1. Department of Surveying and Mapping, Taiyuan University of Technology, Taiyuan 030024, China
2. Gucheng Experimental Station of Ecological and Agricultural Meteorology, Chinese Academy of Meteorological Sciences, Beijing 100081, China
3. Joint Eco-Meteorology Laboratory of Chinese Academy of Meteorological Sciences and Zhengzhou University, Zhengzhou 450001, China
4. Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044, China
Abstract：Plant growth is an important indicator of environmental changes. Under the global environmental change pattern, it is particularly important to study the impact of multiple environmental factors and interactions on plants. In order to explore the spectral characteristics of plants in response to environmental changes, to explore the impact of environmental changes on plant growth, and to realize remote sensing monitoring of plants, this study took the dominant species of Quercus mongolica in Northeast China as the research object, and analyzed and studied different photoperiods, temperature and Changes in spectral reflectance characteristics of the canopy of Quercus mongolica during its leaf development period caused by the interaction of nitrogen deposition. Plant growth is an important indicator reflecting environmental changes. In order to realize the monitoring of plants by remote sensing, this study took Quercus mongolica, the dominant tree species of Northeast China, as the research object, and used a simulation test to analyze the influence on the canopy spectral reflectance of Quercus mongolica in 50% leaves the unfolded stage. The simulation test was carried out in a large-scale artificial climate room and was set up with 3 temperature, 3 photoperiods and 2 nitrogen deposition interactive treatments. There were 18 treatments with 4 replicates in each treatment. When Quercus mongolica entered 50% leaves unfolded stage, three repetitions with small differences in each treatment measured spectral reflectance, and used the FieldSpec Pro FR 2500 back-mounted field hyperspectral radiometer to measure the spectral reflectance. Analyzed the spectral reflectance of the canopy of Quercus mongolica with different treatments, and selected NDVI (Normalized Vegetation Index), Chl NDI (Normalized Chlorophyll Index) and PRI (Photochemical Reflectance Index) three commonly used spectral indices as auxiliary analysis. At the same time, to calculated the first derivative spectrum to obtain the red edge parameters. The spectral reflectance trends of Quercus mongolica in 50% leaves unfolded stage of different treatments are roughly the same, which are in line with the unique spectral reflectance characteristics of plants. There is a small peak in the range of 350~680 nm, the reflectance of 680~750 nm rises rapidly, and the reflection platform enters after 750 nm. The results show that: (1) Photoperiod had no obvious effect on the spectral reflectance of Quercus mongolica canopy; (2) Increasing temperature reduced the spectral reflectance of Quercus mongolica canopy at 350~750 nm; (3) Nitrogen application reduced the spectral reflectance of Quercus mongolica canopy at 350~750 and 750~1 100 nm; (4) The interaction of temperature increase and nitrogen application significantly reduced the spectral reflectance of Quercus mongolica canopy; (5) And the first derivative spectrum can indicate the red edge characteristics of plants. The results can provide a theoretical basis for monitoring phenological changes and the analysis of influencing factors.
