This data set contains measurements of carbon and nitrogen concentrations in aboveground plant biomass of the subplots of the drought experiment. 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.In 2006, a gradient in management intensity was established with five subplots on 80 plots of the main experiment. Management varied in mowing regime and the amount of NPK fertilizer application (more details please see the treatment description file). In 2008 and 2009, drought was induced using transparent rain shelters during six weeks in summer previous to the last annual cut. Control subplots remained unsheltered and received ambient precipitation. One sheltered and one unsheltered subplot of 1.6 m x 2 m size was established for each management treatment in each of the 80 plots. In 2009 an additional roof control was established in all plots, e.g. a sheltered subplot where collected rain water was added.In 2008, C and N concentrations of above ground biomass samples were measured on all four management subplots as well as the core area. Drought was induced from 2008-07-25 to 2008-09-03. Aboveground plant biomass was harvested before mowing in August. Two samples per management and core area subplot were taken, one from the roofed area and one from the control area without roof. Plants were harvested in rectangles of 20 x 50 cm size. Samples were sorted into target species (pool), weeds and dead material and dried at 70 °C for 48 h. C and N concentrations were measured only from the sample with target species. It was homogenized and grounded to powder and then analyzed with an elemental analyzer (Vario El, Elementar Analysesysteme GmbH, Hanau).
The main experiment on the field site of the Jena Experiment comprises a split-plot design in which additional treatments (e.g. no weeding allowing for invasion of other species, or application of fertilizer) have been applied to subplots along the outer margin of the plots (see Treatment description in the section "further details"). While in this dataset only data from the core area (mown and weeding of all none-sown species twice a year, no additional treatments) is reported, all potential treatments are listed as the first parameters in the data file to guarantee compatibility with other datasets that include different treatments. There are two types of missing values contained in the dataset. Empty cells represent missing values that result from the design of the experiment when the respective value does not occur and could thus not be measured. For example, in the columns of species-specific biomass cells are left blank, when the species was not sown into 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 element concentrations in plants in the Jena Experiment. Similar data from other experiments (e.g. Main Experiment, Dominance Experiment; see details above), other years, or other methods quantifying related data might be available (https://doi.pangaea.de/10.1594/PANGAEA.887388).
