The xylem water-conducting system in plants is essential for the transport of water and nutrients, which is vital for plant’s normal growth and development. Therefore, the plasticity of the plant’s water-conducting structures and strategies plays a significant role in determining its capacity to survive under fluctuating environmental conditions. In this study, we evaluated the plasticity of root vessel traits of main roots for 27 herbaceous species along the drought gradients (precipitation from 505 mm to 70 mm) in arid region of China. Research results indicate that as the degree of drought stress increases, herbaceous species in Leguminosae adopt a strategy prioritizing water-conducting efficiency, characterized by an increase in the number of vessels and a larger vessel diameter, leading to a significant increase in the root water-conducting area ratio and overall water-conducting efficiency. In contrast, herbaceous species in Zygophyllaceae adopt a strategy prioritizing water-conducting safety, characterized by an increase in the number of vessels and a decrease in vessel diameter, resulting in a downward trend in overall water-conducting efficiency. The water-conducting strategy of herbaceous species in Leguminosae can effectively enhance root water conduction capacity in the short term, but the increased number and larger diameter of vessels significantly raise the risk of xylem cavitation and embolism, therefore reducing their adaptability to drought stress. In contrast, the water-conducting strategy of herbaceous species in Zygophyllaceae leads to a proportional reduction in root water conduction capacity, but the corresponding increase in vessel number helps maintain a high root water-conducting area ratio, ensuring the stability of root water transport and enhancing their adaptability to drought stress. This study will contribute to a deeper scientific understanding of the ecological adaptation strategies of different herbaceous taxa to drought stress, and provide a theoretical foundation for the sustainable management of grassland ecosystems in arid regions.

Climate change and human activities are changing the structure and function of dryland ecosystems at unprecedented rate, thus threatening the stability of ecosystems. The stability of dryland ecosystems is vital for ecological security and local livelihoods. However, the mechanisms that underlie ecosystem stability in drylands remain uncertain due to limited field data from regional studies. Combined with transect survey in the drylands of China along the aridity gradient and remote sensing data, we characterized community temporal stability and identified its driving mechanisms along the aridity gradient. The results showed the community temporal stability in drylands of China revealed a U-shaped curve with increasing aridity and its major driving mechanisms shifted at an aridity level of ~0.88. In regions where aridity is below 0.88, increasing precipitation and species richness resulted in higher community productivity and community stability. In regions where aridity is above 0.88, however, higher soil organic carbon content and species richness may lead to higher variability of community productivity and lower ecosystem stability. Overall, our findings revealed that there existed an aridity threshold leading to abrupt changes on community stability in drylands of China. Our study also suggested divergent driving mechanisms of community stability above and below the threshold, which should be considered in policy making regarding the ecosystem management of drylands.