Experimental design to investigate the effects of drought (drought and control) and Biochar application (with and without Biochar). A total of 20 plots were cultivated with five individuals from each of the invasive species Avena fatua (black) and the three native species Silene gallica, Brassica nigra and Phalaris minor (green) (in total n = 20 individuals / plot). The treatments were Biochar+drought, Biochar, drought, and control (n = 5 plots per treatment).