Nitrogen and Phosphorus Co-Fertilization Affects Pinus yunnanensis Seedling Distribution of Non-Structural Carbohydrates in Different Organs After Coppicing

The effects of nutritional additions on the non-structural carbohydrates (NSCs) of Pinus yunnanensis Franch. following coppicing were examined in this work. Three levels of phosphorous (P) addition, namely P₀ (0 g/plant), P (2 g/plant), and P+ (4 g/plant), and two levels of nitrogen (N) additions, namely N0 (0 g/plant) and N+ (0.6 g/plant) The treatments consisted of D1 (N₀P), D2 (N+P₀), D3 (N₀P), D4 (N+P), D5 (N₀P), and D6 (N+P+), utilizing an orthogonal design to assess how these nutrients influence NSC levels and their components throughout many plant organs in P. yunnanensis. The findings showed that fertilization enhanced NSCs and their components' contents in P. yunnanensis. P treatment greatly raised NSC levels in sprouts as well as starch (ST) content in stems and sprouts. N treatment greatly raised soluble sugar (SS) and NSC content in stems and greatly accelerated the contents of NSCs and their components in sprouts. The combined application of N and P further improved SS content in stems. Fertilization effects varied over time, with significant increases in NSC content observed at different stages: at 0 d, fertilization significantly raised NSCs and their components in needles; at 90 d, roots and stems showed increases in both NSCs and their components' contents; at 180 d, stem ST content significantly increased; and at 270 d, NSCs and their components' contents across all organs were significantly increased. Especially in roots, stems, and sprouts, the combined N (0.6 g/plant) and P (2.0 g/plant) treatment (D4) produced the highest NSC concentration among the treatments. This suggested that NSC formation in plants might be greatly promoted by a balanced N and P fertilization ratio acting in concert. Moreover, fertilizer, as part of a general management plan, has long-term and significant benefits on plant development, especially after coppicing, accelerating recovery, expanding growth potential, and thereby strengthening the plant's capacity to adapt to environmental changes.