Differential responses of phosphorus accumulation and mobilization in Moso bamboo (Phyllostachys edulis (Carrière) J. Houz) seedlings to short-term experimental nitrogen deposition

Abstract

Key message: Short-term nitrogen (N) deposition stimulates phosphorus (P) demand owing to the growth improvment of Phyllostachys edulis seedlings. Increased N loads led to the acquisition and utilization of sufficient P, while the limitation of P starvation could be alleviated by the higher activity of soil acid phosphatase and P use efficiency rather than P resorption from senescent organs. Context: Plants in most terrestrial ecosystems are usually subjected to natural phosphorus (P) deficiency or surplus by overfertilization associated with increasing global nitrogen (N) deposition. As the widely distributed gramineous plant in Southern China, moso bamboo (Phyllostachys edulis (Carrière) J. Houz) grows fast and it also shows a relatively good growth performance under the variable N and P conditions. However, few studies focus on the special mechanism of P mobilization and utilization of moso bamboo, especially with the N loads. Aims: The objective of this study was to figure out the mechanisms of P mobilization and utilization in P. edulis seedlings under varying levels of soil P and N deposition conditions in the subtropical region of China. Methods: We grew P. edulis seedlings under 3 experimental N deposition rates (0 (N −), 30 (N +), and 60 (N + +) kg N ha−1·a−1) and 3 levels of soil P (2.99 mg·kg−1, soil available P content under natural conditions, denoted as P1; 20 mg·kg−1, P2; and 40 mg·kg−1, P3). We measured growth traits and analyzed the related P use indices. Results: Dry weight and P accumulation of new leaves and stems increased with increasing N loads under the 3 P treatments, with the positive effects of N deposition being stronger in the P2 and P3 treatments. Compared with N − , N + , and N + + significantly increased P use efficiency (PUE) (+ 15.54% and + 12.47%, respectively) regardless of soil P conditions. The P resorption efficiency showed a decreasing tendency under variable P conditions with increasing N, whereas PUE was further increased. Acid phosphatase (APase) activity and soil available P content were significantly improved by N loads in P1. Conclusion: Phyllostachys edulis seedlings showed high growth plasticity and P mobilization mechanisms under different soil P availability with N loads. In general, N addition stimulated P demand of P. edulis seedlings owing to the growth promotion in the short period of experiment. A special P use mechanism in P deficiency conditions was that the limitation of P starvation was alleviated by the higher soil APase activity and PUE instead of P resorption from senescent organs. The long-term effect of N deposition on P mobilization and utilization in P. edulis forests requires further monitoring.