Element analysis of phosphorous (P), calcium (Ca), potassium (K), sodium (Na) and magnesium (Mg) in plants (Main Experiment, year 2004)

This data set contains measurements of P, Ca, K, Na and Mg 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 May 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 was pooled per plot and harvest, shredded and milled for chemical analyses. 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