关键词: 水力性状, 解剖结构, 降水事件, 多枝柽柳, 灌丛沙堆

Abstract: Aims Plant growth in arid desert regions is jointly constrained by water availability and habitat conditions, and their physiological structures and functional traits exhibit pronounced plastic responses. In this study, Tamarix ramosissima growing on different developmental stages of coppice dunes along the southwestern margin of the Gurbantünggüt Desert was investigated to examine the coordinated responses between hydraulic structure and functional traits. Methods Based on simulated precipitation pulses of 4.2 mm and 7 mm, as well as natural drought conditions, we examined the variations in hydraulic traits, anatomical structure, and leaf functional traits during dune development, with the aim of clarifying the response mechanisms linking hydraulic structure and functional traits to natural precipitation variability. Important findings The results showed that (1) The xylem hydraulic conductivity (Ks) of T. ramosissima in the growth stage of coppice dunes was significantly higher than that in the other coppice dunes, whereas both Ks and leaf water content (LWC) were lowest in the declining stage of coppice dunes, indicating a marked reduction in water regulation capacity in this coppice dune. Ks and LWC responded most strongly to the 7 mm precipitation event, but showed relatively weak responses under natural drought conditions and following the 4.2 mm precipitation event. In contrast, the percentage loss of conductivity (PLC) did not differ significantly among precipitation regimes in all coppice dunes, suggesting that although hydraulic conductivity increased to some extent after short-term rainfall, the overall hydraulic status was only marginally improved and a certain degree of xylem embolism persisted. (2) Significant differences were observed in the leaf and xylem anatomical structures of T. ramosissima in all coppice dunes. With dune development, xylem vessel diameter showed an initial increase followed by a decline, and was significantly greater in the growth and stable stages of coppice dunes than in the other coppice dunes. In contrast, T. ramosissima in the declining stage of coppice dunes exhibited smaller vessel diameters, higher vessel density, and significantly thicker leaf epidermis, indicating a greater emphasis on structural configuration to maintain hydraulic safety and reduce water loss. However, neither leaf nor xylem anatomical structures differed significantly between precipitation-pulse and natural drought conditions, suggesting that short-term precipitation events were insufficient to alter stem and leaf structural traits. (3) Correlation analysis showed that Ks was significantly associated with vessel structural traits, whereas PLC exhibited no significant relationship with vessel anatomy. Structural equation modeling further revealed that increases in soil water content improved leaf water status by enhancing Ks, thereby promoting stomatal opening. Overall, T. ramosissima in all coppice dunes achieves adaptation to natural precipitation variability through the coordinated regulation of hydraulic traits, anatomical structure, and leaf functional traits, balancing water transport efficiency with hydraulic safety.

Key words: hydraulic function, anatomical structure, precipitation events, Tamarix ramosissima, coppice dunes