南亚热带3种阔叶树种人工幼龄纯林及其混交林碳贮量比较

如何通过优化造林模式来提高人工林生态系统碳贮量已受到广泛关注。以南亚热带8年生格木(Erythrophleum fordii)纯林(PE)、红锥(Castanopsis hystrix)纯林(PC)、米老排(Mytilaria laosensis)纯林(PM)及格木×红锥×米老排混交林(MECM)生态系统为研究对象,对其碳贮量及其分配特征进行了比较研究。结果表明:格木、红锥和米老排不同器官平均碳含量分别为512.4—561.7 g/kg,474.2—553.4 g/kg和512.8—556.3 g/kg。相同树种不同器官之间碳含量差异显著(P0.05)。各器官碳含量的平均值大小顺序为格木(539.3 g/kg)米老排(532.7 g/kg)红锥(515.3 g/kg)。不同林分间,灌木层、草本层和凋落物层碳含量均以米老排纯林最高,混交林(MECM)居次,红锥纯林和格木纯林最低;不同林分之间的土壤碳含量差异显著(P0.05),0—10cm,10—30cm,30—50cm和50—100cm土壤碳含量均以米老排纯林最高,红锥纯林居次,格木纯林和混交林(MECM)土壤碳含量最低。生态系统碳贮量大小顺序为米老排(308.0 t/hm2)混交林(182.8 t/hm2)红锥纯林(180.2 t/hm2)格木纯林(135.2 t/hm2),相同组分不同林分间以及相同林分的不同组分间均存在显著差异(P0.05),但混交林与红锥纯林间碳贮量总量无显著差异(P0.05)。造林模式对人工林碳贮量及其分配有显著影响,营建混交林有利于红锥和格木地上碳的累积,不利于土壤碳的固定,而营建纯林既有利于米老排生物量碳的吸收,也有利于土壤碳的固定。因而,对碳汇林造林模式的选择,应根据树种固碳特性而定。

Comparison of carbon storage in juvenile monoculture and mixed plantation stands of three common broadleaved tree species in subtropical China

Enhancement of the carbon storage of plantation ecosystems by optimizing afforestation patterns has been extensively researched. In the present study, we investigated carbon storage and allocation in an 8-year-old Erythrophleum fordii stand (PE), a Castanopsis hystrix stand (PC), a Mytilaria laosensis stand (PM), and a mixed E. fordii × C. hystrix × M. laosensis stand (MECM) in subtropical China. We showed that the average carbon contents of different organs in E. fordii, C. hystrix, and M. laosensis ranged from 509.0 g/kg to 572.4 g/kg, 474.2 g/kg to 553.4 g/kg, and 512.8 g/kg to 556.3 g/kg, respectively. We determined significant differences in carbon contents among different organs of the same tree species. Within the same organs, the average carbon contents of different stands were ranked as follows: E. fordii (539.3 g/kg) > M. laosensis (532.7 g/kg) > C. hystrix (515.3 g/kg). In the shrub, herb, and litter layers, the highest carbon contents among the four stands occurred in PM, followed by MECM, PC, and PE. The carbon contents of the 0-10 cm, 10-30 cm, 30-50 cm, and 50-100 cm soil layers differed significantly among the four stands and were the highest in PM, followed by PC, MECM, and PE. The ecosystem carbon storages were ranked as PM (308.0 t/hm²) > MECM (182.8 t/hm²) > PC (180.2 t/hm²) > PE (135.2 t/hm²). We determined significant differences in average carbon contents within and among stands (P < 0.05), but no significant differences in the total ecosystem carbon storage between MECM and PE (P > 0.05). Our results indicate that the mode of afforestation can markedly influence the carbon storage and allocation of plantations. In mixed stands, C. hystrix and E. fordii will benefit from an increase in aboveground biomass carbon, but not from accumulation of soil carbon. On the other hand, in monoculture, M. laosensis will benefit from the sequestration of aboveground biomass carbon and from accumulation of soil carbon. Therefore, the afforestation mode for carbon sequestration forests should be selected according to the carbon accumulation characteristics of the representative tree species.