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用HR-768型光谱仪,实地测定塔里木河下游不同地下水埋深条件下胡杨叶片高光谱数据及其含水率。结果表明:胡杨叶片含水率随地下水埋深下降而降低,但其实测光谱曲线对地下水埋深梯度变化并无明显的响应规律。用ENVI软件去除实测光谱数据包络线后,得出1455nm附近胡杨叶片归一化光谱曲线对地下水埋深梯度变化具有明显的响应规律。采用相关系数法分析所测光谱与含水率的关系,结果表明:1466～1646nm波段是胡杨叶片光谱对水分响应的敏感波段。以1466～1646 nm波段胡杨叶片光谱水分吸收深度和实测含水率构建胡杨含水率估测模型:Y=7.309X1474-5.77X1482-0.629(R2=0.954),模型预测值与实测值的相对误差在1.02%～2.73%之间,平均相对误差为1.59%,模型精度较高。这一研究将为使用高光谱数据进行胡杨生境监测与反演提供依据。
The HR-768 spectrometer was used to determine the leaf hyperspectral data and water cut of Populus euphratica under different groundwater depths in the lower reaches of the Tarim River. The results showed that the leaf water cut of Populus euphratica decreased with the decrease of groundwater depth, but there was no obvious response law to the change of groundwater depth gradient. After ENVI software was used to remove the measured spectral data envelope, the normalized spectral curve of Populus euphratica leaves near 1455nm had obvious response to the groundwater depth gradient. The correlation coefficient method was used to analyze the relationship between the measured spectra and the water cut. The results show that the 1466 ~ 1646 nm band is the sensitive wavelength band of Populus euphratica leaf to water response. The estimation model of Populus euphratica water content was established based on the spectral water absorption depth of Populus euphratica and the measured moisture content in 1466 ~ 1646 nm wave band: Y = 7.309X1474-5.77X1482-0.629 (R2 = 0.954). The relative error between model predictive value and measured value was 1.02 % ~ 2.73%, the average relative error is 1.59%, the model accuracy is higher. This study will provide the basis for the monitoring and inversion of Populus euphratica habitat using hyperspectral data.