南亚热带红锥、杉木纯林与混交林碳贮量比较

造林再造林作为新增碳汇的一种有效途径,受到国际社会的广泛关注。如何通过改变林分树种组成,优化造林模式提高人工林生态系统碳贮量已成为国内外学者关注的重点。通过样方调查和生物量实测相结合的方法,对南亚热带26年生红锥纯林(PCH)、杉木纯林(PCL)及红锥×杉木混交林(MCC)生态系统各组分碳含量、碳贮量及其分配特征进行了比较研究。结果表明:杉木、红锥各器官平均碳含量分别为492.1—545.7 g/kg和486.7—524.1 g/kg。相同树种不同器官以及不同树种的相同器官间碳含量差异显著(P0.05)。红锥各器官碳含量的平均值(521.3 g/kg)高于杉木(504.7 g/kg)。不同林分间地被物碳含量大小顺序为PCHMCCPCL;不同树种之间的土壤碳含量差异显著(P0.05),0—100 cm土壤平均碳含量为PCLMCCPCH。生态系统碳贮量大小顺序为PCL(169.49 t/hm2)MCC(141.18 t/hm2)PCL(129.20 t/hm2),相同组分不同林分以及相同林分的不同组分碳贮量均存在显著差异(P0.05)。造林模式对人工林碳贮量及其分配规律有显著影响,营建混交林有利于红锥生物量和土壤碳的累积,而营建纯林有利于杉木人工林生物量碳的吸收,也有利于土壤碳的固定。因而,混交林的固碳功能未必高于纯林,在选择碳汇林的造林模式时,应以充分考虑不同树种的固碳特性。

Comparison of carbon storage in pure and mixed stands of Castanopsis hystrix and Cunninghamia lanceolata in subtropical China

The focus has been on afforestation and re-afforestation as new methods for improving carbon sequestration, by optimizing the mode of afforestation and adjusting the forest tree species composition. Carbon content and storage of different components, including tree, shrub, herb, litter, and soil layers and their allocations of a 26-year-old Castanopsis hystrix (PCH), Cunninghamia lanceolata (PCL), and mixed C. hystrix × C. lanceolata (MCC) stands in subtropical China were studied using quadrat sampling combined with biomass measurements. The results showed that the average carbon content of different organs in C. lanceolata and C. hystrix were 492.1-545.7 g/kg and 486.7-524.1 g/kg, respectively. Significant differences were found among different organs in the same tree species(P<0.05). The average carbon content of C. hystrix(539.3 g/kg)was higher than C. lanceolata. Carbon content of the ground cover was PCH>MCC>PCL. Soil content in 0-100 cm showed significant differences among the three stands, which was ranked as PCL > MCC > PCH(P < 0.05). The carbon storage in the total ecosystem was ranked as PCL(169.49 t/hm²)> MCC(141.18 t/hm²)> PCH(129.20 t/hm². Significant differences were found among different components in the same stand, and among different stands of the same components (P<0.05). Afforestation significantly affected the carbon storage and allocation in plantations, and the mixed stand benefited from increased carbon biomass and soil carbon for C. hystrix; while monoculture stand benefited from the biomass and soil carbon for C. lanceolata Therefore, we should select the afforestation mode based on the carbon acumination characteristics of tree species regarding carbon sequestration forests, because mixed stands do not always fix more carbon compared with pure forests.