【目的】人工林具有巨大的固碳潜力,在减缓全球气候变化方面发挥着重要作用。然而,作为土壤有机碳(SOC)的主要成分,颗粒有机碳(POC)和矿物结合有机碳(MAOC)在人工林发育过程中的积累与分布机制仍然不清楚。分析各碳组分对不同林龄水杉人工林土壤有机碳积累能力的相对贡献,可为全球气候变化背景下人工林的科学经营和管理提供依据。【方法】选取位于江苏东台林场的7、16、21、26、31、36、42和46 a等8个不同林龄的水杉(Metasequoia glyptostroboides)人工林为对象,每个林龄设置4个重复的野外定位调查样地,分别采集[0,20)、[20,40)、[40,60)、[60,80)、[80,100)cm土壤剖面的样品。通过测定各土层土壤的pH、铵态氮、硝态氮、总磷和有效磷含量等理化性质及各有机碳组分(POC和MAOC)的含量,研究水杉人工林发育过程中土壤POC和MAOC的变化特征。【结果】[0,20)cm土层中POC是土壤有机碳库的主要贡献层,人工林的林分发育过程促进了POC的积累;而[20,100)cm土层中土壤有机碳以MAOC为主,但MAOC对林分发育响应显著。随着林龄的增长,[0,20)cm土层的SOC稳定性降低,更容易被分解利用,而[20,100)cm土层的SOC稳定性更高,更有利于有机碳长久的储存。此外,相关性分析表明POC相比于MAOC对林分发育导致的环境因子的变化更敏感。【结论】随着人工林的生长发育,土壤有机碳的积累主要以POC的形式储存在表层[0,20)cm土壤中,并且在过熟林时期能最大限度地积累有机碳。显然,长期的人工林发育可以有效促进表层土壤有机碳不同组分的积累和固持。因此,延长人工林的主伐年龄可更好地发挥人工林对气候变化的减缓作用。

【Objective】Plantations play significant roles in mitigating climate change. Understanding the dynamics of soil organic carbon (SOC), particularly through its key components—particulate organic carbon (POC) and mineral-associated organic carbon (MAOC)—is crucial for predicting carbon sequestration in soil.【Method】This study investigated Metasequoia glyptostroboides plantations of varying ages (7, 16, 21, 26, 31, 36, 42 and 46 a) located in the Dongtai Forest Farm, Jiangsu Province. For each forest age, four replicated field plots were established, and soil samples were collected from five distinct depths: [0, 20), [20, 40), [40, 60), [60, 80), and [80, 100) cm. A range of soil physicochemical properties—including pH, ammonium nitrogen, nitrate nitrogen, total phosphorus, and available phosphorus—along with SOC fractions (POC and MAOC) were measured to examine the variation in POC and MAOC with the development of the plantations.【Result】POC in the [0, 20) cm soil layer was the dominant contributor to the soil organic carbon pool, and its accumulation was enhanced during the plantation’s development. Conversely, MAOC was the predominant fraction in the [20, 40) cm soil layer, but its response to stand age and development was less pronounced. As the forest age increased, the stability of SOC in the [0, 20) cm layer declined, making it more susceptible to decomposition and utilization. In contrast, SOC stability in the [20, 100) cm layers remained higher, supporting longer-term organic carbon storage. Correlation analysis revealed that POC was more responsive to environmental changes driven by stand development compared to MAOC.【Conclusion】As plantations mature, soil organic carbon accumulates primarily in the surface layer [(0, 20) cm] in the form of POC. The greatest accumulation occurs during the over-mature stage of the forest. Long-term plantation development significantly enhances the accumulation and retention of different fractions of surface soil organic carbon. Therefore, extending the primary cutting age of plantations would further optimize their role in mitigating global climate change.