Unveiling Distribution Patterns and Community Characteristics of Rare and Endangered Plants in the Sanya River Basin, China

Wetlands have an important ecological function and economic value. However, with economic development and urban expansion, wetland plants have suffered serious damage. Rare and endangered plants are "thermometers" that reflect the health processes of their ecosystems. To better protect the wetlands in Sanya, China, we systematically investigated and analyzed the species, quantities, distributions, and community characteristics of the rare and endangered plants in the Sanya River basin using the sample and sample strip methods. We established a total of 152 quadrats, of which 46 contained rare and endangered plants. We identified 27 rare and endangered plants that mainly appeared in the tree and shrub layers. The dominant families and genera of the community were evident. However, the proportion of families and genera with fewer or single species was high, indicating that the species composition of the community is complex, and the plant species diversity is rich. The dominant species in each layer of the community were evident, and the rare and endangered plants are occasional species of the community. The community similarity in the urban areas was high, indicating that the rare and endangered plants in these areas require highly homogenous habitats. The community similarity in the suburbs was low, indicating that the rare and endangered plants in these areas are highly adaptable to different habitats. Threat factors and vegetation coverage degree had a significant impact on the number of species and population size of rare and endangered plants. Finally, according to our study and IUCN classification criteria for the endangered levels, Sonneratia x gulngai meets the CR (Critical Endangered) assessment criteria, thus we recommend upgrading it to the endangered level from VU (Vulnerable).