<b>Impact of Close-to-Nature Forest Management on Increasing Carbon Sequestration Rate in Chinese Pine (</b><b><i>Pinus tabuliformis</i></b><b>) Plantations on Loess Plateau, China</b>

<i>Pinus tabuliformis</i> plantations on the Loess Plateau face challenges such as poor quality and high mortality rates due to high initial value density and improper thinning practices. To prevent further deterioration of these forests, it is essential to identify suitable forest management methods as soon as possible. Within <i>Pinus tabuliformis</i> plantations under different management methods (Structure-Based Forest Management SBFM, Close-to-Nature Forest Management CNFM, and unmanaged), after five years of investigation, we analyzed the changes in forest structural complexity and growth partitioning over time using metrics of size inequality (Gini index), size-growth relationship (SGR), and growth dominance coefficient (GDC), and applied a linear mixed-effects model to evaluate the impact of these practices on stands. We also compared the variation trends of the average annual breast height area increment (BAI) and the carbon sequestration rate across all stands with different management methods. The results showed that: (1) Thinning management temporarily reduced the Gini due to the removal of a certain number of trees. However, the Gini rebounded significantly but did not return to pre-management levels during the study period. (2) In the unmanaged stands, changes in GDC and SGR indicated that larger trees contribute more to stand growth. After thinning, the changes in GDC and SGR reflected an increasing contribution of smaller trees to overall growth. (3) Thinning management increased BAI, and this effect became more pronounced over time. Notably, the average carbon sequestration rate under CNFM increased by 13%, which is higher than the 11% under SBFM. These research results provide a theoretical basis for managing and determining the trees to be harvested for high-density, low-quality <i>Pinus tabuliformis</i> plantations of the Loess Plateau.