Effect of floods on the δ(13)C values in plant leaves: a study of willows in Northeastern Siberia

Although stable carbon isotopic composition (δ(13)C) of plants has been widely used to indicate different water regimes in terrestrial ecosystems over the past four decades, the changes in the plant δ(13)C value under waterlogging have not been sufficiently clarified. With the enhanced global warming in recent years, the increasing frequency and severity of river floods in Arctic regions lead to more waterlogging on willows that are widely distributed in river lowland. To investigate the δ(13)C changes in plants under different water conditions (including waterlogging), we measured the δ(13)C values in the leaves of willows with three species, Salix boganidensis, S. glauca, and S. pulchra, and also monitored changes in plant physiology, under several major flooding conditions in Northeastern Siberia. The foliar δ(13)C values of willows varied, ranging from −31.6 to −25.7‰ under the different hydrological status, which can be explained by: (i) under normal conditions, the foliar δ(13)C values decrease from dry (far from a river) to wet (along a river bank) areas; (ii) the δ(13)C values increase in frequently waterlogged areas owing to stomatal closure; and (iii) after prolonged flooding periods, the δ(13)C values again decrease, probably owing to the effects of not only the closure of stomata but also the reduction of foliar photosynthetic ability under long period of waterlogging. Based on these results, we predict that plant δ(13)C values are strongly influenced by plant physiological responses to diverse hydrological conditions, particularly the long periods of flooding, as occurs in Arctic regions.