Description: This dataset contains cumulative precipitation imposed 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 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 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. The precipitation imposed in the Jena-Ecotron experiment aimed at reconstructing the field-measured values recorded in Jena in year 2007. This year was chosen as a proxy of average climatic conditions at the Jena field site. Note that owing to the higher evapotranspiration rates in the Ecotron, higher precipitation (+28%) was imposed in the Ecotron relative to year 2007. Precipitation was applied to each lysimeter by manual watering using a hose equipped with a sprinkler and a flowmeter. The water was purified by microfiltration (1µ) and reverse osmosis followed by ozone and UV treatments. Precipitation values are provided as cumulative values from 28th of March 2012 to 30th of July 2012.