Bulk density from the Jena Experiment (Main Experiment, year 2002)

This data set contains measurements of soil bulk density in different depth layers. 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. Soil bulk density was determined in spring from undisturbed soil samples to a depth of 100 cm. Soil cores were taken with a metal bulk density ring of ten cm height and partly pooled to obtain depth increments with a resolution of ten cm from ground level to 40 cm depth and 20 cm from 40 cm to 100 cm depth. The bulk material was passed through a sieve with 2 mm mesh size, dried to constant weight at 105 °C and subsequently weighed to calculate the density. In 2002, bulk density was measured at 27 locations before plot establishment. Two of them are now reference plots and thus not included in this data set. The chosen plots represented a spatial gradient across the field site and resulted in average soil bulk density estimations at the beginning of the experiment