Cellulose δ18O as a hydrological proxy: A case study for willows growing in Indigirka river lowland, Northeastern Siberia

Abstract

During the last few decades, stable oxygen isotopic composition of cellulose (δ18Ocell) has been employed as a potential tool for understanding hydrological cycles on modern and past environments. In the present study, we measured the δ18O values of stem water (δ18Osw) and the δ18Ocell values of willows, which are growing on transects along the river with multiple water sources and different levels of humidity in Northeastern Siberia, further to evaluate the contribution of (1) the δ18Osw values, (2) the ratio of ambient/intercellular water (i.e., ea/ei), and (3) the δ18O values of water vapor (δ18Ov), to the δ18Ocell values. The results well demonstrate that the cross-plot of δ18Ocell/δ18Osw can be used to evaluate the contributions of δ18Osw values and ea/ei to the variation of δ18Ocell values. Also, the contribution of the δ18Ov values on the δ18Ocell values are significantly increased, where the water vapor near the plants is isotopically equilibrated to large water pools (e.g., rivers, lakes, ponds, etc.) rather than the source water (e.g., precipitation) of plants. Based on these findings, we predict that full consideration of the above (1)–(3) permits us to enhance accuracy in our understanding of plant δ18Ocell values with respect to hydrological cycles.