Figure 1

Temporal trend in aboveground net primary productivity (ANPP) at the community-level by N addition treatment.

(a), Responses of community ANPP to experimental manipulations of N addition frequencies (filled symbols and solid lines = 2 N additions yr⁻¹, open symbols and dashed lines = 12 N additions yr⁻¹) and N-rate (different colors ranging from blue = low to red = high; g N m⁻² yr⁻¹). The values in 2008 showed the pre-treatment ANPP. F, N addition frequency and N, N-rate (N as the continuous factor), ^ns and ***: statistically significant at P > 0.05 and P < 0.001, respectively. (b), Result of repeated-measures analysis of variance for community ANPP. Regression parameters were estimated using log-linear model with N-rate as the continuous predictor, i.e., ANPP = Intercept + Slope × log₁₀(N + 1). Error bars indicate 1 SE.