Variation of carbon storage by different reforestation types in the hilly red soil region of southern China

Reforestation is a mitigation option to reduce increased atmospheric carbon dioxide levels as well as its predicted climate change. As a result, several forestry-based carbon storage projects have been introduced in many countries. To quantify the dynamics of ecosystem carbon allocation as affected by different forest management practices, we measured the above- and belowground biomass accumulation over 14 years, as well as the tissue carbon concentrations of trees in four different types: three monospecific plantations of slash pine (Pinus elliottii) (SPP), Chinese fir (Cunninghamia lanceolata) (CFP), and tea-oil camellia (Camellia oleifera) (TCP) and one natural secondary forest (NSF) (Pinus massoniana and Cyclobalanopsis glauca). A regression equation was constructed using the diameter at breast height/basal diameter (DBH/BD) and elements of total tree biomass. The equation was subsequently utilized to estimate tree carbon storage. The carbon storage of understory, forest floor, and soil components was also estimated. Results indicated that NSF stored significantly more carbon (141.99 t/ha) than SPP (104.07 t/ha), CFP (102.95 t/ha), and TCP (113.09 t/ha). Most of the carbon was found in the soil pool (60.30% in SPP, 70.42% in CFP, 63.87% in TCP, and 59.36% in NSF). In addition, more than 60% of the soil carbon storage at 0–100 cm depth was stored in the upper 40 cm. With the exception of trees, each component of NSF, including the understudy, forest floor, and soil, possessed significantly higher carbon storage than that of the three plantations (p < 0.05). Soil surface disturbance during forest management practices was one of the main factors reducing the soil and understory carbon storage of tree plantation stands. These results suggest that natural restoration is a superior approach for increasing the carbon storage potential in the hilly red soil region in reforestation projects compared to plantations. In addition, reducing soil surface disturbance during forest management practices might also play an important factor in improving carbon sequestration potential in above tree plantations.