The Hyperspectral Response Of Typical Subtopical Trees Under The Acid Rain And N Stress

The increasing human activities and the extensive using of fossil fuels emit a large number of sulfur and nitrogen compounds, causing more and more serious environmental stresses such as acid rain and nitrogen deposition as well as affecting the normal growth of plants. The phenomena also increase the imbalance of the ecosystem. In this paper, with the typical subtropical plants as the experimental object the author uses the ground-based data of hyperspectral to study the characteristics and patterns of changing in spectral reflectance of plant leaves, getting the following conclusions:This paper analyzes the growth index such as the height and the ground diameter and physiological index such as the chlorophyll content as well as the characteristics and patterns of changing in spectral reflectance of plant leaves of 6 kinds of tested plant under the different pH of the simulated acid rain. The results reveal that tested plants show some resistance to acid rain. And the concrete manifestation is that for evergreen broad-leaved trees (Schima superb, Cyclobalanopsis glauca, Elaeocarpus glabripeta- lus) the height and diameter as well as the chlorophyll content which are under the severe simulated acid rain treatment group are generally higher than the control group; For the deciduous broad-leaved trees, Carya cathayensis presents the trend of"first repress then praise"and it adapts to the stress of acid rain in the later treatment period; For coniferous trees(Pinus massoniana, Cunninghammia lanceolata), they performance differerntly. Pinus massoniana shows a certain restraint while Cunninghammia lanceolata shows some resistance. Compared with the control group, the Elaeocarpus glabripetalus reduces generally in the first derivative spectrum reflectance in visible light area while the Pinus massoniana performs the reserved trend. And the rest four tree species have a conversion process in four years. For example, Schima superba is from decreasing to increasing while Cyclobalanopsis glauca and Carya cathayensis are opposite. From the multiple Comparisons results, the author draw a conclusion that the differences in the visible spectral reflectance mainly focus on green light reflexation peak and nearby red edge under the effect of acid rain. Meanwhile, they also manifest the phenomena of"red shift"and"blue shift"where the wavelength of red edge is in. The results for the features waveband show that differences in the reflectance of plant leaves which result from different treatment of acid rain can be distinguished effectively through the average spectral reflectance within a quite narrow range of wavelength. Besides, according to the interaction analysis of different treatment groups of acid rain and year of experiment, there are obvious differences in the selected features waveband within different years and most different treatment.With the results of observing plant growth, chlorophyll content and reflectance spectrum under simulated nitrogen deposition, the author does a contrastive analysis. The results indicates: for the Schima superba, Elaeocarpus glabripetalus, Carya cathayensis and Cunninghammia lanceolata, the height growth and ground diameter growth are better under low and middle nitrogen treatment. On the contrary, high nitrogen may cause restraint. Contrast results of chlorophyll approve this as well. Through the analysis of first derivative spectrum reflectance, nitrogen treatments reduce clearly in visible light area compare with control treatment. Meanwhile, the red edge also manifest red-shift phenomena, because nitrogen is component of chlorophyll, nitrogen input could make leaf more green. The analysis of result for the different features waveband shows that middle nitrogen and high nitrogen is pretty different with other two treatments. With interaction analysis, it indicates obvious otherness between nitrogen deposition treatment and seasons of experiment.