This dataset contains measurements of soil water content from the 12 macrocosms used in the Jena-Ecotron Experiment in 2012. This experiment was conducted in the Montpellier European Ecotron (CNRS, France), an advanced controlled environment facility for ecosystem research, and aimed at understanding the impact of plant species richness (4 vs. 16 species) for ecosystem carbon and water fluxes.The soil monoliths used in this experiment contained plant communities originating from the long- term Jena Experiment (50°57.1' N, 11°37.5' E, 130 m above sea level; mean annual temperature 9.3°C, mean annual precipitation 587 mm) established in May 2002. Twelve plots from the Jena Experiment were selected for the Jena-Ecotron study according to the following criteria: (1) the four functional groups grasses, legumes, small and tall herbs were present, (2) realized species numbers were close to sown species richness, and (3) plots were equally distributed across the experimental field site to account for different soil textures. Large monoliths (2 m² surface area, diameter of 1.6 m, 2 m depth with a weight of 7 to 8 tons) including intact soil and vegetation were excavated from the twelve plots in December 2011 and placed in lysimeters. In March 2012, before the start of the vegetation growth, the lysimeters were transported and installed in the Macrocosms platform of the Montpellier European Ecotron.Soil water contents used for estimating root water uptake was measured with time domain reflectometry (TDR) sensors TRIME-PICO 32 (IMKO Micromodultechnik GmbH, Germany), which were placed horizontally in six soil depths into the soil monoliths (one sensor at 10 cm, 20 cm, 30 cm, 60 cm, 100 cm, and 140 cm, respectively). The used sensors had a rod length of 110 mm and a rod diameter of 3.5 mm. The total length of the sensor was 328 mm. The measurements were taken every minute from mid of June to end of July (13.06.-28.07.2012). The sensors were installed with a minimum distance of 22 cm to other sensor installations, and the edge of the lysimeter steel wall. As with the other climatic variables in the Jena-Ecotron experiment, we aimed to recreate the environmental conditions measured in the field at the Jena Experiment site in year 2007.

There are two types of missing values contained in datasets from the Jena Experiment. Empty cells represent missing values that result from the design of the experiment. Empty cells result when the respective value does not occur in the design and could thus not be measured. For example, in the case of species-specific biomass cells are left blank, when the species was not sown in the respective plot. Missing values that resulted from methodological problems, sampling errors, or lost samples/data are marked with "-9999".This dataset is part of a collection of measurements of the Jena-Ecotron Experiment, which was part of the Jena Experiment.