Mineral surfaces as hotspots for microbes and element cycling in the Biodiversity Exploratories

Cost-neutral extension 2023-2024

Minerals provide reactive surfaces in soils to which organic matter and nutrients can bind and are thereby protected from decomposition, mineralisation, and leaching. Many soil microorganisms are living attached to mineral surfaces, where they form a unique habitat, the so-called mineralosphere. The interplay of microbial colonisation, and sorption and release of organic matter and nutrients cause continuous changes and transformations within the mineralosphere, with immediate consequences for carbon and nutrient storage and availability in soil. How land use and associated changes in biodiversity affect these interactions and resulting differences in soil carbon and nutrient stocks are hardly understood.

Picture: The photograph shows a piece of soil with grass growth lying on a round flat mineral container and held in front of the camera by two hands in white latex gloves. The size of the piece of soil is about twelve centimetres in height and about fifteen centimetres in diameter. Many predominantly fine roots can be seen in the soil. Long blades of grass grow on the surface of the piece of soil. In the background of the photograph a meadow and a row of leafy trees can be seen under a blue sky with a few clouds.

Background

Therefore, we installed mineral bags filled with pure, carbon-free mixtures of sand and illite (clay mineral) or goethite (iron oxide) at 5 cm depth at all experimental sites (EPs) of the Biodiversity Exploratories in 2015. At all very intensive sites, additional bags were installed at 25 cm depth and for forests also directly below the litter layer to determine the role of soil depth.

Hypotheses

After five years of field incubation, the bags are now being retrieved as well as surrounding soil. We aim at exploring the co-occurrence of mineral-associated microbial communities, organic matter, and nutrients in a coordinated, interdisciplinary approach. We hypothesise that type and intensity of land use and biodiversity affect: (1) the accumulation and quality of mineral-associated organic matter, (2) the contribution of plant and microbial sources to mineral-associated organic matter, (3) the patterns of microbial communities emerging in the mineralosphere, (4) the preservation mechanisms of mineral-associated organic matter, (5) the nutrient accumulation in the mineralosphere, and (6) the soil depth-related differences in mineralosphere.

Methods

The mineral and soil samples will be analysed using a series of state-of-the-art surface-sensitive, biogeochemical, isotopic, mineralogical, and microbiological methods. This collaborative approach will allow for the first time in-depth insight into developing mineralospheres under natural environmental conditions and real land-use intensities.

Picture: The photo shows two scientists kneeling in the grass on a meadow next to a fenced climate measuring station, busy with excavation work. They are using a small spade and a hand shovel. In front of the scientist on the right of the picture lies a transparent empty bag on the grass. Behind the men lies a grey tarpaulin about two metres long, on which there is some excavated earth. To the left of the tarpaulin kneels a female scientist watching the men

Picture: The photograph shows, above the soil of a meadow on the left of the picture, a palm on which lies a mineral container. The hand is in a blue latex glove. On the right of the picture one sees a hand, also gloved, holding a large piece of earth crumb which has been turned on its side. At the bottom of the crumb is a circular recessed area where the mineral container was. Within the circle a network of many fine roots is visible.

Picture: The photo shows the construction of a mineral container for spreading or installing mineral mixtures in the soils of forests and grasslands. In his left hand, a scientist holds the round, flat metal container for the mixture. The container has a diameter of about ten centimetres and is about one centimetre high. It consists of two discs screwed together with a layer of permeable material between them. Approximately one centimetre from the edge of the upper disc is a circumferential elevation of a few millimetres in height and thickness. The mineral mixture is placed inside the elevation. The mixture is fixed by a permeable textile cap that is pulled over the elevation. In the picture, the scientist's right hand can be seen holding the pulled-off cap between his index finger and a knife blade. Both hands are in blue latex gloves.

Picture: The photo shows a ground covered with wilted leaves and twigs photographed from above, with a mineral mixture container partially concealed between the leaves.

Publications

Formation of mineral-associated organic matter in temperate soils is primarily controlled by mineral type and modified by land use and management intensity

Bramble D.E., Ulrich S., Schöning I., Mikutta R., Brandt L., Poll C., Kandeler E., Mikutta C., Konrad A., Siemens J., Yang Y., Polle A., Schall P., Ammer C., Kaiser K., Schrumpf M. (2024): Formation of mineral-associated organic matter in temperate soils is primarily controlled by mineral type and modified by land use and management intensity. Global Change Biology 30 (1), e17024. doi: 10.1111/gcb.17024

Mineral type versus environmental filters: What shapes the composition and functions of fungal communities in the mineralosphere of forest soils?

Brandt L., Poll C., Ballauff J., Schrumpf M., Bramble D. S., Schöning I., Ulrich S., Kaiser K., Mikutta R., Mikutta C., Polle A., Kandeler E. (2024): Mineral type versus environmental filters: What shapes the composition and functions of fungal communities in the mineralosphere of forest soils? Soil Biology and Biochemistry 190: 109288. doi: 10.1016/j.soilbio.2023.109288

Mineral type and land-use intensity control composition and functions of microorganisms colonizing pristine minerals in grassland soils

Brandt L., Stache F., Poll C., Bramble D. E., Schöning I., Schrumpf M., Ulrich S., Kaiser K., Mikutta R., Mikutta C., Oelmann Y., Konrad A., Siemens J., Kandeler E. (2023): Mineral type and land-use intensity control composition and functions of microorganisms colonizing pristine minerals in grassland soils. Soil Biology and Biochemistry 182, 109037. doi: 10.1016/j.soilbio.2023.109037

Einfluss der Landnutzungsintensität von Grünlandflächen auf die mikrobielle Besiedlung von Goethit und Illit

Stache F. (2022): Einfluss der Landnutzungsintensität von Grünlandflächen auf die mikrobielle Besiedlung von Goethit und Illit. Master thesis, University Hohenheim

Exploring C dynamics on mineral surfaces under different management scenarios in temperate forests

Erforschung der C-Dynamik auf mineralischen Oberflächen unter verschiedenen Bewirtschaftungsszenarien in Wäldern der mittleren Breiten

Mainka M. (2022): Exploring C dynamics on mineral surfaces under different management scenarios in temperate forests. Master thesis, University of Hohenheim