Precipitation Pattern Alters the Effects of Nitrogen Deposition on the Growth of Alien Species Robinia Pseudoacacia

Abstract Aims Nitrogen (N) supply and precipitation pattern (amount and frequency) both affect plant growth. However, N deposition is increasing and precipitation regimes are changing in the context of global change. An experiment was conducted to determine the effect of precipitation pattern and N supplies on the growth of a widely distributed and planted N2-fixing alien species Robinia pseudoacacia. Methods Seedlings were grown in a glasshouse at four different N levels combined with different precipitation regimes, including three precipitation amounts, and two precipitation frequencies. After treatment for 75 days, plant height, biomass allocation, leaf and soil nutrient concentrations were measured. Results Plants under high precipitation frequency had greater biomass compared with plants lower precipitation frequency with the same amount of precipitation. Higher N supply decreased biomass allocation to nodules. Nodule growth and N2 fixation of R. pseudoacacia with low precipitation amount was more inhibited by high N deposition compared with plants received higher precipitation amount. Slightly N deposition under higher precipitation inhibited N2 fixation but did not fulfil the N need in plants. Conclusions Nitrogen deposition might inhibit N2 fixation of plants even in low level but low nitrogen in soil cannot fulfil the N need of plants, and caused N2 fixation limitation in plants during seedling stage. There was likely a shift from acquiring N mainly from N2 fixation to acquisition of N directly with root when N supply was increased. High N deposition level, and increased precipitation frequency might increase the invasion risk of R. pseudoacacia.