Study on the mechanism of nitrogen uptake and utilization in Pinus koraiensis: Implications for facilitating optimized nitrogen management and sustaining yields

Korean pine ( Pinus koraiensis ) is a significant woody oil tree species indigenous to Northeast Asia, characterized by substantial nitrogen (N) demand. Nitrogen availability plays a critical role in determining seed yield of Korean pine over the subsequent three years. However, the mechanisms governing nutrient uptake and utilization in Korean pine remain inadequately understood. In this study, a field fertilization experiment was conducted on June 14, 2023, and urea (720 g urea and 80 g 15 N-labeled urea per tree) was applied via the circular trench manuring method (radius in 1.5 m, width in 20 cm, and depth in 15 cm). The reproductive and vegetative organs (needles, buds, cones, and root), soil, and N 2 O samples were collected at specific time intervals from 2 days to 13 weeks after fertilization, which were used to assess nitrogen uptake across organs, soil residues, environmental losses, and associated gene expression related to nitrogen utilization. The findings revealed that nitrogen from labeled fertilizer was transported to the needles, buds, and cones within approximately one week. The peak periods for N 2 O emission and downward migration of the fertilizer (accumulating primarily in the 20–80 cm soil layer) occurred within six weeks post-urea application. The 15 N abundance and nitrogen derived from fertilizer (Ndff) in needles and buds exhibited a dynamic increase, while cones and root showed an initial rise followed by a decline. Notably, cones, buds, and needles exhibited a significant nitrogen demand from mid-June to early July, suggesting that fertilization should align with the reproductive growth period of cones (mid-June and earlier). Moreover, 110 key genes encoding transporters and enzymes involved in nitrogen utilization pathways were identified across the nine organs. The study offers valuable insights for refining fertilization strategies and molecular breeding approaches aimed at enhancing nitrogen use efficiency in Korean pine in the future. • Differential characteristics/mechanisms of N uptake and utilization in organs. • N was transported to the needles, buds, and cones within approximately one week. • N 2 O emission and fertilizer migration occurred within 6 weeks post-urea application. • Cones and buds exhibited a significant nitrogen demand from mid-June to early July. • Total of 110 key genes that encode transporters and enzymes related to nitrogen utilization pathways were identified.