Carbon storage capacity of monoculture and mixed-species plantations in subtropical China

Mixed-tree plantations can be a good silvicultural alternative to large-scale monoculture coniferous plantations for climate change mitigation, which is facilitated by the sequestration of atmospheric carbon dioxide. To evaluate the impacts of tree species compositions on the carbon storage capacity of plantation ecosystems, we measured the above and belowground biomass, as well as the carbon content, in three 27-year old forest plantations of monoculture Castanopsis hystrix (CH stand), monoculture Pinus massoniana (PM stand), and mixed C. hystrix and P. massoniana (mixed CH/PM stand) stands. We developed an allometric equation to estimate tree carbon storage. The carbon storage levels of understory, litter, and soil components were also estimated. Results show that biomass is positively correlated with carbon storage. The ecosystem carbon storage of the mixed CH/PM stand (327.03 Mg ha−1) was higher than those of the CH (314.59 Mg ha−1) and PM (293.60 Mg ha−1) stands. The majority of carbon storage was found in the soil pool (84.73%, 63.54%, and 75.80% in the CH, PM and mixed CH/PM stands, respectively). Almost 40% of soil carbon at a depth of 0–60 cm was stored in the upper 20 cm of the soil pool. Except for the vegetation layer, each layer of the CH and mixed CH/PM stands consisted of a higher amount of carbon than did the layers of the PM stand. These findings suggest that mixed CH/PM plantation stands or valuable indigenous CH plantation stands more substantially improve carbon storage in litter, soil, and ecosystems than do monoculture PM plantation stands. The results also imply that developing valuable indigenous tree species is a good silvicultural option for enhancing carbon sequestration and valuable timber cultivation in subtropical China.

► Biomass is positively correlated with carbon storage.
► Mixed-tree plantation has a larger soil carbon stock than monoculture.
► Developing indigenous valuable tree species is a good silvicultural option for enhancing carbon stock and valuable timber.