An unprotected vulnerable relict subtropical conifer-: Its forests, populations, growth and endangerment by invasive alien plant species in China.

Relict subtropical coniferous forests in China face severe fragmentation, resulting in declining populations, and some are under significant threat from invasive alien species. Despite the crucial importance of understanding forest dynamics, knowledge gaps persist, particularly regarding the impact of invasive plants on vulnerable natives like . In this study, we investigated the impact of invasive plants on the regeneration of forests dominated by . , a subtropical relict species in southwestern China. For this purpose, we characterized forest dynamics of 160 forest plots featuring as the primary dominant species and determined whether the presence of invasive plants was correlated with regeneration of . We identified four distinct forest types in which was dominant. We found that radial growth of trees is faster in younger age-classes today than it was for older trees at the same age. The population structure of in each forest type exhibited a multimodal age-class distribution. However, three forest types lacked established saplings younger than 10 years old, a situation attributed to the dense coverage of the invasive alien . This invasive species resulted in a reduction of understory species diversity. Additionally, our analysis uncovered a significant negative correlation in phylogenetic relatedness (net relatedness index) between native and invasive alien plant species in eastern Yunnan. This suggests closely related invasive species face heightened competition, hindering successful invasion. Taken together, our findings indicate that successful establishment and habitat restoration of seedling/saplings require effective measures to control invasive plants.