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In different-aged sand-fixing zones and shifting sand dunes, the seasonal variations of foliar carbon isotope discrimination (Delta), potassium (K) concentration and ash content were investigated in three dominated deserted plants (Artemisia ordosica, Hedysarum scoparium and Caragana korshinskii) during growth season in Shapotou, which is in the southeast margin of the Tengger Desert. The correlations of foliar Delta with foliar K concentration and ash content were examined to evaluate the foliar K and ash content as surrogates of Delta in those deserted plants. Results showed that there were significant effects of plant species, micro-habitation and growth season on foliar Delta, K concentration and ash content. Foliar Delta of C. korshinskii was significantly lower than those of A. ordosica and H. scoparium, and K concentrations in A. ordosica were 2.14 and 2.36 times those of C. korshinskii and H. scoparium. At the same time, micro-habitation and the conditions in growth seasons had significant effects on foliar Delta, K concentration and ash content. Ash content and K concentration were positively correlated to Delta in A. ordosica and H. scoparium, while there was significantly negative relationship between foliar K concentration and Delta in C. korshinskii. Thus, those findings suggest that foliar ash content and K concentration can serve as surrogates of carbon isotope discrimination (Delta) in A. ordosica and H. scoparium, while they do not in C. korshinskii. This result implied that the correlations of foliar Delta with ash content and K concentration were various due to the physiological features of plant species, and species differences should be fully considered when evaluating the surrogates of carbon isotope discrimination in plants.