Abstract: In this study, the main tree species in the secondary forest ecosystem of Northeast China were selected, including Betula costata, Juglans mandshurica, Fraxinus rhynchophylla,Ulmus laciniata,Quercus mongolica,Acer mono, Populus davidiana, Fraxinus mandschurica,Tilia amurensis, and Tilia tuan. Leaf total nitrogen content of the 10 tree species and their Fourier mid-infrared spectroscopy in the range of 4000-400 cm^-1 were analyzed. The relative peak height of the Fourier midinfrared spectroscopy of leaves was used to semi-quantitatively predict leaf total nitrogen content of tree species. Based on analysis results of the bands with obvious peak such as 3430-3350, 2930-2910, 2860-2850, 1740-1720, 1660-1610, 1460-1420, 1380-1310, 1270-1230, and 1080-1030 (all measured by cm^-1), total nitrogen contents in leaves ranged from 11.9 to 72.6 g·kg^-1. The total nitrogen content of leaves was correlated with the relative peak height of the bands 3430-3350 cm^-1, with a correlation coefficient of 0.690 (P<0.01). These results suggested that leaf total nitrogen content of tree species can be quickly quantified by the relative peak height of the Fourier midinfrared spectroscopy of 3430-3350 cm^-1 band in the secondary forests of Northeast China. Leaf total nitrogen content may be related to N-H bands at 3430-3350 cm^-1 in this area. In the future study, prediction of leaf total nitrogen content of tree species by Fourier mid-infrared spectroscopy can be used as a suitable method.

Key words: photosynthesis characteristic, row ratio, carboxylation., intercropped maize