International Journal of Marine Science, 2025, Vol.15, No.4, 220-232 http://www.aquapublisher.com/index.php/ijms 229 mangrove resource surveys and dynamic monitoring (Pillodar et al., 2023). Medium- and high-resolution satellite images can clearly identify the spectral differences between mangroves and other land cover types, accurately map the spatial distribution of mangroves. Researchers have also developed vegetation index and classification algorithms for mangroves, such as the mangrove vegetation index (MVI) based on Sentinel-2 data, which can quickly extract mangrove information. Through comparative analysis of images at different periods, the changing trend of mangrove area and the specific areas where losses or growth occur can be quantitatively evaluated. On a global scale, NASA and other institutions have jointly launched the Global Mangrove Watch platform, integrating multi-source satellite data to monitor annual changes in global mangrove forests, and providing macro decision-making support to countries. In addition to area changes, satellite remote sensing can also be used to monitor the biomass and health of mangroves. Some studies have also tried to measure the height and crown width of individual trees using drones' LiDAR or structured light technology to more accurately calculate carbon storage. Figure 3 Schematic sketch of patterns of mangrove rapid expansion in Guangxi Beibu Gulf (Adopted from Sun et al., 2025) Image caption: (a) Spatial distribution of mangrove forests in Guangxi Beibu Gulf from 2016 to 2022. (b) Classification of three different coastal mangrove forest types in Guangxi. (c)-(e) Examples of RGB satellite images of Google maps showing the expansion patterns of three different coastal zones types in Guangxi. (f)-(h) Schematic sketch of expansion patterns of three different coastal mangrove types in Guangxi Beibu Gulf (Adopted from Sun et al., 2025) 7.2 Soil carbon storage and biomass dynamic monitoring index system Mangrove carbon sink monitoring should not only focus on the area and health of the forest, but also directly measure its carbon storage and changes. To this end, it is necessary to establish a dynamic monitoring index system covering soil carbon and vegetation biomass to quantitatively evaluate the changing trends of mangrove carbon sink function. In terms of soil carbon storage, monitoring indicators include soil organic carbon content, carbon density, and carbon burial rate. It is usually practiced to set up fixed monitoring sample sites in typical mangrove forests, collect soil profile samples regularly (such as every 5 years), and determine the organic carbon content and dry bulk weight at different depths, thereby calculating soil carbon storage per hectare (Alimbon and Mansegugiao, 2021).
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