Soil algae are the most important primary producers where vascular plants are absent, as in the Arctic and Antarctica. They give rise to species-rich microbial food webs in biological soil crusts (biocrusts). The terrestrial snow- and ice-free areas are in permanent expansion as glaciers retreat, leaving behind extensive areas of uncovered rock and new soil. Biocrusts stabilize the soil surface and have an important role in soil development. However, the microbial food webs and the nutrient and energy flow to higher trophic levels remain largely unexplored. Here, we characterized the microbial predator-prey dynamics of polar soils by combining molecular and traditional culturing techniques. Using high-throughput sequencing of environmental samples, we assessed the biodiversity and function of soil protists, applying a trait-based approach for acquiring and describing functional traits, i.e., the feeding behavior of heterotrophic protists in relation to microalgae. The study encompasses the analysis of biocrust samples of three polar regions. In the Arctic, one region was sampled - Svalbard in the Arctic Ocean (78°N) in July 2021. In Antarctica, two regions were studied, i.e. King George Island (62°S) in the South Shetland archipelago of Maritime Antarctica and the Thala Hills oasis in Enderby Land, East Antarctica (67°S), between January and March 2022.
The Arctic Greening Database v0.1 is an open access database created as part of the ETH+ project "Unraveling biogeochemical, microbial and vegetation feedbacks driving soil development and Arctic greening under a warming climate". The database contains data on soil, vegetation, microbial, and environmental properties from 14 active-layer tundra sites sampled in 2022 and 2023 on Svalbard. The spatially-explicit field observations, field and laboratory measurements provides an interdisciplinary collection of data from a remote and data-poor region to study linkages between vegetation, microbiome and pedogenesis in the context of Arctic Greening.
The database is structured hierarchically with four connected levels: site, plot, sample, and species. At the site level, aggregated data are provided (e.g. GHG fluxes). This is followed by plot-level data (e.g. plant functional type cover) that connects to sample-level data (soil organic matter content) and species-level data. Tables at the same level are connected via one-to-one relationships, from a broader to finer level one-to-many relationships are in place. Sampling and measurement procedures are described in Section 2 of the database description. The metadata file accompanying a specific .csv file provides further information on data creation, sample processing and units. The current version of the dataset consists of a reduced set of tables that will be updated soon with more curated data from Svalbard and Northern Norway (Finnmark). A more extensive overview of the data will be published as a data paper in the future.
Biochar has a great potential to ameliorate arable soils, especially those that are low in organic matter due to intensive use or erosion. Biochar is carbonised organic material with high porosity that brings about changes in physical, chemical and biological soil functions. Biochar amended soils show a higher water and cation exchange capacity with reduced leaching and enhanced availability of plant nutrients. The microbial biomass in biochar amended soils is enhanced and more diverse. Biochar is stabilised organic material, which is likely to remain for hundreds of years in the soil. Photosynthetically fixed atmospheric CO2 stabilised in biochar may thus act as a direct carbon sink and help to mitigate climate change. As feedstock and production conditions produce different biochar qualities predictions of effects in soil need to consider biochar and soil properties case by case. To date biochar has been approved to ameliorate highly weathered tropical soils with positive effects on crop growth and yield. Distinct microbial groups were reported to be enhanced in soils but if this depends on the particular soil or biochar or a combination of both is an open question, especially in temperate climates. Likewise, it is not known if microorganisms colonising biochar surfaces are responsible for its mineralization or if they just use the new niches provided. The aim of the proposed project is to investigate the influence of two biochar types on soil-plant systems by determining i) soil nutrient availability, plant growth and nutrient uptake, ii) structure and function of soil microbial communities, iv) the decomposition and fate of biochar in soils. We will use two loessial soils from the well-known DOK-trial with different soil organic matter content. Other soils from the region will be selected to provide a wider range of soil quality, in particular pH. The biochars will be produced by pyrolysis and hydrothermal carbonization (HTC) from the C4-plant Miscanthus gigantea. Pyrolysis derived material has bigger pore sizes due to the evaporating gasses and is commonly alkaline, whereas the HTC derived biochar has a finer pore size, a much higher oxygen content and more acidic functional groups.
How will the current rate and spatial extent of environmental change affect the functioning of future ecosystems? Food webs are structurally diverse and are remarkably persistent despite multifaceted and spatially variable environmental change. Ecological theory posits that the structural complexity of food webs will help ecosystems weather environmental change, but few experiments have tested this idea. To truly understand how ecosystems and their constituent food webs will respond, we must explore, experimentally, how environmental change affects the structure of food webs, for example the number of species and the interactions among them, and, consequently, the the functioning of ecosystems, for example, the rates of biomass production, decomposition, and sequestration. Our proposed research focuses on the environmental changes associated with rising levels of dissolved organic carbon (DOC) in freshwater ecosystems, but also considers climate warming, eutrophication, and changes in biodiversity. As microbial communities closely regulate the decomposition of DOC, we propose to examine the effect of changes in the environment and in the architecture of food webs on the composition of microbial communities, including viruses and prokaryotes. In doing so, we can link the ecological structure and evolutionary dynamics of food webs to the biogeochemistry of ecosystems. We propose a series of experiments to test how environmental change affects the complex interactions between food web assemblages and ecosystem functioning. The experiments test predictions from three bodies of ecological theory, namely the theory of biodiversity and ecosystem functioning, the theory of evolving metacommunities, and the landscape theory of food-web structure. These theories provide a strong foundation for understanding interactions between environmental change, food-web architecture, and ecosystem functioning, but they fail to fully address the feedbacks between structural changes of food-webs at upper trophic levels (e.g. plankton and fish) and the biogeochemistry of ecosystems that is regulated by microbial communities. Our experiments bridge this gap, and will improve our ability to predict how entire ecosystems respond to environmental change.