The effects of anthropogenic aerosol on carbon uptake and allocation: A gradient study from Beijing metropolitan region, China

Background/Question/Methods

Aerosol reduces the amount of solar radiation reaching the earth’s surface, but increases the proportion of this radiation that is diffused. Number of researches found that CO₂ sink increased with aerosol loading under cloudless conditions, which is so called “diffuse radiation fertilization”. Changing in photosynthesis not only affects aboveground primary production, but also could cause cascading effects on belowground C cycle, such as soil respiration, microbial activity and soil carbon turnover. Although there is increasing attention on the diffuse radiation fertilization effect of aerosol, very few field studies have investigated how anthropogenic aerosol will affect plant C uptake and allocation. Aspen seedling and two different cultivars of soybean were planted at three study sites along an urban-rural aerosol gradient in Beijing metropolitan region in 2011. The responses of leaf chemistry, specific leaf area, carbon allocation among plant tissues and total biomass of the two species were measure. 

Results/Conclusions

We found that leaf production and total aboveground biomass of both species increased along the aerosol gradient, but root biomass and root/shoot ratio of two soybean cultivars decreased along the aerosol gradient. There were no significant difference in leaf chemistry (the concentrations of Chlorophylla a, Chlorophylla b, starch and phenolics) and specific leaf area among the three sites. Our preliminary results suggested that increased aerosol loading may stimulate aboveground growth and reduce belowground C allocation. However, this is a preliminary analysis based only on one year’s data. Further measurements are needed to test whether there is a causality relationship between aerosol loadings and vegetation C uptake/ allocation.