Long-term, high precision lysimeter network an important tool to validate soil models

Abstract:

Long-term highly resolved time series of soil water fluxes and soil moisture are essential for the validation of soil and hydrological models and to understand the impact of climate change and land use change on the water cycle. Within the scope of TERENO (TERrestrial ENvironmental Observatories), four observatories for long-term monitoring of climate change parameters have been established. The observatories are located in areas of Germany that are affected by climate change. SoilCan, a lysimeter-network is part of the TERENO infrastructure which comprises 132 lysimeters of possibly identical technical specification and located at 13 different sites. Primary objectives of SoilCan are:

• Collection of comprehensive long-term data to monitor Global Change on the regional scale.
• Generation of high-quality data to develop and improve the prognosis of regional climate models with the aim to develop and implement options for management strategies.

In the frame of SoilCan, fully automated lysimeter systems were installed on highly equipped experimental field sites within the TERENO-observatories and the relevant status variables of each ecosystem are monitored (e.g. climate, hydrology, biosphere-atmosphere exchange, biodiversity, etc.). The TERENO-observatories are placed in the following four regions of Germany with differing climate conditions.

The lysimeters (1.5 m depth, 1m² surface) were filled with soil monoliths taken at the four TERENO-observatories. In order to capture the expected climate change, 48 lysimeters were transferred along temperature and precipitation gradients within the observatories and/or between the observatories according to the principle „space for time“. The lysimeters are instrumented with high-resolution scales and with TDR, tensiometer, temperature, soil heat flux and CO₂ sensors. Suction rakes were installed at the bottom of the lysimeters controlling the lower boundary condition. To observe matter fluxes, soil solution and percolate were collected regularly. The requirements to generate high quality data from weighable lysimeter systems will be presented as well as first results of observed soil nitrogen, carbon and water balances from selected lysimeters.