Fig. 5
The principle component analysis (PCA) scores plot on the specific two principal components in the second derivative near-infrared spectra with the 8000–4000 cm−1 region based on wood block and tablet samples. a P. densiflora for. erecta, b P. densiflora, c P. sylvestris grown in Russia, d P. sylvestris grown in Germany, CS cross section, RS radial section