Tree species selection and plant diversity changes in vegetation restoration in the subtropical region of south China

This study systematically analyzed the adaptability, growth performance, and plant diversity of different tree species allocation modes during vegetation restoration in China's south subtropical region. The findings aim to provide a theoretical basis and practical support for understanding community succession mechanisms in vegetation reconstruction and restoration, and for scientifically guiding tree species selection and optimal allocation.

Multiple suitable tree species were introduced to establish four allocation modes: species selection mode (Tree allocation I), multi-species mixed forest with precious tree species (Tree allocation II), conifer-broadleaf mixed forest (Tree allocation III), and a control mode (CK) planted with Liquidambar formosana and Schima superba. Permanent plots were established, and continuous vegetation surveys were conducted in 2012 (pre-afforestation), 2016 (4 years after afforestation), and 2024 (12 years after afforestation), comprehensively recording vegetation growth, species composition, and community structure changes.

1) After nearly 12 years of vegetation restoration, 35 of the 63 initially planted tree species survived. Among them, 17 species, including Phoebe zhennan, Aquilaria sinensis, and Michelia macclurei, exhibited high survival rates and good adaptability. Among all surviving species, Pinus massoniana showed the fastest growth, with an average height of 8.7 m and average DBH of 17.1 cm. Tree Allocation III (conifer-broadleaf mixed forest), dominated by P. massoniana, performed outstandingly, with the basal area of planted trees being 5.2 times that of the control mode (CK), and the average tree height (7.4 m) and average DBH (12.6 cm) significantly higher than those of other allocation modes. 2) After 12 years of restoration, species composition was rich, including 77 woody plant species and 30 herb and shrub species. P. massoniana had the highest importance value (48.89), indicating its absolute dominance in the community as the dominant and constructive species, followed by S. superba, Castanopsis hystrix, and others. Among wild tree species, Rhodomyrtus tomentosa had the highest importance value (21.60), followed by Pinus elliottii, Cratoxylum cochinchinense, and others. In the herb-shrub layer, Dicranopteris dichotoma accounted for 78.0% of the total importance value of shrubs and herbs. 3) The Simpson diversity index (D), Shannon-Wiener diversity index (H′), and evenness index (J) for tree species were 0.942 9, 4.841 1, and 1.121 3, respectively, while for herbaceous species they were 0.154 5, 0.706 8, and 0.207 8, indicating a relatively high level of plant diversity.

In the selection of tree species for vegetation restoration in south subtropical regions, garden species and introduced species should be used with caution. If economic tree species are randomly mixed with other species for restoration without proper management, expected economic returns are unlikely to be achieved. For severely degraded ecosystems, selecting the pioneer species P. massoniana and mixing it with native broadleaf species can effectively accelerate vegetation reconstruction and restoration. After 12 years of restoration, a species-rich and structurally stable forest community of trees, shrubs, and herbs has initially formed.