This data set contains environmental variables (imposed cumulative precipitation, measurements of radiation, air relative humidity and air temperature), measurements of soil water content, root water uptake estimated from soil moisture contents and community evapotranspiration derived from root water uptake as well as from weight changes, plant trait data (specific leaf area, leaf dry matter content, leaf water potential measured at predawn and midday, stomatal conductance, leaf greenness, height of species, aboveground biomass, species abundances, community leaf area index, vegetation and soil surface cover) and root trait data (biomass, length, diameter, surface area, tips, forks and crossings) 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 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.These data were used to investigate the characteristics of root water uptake profiles in grassland plant communities with different species richness (4-species and 16-species mixtures) and productivity to gain a deeper understanding of how plant species richness affects efficient use of available soil water.

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".

Supplement to: Guderle, Marcus; Bachmann, Dörte; Milcu, Alexandru; Gockele, Annette; Bechmann, Marcel; Fischer, Christine; Roscher, Christiane; Landais, Damien; Ravel, Olivier; Devidal, Sébastien; Roy, Jacques; Gessler, Arthur; Buchmann, Nina; Weigelt, Alexandra; Hildebrandt, Anke (2017): Dynamic niche partitioning in root water uptake facilitates efficient water use in more diverse grassland plant communities. Functional Ecology