Advancing our understanding of how biotic and abiotic processes control soil organic matter stocks, stability, stabilisation mechanisms, biochemical transformations, and loss from terrestrial ecosystems remains a major focus in biogeochemistry today. This session aims to facilitate discussions that improve our understanding of how complex biotic and abiotic processes interact in the terrestrial ecosystem, in particular during periods of natural- or anthropogenic-induced change and across a range of scales from molecular, profile, plot, landscape, and global scales to control soil organic matter dynamics. Furthermore, the session welcomes submissions that focus on: (a) relationship of soil organic matter transformations with length and intensity of weathering processes that modify minerals and create a distinct soil matrix in which biological processes take place; (b) dynamics of soil organic matter in deep soil layers using experimental and modeling approaches and (c) plant-soil interactions on soil carbon and nutrient cycling. This session will contribute to improving our understanding and future predictive capabilities of carbon dynamics in the earth system by bringing together scientists working on improving our mechanistic understanding of key soil organic matter processing, with the explicit goal of promoting inclusion of the interplay of biology, climate, geochemistry and pedology into large-scale model frameworks.

Ecosystems, particularly soils, are a globally important reservoir for organic carbon (OC) and contribute significantly to CO2 emissions. Soil organic matter is further vital for soil fertility and sustainable agriculture, and has the potential to increase and safeguard agricultural yields against climate change. Reducing losses of organic carbon (OC) from soils and restoring or even further enhancing soil OC stocks therefore offers a strategy to combine the benefits of climate change mitigation with improved soil quality. Nevertheless there are still a range of frontier areas of research on soil OC that have to be tackled to understand and manage the potential of soils to sequester additional or maintain carbon. These include for example soil carbon saturation, carbon stability in subsoils, carbon input quality, soil structure and management practices, as well as ways to verify changes in soil carbon stocks. Also, there is still large uncertainty on the time scales at which carbon stays in soils and other ecosystem compartments, with flux based and modelling approaches often suggesting faster OC turnover than radiocarbon based approaches.
We invite presentations addressing these or other areas of pioneering research on SOM sequestration and temporal dynamics using experimental, synthesis, or modelling approaches.

Dissolved and particulate organic carbon (DOM, POM) are key components of the global C cycle and important as potential sources of CO2, and for the long-term preservation of carbon stabilized in subsoils and sediments. DOM and POM are key sources of energy for microbial metabolism within terrestrial ecosystems, the aquatic continuum, and ultimately the ocean. Despite recent evidence showing this lateral transport of carbon is linked to anthropogenic perturbations, efforts to integrate DOM and POM fluxes across the terrestrial-aquatic continuum are just emerging. A comprehensive understanding of the dynamics of DOM and POM in terrestrial and aquatic ecosystems remains challenging due to complex interactions of biogeochemical and hydrological processes at different scales, i.e. from the molecular to the landscape scale.
This session aims to improve our understanding of organic matter processing at the interface of terrestrial and aquatic ecosystems. We solicit contributions dealing with amounts, composition, reactivity and fate of DOM and POM and its constituents (i.e. C, N, P, S) in soils, lakes, rivers and the coastal ocean as well as the impact of land use change and climatic change on these processes. For example, it is important to recognize the key role of peatlands as sources of organic matter for many streams and rivers as well as soil erosion induced lateral fluxes of sediment and carbon at the catchment scale when assessing C dynamics across the terrestrial-aquatic continuum. Therefore, we aim to bring together scientists from various backgrounds, but all devoted to the study of dissolved and/or particulate organic matter using a broad spectrum of methodological approaches (e.g. molecular, spectroscopic, isotopic, 14C, other tracers, and modeling).

Stability of soil functioning is closely related to biochemical turnover and microbial recycling of carbon (C) and nutrients. Despite numerous studies aimed on soil organic matter (SOM) formation, accumulation, and decomposition, most of them consider only one direction: formation or decomposition, sorption or mineralization. Consequently, the questions of C turnover and nutrients recycling remain opened.
This session invites contributions to cycles of organic substances in soil, turnover processes and rates, as well as recycling of nutrients and soil organic matter compounds by microorganisms. We appreciate studies focused on turnover mechanisms of fast and slow cycling pools, as well as on substances preferably reutilized by bacteria and fungi. Investigations based on an application of isotope labeling (e.g. 13C, 14C, 15N, 33P, 18O), as well as pools dating approaches are very welcome. Soil and environmental controls of turnover and recycling rates are of a special interest.

