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Inter- and Transdisciplinary Sessions
SSS – Soil System Sciences
Programme group chairs:
Jose Alfonso Gomez,
David C. Finger
SSS4 – Soil Biology, Microbiology and Biodiversity
The rhizosphere and plant-soil-microbial interactions (including SSS Division Outstanding ECS Lecture by Bahar S. Razavi)
The interactions between plants and soil microbes are an important focus of terrestrial ecology. While synergistic, mutualistic and antagonistic interactions have been a primary focus in the literature, recent work with high-throughput sequencing methods has found that the whole soil microbial community can have a strong effect on plant success. Thus, much development has been made to understand the mechanisms underlying plant-microbe interactions in a community context.
At the same time, our planet is under increasing global change pressures. Climate change, land-use change, pollution - among other pressures - can disrupt the critical interactions between plants and soil microbes. Yet many questions remain: how disrupted interactions can reorganize and affect ecosystem functions - from soil nutrient cycling to plant productivity. In this session, we welcome studies examining how plant-soil-microbe interactions are affected by global change pressures and the ramification of these disruptions for ecosystem processes. We especially encourage contributions that examine interactions in a community or ecosystem context.
Distribution and functions of soil organisms in terrestrial ecosystems
Soil biodiversity and function are highly responsive to natural and anthropogenically inflicted changes. Soil biota are affected by climatic factors (temperature and soil moisture) as well as by the quality of above and belowground litter. Climatic variables affect soil community structure and activity by direct and indirect interactive factors. Directly, via suppression of particular groups by low/high mean annual temperatures or by drought/flooding, and indirectly, via regulation of plant community composition and productivity. Plant communities determine structure and activity of microorganisms by chemical composition of litter and root exudates (nutrients), as well as modifying soil chemical properties (pH, soil organic matter content and quality). In addition, anthropogenic practices strongly modify climatic conditions, impact nutrient cycling and cause an input of man-made substances and toxins, which may shift or even tilt the natural equilibrium of microbial communities and processes in soil.
In a series of oral and poster presentations this session will present advances in soil biological and functional diversity. Topics presented in this session will include, but are not limitted to, the formation of soil microbial community structures and activities under the effects of i) temperature and soil moisture fluctuations (climatic factors), ii) plant community types (forests, grasslands, biological soil crusts, agricultural lands) iii) various agricultural practices (including flooding, application of mineral and organic fertilizers). Particular attention will be given to the i) separation of the effects of climatic and biotic factors, and ii) simultaneous estimation of microbial community structure and activity to reveal the driving factors for both. Overall, this session will give a broad overview about the effect of environmental conditions on formation and functioning of biological communities in soils and possible new research directions.
Life and death in soils – Impacts of changes in soil conditions, climate and land use on soil biota
Microorganisms living in soil are usually well adapted to environmental fluctuations, but are challenged by unfavourable conditions related to the food supply combined to variations in temperature, soil moisture, electron acceptor availability, predators, viruses, and mechanical forces. Despite being well-adapted, we do not know how microbial metabolism and community composition will be affected by changes in these conditions. In fact, climate scenarios predict not only continued global warming but also strong changes in temperature and precipitation. At the same time, we have seen major shifts in land use with an increase in large-scale agricultural practices and urbanization. Both climate and land-use change alter the metabolism of soil organisms and soil biodiversity from the micro-scale (bacteria, fungi, archea, protozoa, virus) to the macro-scale (soil animals, earthworms, arthropods, nematodes, etc.). This can have significant ramifications for soil functions including soils’ ability to store organic carbon, support agriculture and conserve biodiversity.
This session collects experimental and modelling studies to understand microbial life, propagation, communication, growth, functioning, adaptations, maintenance metabolism, death, and necromass stabilisation in soil. Plant-microbe interactions and soil biota contribution to carbon sequestrations and crop production are also considered. In this broad context, this session also presents contributions on carbon use efficiency (CUE=ratio of biomass production over carbon substrate consumption) as an indicator or microbial metabolism. These include CUE estimation in soil using advanced methods – isotope labelling, kinetic studies, isothermal calorimetry, and approaches disclosing the effect of microbial community composition and activity on CUE – and modelling studies. A major common challenge in all these areas of soil ecology is how to scale observations and model concepts from organism and communities to soil profiles, ecosystems and finally to scales relevant to management and policy, all the way to the global scale. We thus welcome innovative and interdisciplinary studies that are pushing the field of soil ecology from the understanding of ecological and biogeochemical processes in soils to addressing global sustainability issues.
