Pedological monitoring
Immediately after completion of the catchment, area-wide soil samples were taken between October 2005 and April 2006 in a regular 20 m x 20 m grid at two depths (0-30 cm and 30-100 cm). Additional samples were taken in a 40 m x 40 m grid at depths of 100-150 cm, 150-200 cm and >200 cm, i.e. from 2 m depth down to the clay layer. Samples were analyzed for pH (water extract), electrical conductivity (EC), texture, total carbon nitrogen and sulfur content, organic carbon content and lime content. Maps with the original initial soil properties have been drawn as basic information for the scientific projects. Details are available from vol. 1 of the Ecosystem Development series.
To allow permanent access for soil solution sampling four soil pits were installed in the catchment close to grid points C5, F2, I5 and L2. The pits were excavated in October 2007 down to the saturated layer in 2-2.5 m depth by hand and stabilized with a lining of PE rings with a diameter of 1 m. From these pits boron silicate glass suction plates (with a diameter of 10 cm) were installed into the soil. Depending on the groundwater level, suction plates were installed in 2-3 depths per pit (30 cm, 80 cm and 150 cm). All plates are connected to glass sampling bottles and vacuum units that provide a permanent pressure of -10 kPa. Sampling started in November 2007 and is carried out every two weeks. The soil solutions samples are measured for pH and electrical conductivity as well as for concentrations of cations and anions, DOC, TOC, TIC and TN.
Tensiometers are used to measure matrix potential. In each soil pit one tensiometer was installed in 30 cm, and three in 50 cm, 80 cm and 150 cm soil
depth, respectively. Soil water content is measured with FDR-probes. The antennas of the FDR-probes were installed horizontally at 10, 30, 50 and 80 cm soil depth at all four pits. Soil temperature is measured with PT-100 sensors at 10, 30, 50 and 80 cm depth in all pits.
Additional TDR probes were installed in August 2010 at four locations. Each unit was equipped with four TDR-probes installed at 0.15 m, 0.3 m, 0.5 m and 0.8 m depth. The locations of the units mirror the locations of the soil pits along the longitudinal axis of the catchment.