Diverse and well adapted above- and belowground biodiversity of the tropics frequently originates from highly and deeply weathered soils. Aboveground-functional biodiversity is in delicate balance with belowground functional biodiversity and both soil microbiome and related biogeochemical cycles are driven by the habitat properties of the soil. The physical structure and architecture of the soil, i.e., the spatiotemporal arrangement of water- or air-filled pores, organic material and soil particles, does not only determine the aeration status of the soil, but further constrains the accessibility of food resources for soil biota, as well as their ability to move within the soil matrix.

Tropical soils and their associated ecosystem functionality are a result of long-term soil-vegetation feedbacks. However, present anthropogenic influences, such as deforestation or unsustainable management of cattle pastures and agricultural lands, severely impacts soil processes and functions. For example, due to the use of heavy machinery or overgrazing, soil gets compacted and larger pores, which are habitat for micro- and macrofauna and, additionally, impact the transport of water, loose their valuable functions. During heavy precipitation events, compacted soils have higher erosion rates with lower water infiltration and, consequently, loose not only soil material and nutrients but more importantly their functionalities such as to store water in drier periods.

Commonly used biogeochemical models developed for temperate conditions usually fail to accurately reproduce the water and nutrient dynamics of tropical soils. One reason is the existence of water-stable aggregates, so called pseudosands that can be found in the tropics, among other places. The paradox of these aggregates lies in the fact that they behave like sands when it comes to soil hydrology (e.g., high hydraulic conductivity), but still exhibit noteworthy high emissions of greenhouse gases, in particular nitrous oxide (N2O), which in turn are driven by denitrification and high soil moisture (characteristic for finer-textured soil).

These features make pseudosands particularly challenging when it comes to linking the soil´s structure to the biogeochemical processes and (microbial) biodiversity. Most research in that direction has so far ignored the presence of pseudosands and standard laboratory methods for soil texture determination are not designed for these kinds of aggregates.

We propose this session to better connect soil management with physical, chemical and biological properties to rethink soil processes and ecosystem functions of deeply weathered tropical soils. We invite experimental soil studies, as well as reviews and modelling studies, helping to foster the understanding of tropical soil ecosystems.