Δ14CO2 from dark respiration in plants and its impact on the estimation of atmospheric fossil fuel CO2

Publication date: April 2017
Source:Journal of Environmental Radioactivity, Volumes 169–170
Author(s): Xiaohu Xiong, Weijian Zhou, Peng Cheng, Shugang Wu, Zhenchuan Niu, Hua Du, Xuefeng Lu, Yunchong Fu, George S. Burr
Radiocarbon (¹⁴C) has been widely used for quantification of fossil fuel CO2 (CO2ff) in the atmosphere and for ecosystem source partitioning studies. The strength of the technique lies in the intrinsic differences between the ¹⁴C signature of fossil fuels and other sources. In past studies, the ¹⁴C content of CO2 derived from plants has been equated with the ¹⁴C content of the atmosphere. Carbon isotopic fractionation mechanisms vary among plants however, and experimental study on fractionation associated with dark respiration is lacking. Here we present accelerator mass spectrometry (AMS) radiocarbon results of CO2 respired from 21 plants using a lab-incubation method and associated bulk organic matter. From the respired CO2 we determine Δ¹⁴Cres values, and from the bulk organic matter we determine Δ¹⁴Cbom values. A significant difference between Δ¹⁴Cres and Δ¹⁴Cbom (P < 0.01) was observed for all investigated plants, ranging from −42.3‰ to 10.1‰. The results show that Δ¹⁴Cres values are in agreement with mean atmospheric Δ¹⁴CO2 for several days leading up to the sampling date, but are significantly different from corresponding bulk organic Δ¹⁴C values. We find that although dark respiration is unlikely to significantly influence the estimation of CO2ff, an additional bias associated with the respiration rate during a plant's growth period should be considered when using Δ¹⁴C in plants to quantify atmospheric CO2ff.



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