Soil organic matter (SOM) plays a key role not only in soil fertility and quality (by providing a number of physical, chemical, and biological benefits), but also in C cycling. The decline of SOM represents one of the most serious threats facing many arable lands of the world. Beside this, there is an imperative necessity of a sustainable management for the increasing quantity of organic waste. Crop residues and animal manures have long been successfully used as soil organic amendments to preserve and enhance SOM pools. During the last decade, pyrolysis (the combustion of biomass under low or no oxygen supply) is showing a promising approach for managing carbon-rich wastes such as sewage sludge, the pulp and paper industry residues or crop residues and to create added value co-products.
Besides serving as a source of organic matter and plant nutrients, these materials may contribute to fight plant diseases and reduce soil contamination, erosion, and desertification. A safe and useful application of organic amendments requires an in-depth scientific knowledge of their nature and impacts on the soil-plant system, as well as on the surrounding environment. While the benefits biochar or fly ashes as soil ameliorants and fertilizers are very well known, the knowledge of the use of other sorts of pyrogenic organic matter as well as the effects of biochar in SOM composition at a long term are very scarce.
This interdisciplinary session will focus on the current research and recent advances on the use of organic amendments including pyrogenic organic materials such as biochar or wood ash in modern agriculture as well as for the restoration of degraded soils, covering physical, chemical, biological, biochemical, environmental and socio-economical aspects by bringing together scientists from the diverse fields of soil, applied pyrolysis, bioenergy waste management, SOM characterization, carbon dynamics and plant nutrition.

Tropical ecosystems play an important role for the regional and global climate system through the exchange of greenhouse gases (GHG), water and energy and provide important ecosystem services that we as humans depend on, such as wood, foods, and biodiversity. Historic and recent human activities have, however, resulted in intensive transformation of tropical ecosystems impacting on the cycling of nutrients, carbon, water, and energy.

Here we invite contributions that provide insights on how land-use and land-use change influences biogeochemical cycles and ecohydrology in tropical ecosystems at the plot, landscape, and continental scale. Examples include nitrogen and carbon cycles in soil and vegetation, the exchange of GHG between soil and atmosphere as well as ecosystem and atmosphere, changes in the energy balance, impacts on the water cycle, scaling issues from plots to country to continent; and the influence of management activities (i.e. fertilization, drainage, etc.) on GHG fluxes.

The session covers forests, but also managed land-use systems such as agriculture, pastures or oil palm plantations. Experimental studies (chamber or eddy covariance flux measurements, stable isotopes, sap flux), inventories, as well as remote sensing or modelling studies are welcomed.

Soil is an environment where minerals undergo steady changes with consequences to the bioavailability and cycling of elements. Chemical weathering of primary minerals provides nutrients to soil biota and results in the formation of secondary minerals that react strongly with pollutants, organic matter, and organisms. Soil minerals, therefore, are major controls in the biogeochemical cycling of elements in soil. The complex interactions between minerals and their abiotic and biotic environment offer numerous challenges to modern environmental research, such as (1) the identification of relevant mineral-related processes at different spatial and temporal scales, (2) the determination of properties of soil minerals, and (3) the resulting impact of soil minerals on element speciation, mobility, and bioavailability. The session aims at bringing together expertise in field, laboratory, and modelling studies for shedding light on all aspects of soil minerals as determinants in the biogeochemical cycling of major (e.g., carbon, nitrogen, phosphorus, and sulphur) and trace elements (e.g., antimony, cadmium, molybdenum, and selenium).

Terrestrial and aquatic ecosystems of the boreal to polar regions face tremendous alterations due to a fast changing climate. Besides geophysical and hydrological impacts like vanishing permafrost, coastal erosion and altered runoff, biogeochemical cycles are highly affected by the ongoing changes. Although we are completely aware of the importance of high latitude ecosystems for instance for carbon sequestration, we have a restricted understanding of the biogeochemical processes especially in terrestrial ecosystems. This session aims to bring together scientists working on terrestrial and aquatic ecosystems in the high latitudes, both in Arctic, Antarctic, and Boreal regions, reaching from microbiological functioning and stoichiometric constraints of organic matter turnover and nutrient cycling (e.g. nitrogen, phosphorus) to carbon stabilization and trace gas emissions. We further welcome contributions on interactions between vegetation, microbiota and soils and/or sediments, and the exchange between terrestrial and aquatic systems. Let’s come to together and share results, views and concepts to better understand biogeochemical cycling in boreal and polar regions.