Natural secondary Carya dabieshanensis forests comprise the natural wealth of the Dabie Mountains, which maintain the ecological balance of this region and enhance the incomes of farmers. However, forest ecosystems are being increasingly challenged due to increasing long-term anthropogenic development and management. Elucidating the impacts of management intensity and duration on the diversity and stability of vegetation communities in natural secondary Carya dabieshanensis forests is of great significance toward achieving sustainable forest management. For this study, we compared the effects of three forest management intensities (no management (CK), extensive management (EM), and intensive management (IM)), and five management durations (0, 3, 8, 15, and 20 y) on species diversity and the stability of vegetation communities (trees, shrubs, and herbaceous layers) of a Carya dabieshanensis forest. Our results revealed that the diversity of the vegetation communities continued to decline following the onset of management activities. The diversity, dominance, evenness, and richness indices of the vegetation communities decreased by 53.37%–62.77%, 46.04%–59.17%, 32.58%–53.55%, and 50.18%–51.30%, respectively, after 20 y of forest management. Intensive management translated to species diversity loss more so than extensive management. All vegetation communities of the forest stands under study were generally unstable; however, the stability they did have was not at risk under greater management intensity and duration, and neither did greater species diversity enhance it. This study provides new evidence to support the non-synchronicity of species diversity and community stability in forest resident vegetation communities. Since the species diversity and structural composition of tree layers have a positive effect on community stability, so we suggest that both extensive and intensive forest lands need to retain or replant more tree species other than Carya dabieshanensis.

Overstory and understory vegetation play a vital role in forest ecosystem functionality. However, it is necessary to enhance the knowledge of their diversity and compositional dynamics following cessation of disturbance, which is required to inform restoration approaches and the mechanisms required for maintaining disturbance cessation. We conducted a chronosequence spanning 0–1, 5–6, 11–12, 20–24, and 28–34 years since disturbance cessation, and old-growth forests to investigate the dynamic changes in overstory and understory vegetation diversity and composition, as well as maintenance mechanisms following the cessation of anthropogenic disturbances in subtropical regions of Eastern China. The current study results indicated a decrease in understory cover and periodic fluctuations in the diversity of overstorey and understory vegetation following disturbance cessation efforts. Specifically, the shrub layer exhibited the highest richness in 28–34 years, while the herb layer showed the lowest evenness. Multivariate analysis using multiple-response permutation procedures indicated that the species composition and interspecific quantity ratio of understory plants in the forest at 28–34 years significantly differ from those in the early closure stage. An indicator species analysis revealed that more support was given to sun-loving plants after 0–1 years of the enclosure, while species with shade tolerance and low nutrient requirements were supported after 28–34 years. The structural equation model results show that 38.8% of the impact on herb evenness was related to light and substrate diversity. The ecological restoration time mainly indirectly affects understory vegetation by influencing the upper vegetation, light availability, and substrate heterogeneity. Overall, this study revealed that cessation of anthropogenic disturbance can maintain and care for understorey plant diversity and contribute to the sustainable management of forests.

Ecological restoration and biodiversity are currently hot issues of global environmental concern. However, knowledge about the specific impacts of restoration duration on understory vegetation diversity remains limited. Therefore, this study comprehensive employed a spatial approach to compare the differences in understory plant diversity and species composition among secondary forests with varying ecological restoration ages (0, 10, 30, 60, and 90-year-old stands) in Huangfu Mountain National Forest Park. This methodology allowed us to clarify the key factors affecting the composition of the understory plant community and investigate the regulatory mechanisms influencing changes in understory plant diversity. The results showed that shrub Shannon’s index value, shrub evenness, herb Shannon’s index value, herb richness, and herb evenness were significantly affected by the years of restoration, with 10 years and 90 years being the highest and 60 years being the lowest. Substrate diversity was the main factor influencing plant diversity in the shrub layer. Overstory richness, soil C/N, soil C, soil N, soil bacterial Observed OTUs, soil bacterial Chao1, soil bacterial Pielou_e, and substrate diversity were the drivers of plant diversity in the herb layer. Overstory evenness had a direct effect (0.256) and an indirect effect (0.284) on herb evenness through light availability and fungal Simpson’s index value. Light availability directly negatively affected herb evenness (−0.360). In addition, 52.6% of the factors affecting the herb evenness index were from the arboreal layer evenness, light availability, and fungal Simpson’s index value. To sum up, moderate disturbance of the understory environment of natural secondary forests can be carried out after 10 years of restoration, which is more conducive to the increase of understory plant diversity. This comprehensive study provides a theoretical basis for formulating ecological restoration measures for secondary forests, particularly in understanding the optimal timing and nature of disturbance in the restoration process, reassuring the audience about the validity and reliability of the findings.