Tuesday August 27
Professor Johannes Lehmann, Cornell University
Soil Organic Matter: From changing form to changing function

The science and policy of soil organic matter have undergone large shifts over the last decade, changing the way we have to manage soils and catapulting soil health and carbon sequestration onto the world stage. The demands on soil for securing food production, water quality and mitigating climate change are daunting in the face of concurrent changes in fundamental understanding of the forms and cycles of organic matter in soil. The notion takes hold that rather than the formation of recalcitrant molecules, life traits of soil biota and interactions with the mineral matrix determine the forms and amounts of soil organic matter. This puts biological controls on soil organic matter under scrutiny with a delicate balance of input and mineralization, recognizing that soil is a flow-through reactor of plant carbon rather than a store where carbon can be biologically sequestered for the long term. Indeed, most soil organic matter is of microbial origin and of large molecular diversity in complex spatial arrangement. Recent modelling efforts were able to describe long-term and large-scale soil carbon dynamics using ecological equilibrium theory and without invoking pools with long residence times. The focus on soil biota as agents of both mineralization as well as stabilization of soil carbon appears as a contradiction and emphasizes the concept of ecosystem control rather than stabilization and sequestration for the long term, even though large portions of soil carbon have old radiocarbon ages. This focus also reflects the growing interest in soil health that puts a spotlight on biological functions rather than only on provisioning and storing nutrients. With these described shifts in understanding of form and function of soil organic matter comes the realization that soil ecosystem services require constant care rather than one-time fixes. Soil management is then a continuing commitment requiring policy, regulatory and market mechanisms that finance soil health practices in the framework of climate-smart solutions.

Watch the keynote video here.

Wednesday August 28
Dr Edith Hammer, Lund University
Build your own soil: Micro-structured Soil Chips allow to investigate soil functions at microbial scale

Soils form the foundation of life on earth and are likely the most species dense habitats on our planet. But despite their fundamental importance, soils and their complex microbial communities have historically been one of the most challenging habitats to study because of their blend of diverse materials and organisms in a complex spatial arrangement, and their opacity. We recently developed microfluidic and micro-engineered model systems that simulate the spatial microstructure of soil microbial habitats in a transparent material, which we call Soil Chips. They allow us to study soil functions at relevant micro-scales: Microbial behaviour and interactions in response to a spatially refined habitat with heterogeneous nutrient distribution, and soil functions such as e.g. physical soil carbon stabilization in the labyrinth of the soil pore space. We can colonize our chips with fluorescent microbial strains and fluorescent substrates to e.g. study foraging strategies and organic matter cycling, or with a whole natural soil including the complex microbial community and soil mineral particles. The chips act like a window into the soil, through which we can eaves-drop on a world that otherwise is largely hidden to us: Jostling protists, tsunami-like drying-rewetting events, and fungi with character.  Beyond the scientific potential, the chips can also bring soils closer to people and hopefully increase engagement in soil health conservation.

Watch the keynote video here.

Thursday August 29
Dr Thomas Crowther, ETH Zurich
Mapping microorganisms to understand the feedbacks between warming and soil carbon loss at a global scale

By driving the fixation, stabilization and mineralization of soil organic matter, soil organisms regulate the exchanges of carbon and nutrients between the biosphere and atmosphere. Predicting how soil organisms regulate these organic matter pools is central to our understanding of soil fertility, atmospheric composition and climate.

Despite the hyper-diverse nature of soil communities, the exploration of global ecological trends across regions in the last decade is beginning to provide a unified perspective. The immense global communities are generally dominated by a relatively small number of cosmopolitan species that show consistent global patterns of diversity and biomass distribution. Shaped by a combination of environmental filtering, biotic sorting and random dispersal, these soil communities form unique biogeographic patterns that determine how soil organic matter is processed across the globe.

As the global soil ecological data explosion continues, it is critical that ecologists generate a quantitative, spatially-explicit understanding of soil functional group composition, and the variation in trait expression within these distinct ecological pools. This information can be valuable for parameterizing, scaling and benchmarking model projections of global SOM turnover under current and future climate scenarios.

Watch the keynote video here.

Friday August 30
Professor Victoria Ballester, University of Sao Paulo
“Soil functions and land management: potential synergies and tradeoffs at the tropical agricultural frontier (Brazil)” 

Using a conceptual GIS Based Multi-model tool designed to support policy making to manage five selected soil functions and demands, we are addressing sustainable land management to preserve ecosystem services at the tropical agricultural frontier in Brazil.  By assessing how land use change due to agricultural expansion and intensification are affecting soils functions at the arch of deforestation in two large Brazilian Biomes, the Amazon forest and Cerrado (savannah). As  supply proxys for foil indicator we used a 2015 land use map derived from remote sensing data. Demand was expressed as annual productivity (kg/ha/y) from census data spatialized by land use type. Evapotranspitation as the proxy for water availability and water yield for demands. For Biodiversity indicator we used Indigenous Land and Conservation Units as suppliers and Legal Reserve and Permanent Protection Areas as demand (legal instruments). Nutrient Cycling supply was mapped base on Base saturation of 0-30 cm of almost 400 soil profiles and demand by average fertilizer application (NPK) spatialized by land use. Carbon storage and GHG Seq. Carbon sequestration were derived from field measurements spatialized by land use and demands by field carbon sequestration measurements and policy (Zero illegal deforestation target). Our result show that this approach can be applied to a range on landscapes and is a useful tool for decision making and policy implementation and support.

Watch keynote video here.