In recent years, numerous rubber-based agroforestry systems, using a biological approach to enhance ecosystem services, have been developed. Intercropping rubber with Flemingia macrophylla, a leguminous shrub, has been widely established in rubber plantations area of China. 

Previous studies showed that greenhouse gas emissions in rubber and rubber-F. macrophylla systems would be affected by their plantation age. However, the effect of different-aged rubber and rubber-F. macrophylla systems on CO₂, N₂O, and CH₄ emissions from soils is unknown. 

In a study published in Forest Ecology and Management, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) investigated the effect of introducing F. macrophylla to different-aged rubber plantations on the emissions of CO₂, N₂O, and CH₄ in Xishuangbanna.  

They found that the emissions of CO₂, N₂O and CH₄ decreased as the trees aged in the rubber plantations. The introduction of F. macrophylla to different-aged rubber plantations significantly decreased CO₂ and CH₄ flux but increased N₂O flux. 

Furthermore, the CO₂ and N₂O fluxes were mainly affected by soil temperature at 10 cm depth, and CH₄ flux was mainly affected by both soil water content in the 0–10 cm soil layer and soil temperature at 10 cm depth. 

Moreover, they found that the rubber-leguminous shrub systems significantly improved soil organic carbon sequestration rate and reduced greenhouse gas emissions, relative to the same-aged rubber plantations. 

Decrease of CO₂ emissions is crucial for the reduction of greenhouse gas emissions in rubber plantations worldwide. 

"We therefore propose that rubber-leguminous shrub systems should be popularized in the rubber planting area for reducing greenhouse gas emissions," said Prof. TANG Jianwei, principal investigator of the study. 

Rubber-Flemingia macrophylla plantation in Xishuangbanna. (Image by LIU Changan) 

Sloping fields in the rubber–Flemingia macrophylla plantations. (Image by LIU Changan)