This dataset contains measurements of radiation, air relative humidity and air temperature 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 m**2 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.The respective climatic variables imposed in the Ecotron facility during the Jena-Ecotron experiment aimed at reconstructing the field-measured values recorded in Jena in year 2007. This year was chosen as a good proxy of average spring-summer conditions in the Jena Experiment. In order to recreate the air temperature and humidity daily profiles from the Jena Experiment, field-recorded weather data was used as set points in the Ecotron (at 10 min interval). Air relative humidity and temperature were measured with the DT269 digital sensor (Michell 706 Instruments Ltd, Ely, UK) in the outlet conduit of the macrocosm, 20 cm above lysimeter/experimental ground level. Radiation was measured outside of the Ecotron domes with a BF5 Sunshine Sensor (Delta-T Devices, Cambridge, UK) 1.5m above the lysimeter/experimental ground level. The radiation within the macrocosms was calculated as 56% of the outside measured values based on the fact that 44% of the radiation was blocked by the Ecotron cover and the additional mesh installed in order to bring the radiation values to the same level as in the Jena Experiment. All tree time series are given with a temporal resolution of 12 min from 28th of March 2012 to 31st of July 2012.

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.