Community distribution and landscape pattern of the mangrove on the Qi'ao Island, Zhuhai.
Objective: This study was aimed to analyze the structure of mangrove-forest community and its corresponding landscape characteristics, to provide valuable information for mangrove reforestation and protection, important for regional biodiversity conservation and ecological environment improvement in the future. Method: Using Qi'ao Island as the study area, based on the datasets from interpretation of remote sensing images and field investigation, spatial-distribution of the mangrove-forest communities, population dominance and landscape pattern after low temperature damages were investigated. Result: True mangroves are the dominant species in the study area, including two primarily exotic species (Sonneratia apetala and Sonneratia caseolaris) and three major local mangrove species, namely, Acanthus ilicifolius, Kandelia candel and Acrostichum aureum. Sonneratia apetala, with an area contribution of 85.17%, is absolutely the first dominant species. Other major species include Kandelia candel, Acrostichum aureum, and Acanthus ilicifolius community, with area contributions of 4.2%, 3.1%, and 2.65%, respectively. The total area contribution by the aforementioned species was 95.12%. Semi-mangrove plants primarily include Cerbera manghas, Heritiera littoralis and Pongamia pinnata, with relatively low importance. The biggest aggregation at population level was Laguncularia racemosa, followed by Pongamia pinnata. For other species, such as, Sonneratia caseolaris, Kandelia candel, Acrostichum aureum, Sonneratia apetala, and Acanthus ilicifolius, the aggregation was relatively weak. The highest aggregation at the community level was Sonneratia caseolaris and Sonneratia apetala, while the aggregation values for the communities of Acrostichum aureum, Excoecaria agallocha + Thespesia populnea were relatively low. Two exotic species, Sonneratia apetala and Sonneratia caseolaris, developed well in medium and shallow waters, which can inhibit the local species, Kandelia candel. Conclusion: The mangrove-forest communities in Qi'ao Island are dominated by the Sonneratia apetala, Kandelia candel, Acrostichum aureum, and Acanthus ilicifolius community. The investigation at both population and community levels showed that the mangrove forest in the study area is in aggregated distribution. The results suggest that in the future program for species introduction and mangrove reforestation, Sonneratia apetala and Sonneratia caseolaris should be moderately introduced, which can strengthen the local mangrove planting, protect mangrove species diversity, and maintain the balance of mangrove ecosystems.