基于高光谱技术的滇池流域湿地植物氮含量估算模型构建

Estimation Modelling of Nitrogen Content of Wetland Plants in Dianchi Lake Basin Using Hyperspectral Technology

  • 摘要: 以滇池流域为研究区,利用S−R3500光谱仪采集芦苇、菰、香蒲和风车草4种典型滇池湿地植物的光谱数据,应用A33型连续流动分析仪测定湿地植物叶片氮含量,筛选出氮含量最敏感的光谱特征波段和变换形式参量,建立湿地植物叶片高光谱氮含量估算模型。结果表明:4种湿地植物的光谱曲线与健康绿色植被的光谱曲线趋势一致,但在800~1350 nm和1650~1800 nm波段存在差异,一阶微分、二阶微分和“三边”参数光谱变换可以更加突出4种湿地植物的光谱特征;芦苇二阶微分1836 nm、香蒲二阶微分881 nm、菰一阶微分1264 nm、风车草二阶微分1665 nm波长和氮含量相关系数绝对值最大;菰的“三边”参数红边面积和蓝边面积的比值、红边面积和蓝边面积的归一化值,香蒲的红边幅值、红边面积、“绿峰”反射率和“红谷”反射率比值、红边面积和蓝边面积比值和氮含量相关系数绝对值最大,且呈极显著相关(P<0.01);4种湿地植物基于光谱二阶微分构建的氮含量估算模型精度比一阶微分高,基于光谱“三边”参数构建的氮含量的估算模型精度最高且误差最小;4种湿地植物基于“三边”参数构建的氮含量估算多元逐步回归模型估测效果较好。基于高光谱技术的湿地植物养分含量估算模型技术可以长时序快速地监测大面积湿地植被养分含量的时空动态变化,为湿地植物远程管理提供基础数据和技术支持。

     

    Abstract: The study area is Dianchi Lake Basin, the spectral reflectance of 4 typical wetland plants, including Phragmites australis, Zizania latifolia, Typha orientalis and Cyperus involucratus, was acquired by S-R3500 spectrometer, nitrogen content of wetland plant leaves was determined by model A33 of continuous flow analytical instrument, the most sensitive spectral bands and spectral transformation formal parameters in leaves of 4 wetland plants with nitrogen contents were selected, and the nitrogen contents estimation models of wetland plants were established with hyperspectral data. The results revealed that the spectral curves of 4 wetland plants were consistent with those of the healthy green plants, there are differences in the wavelength of 800–1350 nm and 1650–1800 nm, the spectral characteristics of 4 wetland plants can be more highlighted through transformation of spectral includ first-order differential, second-order differential and "three-edge" parameters; the highest absolute correlation coefficient between wavelength and nitrogen content is found in the second-order differential band spectrum of P. australis(1,836nm), the first-order differential band spectrum of Z. latifolia(1264 nm), the second-order differential band spectrum of T. orientalis(881 nm), the second-order differential band spectrum of C. involucratus(1665 nm). The correlation of the "three-edge" parameters that ratio of red-edge and blue-edge area and the normalized value of red-edge and blue-edge area of Z. latifolia, the red-edge amplitude, red-edge area, the ratio of "green peak" and "red valley" reflectance and ratio of red-edge area and blue-edge area of T. orientalis with the nitrogen contents were the largest and significantly correlated(P<0.01); the accuracy of nitrogen content estimation models of wetland plant leaves based on spectral second-order differentiation was higher than that of first-order differentiation, the nitrogen content estimation models based on the "three-edge" of the spectral parameters had the highest accuracy and the least error; the estimation results for nitrogen content based on "three-edge" parameters of 4 wetland plants are good using a multiple stepwise regression estimation model. The estimation models techniques of wetland plants of nutrient contents based on hyperspectral technology can rapidly monitor the spatio-temporal dynamic changes of nutrient contents of large-scale wetland plants in a long time series, providing basic data and technical support for remote management of wetland plants.

     

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