Leaf functional traits of Populus euphratica and its response to groundwater depths in Tarim extremely arid area

Plant functional traits, defined as morpho-physio-phenological traits, reflect the response and adaptation of plants to the environment, and function as a bridge between the plant and environmental factors. In this study, we explored how leaf functional traits responded to groundwater depth(GWD) and their interactions of P. euphratica growing in different arid habitats, and examined the relationship between leaf functional traits and groundwater depths in Tarim extremely arid area, in order to reveal the potential ways of P. euphratica in adapting arid desert environment. The experiments were carried out at eight sampling points(50 m×50 m) with different GWD in the upper reaches of Tarim river, Xinjiang Province, northwestern China in the summer 2019. Seven leaf functional traits of ten P. euphratica individuals in each plot with stem base diameter(BDH)>10 cm were measured, and the GWD and soil moisture of each plot were measured. We then carried out one-way ANOVA and Duncan tests to assess differences in leaf functional traits(specific leaf area, SLA; leaf area, LA; individual lamina mass, LDM; leaf water content, LWC; leaf thickness, LT; leaf dry mass content, LDMC; and leaf tissue density, LTD) under eight GWD. Pearson correlation and the stepwise regression were conducted to determine the quantitative relationships between leaf functional traits and GWD. The results showed that seven leaf traits varied in varying degrees from 9.02% to 40.02%, while the maximum and minimum coefficient of intraspecific variation were LA and LWC, LDMC, respectively. The leaf traits showed large variation along groundwater depth gradient. The leaf functional traits had significant difference in the eight groundwater depths, and were extremely significant correlation with GWD(P