Controls of seasonality and altitude on generation of leaf water isotopes

Abstract. Stable oxygen and hydrogen isotopes (δ18O and δ2H) of leaf water which bridges between hydrological processes and plant-derived organic materials that vary spatially and temporally. It is crucially critical to study what controls the δ18O and δ2H values of leaf water for a wide range of applications. Here, we repeatedly sampled soil water, stem water, and leaf water along an elevation transect across seasons on the Chinese Loess Plateau, and analyzed the variations of in the δ18O and δ2H values from precipitation, soil water, stem water, and ultimate leaf water. We found a consistency in the δ18O and δ2H values from in precipitation, soil water, stem water, and leaf water across seasons. , indicating that leaf water can record well the isotopic signals of precipitation well. Importantly, leaf water isotope lines are were generated by the first-order control of source water (soil water and precipitation) associated with seasonality and altitude, and as well as the secondary control of hydroclimate and biochemical factors resulting in weak correlations of the δ18O and δ2H values in leaf water. This study is helpful to better understandimproves our understanding of the generation of leaf water isotopes.