Abstract: Chlorophyll content is an important indicator for the stress state of reeds. Phragmites australis affected by Hyalopterus pruni were selected as research objects. The reflectance spectra of leaves were recorded by an ASD FieldSpec 4 portable ground object spectrometer and the chlorophyll contents (SPAD readings) were measured using a SPAD-502 Plus Chlorophyll Meter. Univariate linear regression and partial least squares (PLS) regression were used to analyze the relationships between the spectral reflectance and the chlorophyll content of the leaves. We established two models, a full wave band spectrum model and a red-edge position regression model, to estimate the chlorophyll content of the reeds. The results showed that the reflectance of healthy reed leaves was higher than that of the leaves suffered by pests. The correlation of chlorophyll content with hyperspectrum was different between the two types of leaves, especially in the spectral range of 1400-2500 nm. The full wave band hyperspectral estimation model had high accuracy, with the determination coefficient of healthy leaves regression model being 0.965, the mean square root error (RMSE) being 0.813, and the predicted deviation ratio (RPD) being 3.940. The determination coefficient of pest-bearing leaves regression model was 0.966, RMSE being 0.989, and RPD being 3.855. The crossvalidation and offsitevalidation results further demonstrated that full-wave band hyperspectral data inversion could estimate the relative chlorophyll content of reeds suffered by H. pruni, indicating that it was feasible to use full wave band hyperspectral data to estimate the relative chlorophyll content of vegetation suffered by pests.

Key words: PM₂₅, urban greenspace, land use, landscape pattern