*2.1. Study Area*

The present study was conducted in Can Gio, a coastal district located approximately 50 km south of Ho Chi Minh City (formerly Sai Gon) along the Southern coast of Vietnam. The geographical coordinates are 10◦22–10◦40 latitude and 106◦46–107◦01 longitude. The climate is tropical monsoon and has two typical seasons. The dry season begins in April and ends in November of the following year, whereas the rainy season occurs between May and October. The average temperature is approximately 26 ◦C, the annual rainfall is roughly 1300–1400 mm, and the relative humidity is approximately 80% [35]. This district is well-known for its mangrove reforestation and rehabilitation programs, not only in Vietnam but also throughout Southeast Asia [36]. The wetland ecosystem of Can Gio is diverse and includes the mangrove areas distributed in zone IV, which contains the largest mangrove forest among the four mangroves zones (See Figure 1) in Vietnam [37].

**Figure 1.** Location map of study areas.

The Can Gio mangrove forests were declared as a biosphere reserve by the United Nations Educational, Scientific, and Cultural Organization (UNESCO) in 2000 [38]. The dominant species are *Rhizophora apiculate*, *Sonneratia alba*, *Avicennia alba*, *Rhizophora mucronata*, and others. Approximately 33 species belonging to 15 families have been identified in the CGBRS [36].

#### *2.2. Field Survey Data Collection*

With permission from the local authorities, the 2018 field survey of the CGBSR was conducted during the dry season, when the coastal tides impacting the mangrove forest were lowest. A total of 121 plots were sampled by the stratified random sampling approach. Each plot sampling was initially assisted by a local counterpart to guarantee the whole range of AGB values over the reserve. During the surveying, the experimenters measured the diameter at breast height (DBH), tree height (H), and tree density. All living mangrove forest stands with DBH > 5 cm in a strata plot size of 25 × 20 m (0.05 ha) were measured. The location (accuracy ± 2 m) of each sampling plot was measured by the Garmin eTrex global positioning system (GPS) (Figure 2).

**Figure 2.** Aboveground biomass measurements in the study area. (**a** & **b**) Biophysical parameters measurement (Photographs were taken by L.V. Nguyen during the 2018 dry season).

The mangrove AGB of each species was estimated by a specific allometric equation (see Table 1).


**Table 1.** Allometric equations for estimating the mangrove species in the study site.

Note: AGB is the above-ground biomass (kg) of a mangrove tree, DBH is the diameter (cm) at breast height (1.3 m), ϕ is the wood density (tons dry matter per m<sup>3</sup> fresh volume).

#### *2.3. Remote Sensing Data Acquisition and Image Processing*
