Aims To improve our understanding of N cycle development during primary succession after glacial retreat, we (i) assessed the role of biological N 2 fixation, (ii) determined gross ammonification rates to identify the onset of mineralization, (iii) quantified the retention of 15 NH 4 + and 15 NO 3 − in various ecosystem compartments to evaluate the accumulation of deposited N and (iv) followed the 15 NH 4 + label into the soil...