Survive together: soil biodiversity, functional processes, and EPS as key substances
Soils host a vast biodiversity across various kingdoms, with multiple interactions within and between communities and with the surrounding environment. In this session, we will investigate how biodiversity in soils responds on biotic and abiotic factors across various spatial scales. We will study the functional roles of these communities in processes like nutrient and water cycling, trace gas exchange with the atmosphere, soil erosion, mineral weathering, and vascular plant germination and growth. We will put one special focus on extracellular polymeric substances (EPS) and their role in promoting microbial adhesion to surfaces, reducing cellular desiccation, protecting against antibiotics or toxic molecules, and even acting as a final source of nutrition under extreme scarcity. The amount, composition and functionality of EPS in soils, biological soil crusts, sediments or other porous media will be investigated. Responses of soil communities to land use and climate change as well as other potential threats will also be included in this session. Besides temperate soil communities, we will focus on biological soil crusts occurring in hot and cold deserts around the world, and biofilms forming in coastal regions of freshwater and marine environments.
Interactions between biota, soil structure and function across scales: physics, imaging and ecology
Soil is a heterogeneous and structured environment that is characterised by variable geometry, composition and stability, across spatial scales spanning several orders of magnitude. The physical structure of solid and pore space results in a complex distribution of oxygen, water films and gradients of solutes spanning distances as small as a few micrometers, all of which have a profound effect on the ecological and hydrological functioning of soil.
The soil structure is determined by an interplay of physical, chemical and biological mechanisms, the quantitative role of which is still poorly understood. Soil structure is difficult to study as it is a 3D opaque matrix. To shed light into soil structure, the concept of aggregate has often been used and defines “pieces” of soil structure, that remain bounded under disrupting forces. Microaggregates (250µm) are larger soil units, composed by microaggregates and primary particles, bound together by biological agents, such as roots, fungal hyphae or even earthworm activity. Cutting edge imaging techniques are as well used to observe “in situ” associations of mineral and organic material at micro- and macro-scales and the resulting ever changing pore space, which is partly destroyed when focusing on aggregates, even though it has a fundamental role in soil ecology and functioning.
In this session we integrate the description of structure and its dynamics, using new imaging techniques, with the ecological, functional and physical consequences of the spatial arrangement of soil constituents. A strong interdisciplinary approach is thus required, merging soil physicists, chemists and ecologists. 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, in order to create models of soil functioning that integrate structure dynamics.
This session is divided into two oral blocks, one focusing more on the micro-scale in relation to microbial activities and the other accounting for micro- and macro-scale in relation to soil ecology of larger organisms and soil functioning. Carsten Mueller is the solicited speaker of the first oral block and Matthias Rillig is solicited for the second oral block.
The interactions between plants and their environment in biogeochemical cycles have drawn substantial attention in the domains of soil science, hydrology, plant physiology, ecology and climatology in recent years. This interest stems from the need for improved predictability of plant-related transfer processes to face fundamental environmental and agricultural issues, like for instance crop drought tolerance, contaminant transport, and the impact of global change on plant-mediated resource and energy fluxes in terrestrial systems.
Emerging experimental techniques and system modeling tools have deepened our insights into the functioning of water and nutrient transport processes in the soil-root system. Yet, quantitative approaches connectable across disciplines and scales nowadays constitute step stones to foster our understanding of fundamental biophysical processes at the frontier of soil and roots.
This session targets researchers investigating plant-related resource transfer processes from the rhizosphere to the field scale, and aims at gathering scientists from multiple disciplines ranging from soil physics to plant physiology. This includes:
- Novel experimental techniques assessing below-ground plant processes
- Measuring and modeling soil and plant water fluxes across scales
- Bridging the gap between biology and soil physics through numerical modeling
- Plant water and nutrient uptake under abiotic stress
- Impact of plant uptake on solute transport in soil
Prof. Dr. Andrea Carminati from the Chair of Soil Physics, University of Bayreuth, Germany.
Prof. Dr. Paul Hallett from the Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, United Kingdom
1) Prof. Dr. Andrea Carminati from the Chair of Soil Physics, University of Bayreuth, Germany.
2) Prof. Dr. Paul Hallett from the Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, United Kingdom
Water, isotope and solute fluxes in the soil-plant-atmosphere interface: Investigations from the canopy to the root zone
During the passage of precipitation through the soil-plant-atmosphere interface, water and solutes are redistributed by the plant canopy, subsurface flow and transport processes. Many of these dynamic interactions between vegetation and soil are not yet well understood. This session brings together the vibrant community addressing a better understanding of ecohydrological processes taking place between the canopy and the root zone. Innovative methods investigating throughfall, stemflow, hydraulic redistribution, and root water uptake in various environments shed light on how water and solutes are routed in the thin layer covering the terrestrial ecosystems. The session further covers open questions and new opportunities within the ecohydrological community regarding methodological developments such as the analysis of stable isotope, soil moisture, throughfall or solute dynamics.