## Materials and Methods
### Satellite Data Pre-Processing and Predictors Derived  
Sentinel-1 Synthetic Aperture Radar (SAR) and cloud-free Sentinel-2 multispectral imagery from the European Space Agency used in this study (Table 1) were downloaded from the agency's Copernicus Sentinel Scientific Data Hub ([[https://scihub.copernicus.eu/dhus/#/home](https://scihub.copernicus.eu/dhus/#/home)]([https://scihub.copernicus.eu/dhus/#/home](https://scihub.copernicus.eu/dhus/#/home))). Sentinel-1 C-band images adopted in this study were collected in the interferometric wide swath mode of the VH (vertical transmit-Horizontal receive) and VV (vertical transmit-vertical receive) polarizations. With a pixel size of 10 m, the SAR images are at a high-resolution (HR) Level-1 ground range detected (GRD) processing level. The Sentinel-2 Level 1C data involved were top-of-atmosphere reflectance images, and they were processed for orthorectification and spatial registration. The imagery had 13 spectral bands in the visible, near infrared, and short-wave infrared regions, and had 10 m (band 2-4, 8), 20 m (band 5-7, 8a, 11-12), and 60 m (band1, 9-10) spatial resolutions. In addition, elevation data (30 m) \begin{table}
\begin{tabular}{c c c c} \hline \hline
\begin{tabular}{c} S2A\_MSIL\_IC\_20170923T022551.N0205 \\ \_R046\_T52T01\_20170923T023519,SAFE \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of Sentinel imagery acquired for the study. \begin{table}
\begin{tabular}{c c} \hline \hline
**Tree Species** & **Allometric Equations** \\ \hline _Bestal platphys/lla_ Suk. & AGB = T + B + L = 0.04939 \(\times\) (D\({}^{2}\times\) H)\({}^{0.0011}\) + 0.04177 \(\times\) (D\({}^{2}\times\) H)\({}^{0.7866}\) + 0.0109 \(\times\) (D\({}^{2}\times\) H)\({}^{0.8472}\) \\ _Acer mono Maxim._ & AGB = T + B + L = 0.3274 \(\times\) (D\({}^{2}\times\) H)\({}^{0.728}\) + 0.01349 \(\times\) (D\({}^{2}\times\) H)\({}^{0.02347}\) + 0.  
from the Shuttle Radar Topography Mission (SRTM) product was acquired from the United States Geological Service's Earth Explorer ([[https://earthexplorer.usgs.gov/](https://earthexplorer.usgs.gov/)]([https://earthexplorer.usgs.gov/](https://earthexplorer.usgs.gov/))) for inclusion in the analysis of the Sentinel imagery [55]. The processing steps used in the study are summarized in Figure 2. Sentinel application platform (SNAP) software (version 6.0, European Space Agency) was used to pre-process Sentinel-1 and Sentinel-2 imagery. The steps for the SAR imagery based on the Sentinel-1 Toolbox consisted of image calibration, speckle reduction using the Refined Lee Filter, and terrain correction using the Range-Doppler to acquire an accurate radar intensity backscatter coefficient with a map projection [56; 57]. Multispectral imagery was atmospherically corrected and processed by the radiative transfer model-based Sen2 Cor atmospheric correction processor (version 2.5.5, European Space Agency) to a Level-2A product, a bottom-of-atmosphere-corrected reflectance image. The pre-processed Sentinel images, as well as the elevation data, were brought into a common map projection, universal transverse mercator (UTM) Zone 52 WGS84, and resampled to 10 m pixel sizes. Subsetting and mosaicking were done to cover the study area. In this study, 44 predictors were selected and extracted according to previous research [55; 58]. Shown in Table 3, 23 predictors were from Sentinel-1 and 18 variables were from Sentinel-2, as well as  
Figure 2: Flowchart of steps used for forest above-ground biomass mapping using Sentinel SAR and multispectral imagery. DBH is the abbreviation of diameter at breast height. elevation (H) from SRTM. Additionally, the other two variables were longitude and latitude. The first and second part derived from the Sentinel-1 imagery consisted of relating the field AGB with Sentinel SAR polarization channels, and their calculation and texture characteristics. The third to fifth parts based on the Sentinel-2 images proceeded with relating the field AGB to the multispectral bands, vegetation indices, and biophysical variables.