Morphological root parameters of newly formed roots from the Jena Experiment (Main Experiment, year 2003)

This data set contains measurements of morphological root parameters, i.e. length and diameter of newly built roots. 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). Since 2010, plots were weeded three times per year. In June 2003, five soil cores with a 4.8 cm diameter per plot were taken to 30 cm depth. The removed soil was replaced by root-free soil from the field site. In September 2003, the initially root-free ingrowth cores were removed and the holes were refilled with root-free soil until the following withdrawal in July 2004. To extract the newly formed roots, each ingrowth core was first weighed and carefully homogenized. A subsample of 50 g of soil was suspended in water and rinsed over a 0.5 mm screen. Roots collected in the screen were transferred into a water-filled clear acrylic tray and scanned. Total root length and mean diameter were determined by using WinRhizo (Regent Instruments, Quebec, Canada). Afterwards, root length density (cm root length per cm3 soil volume) was calculated.