Nondestructive measurement of water content in hardwood leaves using near-infrared spectroscopy

Near infrared (NIR) spectroscopy was applied to conduct nondestructive measurements of water content in hardwood leaves. The authors developed a prediction method using a partial least squares regression (PLSR) analysis of NIR spectra data of six hardwood species. The pretreated spectra were compared by the full spectral range (1200 nm to 2500 nm) and short spectral ranges (1300 nm to 1600 nm [short range 1 (S1)] and 1800 nm to 2100 nm [S2]). Good prediction results were obtained for the full spectral range with six species. The correlation coefficient for prediction of each of the species ranged from 0.94 to 0.97, and the root mean standard error of prediction ranged from 1.59 to 7.72. Compared with the full spectral analysis, predictions based on S1 and S2 were less accurate. However, leaf water content could be predicted based on measurements in the S1 and S2 ranges. It was worth comparing the wavelengths in a preliminary experiment. In this research, NIR spectroscopy was a powerful nondestructive technique for determining the moisture content of tree leaves.