Climatic Change Characteristics towards the “Warming–Wetting” Trend in the Pan-Central-Asia Arid Region

Unraveling the impact of climatic warming and wetting on eukaryotic microbial diversity and assembly mechanisms: A 10-year case study in Lake Bosten, NW China

Over the last six decades, northwest China has undergone a significant climatic shift from "warm-dry" to "warm-wet", profoundly impacting the structures and functions of lake ecosystem across the region. However, the influences of this climatic transition on the diversity patterns, co-occurrence network, and assembly processes of eukaryotic microbial communities in lake ecosystem, along with the underlying mechanisms, remain largely unexplored. To bridge this knowledge gap, our study focused on Lake Bosten, the largest inland freshwater body in China, conducting a comprehensive analysis. Firstly, we examined the dynamics of key water quality parameters in the lake based on long-term monitoring data (1992-2022). Subsequently, we collected 93 water samples spanning two distinctive periods: low water level (WL) and high total dissolved solids (TDS) (PerWLTDS; 2010-2011; attributed to "warm-dry" climate), and high WL and low TDS (PerTDSWL; 2021-2022; associated with "warm-wet" climate). Eukaryotic microorganisms were further investigated using 18S rRNA gene sequencing and various statistical methods. Our findings revealed that climatic warming and wetting significantly increased eukaryotic microbial α-diversity (all Wilcox. test: P<0.05), while simultaneously reducing β-diversity (all Wilcox. test: P<0.001) and network complexity. Through the two sampling periods, assembly mechanisms of eukaryotic microorganisms were predominantly influenced by dispersal limitation (DL) and drift (DR) within stochastic processes, alongside homogeneous selection (HoS) within deterministic processes. WL played a mediating role in eukaryotic microbial DL and HoS processes in the PerTDSWL, whereas water quality and α-diversity influenced the DL process in the PerWLTDS. Collectively, these results underscore the direct and indirect impacts of "warm-wet" conditions on the eukaryotic microorganisms within Lake Bosten. This study provides valuable insights into the evolutionary dynamics of lake ecosystems under such climatic conditions and aids in predicting the ecological ramifications of global climatic changes.

Changes in the spatial and temporal characteristics of China's arid region in the background of ENSO

Arid regions are sensitive to changes in precipitation, while El Niño-Southern Oscillation strongly influences worldwide hydrometeorological processes. Temporal and spatial changes of characteristics including precipitation, annual mean temperature and area in China's arid region were analyzed, using daily precipitation and temperature data from 117 meteorological stations of 1961-2016. The results show that: (1) The arid region is getting warmer and wetter. During the past 56 years, the precipitation in the arid region have shown an increasing trend. The annual and quarterly precipitation all exist a cycle of about 4 years. There is a negative correlation between the area of the arid region and the annual mean temperature, which is significant at the 0.01 level. (2) The area of arid region has been on a downward trend since 1968, and there was a mutation in 1992. There are three main cycles of 24 years, 13 years and 5 years in the area of the arid region. During the study period, the spatial center of the arid region's precipitation moved 0.14° to the north and 0.77° to the east. (3) The response of precipitation to ENSO is different between the eastern and the western arid region. El Niño events increased the area of China's arid region in El Niño years and La Niña events increased the precipitation of China's arid region in La Niña years. The response of China's arid region to ENSO in the first half of the following year is opposite and the response in spring is the most significant. To sum up, in El Niño years the eastern arid region increased in area and precipitation, while in La Niña years the western arid region decreased in area and the eastern arid region increased in precipitation, which was related to the eastward movement of the spatial center of the precipitation.