The Estimation Model for Phosphorus Content of Zizania Cuciflora in Jianhu Wetland Based on Hyperspectral Technology

Taking the dominant species of sturgeon of Jianhu wetland in Yunnan Province as the research object, the reflectance spectrum of Zizania Cuciflora was collected by ASD Filed Spec 3 spectrometer, and its phosphorus content was measured. The estimation model of Z. Cuciflora phosphorus content was established by hyperspectral data. The results showed that the reflectance spectrum curve direction of the Z. Cuciflora is consistent with the healthy green vegetation. The detailed characteristics of the original spectrum can be analyzed more clearly by the first derivative transformation. The spectral characteristics of the Z. Cuciflora can be quantitatively analyzed by" three edges”parameters as a unique for vegetation spectrum. The correlation was analyzed between the spectral reflectance, first-order differential of reflectance," three edges”parameters and phosphorus content, the highest correlative variables were respectively B1 085 (1 085 nm of smoothed spectrum), D1259 (1 259 nm of spectral first order differential) and SDr (red edge area), and the correlation coefficients were respectively 0.528, 0.619 and 0.526. The low-dimensional spectral data of resampling Based on Landsat 8 OLI spectrum, the near infrared band was more sensitive to the phosphorus content of Z. Cuciflora and the correlation coefficient was 0.519 on the low-dimensional spectral data of resampling Based on Landsat 8 OLI spectrum. The correlation coefficients of BF1 (first component extracted from smoothed spectrum) and DF1 (first component extracted from first order differential spectral) with phosphorus content were respectively 0.547 and 0.494. The multivariate stepwise regression models have better estimation effect, followed by the principal component regression models and the univariable regression models in all estimation models. The best phosphorus content estimation model of Z. Cuciflora was a multivariate stepwise regression model based on the first order differential of reflectance, R², RMSE, P and MAE were respectively 0.76, 13.69, 91.08 % and 10.75.