连续年龄序列桉树人工林碳库

Carbon pools in an age sequence of Eucalyptus plantation forests

随着桉树人工林栽培面积的扩大,桉树人工林对生物多样性与土壤过程的影响,引发学术界的广泛讨论,更值得关注是的短论轮伐期桉树人工林对森林碳汇增加的贡献缺乏定量化的评估。因此,要合理评价桉树人工林对于生态系统碳吸存的影响,开展野外定位研究十分必要。正是基于这种考虑,项目组对闽南山区连续年龄序列(2a、3a、4a、5a、6a)的尾巨桉人工林碳库进行了分析,以空间替代时间的方法探讨了桉树人工林生长发育过程中的碳库动态,以期对桉树人工林可持续发展提供理论指导。研究结果显示:连续年龄序列桉树人工林生态系统碳库总量分别为152.88、199.97、241.67、221.94和210.95t·hm-2,表现为先期随年龄增加而增加,4年生后则出现下降趋势。其中乔木层C储量次为20.49、32.57、41.86、49.84和83.16 t·hm-2,占总贮量的13.54%～30.09%;林下植被C贮量分别为2.24、2.97、2.46、1.76和4.01 t·hm-2,占3.39%～9.74%;地被物C贮量分别为1.76、2.49、1.44、2.19和6.43 t·hm-2,占0.60%～3.05%;土壤C贮量所占比例最大(56.96%～84.17%),且主要分布在0-40 cm土层。各年龄段桉树人工林生态系统净初级生产力分别为22.86、26.07、32.64、32.71和46.69 t·hm-2.a-1,年固C量分别为10.37、11.72、14.98、15.02和21.51 t·hm-2.a-1,表现为固碳能力随林龄的增大而增大。由此可见,大力发展集约经营的桉树人工林,是解决大气中CO2浓度升高,缓解温室效应潜在的重要途径之一。

Abstract： During the last decades, the area of Eucalyptus plantations has expanded quickly in southern China. Plantations of Eucalyptus on understory biodiversity and soil processes have received extensive attention, however, their effects on ecosystem carbon storage are still unclear. It is necessary to evaluate the potential carbon sequestration by Eucalyptus plantations based on the field experiment and investigation. The carbon pools in an age sequence （2-, 3-, 4-, 5-, and 6-years-old） of eucalyptus plantations were analyzed in the mountainous region of southern Fujian, China, to estimate the changes of carbon sequestration with increasing stand ages. The results indicated that the total carbon pools in the eucalyptus plantation ecosystems were 152.88, 199.97, 241.67, 221.97 and 210.95 t.hm-2, respectively, in the 2-, 3-, 4-, 5-, 6-year-old plantations, suggesting carbon accumulation increased with age from the 2-to 4-year-old plantations, but decreased thereafter. The carbon storage was estimated at 20.49, 32.57, 41.86, 49.84 and 83.16 t·hm-2, respectively, for trees, accounting for 13.54%~30.09%of the total ecosystem carbon pools;at 2.24, 2.97, 2.46, 1.76 and 4.01 t·hm-2, respectively, for undergrowths, accounting for 3.39%~9.74%of the total;at 1.76, 2.49, 1.44, 2.19 and 6.43 t·hm-2, respectively, for forest floor, accounting for 0.60%~3.05% of the total. The amount of carbon stored in the soil was the largest C reservoir, making up 56.96%~84.17%of the ecosystem, especially in the topsoil （0~40 cm）. In the chronosequence of plantations, the net primary productivity was 22.86, 26.07, 32.64, 32.71 and 46.69 t·hm-2·a-1, respectively, with C accumulation of 10.37, 11.72, 14.98, 15.02 and 21.51 t·hm-2·a-1, respectively, indicating carbon sequestration increased with stand age. Our findings suggest that Eucalyptus plantations respresent an important carbon sink, which would be helpful to mitigate increasing atmospheric CO2.