The structure and species diversity of plant communities in ecological safety islands of urban Guangzhou

Abstract

The community structure and species diversity of natural and semi-natural plant communities in six ecological safety islands, located in urban Guangzhou, were studied by the sample-plot survey method. The results show that 495 species belonging to 145 families and 342 genera were recorded in the six ecological safety islands, which have a total area of 3.238hm 2. Among the 495 recorded species, 30 species are ferns belonging to 19 families and 15 genera; 10 species are gymnosperms belonging to 6 families and 8 genera; 90 species are monocotyledon belonging to 27 families and 68 genera; 365 species are dicotyledon belonging to 93 families and 241 genera. The geographical elements of the genera are mainly composed of tropical and subtropical types. In addition, 7 rare and endangered species belonging to 6 families and 7 genera were recorded, which fall into different protection grades. The rare and endangered species were mainly found in fengshui forest communities. The communities in the middle and later stage of succession had a complex vertical structure and most of the arbor layer could be divided into sub-layers. The communities in the initial stage of succession had a relatively simple structure. The Patrick Index varied from 22 to 100, whilst the Shannon-Wiener Index varied from 0.3861 to 3.0901. Values of between 0.1380 and 0.9261 were observed for the Simpson Index, while the Pielou Index (J sw) was between 0.1289 and 0.9427. A difference could be identified between the Sorenson Index and the Bray-Curtis Index. The Shannon- Wiener Index and the Patrick Index exhibited similar patterns, but the Simpson Index and the Pielou Index had different patterns. The index of β diversity showed that there was a high coefficient of community similarity among the fengshui forest communities. As the succession progressed, the β diversity of other communities would increase gradually. Plant communities in the ecological safety islands of urban Guangzhou are in positive succession with an increase in species diversity. As the distance between sample-plot and city center increases, the number of species, the proportion of native species, and the coefficient of community similarity also increase. In comparison with the typical southern subtropical zonal vegetation in Dinghushan, vegetation of the ecological safety islands in urban Guangzhou have similar floristic characteristics. In general, species diversity in the ecological safety islands of Guangzhou may not be as rich as that in Dinghushan. However, some communities in Guangzhou, with a longer succession history, have nearly reached the climax stage, with a rich diversity, and may be equivalent to the same stage in Dinghushan. Species diversity is affected by different habitat conditions, such as the spatial distance among vegetation patches, the distance between habitats and the city center, and human disturbance. In highly urbanized areas, by strengthening conservation, vegetation communities that have a similar structure and species diversity to the zonal climax community may develop.