甘肃亚高山云杉人工林生态系统碳、氮储量动态和分配格局

云杉是甘肃亚高山地区重要的造林树种,研究其生态系统碳、氮储量的动态变化和分配格局有利于评价云杉人工造林后的生态恢复效果。以甘南、定西地区不同林龄(包括幼龄林、中龄林、近熟林和成熟林)的云杉人工林为研究对象,共设置16块调查样地。在野外调查、样品采集和分析的基础上,估算了其生态系统的碳、氮储量。结果显示:云杉林乔木不同器官的碳含量相对稳定,氮含量则与器官类型有密切关系;同一土层不同龄级的土壤碳、氮含量无明显差异。从乔木层、灌木层、枯落物层到草本层碳氮含量比值依次减小,土壤层碳氮含量比值最低。该地区云杉人工林生态系统总碳、氮储量分别为257. 75—430.23 t/hm~2和20.50—29.88 t/hm~2。随着林龄的增加,植被层碳、氮储量增加显著,分别从15.5 t/hm~2和0.24 t/hm~2增加到143.51 t/hm~2和1.65 t/hm~2。土壤层(0—100 cm)碳、氮储量分别为242.23—367.79 t/hm~2和20.26—29.58 t/hm~2,在整个生态系统各龄级中所占比例均超过60%和90%。生态系统和土壤层(0—100 cm)碳、氮储量在不同龄级间无显著差异。生态系统中土壤层、乔木层及灌、草、枯落物层的碳储量比例分别为85.72%、13.44%和0.84%,氮储量比例分别为97.60%、2.08%和0.32%。

Dynamics and allocation patterns of carbon and nitrogen storage in Picea asperata plantations in subalpine areas of Gansu Province

Picea asperata is an important afforestation species in the subalpine region of Gansu Province. The estimation of carbon and nitrogen storage in P. asperata plantations is helpful to evaluate the ecological restoration effects after afforestation. To estimate the dynamics and allocation patterns of carbon and nitrogen storage, 16 field plots of different forest ages (including young forests, mid-aged forests, near-mature forests, and mature forests) in the P. asperata plantations in Gannan Tibetan Autonomous Prefecture and Dingxi City were established. Vegetation, litter, and soil were investigated and sampled for laboratory analyses. The results showed that carbon contents of different organs in the tree layer were relatively stable, while nitrogen contents were closely related to organ types. Carbon and nitrogen contents in the same soil layer had no significant difference among different stand ages. The ratio of carbon to nitrogen content was higher in tree layer than that in shrub, grass, and litter layer, and soil layer had the lowest ratio. In this area, the total storage of carbon and nitrogen in the ecosystem was up to 257.75-430.23 and 20.50-29.88 t/hm², respectively. As stand age increased, the biomass carbon storage increased from 15.51 to 143.51 t/hm² while the nitrogen in biomass increased from 0.24 to 1.65 t/hm². However, carbon and nitrogen storage in the soil (0-100 cm) was 242.23-367.79 and 20.26-29.58 t/hm², respectively, and showed no significant differences among stand age groups. Soil stored more than 60% of carbon storage and more than 90% of nitrogen storage in the total ecosystem in each age class. Carbon storage in soil layer, tree layer, and shrub/grass/litter layer accounted for 85.72%, 13.44%, and 0.84% of that in the whole ecosystem, while nitrogen storage in the corresponding layers were 97.60%, 2.08%, and 0.32%, respectively.