Species and productivity relationships with altitudinal variation among different grassland types in the Burqin forest region of the Aletai Mountains

In this study, the species lists for 137 sample plots in five grassland types in the Burqin Forest region were investigated, and the variation characteristics of different grassland plant families and species were analyzed. In addition, the interrelationship between plant species diversity of different grassland types and aboveground biomass with their vertical variation characteristics were explored. The results showed: 1) desert steppe were dominated by Gramineae, Compositae, and Leguminosae; montane steppe and mountain meadows were dominated by Umbelliferae, Gramineae, and Liliaceae; Gramineae, Ranunculaceae, and Liliaceae were the dominant families in both mountain meadow steppe and alpine steppe, but in varying proportions. 2) The variation in plant numbers at the family-species level was characterized by: Mountane steppe > alpine meadow > mountane meadow steppe > desert steppe > mountain meadows. 3) Aboveground biomass and Alatalo evenness index were significantly and positively correlated only in desert steppe, and Simpson dominance index and aboveground biomass were only positively correlated in this region; with the exception of montane meadow steppe, aboveground biomass and Shannon-Wiener diversity index were significantly and positively correlated; the aboveground biomass and Margarlef richness index in desert steppe and mountain meadows were significantly and positively correlated; The aboveground biomass in desert steppe and montane steppe was significantly and positively correlated with the Margarlef richness index. 4) In the altitude range of 1100～2400 m, from low to high altitude, diversity indices of various species had a trend of increasing, decreasing, and increasing again; the aboveground biomass had a “V” pattern of decreasing and then increasing. In short, the study provided data to support the management and maintenance of grasslands in the Burqin Forest Area and the ecological security of grasslands in the northwest arid zone of China.