The Collaborative Research Centre AquaDiva
The Earth's Critical Zone (CZ) is the thin, living, and permeable layer that connects the atmosphere with the geosphere, and provides the living environment for most terrestrial biota. Humans live in the CZ, and benefit from the vital services it provides, including clean water resources. Pollution, land-use, and climate change increasingly alter the surface compartments of the CZ, but we have not yet explored this part of the earth enough to fully understand the consequences for the subsurface, the zone beginning below the highest density of plant roots and extending into the aquifers.
Please feel free to watch our corporate video, illustrating the work performed during an AquaDiva sampling campaign by clicking on the image below:
The principle aim of the CRC AquaDiva is to increase our understanding of the links between surface and subsurface, especially how organisms inhabiting the subsurface CZ reflect and influence their physical, ecological, and geochemical environment, and affect water and matter transiting the CZ. To achieve this, we have constructed a novel infrastructure platform, the Hainich Critical Zone Exploratory (CZE), to study how water and gas fluxes link surface vegetation and soils under different land management to aquifer complexes.
The Coupling theme uses a range of physical, chemical, and biological signals to test the degree, to which subsurface functional biodiversity reflects characteristics traceable to surface conditions, especially vegetation cover.
The Event theme takes advantage of multi-year time series observations of climate, fluxes, chemistry, and functional biodiversity to follow singular events (e.g., extreme weather, snowmelt, or disturbances) and quantify the role they play in shaping the subsurface environment.
In the first phase, a suite of biotic and chemical "fingerprints" specific to surface properties or biotic processes were developed to indicate how signals are transported and transformed as they transit the unsaturated zone into aquifers. We investigated the role of temporal variations and extremes in surface inputs of water and matter impacting the subsurface. Important and surprising results demonstrate dramatic spatial differences in how surface and subsurface are coupled. Based on results of hydrochemistry and omics technologies, we identified several distinct biogeochemical zones that reflect differences in geology, structure, fluid flow, and land-use in their respective recharge areas. In the second phase of the CRC AquaDiva, we will move from characterization of differences to explaining how they evolve. Our plan to link observations to biogeochemical fluxes provides the chance to understand the ecology of the subsurface, especially how subsurface biota in turn shape their environment and CZ services like water quality. The Hainich CZE provides field training sites for our doctoral researchers and students and is part of an international network of Critical Zone Observatories. Our field infrastructure is already attracting national and international collaborators. We are thus well on our way to our long-term vision of being the premier international subsurface biodiversity platform.
Critical Zone Exploratory
The Hainich CZE was established in an alkaline geological setting and encompasses two main aquifer assemblages along a ~6 km transect in limestone and marlstone rock, spanning forest, pasture and agricultural land-uses. Our interdisciplinary team applies new tools from the fields of biology, chemistry, geoscience, and informatics to document the state and function of the subsurface: who is there, what are they doing, and how does it matter.