Spatiotemporal dynamics of woody plant species diversity and aboveground biomass during near-nature forest reconstruction in Shanghai: A case study from the eco-island in Minhang District

Aims: Reconstruction of near-nature forests is an important approach to accelerate the recovery of urban vegetation and forest restoration. However, the spatial and temporal dynamics of species diversity, canopy structure, and biomass during the subtropical forest restoration remain unclear, especially in highly urbanized regions. Methods: Based on long-term subtropical near-nature forest plant community that planted with native tree species in 2006 in Minhang District of the megacity Shanghai, we did the resurvey of plant community in 2023, and compared with the compositional changes of plant community through five historical surveys of core plots from 2007 to 2023. Aboveground biomass and the relations among aboveground biomass, species richness and tree height across temporal and spatial scales were analyzed using general linear regression. Results: Along with near-nature forest succession, woody plant richness increased from 11 in 2007 to 18 in 2023, and stem density increased at early stages and then decreased. The aboveground biomass increased from 3.51 t/ha in 2007 to 208.83 t/ha in 2023. Evergreen tree species such as Camphora officinarum and Quercus myrsinifolia gradually became the dominant species. Aboveground biomass showed significant positive correlations with species richness (P < 0.01) and mean tree height (P < 0.001), and a significant negative correlation with stem density (P < 0.01). When comparing the compositional changes over space, at three scales of 5 m, 10 m and 20 m, the relations between aboveground biomass and stem density remained highly significantly positive (P < 0.001), but the relations with mean tree height shifted from no significant at 5 m scale to significantly negative at 10 m (P < 0.05) and 20 m (P < 0.05) scales. Conclusion: During the 17-year subtropical forest restoration, the model of near-nature forest construction has clearly exhibited its efficacy in accelerating the succession process. These preliminary findings suggest that, during the construction and restoration of near-nature forests, we should pay attention to the dominant role of native tree species, and consider diverse species composition to effectively promote plant diversity and carbon storage.