Evaluating the Losses and Recovery of GPP in the Subtropical Mangrove Forest Directly Attacked by Tropical Cyclone: Case Study in Hainan Island

The gross primary production (GPP) of the mangrove ecosystem determines the upper limit of the scale of its blue carbon sink. Tropical cyclones (TCs) are among the most important extreme events that threaten the subtropical mangrove ecosystem and have a serious impact on mangrove ecosystem GPP. However, there are somewhat insufficient scientific findings on regional-scale mangrove ecosystem GPP responding to large-scale weather events such as TCs. Therefore, we selected the subtropical Hainan Island mangrove ecosystem, where more than two TCs pass through per year, as the research area; selected direct-attack TCs as the research object; and took the mangrove vegetation photosynthesis light-use efficiency model established based on the eddy covariance observation data as the tool to evaluate the loss and recovery of mangrove ecosystem GPP after TCs attacked at a regional scale. We found that the TC impacted the mangrove ecosystem GPP through the photosynthetic area and rate, and the recovery of the rate occurred prior to the recovery of the area; the loss of mangrove ecosystem GPP is inversely proportional to the distance to the center of the TC and the distance to the coastline; and the canopy height, diameter at breast height, and aspect where the tree stands significantly influence the response of the mangrove ecosystem GPP to TCs. However, the response varies for different mangrove community compositions, soil conditions, and planting densities as well as different frequencies and intensities of TCs, and they should be analyzed in detail. This study is expected to provide technical and data support for the protection of blue carbon in a subtropical island mangrove ecosystem in response to extreme events and post-disaster recovery.

Automated summary

The impact of tropical cyclones on the gross primary production (GPP) of mangrove ecosystems is significant, but there is a lack of scientific research on the effects of large-scale weather events such as cyclones on mangrove ecosystem GPP. In this study, the subtropical Hainan Island mangrove ecosystem, which experiences more than two cyclones per year, was chosen as the research area. The study evaluated the loss and recovery of mangrove ecosystem GPP after direct-impact cyclones using a vegetation photosynthesis light-use efficiency model based on eddy covariance observation data. The findings showed that cyclones affect mangrove ecosystem GPP through photosynthetic area and rate, with the rate recovering before the area. The loss of GPP is inversely proportional to the distance to the center of the cyclone and the coastline. Factors such as canopy height, diameter at breast height, and tree stand aspect significantly influence the response of mangrove ecosystem GPP to cyclones. However, further analysis is needed to understand the response variations based on mangrove community compositions, soil conditions, planting densities, cyclone frequencies, and intensities. This study is expected to provide technical and data support for the protection of blue carbon in a subtropical island mangrove ecosystem in response to extreme events and post-disaster recovery.