Seedling composition and its interannual dynamics of woody plants in karst evergreen deciduous broadleaved mixed forest

  Objective  The study of seedling regeneration is of great significance to reveal the mechanism of community regeneration and the distribution pattern of vegetation patches.

  Method  Based on the 1.28 ha fixed sample plot of karst evergreen deciduous broadleaved mixed forest in Maolan National Nature Reserve of southwestern China, the seedlings with DBH < 1 cm in 128 sample plots (1 m × 1 m) were investigated for three years. We analyzed the species, quantity, germination and death characteristics of woody plant seedlings in the forest community, and explored the annual distribution pattern of seedlings of main tree species.

  Result  (1) There were significant differences in the number and species composition of woody plant seedlings between different years. A total of 971 seedlings (8 plant/m²) were found in 2017, belonging to 55 families, 96 genera and 121 species; 767 seedlings (6 plant/m²) were found in 2018, belonging to 40 families, 66 genera and 78 species; and 1 342 seedlings (10 plant/m²) were found in 2019, belonging to 39 families, 70 genera and 87 species. Among them, the woody vine seedlings were important components of seedlings under the forest. (2) Main tree species composition of seedlings under forest was similar to that of main tree species in the sample plot, and also maintained the dominant position under the forest. (3) The number of individuals and species of woody plant seedlings showed a partial peak at the height classes, which reached the highest at the 10−20 cm height classes and then decreased gradually, indicating that there was a certain negative density dependence on the seedlings. (4) The number of individuals and species of woody plant seedlings increased with the increase of elevation and slope, and the density of woody plant seedlings showed a complex patch distribution.

  Conclusion  There are abundant species of woody plant seedlings under Maolan karst evergreen deciduous broadleaved mixed forest, showing complex patch distribution in space, and there is a certain negative density restriction effect due to the significant influence of altitude and slope. The long-term monitoring of seedlings will help us to understand the process of community renewal more accurately, and provide a basis for the rational protection and scientific management of karst forest in the future.