Rubber (Hevea brasiliensis) is an  important tree crop that is propagated in Xishuangbanna. Although rubber cultivation improves local economic and social situations in Xishuangbanna, monoculture rubber plantations often cause various ecological problems. To decrease the negative effects of rubber plantations, the concept of ecological-economic rubber plantation (EERP) system was proposed. The EERP concept proposed that rubber plants are intercropped with other native economic plants, which would not only decrease the ecological impact of rubber plantations, but also maintain and potentially increase profitability, compared with rubber monoculture. One important step in the EERP system is the selection of appropriate species to intercrop with the rubber plants. Irradiance is an important resource for plants, with survival, growth, and reproduction all depending on it. 

In order to select the appropriate species and intercropping pattern in the EERP system, Dr. ZHENG Yulong of Xishuangbanna Tropical Botanical Garden (XTBG) and his collaborators compared the photosynthetic parameters of five economically important trees (Swietenia mahagoni, Coffea arabica, Mesua ferrea, Myristica yunnanensis and Paramichelia baillonii) at four irradiance levels. They aimed to determine the effects of irradiance on the photosynthetic system of the five species and the appropriate intercropping patterns for each species in an EERP system. 

They found that the irradiance level had a significant effect on the photosystem of the five species. Nitrogen allocation played an important role in acclimation to irradiance. In the EERP system, the planting pattern was site- and species-specific. The most suitable irradiance for Coffea arabica and Myristica yunnanensis  was 20–40%, which thus could be planted in the understory of adult rubber forest. In contrast, the other three species (Swietenia mahagoni, Mesua ferrea, Paramichelia baillonii) grew well in full irradiance. The researchers suggested that they be planted in sites that are inconvenient or uneconomic for rubber plantation. 

The study entitled “Shade tolerance and suitability of tree species for planting in rubber plantations” has been published online in Southern Forests: a Journal of Forest Science.