植被的光谱特征是监测植被生长发育状态、 健康状况的基础, 探索玉米苗期干旱胁迫后的关键发育期光谱特征变化, 不仅为植被光谱数据库的建设提供理论数据, 也为植被水分胁迫高光谱识别提供理论依据。 以辽宁西部锦州生态与农业气象站大型农田土壤水分控制场为研究区, 对玉米苗期、 拔节期、 抽雄期和乳熟期4个发育期进行苗期干旱胁迫小区和水分适宜小区光谱观测, 通过分析原始光谱、 一阶导数光谱、 光谱参数和水分敏感植被指数, 对比苗期干旱胁迫光谱与同期对照的光谱特征差异性。 结果表明: (1)对于原始光谱来说, 玉米在苗期受到干旱胁迫后, 与同期水分适宜的玉米光谱特征有较为明显区别, 在可见光波段和短波红外波段反射率均高于同期对照反射率, 近红外波段明显低于同期对照反射率, 拔节期差异性最为显著, 达到了5%左右, 随着作物的生长, 差异性逐渐减弱。 (2)4个发育期玉米一阶导数光谱在可见光波段均出现双峰, 红光位置峰值在抽雄期达到最大； 苗期干旱胁迫一阶导数光谱的红光位置峰值均低于同期对照, 拔节期差异明显, 在0.003左右, 乳熟期差别明显减小, 可区分性减弱。 (3)苗期胁迫玉米光谱参数与同期对照相比, 从苗期到乳熟期, 红边位置存在“蓝移”—“红移”—“蓝移”的现象, 绿峰位置均存在向长波方向移动的现象； 在抽雄期和乳熟期, 蓝边位置、 蓝边幅值、 黄边位置和黄边幅值两者差异不明显； 在三边面积中, 红边面积均低于同期对照, 黄边面积均高于对照, 两者的蓝边面积无明显差异。 (4)在8个水分敏感植被指数中, NDWI和NDW_2的差异性指数在玉米四个关键发育期均达到50%以上, 可区分性明显。 该研究旨在为植物水分胁迫光谱库提供基础数据, 为作物干旱识别的谱段选择及高光谱波段设置提供基础依据。

The spectral characteristics of vegetation can be used to monitor their growth and development. Additionally, exploring the changes in spectral characteristics of maize throughout its developmental period following water stress during the seedling stage provides theoretical data for building vegetation spectral databases, as well as a basis for the hyperspectral identification of vegetation water stress. Using the large-scale farmland soil moisture control field of Jinzhou Ecological and Agricultural Meteorological Station in western Liaoning as the research area, an ASD FieldSpec Pro spectrometer was used to spectrally observe maize at the seedling, jointing, tasseling and milk stages in the seedling water stress and water-suitability control areas. The differences in the spectral characteristics of the water stressed seedlings and those of the controls were identified based on the original spectrum, the first derivative spectrum and multiple spectral parameters. The results were as follows: (1) The characteristics of the original spectrum of maize subjected to drought stress in the seedling stage are significantly different from those of maize that receives suitable water in the same stage. Specifically, the reflectance in the visible or short-wave infrared band was higher than that of control maize at the same stage, while that of the near-infrared band was significantly lower than that of control maize, especially at the jointing stage, the difference was about 5%; however, these differences gradually decreased with crop growth. (2) The first derivative spectra of maize at the seedling, jointing, tasseling and milk stages revealed double peaks in the visible bands, and the peak of the red light position reached the highest level at the tasseling stage. The peaks of the red light position for the first derivative spectrum of maize from seedlings subjected to water stress were lower than those of control maize, and the differences were significant, especially in the jointing stage, when the difference was about 0.003. In the milk stage, the peaks of red were significantly reduced relative to the concurrent control maize and the distinguishability was weakened. (3) Comparison of the spectral parameters of maize under seedling water stress with those of control maize revealed that the red edge position undergoes a blue shift-red shift-blue shift from the seedling stage to the milk stage, while the green peak position undergoes a shift in the long-wave direction. However, the difference between the blue edge position and blue edge amplitude and the yellow edge position and yellow edge amplitude was not significant at the tasseling and milk stages, the red edge area is lower than that of the control, and the yellow edge area is higher than that of the control. (4) Among the eight water-sensitive vegetation indices, the difference index of NDWI and NDW-2 reached more than 50% in the four Critical developmental stages of maize, and the distinguishability was enhanced. Overall, this study provides basic data that can be useful for plant water stress spectral libraries and a basis for selecting spectral bands and setting hyperspectral bands for identification of crop drought.