Effect of floods on the δ13C values in plant leaves: a study of willows in Northeastern Siberia

Although stable carbon isotopic composition (δ13C) of plants has been widely used to indicate different water regimes in terrestrial ecosystems over the past four decades, the changes in the plant δ13C 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 δ13C changes in plants under different water conditions (including waterlogging), we measured the δ13C 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 δ13C 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 δ13C values decrease from dry (far from a river) to wet (along a river bank) areas; (ii) the δ13C values increase in frequently waterlogged areas owing to stomatal closure; and (iii) after prolonged flooding periods, the δ13C 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 δ13C values are strongly influenced by plant physiological responses to diverse hydrological conditions, particularly the long periods of flooding, as occurs in Arctic regions

Short-term root and leaf decomposition of two dominant plant species in a Siberian tundra

In tundra ecosystems, global warming is expected to accelerate litter decomposition and to lead to shifts in vegetation composition. To understand these shifts, it is important to understand the interactions between global warming, vegetation composition, litter quality and decomposition in the tundra. In addition, it is important to consider root litter since roots are the major part of plant biomass in the tundra. In order to increase our understanding of decomposition, and root decomposition in particular, we performed a litter transplant experiment in northeastern Siberia, in which we measured mass loss for leaf and root litter (live and dead material) of the two dominant plant species, graminoid Eriophorum vaginatum and shrub Betula nana, in three vegetation types (E. vaginatum or B. nana dominated and mixed vegetation) during the growing season.Our results show that although leaf decomposition did not differ between the two species, root decomposition showed significant differences. Mass loss of live roots was higher for E. vaginatum than for B. nana, but mass loss of E. vaginatum dead roots was lowest. In addition, we found evidence for home-field advantage in litter decomposition: litter of a plant decomposed faster in vegetation where it was dominant. Mass loss rates of the litter types were significantly correlated with phosphorus content, rather than nitrogen content. This indicates that phosphorus limits decomposition in this tundra site.The low decomposition rate of B. nana live roots compared to E. vaginatum live roots suggests that the acceleration of decomposition in the Arctic may be partly counteracted by the expected expansion of shrubs. However, more information on litter input rates and direct effects of climate change on decomposition rates are needed to accurately predict the effects of climate change on carbon dynamics in tundra ecosystems.</p

Inter-annual variation in CH4 efflux and the associated processes with reference to delta-13C-, delta-D-CH4 at the Lowland of Indigirka River in Northeastern Siberia

第6回極域科学シンポジウム分野横断セッション：[IA] 急変する北極気候システム及びその全球的な影響の総合的解明―GRENE北極気候変動研究事業研究成果報告2015―11月19日（木）　国立極地研究所１階交流アトリウ

Methane Oxidation Potential of Arctic Wetland Soil of a Taiga-Tundra Ecotone in Northeastern Siberia

第6回極域科学シンポジウム分野横断セッション：[IA] 急変する北極気候システム及びその全球的な影響の総合的解明―GRENE北極気候変動研究事業研究成果報告2015―11月19日（木）　国立極地研究所１階交流アトリウ