Collection of data on element concentrations in plants in the Jena Experiment (Main Experiment)

This collection contains measurements of element concentrations in plants on 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 by bi-annual weeding and mowing. The following series of datasets are contained in this collection: 1. Carbon and nitrogen concentration in plants: C and N concentration in aboveground plant biomass was measured twice a year (once in 2002 and 2009) from 2002 to 2012. Plants were clipped at 3 cm above ground level in three or four rectangles of 20 x 50 cm size per plot. Target species were pooled per plot and harvest, dried at 70 °C for at least 48 h and cut up with an analysis mill (Kinematica, Littau, Schweiz). The cut material was milled in a ball-mill and carbon and nitrogen concentration was determined with an elemental analyzer. In 2010, phosphorous and potassium concentration was measured additionally. For this purpose, a subsample of the dried and cut material was milled and digested with HNO3 at 200 °C and at about 600-700 MPa using the microwave-assisted high pressure digestion unit (Ethos, Mikrowellen-Laborsysteme (MLS), Leutkirch, Germany). Phosphorus concentrations were determined in a Continuous Flow Analyzer, AA3-system (Bran and Lübbe, Hamburg-Norderstedt, Germany). For K measurement, atom absorption spectroscopy (AAS, Zeenit 700P, Analytik Jena, Jena, Germany) was used. 2. Carbon and nitrogen concentration in plants of the drought experiment: C and N concentration in aboveground plant biomass was measured once a year in 2008 and 2009 on the subplots of the drought experiment. Plants were harvested in rectangles of 20 x 50 cm size. Target species were dried at 70 °C for 48 h, grounded to powder and analyzed with an elemental analyzer. 3. Element analysis of phosphorous (P), calcium (Ca), potassium (K), sodium (Na) and magnesium (Mg) in plants: P, Ca, K, Na and Mg concentrations in aboveground plant biomass were measured twice a year (once in 2004) from 2003 to 2007. Plants were clipped at 3 cm above ground level in three or four rectangles of 20 x 50 cm size per plot. Target species were pooled per plot and harvest, dried at 70 °C for at least 48 h, shredded and milled. Each sample was digested with HNO3 at 200 °C and at about 600-700 MPa using the microwave-assisted high pressure digestion unit (Mars 5 Express, CEM, Lintfort, Germany). Phosphorus concentrations were determined in a Continuous Flow Analyzer, AA3-system (Bran and Lübbe, Hamburg-Norderstedt, Germany). For Ca, K, Na and Mg measurement, atom absorption spectroscopy (AAS, AS240FS Fast Sequential AAS, Varian, Palo Alto, USA) was used