The Nanling mountain region is a critical component of China's ecological security barrier. Its ecosystems are becoming increasingly fragile due to the dual pressures of human activities and natural disturbances, leading to prominent issues such as biodiversity loss and elevated ecological risks. So, there is an urgent need to develop restoration and security assurance technologies for degraded ecosystems to support regional sustainable development. Accordingly, this paper aims to review the current degradation status of natural forests and the research progress on ecological restoration technologies in the Nanling mountain region, thereby providing a scientific basis for forest ecosystem restoration and sustainable development. It is expected to promote the research and application of natural forest protection and ecological security technologies. Under the context of global climate change, this study systematically synthesizes relevant domestic and international literature to comprehensively analyze the driving factors of natural forest degradation, restoration technologies, and their practical effectiveness in the Nanling mountain region. The results indicate that natural disturbances such as ice-snow disasters are the primary causes leading to the destruction of stand structure and regressive succession of natural forests in the Nanling mountains, while anthropogenic disturbances such as bamboo expansion further exacerbate biodiversity loss and soil degradation. In the research and development of technologies for enhancing the functions and stability of degraded natural forest ecosystems, strengthening sprout management, close-to-nature mixed silviculture and intelligent decision-support systems can significantly enhance the efficiency of restoration technology application. Meanwhile, the synergistic model of classified management and carbon sink function plays a positive role in the increase of stand volume and the restoration of ecological functions. In summary, the findings provide technical support for the scientific restoration of degraded natural forests in the Nanling mountains, and have important theoretical and practical value for ensuring the continuous improvement of the ecological barrier function of the Nanling mountains.
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This paper discussed the growth differences and diameter structure distribution in the afforestation experiments with different stand densities, so as to provide theoretical references for the reasonable density cultivation of Cunninghamia lanceolata in a short-cycle plantation management mode.
This study took the 4-6 year old Cunninghamia lanceolata test forest in Xianning, Hubei Province as the research object, we compared and analyzed the distribution laws and effects of four different stand densities (A (2 500 tree /hm2), B (3 333 tree /hm2), C (4 444 tree /hm2) and D (6 666 tree /hm2)) on the DBH, tree height, single tree volume, volume per unit area and diameter structure of C. lanceolata seedlings.
The average DBH, average volume per tree and their annual growth as well as the mean of the annual growth decreased with the increase of density, and the decreasing range of the total growth increased with the increase of stand age. The effect of density on the average tree height of the stand was not significant, and its effect on the growth of the average DBH and volume per tree did not reach a significant level. The stand volume per unit area, its annual growth and average annual growth increased with the increase of density, and the difference among planting densities reached a significant level (P < 0.05). The density of stands B, C and D was 30.5%-128.0% higher than that of stand A, but the increase of B, C and D decreased with the increase of stand age. The distribution of stand diameter structure showed a single peak right deviation curve, with an overall large taper. The proportion of standing trees with a diameter ≥ 8 cm in the high-density stand was slightly smaller than that in the low-density stand, but the number of standing trees was significantly higher than that in the low-density stand (P <0.01). The number of standing trees with a diameter ≥ 8cm in the 6-year-old D-density stand was twice that in the A-density stand.
Afforestation density has no significant effect on average DBH, average height and average volume per tree of medium and young forests, while the volume per unit area and the number of standing trees with a diameter ≥ 8 cm have increased significantly in the high-density stand, indicating that high-density stands may yield more timber income.
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