How deep can surface signals be traced in the Critical Zone? Merging biodiversity with biogeochemistry research in a karst central German landscape

Abstract:

The collaborative research center AquaDiva investigates the key role of organisms in shaping the subsurface components of the Critical Zone, those portions below the rooting zone, and extending down through the unsaturated zone into the first aquifers. Key questions about this zone still need to be answered, including: What organisms inhabit it? Where do they derive the energy for their metabolism? To what degree are biota and biogeochemical function in the subsurface influenced by surface properties, including land cover and land management, as opposed to the geologic properties of the local rock? How do extreme events at the surface impact subsurface community structure and function? The newly established Hainich Critical Zone Exploratory in central Germany provides an infrastructure platform to study these questions in a karst parent material setting. It includes specialized wells to access shallow (6m to 100m deep) groundwater along a ~6km transect in the direction of hydrologic flow through limestone parent material, and spanning forest, pasture and agricultural land uses. Collaborating researchers combine ‘omics’ technologies with biogeochemistry, tracer measurements and hydrogeology, including new data platforms to better inform across disciplines and groups. We will present some initial results, which demonstrate fundamental differences in the biota and biogeochemistry of two shallow aquifers, likely related to the land use in their respective recharge areas. We will also document the impact of singular and extreme precipitation events on the flow, biology and groundwater chemistry in the two aquifers.