During the past decades, large areas of forests have been converted into rubber (Hevea brasiliensis ) plantations in Xishuangbanna, resulting in major alterations in ecosystem carbon (C) dynamics due to deforestation and soil erosion. However, information on the role of various-aged rubber plantations in the C sequestration including its latex C is still lacking. 

Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences examined the biomass C accumulation including latex C and C distribution in soil of five different-aged stands (7, 13, 19, 25 and 47 years old) of rubber plantations in Xishuangbanna.  

They found that the total biomass carbon stock and total net primary productivity had a close quadratic relationship with stand age. Regardless of stand age, about 68% of the C was stored in aboveground biomass, and latex net primary productivity contributed to approximately 18% of C sequestration. 

They found no significant correlation between soil organic C (SOC) stock and stand age, indicating fast organic C turnover in rubber soils. However, SOC stock in the 100 cm depth was age-independent, and decreased with soil depth for each stand. 

The total ecosystem C stock (TEC) increased by nearly 82.9% with stand age and would reach maximal value in a 54-year-old stand according to quadratic model including latex C, indicating a considerable C sequestration potential in rubber plantation. 

Regression analysis showed that rubber plantations have a potential role in improving the regional C budget in the long term, and thus they can be considered as alternative land use without affecting forest ecosystem C storage. 

The researchers suggest that further studies on ecosystem C stock of rubber plantations should include not only potential ecological issues associated with monocultures but also comparisons to mixed agroforestry systems in general. 

The study entitled "Carbon Stocks across a Fifty Year Chronosequence of Rubber Plantations in Tropical China" has been published in Forests.

Rubber plantation in Xishuangbanna (Image by LIU Chenggang)