Aims: The forest dynamics plots have been used as an effective platform to study the mechanism of biodiversity maintenance and community assembly. The semi-humid evergreen broad-leaved forest (SHEBF) is the zonal vegetation in the Central Yunnan Plateau. Because of the long-term influence of human activities and natural disturbance such as wildfires, the original SHEBF communities have been mostly destroyed, and replaced by secondary vegetation types. The extreme shrinkage of this zonal vegetation has raised increasing concern of conservation. Based on three forest dynamics plots we established in the Central Yunnan Plateau, we aim to explore the general characteristics of SHBEF in its floristic composition, community structure and diversity
Methods: According to the Center for Tropical Forest Science (CTFS) standards at the Smithson Institute for Tropical Research, we established three forest dynamics plots (10 ha (500 m × 200 m), 8.24 ha (one subplot with 260 m × 240 m and two subplots with 100 m × 100 m), and 20.16 ha (720 m × 280 m)) as the data collection source of SHEBF from the following three areas: Zhujiangyuan (ZJY) in Qujing City, Diaoling Mountains (DLS) in Chuxiong City, and Jizu Mountains (JZS) in Dali City, respectively. The community data of the three forest dynamics plots were obtained using a portable backpack LiDAR and a laser rangefinder. We implemented floristic analysis, community classification, and community structure analysis for the communities in the plots.
Results (1) A total of 619 species of vascular plants belonging to 120 families and 355 genera were found in the three plots, including 70 families, 120 genera, 157 species in the ZJY plot, 92 families, 224 genera, 319 species in DLS plot, 100 families, 255 genera, 353 species in JZS plot. (2) A total of 103,951 woody individuals with DBH ≥ 1 cm were found in the three plots, including 24,932 individuals in the ZJY plot, 25,222 individuals in the DLS plot, 53,797 individuals in the JZS plot, with densities of 2,493, 3,061, and 2,690 ind./ha, respectively. (3) The proportion of temperate floras at the genus and species levels of all vascular plants in three plots was 51.3% and 24.7%, and the proportion of endemic species in plots was 33.0%. (4) The plant communities in plots were divided into eight alliances, Castanopsis orthacantha alliance, C. delavayi alliance, Lithocarpus craibianus alliance, L. dealbatus alliance, Pinus yunnanensis alliance, Cyclobalanopsis delavayi alliance, L. mairei alliance and Quercus senescens alliance; the DLS plot had the highest alliances diversity and ZJY plot the least. (5) The DBH class structure of tree species in the JZS plot and DLS plot were inverted “J” type, and unimodal in ZJY plot. The community data indicated that an intensive fire disturbance covered a part of the JZS plot 80-100 years ago, and a light-to-moderate disturbance swept across the DLS plot 50-80 years ago, and a stand replacing fire occurred the ZJY plot 36 years ago.
Conclusion: This study laid a foundation for long-term systematic monitoring of the SHEBF community based on the forest dynamics plots while providing a theoretical basis for the diversity protection of this vegetation type and the sustainable forest management.