Effects of simulated nitrogen deposition on growth of Acer mono seedlings.

To evaluate the effects of simulated nitrogen deposition on growth and biomass allocation of Acer mono seedlings, we collected 3-year-old seedlings from three provenances, Beijing (BJ), Shanxi (SX) and Inner Mongolia (NMG) planted in a common garden. Five nitrogen fertilization treatments were set: control (N0, 0 kg/(haa)), low-N (N1, 15 kg/(haa)), medium-N (N2, 25 kg/(haa)), high-N (N3, 50 kg/(haa)) and supersaturated-N (N4, 150 kg/(haa)). The differences in stem basal diameter (D), seedling height (H), biomass and the biomass allocation ratio between treatments were examined. The results showed that: 1) simulated nitrogen deposition significantly improved D, H, and monthly growth of D and H (D, H) of seedlings of different provenances; 2) simulated nitrogen deposition had little effect on the biomass of seedlings from BJ, while the biomass of seedlings from SX and NMG had obvious response to the addition of nitrogen, and the maximum values showed in N2 for SX seedlings and N3 for NMG seedlings; 3) simulated nitrogen deposition had significant influence on seedling biomass allocation: RMR and RSR decreased while SMR and SLR increased, indicating that seedlings cut down the investment on the development of root and leaf, but reinforced on stem construction; 4) the analysis of sources of variation showed that the variation of D, H and biomass of different organs related closely with both nitrogen treatment and provenance, but SMR, LMR and SLR were only associated with nitrogen treatment and independent of provenance.