Aims <p>To improve our understanding of N cycle development during primary succession after glacial retreat, we (i) assessed the role of biological N₂ fixation, (ii) determined gross ammonification rates to identify the onset of mineralization, (iii) quantified the retention of ¹⁵NH₄⁺ and ¹⁵NO₃⁻ in various ecosystem compartments to evaluate the accumulation of deposited N and (iv) followed the ¹⁵NH₄⁺ label into the soil NO₃⁻ pool to explore the development of nitrification along the subtropical alpine Hailuogou glacial retreat chronosequence, SW China.</p> Methods <p>We measured N stocks and δ¹⁵N values in the dominant tree species, organic layer and 0–10&#xa0;cm of the mineral soil and quantified N turnover rates and accumulation via ¹⁵N tracer experiments.</p> Results <p>N accumulated in the ecosystem at a fast mean rate of 4.5 ± 1.0&#xa0;g&#xa0;m⁻²&#xa0;yr⁻¹ favored by an initially near-neutral soil pH value. The δ¹⁵N values of the vegetation started near 0‰ and decreased to a range of -2.7 to -4.4‰ in 127&#xa0;years. Gross ammonification rates were initially low but increased with ecosystem age from 0.025 to 50.6&#xa0;mg&#xa0;kg⁻¹&#xa0;d⁻¹&#xa0;N, matching those of mature (sub)tropical forests. The maximum accumulation of deposited N shifted from the bryophyte via the shrub layer to the soil organic layer. The ¹⁵NH₄⁺ label hardly appeared in the NO₃⁻ pool reflecting little nitrification.</p> Conclusions <p>Strong initial biological N₂ fixation and retention of deposited N was succeeded by a tight N cycling between soil and vegetation at the older sites within approximately 120&#xa0;yr.</p>