关键词: 塔克拉玛干沙漠, 树木年轮, 帕尔默干旱指数, 径流

Abstract: Aims Populus euphratica and Tamarix ramosissima are two dominant species in the Daliyaboyi oasis, located at the tail of the Keriya River in the hinterland of the Taklamakan Desert. Against the backdrop of a warming and wetting climate trend in Northwest China, the relationship between the radial growth of these two species and climate change remains unclear. This study aimed to identify the limiting factors for the radial growth of P. euphratica and T. ramosissima and to examine the characteristics of their growth-climate relationships in the conditions of a warming and wetting climate. Methods Tree-ring samples of P. euphratica and T. ramosissima were collected from two sites with different groundwater depths (1.0 m and 4.4 m) at the Daliyaboyi oasis. Standard chronologies were established for the two species, and the relationships between tree-ring width index and runoff and climatic factors for both species were analyzed. The differences in the climate responses of these two species were also explored. Important findings The results indicated that P. euphratica and T. ramosissima with different groundwater depths have different responses to climate factors. With a groundwater depth of 1.0 m, the radial growth of P. euphratica was significantly and positively correlated with precipitation in April of the previous year and April of the current year. Meanwhile, the radial growth of T. ramosissima was significantly and positively correlated with runoff in June of the previous year and precipitation in February of the current year, and was significantly and negatively correlated with air temperature in December of the previous year. With a groundwater depth of 4.4 m, the radial growth of P. euphratica was significantly positively correlated with air temperatures in January of the previous year and January of the current year, as well as with the Palmer Drought Severity Index (PDSI) from January of the previous year to June of the current year and from August to September of the current year. Meanwhile, the radial growth of T. ramosissima was significantly and positively correlated with runoff in June of the previous year, temperatures in September of the previous year, and precipitation in December of the previous year, as well as with temperatures in April of the current year. Sliding correlation analysis suggested that, under the influence of climate warming and wetting in the Taklamakan Desert, the positive response of P. euphratica radial growth to runoff factors (January–March) weakened at a groundwater depth of 1.0 m. In contrast, T. ramosissima showed an increased positive response to precipitation in April of the previous year and runoff from January to February of the previous year. With a groundwater depth of 4.4 m, the radial growth of P. euphratica showed a shift from a positive to a significant negative correlation with air temperature during April–May and July–August of the previous year, as well as during April–May and July–August of the current year, and the relationship between radial growth of P. euphratica to PDSI changed from significant positive correlation to non-significant correlation. The relationship between radial growth of T. ramosissima to precipitation and PDSI changed from negative correlation to positive correlation. In conclusion, P. euphratica demonstrates greater dependence on long-term climate factors at the deep groundwater depth, while T. ramosissima is more sensitive to short-term hydrological factors.

Key words: Taklamakan desert, Ring, Palmer Drought Severity Index, runoff