Effect Of Waterlogging On Carbon Isotope Discrimination During Photosynthesis In Larix Gmelinii

Soil moisture is a major factor controlling carbon isotope discrimination (C-13), which has been demonstrated to decrease under dry conditions in many studies; however, few studies on C-13 under waterlogging condition have been conducted. In this study, a pot experiment was conducted with Larix gmelinii, a major larch species in the east Siberian Taiga, to investigate the effect of waterlogging on C-13 during photosynthesis. Assimilation rate and C-13(RD) (instantaneous C-13 calculated with Rayleigh distillation equation) decreased drastically soon after waterlogging, followed by recovery in their values, which was caused by a change in stomatal conductance. Thereafter, assimilation rate decreased gradually, whereas C-13(RD) decreased more gently. These results were thought to be caused by the decrease in both stomatal conductance and carboxylation. Our results indicate that extreme wet events may cause a decrease in C-13, which is important information for detecting flooding events in the past using tree-ring isotope analyses and for studying impacts of flooding on plants in areas where waterlogging might occur.