THE STUDY OF EDGE-EFFECT OF DAVIDIA INVOLUCRATA NITROGEN STATUS WITH FTIR
利用红外光谱分析珙桐幼树氮素状况的边缘效应

The practicability of edge effect research with FTIR (Fourier transform infrared spectroscopy) was investigated by two experiments. In the first, Davidia involucrata seedlings were treated with nitrogen fertilizer and nitrogen content of both tip and middle parts of seedling leaves was detected with FITR and the method of Kjeldahl. The results showed that there were significant differences in nitrogen content among five treatment levels, either between tips or between middle parts of leaves. The nutritional status could be well estimated by leaf tips in terms of nitrogen content compared with that of middle parts of leaves according to correlation analysis. Spectral index (A1653 - A3400)/(A1653 + A3400) was revealed to be raised with the increase in availability and of leaf content of nitrogen, which suggested that it is possible to detect the nutritional status of D. involucrata seedlings in terms of nitrogen content by FTIR. In the second, D. involucrata leaves were collected from four aspects in Bainigang, Wolong National Nature Reserve. Tips of the leaves were analyzed with FTIR. The edge effects of nitrogen status of D. involucrata in Bainigang in terms of FTIR showed that the nitrogen levels rose from border to core areas of the forest within certain distance and the average nitrogen levels varied among different aspects and distances to different extents. It suggested that the nitrogen status of D. involucrata was significantly affected by aspect. The D. involucrata fragmentation of forest would impact the regular physiology of internal trees growing at least 30 to 40 meters away from the fragmented border. The impacts were at least 90 to 100 meters from the edge. It suggested that the growth of remaining D. involucrata was impacted seriously by human activities in the east of the forest. The results were consistent with those of previous studies of nitrogen distribution and plant nitrogen absorption at the forest edge. It showed that studying edge-effect of D. involucrata with FTIR is practicable. In our experiments, we discovered that accurate results require that the sample must be kept dry and flat.