Estimation of Mangrove Aboveground Biomass in China Using Forest Canopy Height through an Allometric Equation

Mangroves, which have extremely high primary productivity, are efficient coastal blue carbon ecosystems. Aboveground biomass (AGB) is an important component of vegetation carbon pools. Thus, accurate estimation of mangrove AGB is critical for studying carbon cycle and climate change. While the practical significance and application of information obtained on mangrove AGB in China is apparent, studies of this nature in China at a national scale have rarely been reported. Remote sensing technology is convenient, efficient, has a wide observational range, and can be used for large-scale ecosystem monitoring. Canopy height is a structural parameter that is positively correlated with the AGB of vegetation. The Global Ecosystem Dynamics Investigation (GEDI) spaceborne Light Detection and Ranging (LiDAR) satellite, launched in recent years, is able to obtain vegetation canopy height. This study employed forest canopy height derived from GEDI satellite-based LiDAR and an allometric equation based on the allometric theory to estimate mangrove AGB in China in 2019, and the quantitative and spatial distribution of mangrove biomass and their main influencing factors were analyzed. The results showed that the total and mean AGB of mangroves in China in 2019 were about 1,974,827 t and 73.0 t/hm2, respectively. Guangdong-Hong Kong-Macao area showed the largest total mangrove AGB, reaching 843,836 t. The mean values of AGB in each province (region) with mangrove ecosystems nationwide ranged from 53.3 to 92.1 t/hm2, of which the largest was found in Hainan Province, reaching 92.1 t/hm2. In Hainan, Taiwan, and Fujian provinces, mean mangrove AGB was higher than the national mean. Considering nature reserves, the mean AGBs of mangroves in Neilingdingdao-Futian and Mai Po mangrove nature reserves in Shenzhen Bay in the Guangdong-Hong Kong-Macao area and Dongzhaigang mangrove nature reserve in Hainan province were relatively high, with values greater than 110 t/hm2. The accumulation and distribution of mangrove AGB in China are affected by latitude and anthropogenic factors. This study provides a comprehensive analysis of mangrove AGB in China based on remote sensing and an allometric equation and can provide a database and technical reference for estimating carbon storage in mangrove ecosystems. It will also contribute to the implementation of ecological restoration and protection measures for coastal mangroves, as well as carbon emission control in China.