Abstract: The distance from the river is a crucial factor that affects the structure and function of desert riparian forests, impeding their regeneration and biodiversity due to water conditions. However, few studies have confirmed the long-term variation in structure and function of this azonal riparian forest type caused by water stress. We hypothesize that a complex and diverse stand structure is associated with the distance from the river, and tree size plays a crucial role in establishing random frameworks for stability in forest stands. Our investigation was conducted in the lower Trim River. Based on long-term observation from 2005 to 2023, both stand structure parameters and diversity index were used. The variation in stand structure was analyzed using the least significant difference, and stand stability was assessed using Gaussian distribution and bivariate regression methods. Our study indicated that there were no significant differences in the response of size differentiation and crowding to distance from the river. However, a significant divergence in spatial pattern was observed at greater distances from the river, which became more pronounced over time. Regardless of the distance from the river or time-scale, there were significant differences in DBH, crown diameter and length. Furthermore, structural diversity exhibited varying trends with distance from the river and time-scale, indicating a diverse and complex pattern in stand structure due to water stress. The proportion of random frameworks for stability is influenced by the distance from the river, and tree size, especially crown diameter and length, plays an important role. Our research examines the multiple relationships among water conditions, forest structure, and function in an arid region, highlighting the significance of water conditions in the natural restoration of desert riparian forest ecosystems. The findings provide new insights for further exploration of the relationship between stand structure and stability, enhancing our understanding of the theory of random frameworks-stability. Overall, the study provides scientific guidance for sustainable forest management and conservation in the context of a changing climate, particularly regarding water stress.

Key words: Stand structure, Diversity, Stability, Desert riparian forest, Distance from the river