Abstract: In the last 30 years, China has achieved a great success in the increase of both forest area and stocking volume. However, a large scale of low-value forests, in terms of timber yield and ecological services, have appeared all over China, mainly resulted from illegal logging, inappropriate choice of tree species for specific site conditions, insufficient unit investment for forestation, poor quality of seedlings and lack of effective tending and forest management, as well as frequent natural disasters. In recent years, Chinese government has initiated and enhanced the improvement of low-value forests including establishing financial incentive mechanism, and formulated a quantitative target in the Guidelines on the National Forest Plan (2010-2020). However, few studies on the carbon sequestration potential of the improving low-value forests have been conducted. Through scenario analysis on the case of improving low-value Chinese fir and masson pine forests implemented in Southeast Guizhou Province, we found that the carbon sequestration potential of improving low-value forests depends highly on existing state of low-value forests, measures for improvement to be taken and the management goals. For the purpose of long-term timber forests (without final harvest within 30 years), apparent net carbon credits are expected relative to the baseline scenario. However, for the purpose of short-term industrial material or fast-growth timber forest, the net carbon credits are very limited, with a long-term carbon stock in the tree biomass in some cases even lower than the baseline scenario. Selective harvest would largely increase the long-term carbon stock and result in apparent net carbon credits relative to the baseline scenario. We concluded that for the purpose of carbon sequestration, especially for the carbon offsetting, short-rotation should be avoided. Long-term rotation and selective harvest or no harvest are desired measures in order to increase the long-term carbon stock.

Key words: improving low-value forest, carbon sequestration potential, scenario case analysis