荒漠植物长势、 变化、 演替是反映荒漠地区生境状况的重要指标。 目前荒漠植物监测与光谱研究多基于定时采样数据, 波谱时序动态研究相对薄弱。 荒漠植物光谱因受时间尺度影响, 常引起辨识误差。 将荒漠植物中最具代表性的灌木——柽柳、 白刺、 梭梭作为样本, 旨在揭示三种荒漠植物光谱生长期变化规律及种间动态分异特征, 为荒漠植被空间遥感辨析奠定基础。 实验选取旺盛植株采集生长期内(5月—10月份)光谱数据, 对不同月份植物光谱曲线分析比较并剖析机理, 得出荒漠植物生长期光谱特征变化规律及其物候现象对应波谱表现。 结论指出: (1)三种荒漠植物反射率曲线总体特征均符合绿色植被波谱规律, 可观察到较明显的12峰谷分布, 红边斜率与面积从大到小分别为: 梭梭、 柽柳、 白刺。 其光谱曲线峰谷幅度值相对较小, 且变化较快, 红边参数表现活跃期分别为柽柳8月、 白刺10月、 梭梭9月。 (2)荒漠植物的光谱变化与植物本身物候特征、 气候变化植物响应密切相关。 光谱特征在可见光波段与营养期、 花期、 落叶期有一定响应关系; 近红外波段与结实期、 休眠期、 降雨情况相关; 短波红外波段与营养期、 落叶期、 降雨状况呈现关联性。 (3)7月份三种植物的生长状况差异光谱曲线表现为: 衰败植株地物光谱反射率可见光、 短波红外波段呈高反射, 近红外波段反射减弱, 趋近于土壤光谱反射率曲线。

The growth, change and succession of desert plants are significant indicators of the ecosystem in desert areas. At present, there are many studies on desert plant monitoring and desert plant spectrum based on fixed time sampling data, but few studies on a long time dynamic spectrum. The spectral discrimination of desert plants is due to the fact that it is affected by the time scale. In this paper, we selected plants which were representative of the desert shrubs—Tamarix ramosissima, Nitraria, Haloxylon ammodendron as samples, aiming at finding out the variation law and interspecific dynamic differentiation characteristics of the three desert plants, which was the basis for the identification of desert vegetation by spatial remote sensing. The spectral data of the vigorous plants were collected during the growing season (5~10 months) in the experiment, and the spectral curves of plants in deferent months were compared and analyzed. Results showed changes of the spectral characteristics and a corresponding phenology of desert plants in growing season. The conclusions are as follows. (1) The reflectivity curves of desert plants are consistent with the green vegetation spectrum. There are obvious peaks and valleys distribution. The slopes and areas of red-edge from large to small were as follows: Haloxylon ammodendron, Tamarix ramosissima, Nitraria. The amplitude of their spectral curve is relatively small, with rapid change. The active period of Red edge parameters is August for Tamarix, October for Nitraria, September for Haloxylon. (2) The spectral changes of desert plants are connected with the plant phenology and climate change. The spectral characteristics are related to the vegetative period, flowering period and deciduous period in the visible band, which are related to fruit period, dormancy period and rainfall in the near infrared band, and related to nutrition period, deciduous period, rainfall situation in the shortwave-infrared band. (3) In July, the spectral curves of three plants’ growth status showed that the spectral reflectance of decaying plant are higher than vigorous one in the visible band and mid-infrared band, while they are lower in the near-infrared band, which is close to the curve of soil reflectance.