Understanding the relationship between modern pollen assemblages and vegetation/climate for various elevations is essential for accurately interpreting fossil pollen records and conducting quantitative climate reconstructions in mountainous regions. However, these relationships for the Tibetan Plateau, which is the highest and one of the most ecologically sensitive regions globally, are still scarce. We present modern pollen assemblages from 78 topsoil samples collected along altitudinal gradients from 498 to 4046 m above sea level on the eastern Tibetan Plateau. They were distributed in alpine shrub meadows, coniferous forests, and mixed broad-leaved and coniferous forest vegetation types. Multivariate statistical methods, including discriminant analysis, indicator species analysis, logistic regression, and redundancy analysis, were employed to identify relationships among modern pollen assemblages, vegetation types, and climate along an altitudinal gradient. The results revealed that (1) vegetation types along the altitudinal gradient can be effectively differentiated by comparing pollen assemblages, discriminant analysis, and indicator species analysis; (2) the conifer/broadleaf pollen ratio (C/B) efficiently distinguished coniferous forests (C/B > 5) from mixed forests (C/B < 5); and (3) variations in modern pollen assemblages are primarily influenced by temperature, with pollen ratios, such as Artemisia/Cyperaceae (Art/Cy) and Tsuga/(Tsuga + Abies + Picea) (T/TAP), displaying notable altitudinal and temperature differences. These findings demonstrate that variations in modern pollen assemblages on the eastern Tibetan Plateau differentiate between vegetation types and correlate with temperature variations associated with elevation. The results provide insights for future paleovegetation and paleoclimatic reconstructions for similar mountainous regions.

As an important aspect of plant water consumption, nocturnal water use (E_n) behavior provides reliable information on the effect of plantation carbon and water budgets at stand and regional scales. Therefore, quantifying E_n and its environmental and stomatal controlling mechanisms is urgent to establish adaptation strategies for plantation management in semiarid regions. With the help of the sap flow technique, our study investigated the seasonal variations in canopy transpiration and canopy conductance in a Caragana korshinskii Kom plantation. Environmental variables were measured concurrently during the growing seasons of 2020 and 2021. The results indicated that the average E_n values were 0.10 mm d⁻¹ and 0.09 mm d⁻¹, which accounted for 14% and 13% of daily water use, respectively, over two years. The proportions of nocturnal transpiration (T_n) to E_n were approximately 49.76% and 54.44%, while stem refilling (R_e) accounted for 50.24% and 45.56% of E_n in 2020 and 2021, respectively, indicating that C. korshinskii was able to draw on stored stem water to support transpiration. E_n was predominantly affected by nocturnal canopy conductance (G_c–n), air temperature (T_a–n) and wind speed (u_2-n). In contrast, G_c–n and T_a–n explained the highest variation in T_n and nocturnal vapor pressure (VPD_n), and u_2-n explained the highest variation in R_e. Total effects of the five environmental and stomatal variables explained 50%, 36% and 32% of E_n, T_n and R_e variation, respectively. These findings could enable a better understanding of nocturnal water use dynamics and their allocation patterns in C. korshinskii plantations on the Bashang Plateau. Moreover, our results reveal the water use strategies of artificial shrubs and highlight the importance of incorporating nocturnal water use processes into large-scale ecohydrological models in semiarid regions.

Understanding how past societies adapted to climatic and environmental changes offers valuable perspectives for contemporary sustainability challenges. This study investigates the long-term interplay between climate, vegetation, and human settlement patterns in the Liaoxi Corridor—a sensitive forest-steppe transition zone at the northern margin of the East Asian Summer Monsoon. We provide a quantitative assessment of how Holocene climate variability influenced human habitat preferences through mediating changes in vegetation cover.We integrated multi-proxy datasets to address this question. Thirty high-resolution pollen records were analyzed using the REVEALS model to reconstruct vegetation dynamics across the Holocene. Archaeological site distributions were examined through kernel density estimation and spatial clustering techniques to identify settlement aggregation patterns. For each period, we calculated site elevation, slope, and distance to rivers to assess topographic and hydrological preferences. To synthesize these variables, we applied a Human Ecological Niche Model (HENM), which allowed us to evaluate the relative importance of environmental factors in driving settlement location and to detect shifts in human habitat selection over time.The results highlight several key findings. First, the forest-steppe boundary shifted markedly in response to Holocene monsoon variability, with forest expansion during humid phases and steppe dominance during arid intervals. Second, human settlements consistently clustered in environmentally favorable niches, but these niches changed over time. During warm-wet periods associated with forest expansion, populations dispersed into upland areas. In contrast, cooler and drier conditions led to settlement contraction into lowland river valleys, reflecting a strategic shift toward resource-security under climatic stress. Third, the HENM identified vegetation type, water accessibility, and gentle terrain as the primary factors influencing site location, with their relative weights varying across climatic phases.This study underscores the role of vegetation as a critical intermediary between climate and human behavior. By quantifying past human-environment linkages in a climatically sensitive region, we offer a refined framework for understanding adaptive responses to environmental change. These insights not only deepen our knowledge of East Asian prehistory but also inform current models of landscape resilience and sustainable habitat planning under future climate scenarios. In an era of rapid global change, such long-term perspectives are essential for anticipating human-environment feedbacks and fostering resilient socio-ecological systems.