ALBERT

Description: This dataset contains stomatal conductance, leaf greenness, and height of species 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. Stomatal conductance (gs, mmol/m²/s) was measured with a portable leaf porometer (SC-1 Leaf porometer, Decagon Devices, Pullman, USA). Measurements were done in the auto mode using the first 30 s of stomatal conductance data to predict the final stomatal conductance under true steady state conditions. Leaf greenness (SPAD; unitless), an estimate of chlorophyll concentrations, was obtained by measuring the absorption of two different wavelength (650 nm and 940 nm) with a portable chlorophyll meter (SPAD-502; Konica-Minolta, Osaka, Japan). The growth height of three shoots (Ind h; cm) per species and unit was measured with a ruler. Values of stomatal conductance, leaf greenness and growth height of the individual measurements were averaged per species per plot.

Description: This data set contains measurements of carbon and nitrogen concentrations in aboveground plant biomass. Data presented here is from the Main Experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained in general by bi-annual weeding and mowing. Since 2010, plot size was reduced to 5 x 6 m and plots were weeded three times per year. Aboveground plant biomass was harvested once in September at estimated peak standing biomass before mowing. Plants were clipped at 3 cm above ground level in four rectangles of 20 x 50 cm size per plot. All material was sorted to species, weeds and rest (dead). Samples were dried at 70 °C for at least 48 h and weeds and rest were thrown away. All other material from one plot was combined to one sample and cut up with an analysis mill (Kinematica, Littau, Schweiz). The cut material was milled to fine powder in a ball-mill (Cyclotec 1093 Sample Mill, Foss Tecator, Hoganas, Sweden). From the milled material appr. 20 mg were weighed in for CN analysis. Carbon and nitrogen concentrations of this subsample were then determined with an elemental analyzer (vario EL element alalyser).