College of Mechanical and Electrical Engineering, Northeast Forestry University, Harbin 150040, China; Department of Forest Resources Management, University of British Columbia, Vancouver, Canada.
Department of Forest Resources Management, University of British Columbia, Vancouver, Canada.
Sci Total Environ. 2024 Nov 15;951:175540. doi: 10.1016/j.scitotenv.2024.175540. Epub 2024 Aug 14.
Given global climate change and the projected increases in the greenhouse effect, enhancing the carbon storage capacity of forest ecosystems is especially critical. To fully realize the potential carbon sequestration, it is imperative to understand the drivers affecting carbon storage in forest ecosystems, particularly with disturbances that disrupt existing balance. In this study, we explored the effects of stem-only harvest at various thinning intensities on forest structure and carbon density in middle-aged natural secondary forests, located in the northern temperate zone. Carbon density included aboveground carbon density (ACD), soil organic carbon stocks (SOCD), and total carbon density (TCD), which was the sum of ACD and SOCD. We employed the random forest analysis method to identify significant variables influencing changes in carbon density. Structural equation modelling (SEM) was then used to determine the drivers of changes in forest carbon density. The results showed that moderate thinning (20 %-35 % trees removed), is an effective management practice for increasing the TCD in forests. Although heavy thinning (35.1 %-59.9 % trees removed) accelerated individual growth, it did not fully offset the carbon removed due to thinning. It is noteworthy that light thinning (0-19.9 % trees removed) not only reduced the species richness but also caused a significant number of tree deaths. Large live trees were an important direct determining factor of ACD, but not the only one. In addition, thinning indirectly influenced ACD by reducing canopy density and deformed tree density. The increase in dead tree density had an adverse impact on SOCD, and this phenomenon increased with the passage of recovery time. Conversely, greater thinning intensity enhanced SOCD. Moreover, TCD was directly influenced by tree height, large live trees, and stand density. Furthermore, thinning altered the conifer ratio, thereby influencing tree growth and indirectly controlling the TCD. We believe that this knowledge will be highly beneficial for successful forest management and enhancing the carbon sequestration capacity of forest ecosystems.
鉴于全球气候变化和预计的温室效应增加，增强森林生态系统的碳储存能力尤为关键。为了充分实现潜在的碳固存，必须了解影响森林生态系统碳储存的驱动因素，特别是那些破坏现有平衡的干扰因素。在这项研究中，我们探讨了在不同疏伐强度下仅伐树干对位于北温带的中龄天然次生林的森林结构和碳密度的影响。碳密度包括地上碳密度（ACD）、土壤有机碳储量（SOCD）和总碳密度（TCD），即 ACD 和 SOCD 的总和。我们采用随机森林分析方法来识别影响碳密度变化的显著变量。然后，我们使用结构方程模型（SEM）来确定森林碳密度变化的驱动因素。结果表明，适度疏伐（去除 20%-35%的树木）是增加森林 TCD 的有效管理实践。虽然重度疏伐（去除 35.1%-59.9%的树木）加速了个体生长，但并未完全抵消因疏伐而去除的碳。值得注意的是，轻度疏伐（去除 0-19.9%的树木）不仅降低了物种丰富度，而且导致大量树木死亡。大活立木是 ACD 的一个重要直接决定因素，但不是唯一因素。此外，疏伐通过降低林冠密度和变形树密度间接影响 ACD。死树密度的增加对 SOCD 产生了不利影响，而且随着恢复时间的推移，这种现象会加剧。相反，更大的疏伐强度增强了 SOCD。此外，TCD 直接受树高、大活立木和林分密度的影响。此外，疏伐改变了针叶树比例，从而影响树木生长，并间接控制 TCD。我们相信，这些知识将对成功的森林管理和增强森林生态系统的碳固存能力非常有益。
