杉木火力楠混交林与杉木纯林土壤碳氮库研究

Comparison of soil organic carbon and nitrogen pool between mixed and pure forests of Chinese fir

通过实地调查取样和室内C、N元素分析仪的测定，比较了杉木纯林与杉木火力楠混交林的土壤碳库及垂直分布差异，结果显示：混交林的土壤有机碳含量比纯林高，其有机碳贮量比杉木纯林大17．57％，主要差异在枯枝落叶层，分别为3．620t·hm^-2和12．610t·hm^-2。有机碳富集指数20～40cm差异最大，混交林富集指数是纯林的1．18倍。混交林土壤有机碳贮量（79．460t·hm^-2）大于杉木纯林（67．583t·hm^-2），且均以表层（0～20cm）碳贮量为主。混交林的全氮含量高于纯林，C／N则低于纯林。这些差异主要是由不同林分凋落物数量和性质上的差异引起的。杉木和火力楠混交林比杉木纯林更有利于碳的贮存，人工造林应多发展混交林。

Based on the on-the-spot investigation and indoor analysis by CN dement analyzer, soil organic carbon pool was compared between pure forest of Chinese fir and mixed forest of Chinese fir and Michelia macclurei. The results showed that soil organic carbon content in the mixed forest was higher than that of the pure forest, and soil carbon pool in mixed forest was 17.57% higher than that of pure forest. The main difference occurred in forest floor, which contained 12. 610 t·hm^-2 and 3. 620 t·hm^-2organic carbon, respectively, because of differences in quantity and quality of litter-fall between the two forests. The most deference is that in 20-40 cm in the organic carbon enrichment index which of the mixed is 1.18 times as much as the pure. The Total of carbon store of the mixed （79. 460 t·hm^-2） is more than that of the pure （67. 583 t·hm^-2）, and they are mainly discovered in surface layer （0-20 cm）. The total nitrogen of the mixed is more than that of the pure, whereas its C/N is contrary. These differences are caused by the quantitative and qualitative variation between the two style forests. The results indicated that mixed forest is more advantageous than pure Chinese fir plantation in carbon sequestration, and mixed forest should be encouraged for afforestation.