Characteristics of herbaceous plant diversity in the understory of Caragana korshinskii sand-fixing forest of Baijitan in Lingwu

Species composition of understory vegetation is important for the stability and ecological function of Caragana korshinskii forests. In this study, a spatial method rather than temporal method was used to investigate and analyze the species composition and diversity of understory herbs in C. korshinskii sand-fixing forests of different ages (3, 5, 10, 20, 30, 40, 50, 60, and 70 a) located at the southwest edge of Mu Us Sandy Land. The results showed that:1) In each planting year, the number of herb species was the lowest at 10 a and the highest at 40 a, and the total number of plant species reached 38 up to August 2023; 2) With an increase in stand age, the importance value of annual herbaceous plants gradually decreased, and that of perennial herbaceous plants gradually increased; 3) The richness, diversity, and evenness indices of herbage in the C. korshinskii forest changed uniformly between 3～10 a, and decreased with the increase in stand age. Richness increased with the increase in stand age between 10～40 a. Diversity and evenness indices also increased with the increase in stand age between 10～30 a, and all indexes stabilized between 40～70 a; and 4) The similarity index of the understory herbaceous community fluctuated greatly between 3 to 30 a, but after 30 a, the similarity coefficient index of the understory herbaceous community exhibited minimal variation and gradually stabilized. This indicates that the herb community in the C. korshinskii forest gradually stabilized after 30 a of its establishment. Cultivation of C. korshinskii is conducive to the restoration of the desert ecosystem, and its proper care and management after 30 a of cultivation will be conducive to the maintenance of herb diversity in the forest.