[Applications of compound-specific isotope analysis in tree non-structural carbohydrates research: A review.]

Compound-specific isotope analysis (CSIA) can precisely determine the carbon isotopic composition (δ¹³C) of specific compounds in a complex substrate. The δ¹³C values in tree non-structural carbohydrates (NSC) compounds, e.g. sugars, organic acids, and sugar alcohols, measured via CSIA could help tracing the newly assimilated photosynthate during carbon transfer and exchange with atmosphere. Further, they can act as sensitive indicators of the physiological response of trees to environmental change. In this review, we first systematically introduced the methods of CSIA with respect to sampling, purification, and analysis. Then, compound-specific δ¹³C difference among different NSCs and across tree carbon pools, as well as temporal pattern and mechanism underlying the variation of δ¹³C were described. Finally, we discussed the interaction between δ¹³C in tree NSCs, the main substrates of respiration, and respired CO₂(δ¹³C_R). Further studies on the post-photosynthetic discrimination, tree stress physiology, and tree-ring δ¹³C formation with the promising applications of CISA were suggested.