Technical note: Lys-clim, a combination of lysimeters and an atmospheric conditions simulator to study biogeochemical processes in the shallow critical zone

Abstract. Studying the Critical Zone (CZ), i.e. the outermost envelope of Earth, and its bio-geochemical processes requires an interdisciplinary approach. The deployment of critical zone observatories has led to significant scientific advances but does not offer the possibility of comparing treatments or apprehending different climatic scenarios. Conversely, mesocosm studies are often discipline-specific and can be limited in scope. Here, we propose a complementary approach that relies on the combination of 15 lysimeters and a climate chamber. The lysimeters have been equipped to allow for a detailed monitoring of the water flow, which connects most biogeochemical processes in the critical zone. This monitoring relies on scales, tipping buckets, soil moisture sensors and a facilitated high frequency sampling of discharge water. Besides, in-situ continuous gas analysis is enabled by a 45-channel manifold. The climate simulator is a 81 m³ isolated chamber that enables regulation of temperature; atmospheric CO₂; relative humidity; quantity and quality of irrigation water and quantity and quality of light. We evaluate the design in terms of its ability to assess the interactions between CZ processes. The main advantages of this set-up are as follows: it allows for the simulation of future climates or extreme events; it enables replication and the application of different treatments, facilitating the isolation of processes and the assessment of anthropogenic impacts; and it provides automated data acquisition.