In 2016, we set up the ΔBEF Experiment to explore mechanisms underlying the strengthening relationships between biodiversity and ecosystem functioning over time (Vogel et al. 2019). We therefore reestablished the plant communities of the Main Experiment that had started in 2002 (Roscher et al. 2004) with new seeds and old or new soil again in 2016. Comparing these treatments with the original communities set up in 2002, we test whether old communities have stronger plant diversity effects on plant productivity than young ones and if this depends on soil- or plant-related processes.
In May 2016, we set up 3 subplots of 1.5 x 3 m size on all 80 plots of the Main Experiment (Roscher et al. 2004). The three subplots vary in soil history and in plant community history. In subplots without soil history and without plant history (treatment 1), we excavated the soil and plant layer to a depth of 30 cm, replaced it by soil of an adjacent arable field of the same soil layer, and sowed the same plot-specific plant species mixtures as in 2002 (new seeds). In subplots with soil history and without plant history (treatment 2), we removed the plant sod by using a digger, while keeping the soil of the respective plots, homogenized the upper 30 cm, and sowed the same plot-specific plant species mixtures as in 2002 (new seeds). As the third subplot (treatment 3), we used parts of the existing Main Experiment, which has a grown soil and plant history since 2002. Treatment 3 serves as a long-term control.