Abstract:

Aims: Under the influence of Quaternary climate fluctuation, xerophytes may have experienced large-scale migration and expansion. It is highly important to study the historical and geographical distribution pattern of xerophytes to understand the evolution of xerophyte flora under the background of climate fluctuation. The purpose of this study is to reveal the distribution pattern and driving mechanisms of Haloxylon in China since the last interglacial period (LIG) and the last glacial maximum period (LGM).

Methods: Based on 85 natural distribution sites and 2 sets of environmental factors, the geographic distribution pattern change, and driving mechanisms of Haloxylon since the LIG were analyzed by integrating GIS spatial analysis and 9 species distribution models. Based on the chloroplast gene data of 62 Haloxylon populations, we used the least cost path method to simulate the possible diffusion paths of Haloxylon since the LIG. Principal component analysis (PCA) of environmental variables affecting the distribution of Haloxylon was carried out by using the prcomp function in R 4.1.1. The contribution of environmental variables to the suitable distribution of Haloxylon was evaluated, and the correlation between key variables and the degree of suitability was analyzed.

Results: We found that the precision of the integrated model was significantly improved compared with that of the single model. Since the LIG, the distribution of Haloxylon has undergone a significant decrease and post-glacial expansion. From the LIG to the LGM, Haloxylon ammodendron retreated westward from Junggar Basin and western Tarim Basin to the northwest and eastern margin of Junggar Basin and northwest margin of Tarim Basin. Haloxylon persicum retreated from the western end of Junggar Basin and Tarim Basin to the south of Junggar Basin. Since the LGM, H. ammodendron has expanded eastward, through northern Gansu and eastern region of the Qaidam basin to Alxa Desert in western Inner Mongolia. Haloxylon persicum has expanded northeast on a small scale, occupying the central and western part of Junggar Basin. The change of key climatic factors in the suitable distribution area of Haloxylon is relatively low. PCA results showed that the score coefficient of the precipitation factor in the first principal component is higher. The analysis of the relationship between the environmental factors affecting the distribution of Haloxylon and the suitability of the distribution area demonstrated that there is a significant correlation between temperature factors and the suitability of the distribution of Haloxylon.

Conclusion: The climate change in Quaternary caused the geographical distribution of Haloxylon to narrow and then subsequently expand. The main migration paths of Haloxylon are through the Junggar Basin and Hexi Corridor. Precipitation factors mainly affect the change of suitable distribution area of Haloxylon, while temperature factors mainly affect the degree of distribution suitability of Haloxylon.

Key words: Haloxylon, historical distribution pattern, post glacial diffusion path, last glacial maximum period, last interglacial period