## 3 Materials
### Satellite Image Pre-Processing
#### 3.3.1 HR Reflectance Data  
We used HJ-1, GF-1, and Landsat 5/7/8 observations to produce HR reflectance datasets during 2011-2014. The HJ-1 satellite was launched on September 6, 2008; two CCD cameras with the same design principle were placed symmetrically according to the subsatellite point. The resulting data have a spatial resolution of 30 m. With two CCD cameras, the field of view is divided equally, and observations can be performed in parallel; in addition, push-broom imaging is conducted jointly for four spectrum bands with a swath width of 700 km over the ground. Because the revisit cycle is only four days, a large amount of data can be acquired within a short period. The GF-1 satellite was launched on 26 April 2013; it was the first satellite of the HR Earth observation system in China. The spatial resolution of its multispectral large-width camera is 16 m, and the revisit cycle is two days; in addition, the composite width of its four multispectral image cameras with 16 m resolution is greater than 800 km. Therefore, this satellite has unique advantages for large-scale surface observation and environmental monitoring. These two satellites have the characteristics of HR data and a short revisit cycle and have unique advantages for large-scale surface observation and environmental monitoring. With respect to the revisit cycle, the HJ-1 satellite data are superior to Landsat data, and constructing a long time series dataset is easier with HJ-1 data. All Landsat 5/7/8 scenes for the study area covering the growing season were acquired through the United States Geological Survey (USGS) ([[https://earthexplorer.usgs.gov](https://earthexplorer.usgs.gov)]([https://earthexplorer.usgs.gov](https://earthexplorer.usgs.gov))). Landsat 5/7 images were preprocessed using the Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS) [43]. LEDAPS applies atmospheric correction routines to Landsat TM data, similar to routines derived from MODIS. The Second Simulation of a Satellite Signal in the Solar Spectrum (6S) [44] radiative transfer model was used to generate Landsat surface reflectance. Landsat-8 OLI surface reflectance data are generated from the Landsat Surface Reflectance Code (LaSRC) [45], which is distinctly different with the LEDAPS algorithm. The LaSRC makes use of the coastal aerosol band to perform aerosol inversion tests, uses auxiliary climate data from MODIS and uses a unique radiative \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Data** & **Band** & \begin{tabular}{c} **Spectral** \\ **(nm)** \\ \end{tabular} & \begin{tabular}{c} **Spatial** \\ **(m)** \\ \end{tabular} & \begin{tabular}{c} **Temporal** \\ **(day)** \\ \end{tabular} & \
\begin{tabular}{c} **Year** \\ **Year** \\ \end{tabular} &
\begin{tabular}{c} **Images for** \\ **Huailai** \\ \end{tabular} \\ \hline \multirow{3}{*}{HJ-1 CCD} & Red & 630–690 & & & 2011 & 31 \\ \cline{2-6}  & NIR & 760–900 & & 4 & 2012 & 25 \\ \cline{2-6}  & NIR & 760–900 & & & 2013 & 40 \\ \hline \multirow{2}{*}{GF-1 WFV} & Red & 630–690 & \multirow{2}{*}{16} & \multirow{2}{*}{2} & 2013 & 9 \\ \cline{2-6}  & NIR & 770–890 & & & 2014 & 8 \\ \hline Landsat 5 & Red & 630–690 & \multirow{2}{*}{30} & \multirow{2}{*}{16} & \multirow{2}{*}{2011} & \multirow{2}{*}{7} \\ \cline{2-6} TM & NIR & 760–900 & & & 2014 & 8 \\ \hline Landsat 7 & Red & 630–690 & \multirow{2}{*}{30} & \multirow{2}{*}{16} & \multirow{2}{*}{2012} & \multirow{2}{*}{6} \\ \cline{2-6} ETM+ & NIR & 770–900 & & & 2014 & 8 \\ \hline Landsat 8 & Red & 640–670 & \multirow{2}{*}{30} & \multirow{2}{*}{16} & \multirow{2}{*}{2013} & \multirow{2}{*}{6} \\ \cline{2-6} OLI & NIR & 850–880 & & & 2014 & 8 \\ \hline \multirow{3}{*}{MCD43A4} & Red & 620–670 & \multirow{3}{*}{500} & \multirow{3}{*}{8} & 2008 & 12 \\ \cline{2-6}  & NIR & 841–876 & & & 2010 & 12 \\ \hline \multirow{3}{*}{MCD15A2} & \multirow{3}{*}{-} & \multirow{3}{*}{-} & \multirow{3}{*}{500} & \multirow{3}{*}{8} & 2008 & 12 \\ \cline{1-1} \cline{3-4}  & & & & 2010 & 12 \\ \hline \hline \end{tabular}
\end{table}