Wetland Plant Taxonomic Diversity in the Middle Reaches of the Yellow River

Thirteen typical wetland sites located between Yumenkou and the Fenhe River estuary in the middle reaches of the Yellow River were investigated, with the taxonomic index used to measure species diversity. Results showed that a total of 75 species, belonging to 61 genera, 23 families, 18 orders, three classes and two phyla were recorded from the 13 sites. At the phylum level, 73 species were mainly distributed in Angiospermae. At the class level, 57 species were mainly distributed in Dicotyledons. At the family level, 36 species were mainly distributed in Leguminosae, Compositae and Gramineae. At the genus level, 12 species were mainly distributed in Chenopodium, Lespedeza, Artemisi and Typha. Annual or biennial plants were the most abundant, closely followed by chamaephytes, hemicryptophytes and geophytes, and the life-form spectra reflected the hot rainy summers and cold dry winters of the middle reaches of the Yellow River. Plant species diversity was studied using average taxonomic distinctness (Δ ⁺ ) and variation in taxonomic distinctness (Λ ⁺ ), and the expected values of Δ ⁺ and Λ ⁺ were 84.25 and 425.43, respectively. Using bivariate analysis to evaluate Δ ⁺ and Λ ⁺ together showed that the expected value of plot S12 located at the Fenhe River estuary was the lowest, while the expected values of plots S8, S9 and S10 were higher, showing that the taxonomic diversity index of species was larger and the distribution of species was more uniform in S12 than that found in S8, S9 and S10. Pearson's test results showed that Δ ⁺ ,Λ ⁺ and the Shannon-Wiener, Pielou, Simpson and Patrick indices were not correlated (P > 0.05).