Figure 3

PCA based on the concentrations of major chemical characteristics. Two principal components explain a variance of 65.9% (PC1) and 27.0% (PC2). Ambient: ambient UV-B radiation during growth; UVB: enhanced UV-B radiation during growth; N0: control treatment without N addition; N1: 30 kg ha−1 yr.−1; N2: 60 kg ha−1 yr.−1; 3 m: 3 months, 9 m: 9 months, 15 m: 15 months.