesis, University Hohenheim

Impact of soil disturbance on microorganisms in differently managed grassland soils linked to the ecosystem resilience

Binder I. (2016): Impact of soil disturbance on microorganisms in differently managed grassland soils linked to the ecosystem resilience. Master thesis, University Hohenheim

Linking Microbial Abundance and Function to Understand Nitrogen Cycling in Grassland Soils

Regan K. M. (2016): Linking Microbial Abundance and Function to Understand Nitrogen Cycling in Grassland Soils. Dissertation, University Hohenheim

Do general spatial relationships for microbial biomass and soil enzyme activities exist in temperate grassland soils?

Gibt es allgemeine räumliche Verteilungsmuster von mikrobieller Biomasse und Enzymaktivitäten in Grünlandböden?

Boeddinghaus R. S., Nunan N., Berner D., Marhan S., Kandeler E. (2015): Do general spatial relationships for microbial biomass and soil enzyme activities exist in temperate grassland soils? Soil Biology & Biochemistry 88, 430-440. doi: 10.1016/j.soilbio.2015.05.026

Effects of warming and drought on potential N2O emissions and denitrifying bacteria abundance in grasslands with different land use

Einfluss von Temperaturerhöhung und Dürre auf Lachgasemissionen und die Häufigkeit von denitrifizierenden Bakterien in Grünlandböden mit unterschiedlicher Landnutzungsintensität

Keil D., Niklaus P. A., von Riedmatten L. R., Boeddinghaus R. S., Dormann K. F., Scherer-Lorenzen M., Kandeler E., Marhan S. (2015): Effects of warming and drought on potential N2O emissions and denitrifying bacteria abundance in grasslands with different land use. FEMS Microbiology Ecology 91(7), pii: fiv066. doi: 10.1093/femsec/fiv066

Einfluss der Landnutzungsintensität auf die mikrobielle Biomasse und Enzymaktivitäten im Rhizosphärenboden verschiedener Grünlandpflanzenarten

Boob M. (2015): Einfluss der Landnutzungsintensität auf die mikrobielle Biomasse und Enzymaktivitäten im Rhizosphärenboden verschiedener Grünlandpflanzenarten. Master thesis, Universität Hohenheim

Influence of land use on abundance, function and spatial distribution of N-cycling microorganisms in grassland soils

Einfluss von Landnutzung auf Abundanz, Funktion und räumliche Verteilung von N-umsetzenden Mikroorganismen in Grünlandböden

Keil D. (2015): Influence of land use on abundance, function and spatial distribution of N-cycling microorganisms in grassland soils. Dissertation, University of Hohenheim

Seasonal controls on grassland microbial biogeography: Are they governed by plants, abiotic properties or both?

Zeigen Pflanzen oder abiotische Bodeneigenschaften saisonal bedingt mehr Einfluss auf die Verteilung von Mikroorganismen in Grünlandböden?

Regan K. M., Nunan N., Boeddinghaus R. S., Baumgarten V., Berner D., Boch S., Oelmann Y., Overmann J., Prati D., Schloter M., Schmitt B., Sorkau E., Steffens M., Kandeler E., Marhan S. (2014): Seasonal controls on grassland microbial biogeography: Are they governed by plants, abiotic properties or both? Soil Biology and Biochemistry 71, 21–30. doi: 10.1016/j.soilbio.2013.12.024

midDRIFTS-based partial least square regression analysis allows predicting microbial biomass, enzyme activities and 16S rRNA gene abundance in soils of temperate grasslands

Eine neue Methode (midDRIFTS basierte Spektroskopie) erlaubt die schnelle und kostengünstige Vorhersage von mikrobieller Biomasse und Aktivität in Grünlandböden

Rasche F., Marhan S., Berner D., Keil D., Kandeler E., Cadisch G. (2013): midDRIFTS-based partial least square regression analysis allows predicting microbial biomass, enzyme activities and 16S rRNA gene abundance in soils of temperate grasslands. Soil Biology and Biochemistry 57, 504–512. doi: 10.1016/j.soilbio.2012.09.030

Influence of land-use intensity on spatial distribution of N-cycling microorganisms in grassland soils

Einfluss von Landnutzungsintensität auf die räumliche Verteilung Stickstoff umsetzender Mikroorganismen in Grünlandböden

Keil D., Meyer A., Berner D., Poll A., Schützenmeister A., Piepho H.-P., Vlasenko A., Philippot L., Schloter M., Kandeler E., Marhan S. (2011): Influence of land-use intensity on spatial distribution of N-cycling microorganisms in grassland soils . FEMS Microbiology Ecology 77 (1), 95-106. doi: 10.1111/j.1574-6941.2011.01091.x

Land-Use Intensity Modifies Spatial Distribution and Function of Soil Microorganisms in Grasslands

Die Landnutzungsintensität verändert die räumliche Verteilung und Funktion von Bodenmikroorganismen im Grünland

Berner D., Marhan S., Keil D., Schützenmeister A., Piepho H.-P., Poll C., Kandeler E. (2011): Land-Use Intensity Modifies Spatial Distribution and Function of Soil Microorganisms in Grasslands. Pedobiologia 54 (5-6), 341-351. doi:10.1016/j.pedobi.2011.08.001

Einfluss von Landnutzungsintensität auf Mikroorganismen in Grünlandböden der Schwäbischen Alb

Breuer B.S. (2008): Einfluss von Landnutzungsintensität auf Mikroorganismen in Grünlandböden der Schwäbischen Alb. Bachelor Thesis, University Hohenheim

Räumliche Heterogenität mikrobieller Enzymaktivitäten in Grünlandböden der Schwäbischen Alb

Glatzle S.(2008): Räumliche Heterogenität mikrobieller Enzymaktivitäten in Grünlandböden der Schwäbischen Alb. Bachelor thesis, University Hohenheim