Environmental Evolution Recorded by Tamarix Nebkhas in the Qaidam Basin

A typical Tamarix nebkha was studied in the southern Qaidam Basin, China. K-feldspar pIRIR dating was applied to establish a reliable chronological framework, and an Undatable age–depth model was constructed. Accumulation rates (AR) declined in stages: rapid (~1.33 cm/a; ~370–260 yr BP), slower (~0.75 cm/a; ~260–130 yr BP), and slowest (~0.31 cm/a; ~130 yr BP-present). This dynamic pattern is likely influenced by a combination of regional aeolian activity variations, geomorphological evolution, and the intrinsic growth dynamics of the nebkha itself. To further understand the relationship between nebkha development and climatic conditions, a δ13C sequence was reconstructed using Tamarix plant remains preserved within the sediments. Based on shifts in leaf-level δ13C values, which indicate changes in water use efficiency, water availability over the past 370 years was inferred and divided into three main phases: relatively sufficient from 1650 to 1690, gradually decreasing during 1690–1870, and increasing again after 1870. The δ13C trend closely correlates with temperature variations derived from δ18O records of the Malan ice core. This suggests that in this hyper-arid region, the development of Tamarix nebkhas is primarily controlled by glacial meltwater and snowmelt runoff from the Kunlun Mountains, rather than by local precipitation.