Relationships between foliar carbon isotope discrimination with potassium concentration and ash content of the riparian plants in the extreme arid region of China

Carbon isotope discrimination (Delta) has been proposed as an indirect estimation criterion for water use efficiency in C-3 plants. Because of the higher cost for Delta analysis, ash content or K concentration has been proposed as an alternative criterion for Delta in many species. In five typical habitats of the extreme arid Ejina desert oasis in northwest of China, the seasonal variations of foliar delta, ash content, and potassium (K) concentration were researched in two constructive desert riparian plants (Populus euphratica Olivier, Tamarix ramosissima Ledeb). The correlations of foliar Delta with ash content and K concentration in both species were also examined to evaluate the feasibility of the foliar ash content and K concentration as surrogates of Delta in P. euphratica and T. ramosissima. Results showed that there were significant effects of plant species, habitats and growth season on foliar Delta, ash content, and K concentration. Foliar Delta and K concentration in P. euphratica were significantly higher than those in T. ramosissima, whereas, the ash content was reverse. Among habitats, the trends of delta signatures in both P. euphratica and T. ramosissima were similar, delta values and ash content in both species were the lowest in the dune. Both in the Gobi and dune sites, K concentration in P. euphratica and T. ramosissima was different. In the whole growth period, foliar Delta values and ash content in both species were gradually increased, but K concentration was decreased. Ash content was significantly and positively related to delta in both P. euphratica and T. ramosissima. However, significantly negative correlations between foliar delta and K concentration as well as between ash content and K in P. euphratica were found. In T. ramosissima, the relationship was positive but very weak.