Impact of underplanting on carbon storage in Cunninghamia lanceolata plantations

This study aims to systematically evaluate the relationship between tree underplanting intensity and carbon storage in Cunninghamia lanceolata plantations, explore the effects of underplanting tree species number and diversity on carbon storage, and to provide theoretical support for optimizing the management model of Cunninghamia lanceolata plantations. Experiments with different underplanting intensities and tree species combinations were conducted to identify the optimal underplanting strategy that balances carbon sequestration and forest biomass gain.

The study selected Cunninghamia lanceolata plantation sample plots in four typical subtropical regions of Hunan Province. These plots were grouped according to different underplanting intensities (no underplanting, low-intensity underplanting, medium-intensity underplanting, and high-intensity underplanting), and biomass and carbon storage were monitored over two years. The study measured the diameter at breast height (DBH), tree height, and biomass of underplanted species, and analyzed the relationship between underplanting intensity and carbon sequestration through carbon storage calculations.

The results showed that underplanting intensity significantly affects the changes in carbon storage in Cunninghamia lanceolata plantations. Medium-intensity underplanting (20-50 trees) not only significantly enhanced the growth rate of individual tree biomass but also promoted an increase in carbon storage while maintaining a relatively high carbon stock. Specifically, the carbon storage growth rate in medium-intensity underplanting plots was significantly higher than that in plots without underplanting. Additionally, the diversity of underplanted species contributed differently to the carbon storage, with fast-growing species such as Phoebe zhennan (Minnan) and Michelia compressa (Wood oil camphor) playing a prominent role in enhancing the carbon sequestration capacity of the community.

Medium-intensity underplanting effectively promotes the increase of carbon storage in Cunninghamia lanceolata plantations and provides scientific basis for diversified forest management. Future studies should optimize underplanting schemes according to different ecological conditions and tree species characteristics, balancing carbon sequestration and biodiversity enhancement, thereby achieving a dual improvement in forest productivity and carbon storage.