Carbon and nitrogen concentrations in plants (Main Experiment, year 2008)

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 twice in May and August at estimated peak standing biomass before mowing. Plants were clipped at 3 cm above ground level in three 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). A small subsample of this material was milled to fine powder in a ball-mill (Retsch 2000 M). From the milled material appr. 10 mg were weighed in for CN analysis. Carbon and nitrogen concentrations of this subsample were then determined with an elemental analyzer (VarioEL CHNS).