Abstract: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.
