Water use characteristics of different pioneer shrubs at different ages in western Chinese Loess Plateau: Evidence from δ2H offset correction

Caragana korshinskii Kom. and Tamarix ramosissima Ledeb. are pioneer shrubs for water and soil conservation, and for windbreak and sand fixation in arid and semi-arid areas. Understanding the water use characteristics of different pioneer shrubs at different ages is of great importance for their survival when extreme rainfall occurs. In recent years, the stable isotope tracing technique has been used in exploring the water use strategies of plants. However, the widespread delta 2H offsets of stem water from its potential sources result in conflicting interpretations of water utilization of plants in arid and semi-arid areas. In this study, we used three sets of hydrogen and oxygen stable isotope data (delta H-2 and delta O-18, corrected delta H-2(_c1) based on SW-excess and delta O-18, and corrected delta H-2(_c2) based on -8.1 parts per thousand and delta O-18) as inputs for the MixSIAR model to explore the water use characteristics of C. korshinskii and T. ramosissima at different ages and in response to rainfall. The results showed that delta H-2(_c1) and delta O-18 have the best performance, and the contribution rate of deep soil water was underestimated because of delta H-2 offset. During the dry periods, C. korshinskii and T. ramosissima at different ages both obtained mostly water from deeper soil layers. After rainfall, the proportions of surface (0-10 cm) and shallow (10-40 cm) soil water for C. korshinskii and T. ramosissima at different ages both increased. Nevertheless, there were different response mechanisms of these two plants for rainfall. In addition, C. korshinskii absorbed various potential water sources, while T. ramosissima only used deep water. These flexible water use characteristics of C. korshinskii and T. ramosissima might facilitate the coexistence of plants once extreme rainfall occurs. Thus, reasonable allocation of different plants may be a good vegetation restoration program in western Chinese Loess Plateau.

Automated summary

This study explored the water use characteristics of different age groups of pioneer shrubs in response to extreme rainfall using stable isotope tracing technique. The results showed that plants obtained water from different soil layers and had different response mechanisms to rainfall. Therefore, reasonable allocation of different plants may be a good choice for vegetation restoration in the Loess Plateau.