Abstract: The ecologically fragile arid valleys in western China have low afforestation survival rates, and the lack of adaptable superior variety is key to restricting forestry production and ecological restoration in this region. The native poplar trees are important germplasm resources in this region, with a wide range of taxa, rich genetic variations, and great potential for breeding and utilization. Six clones of native poplars were used in a field trial to investigate variations in survival, growth and adaptation to arid-warm and arid-hot valleys. In the arid-hot valley, clone Y1-2 exhibited the highest survival rate and growth condition, surpassing other clones, while clones B7-4 and P3-6 demonstrated superior survival and growth performance in the arid-warm valley. Clone B7-4 displayed the highest soluble sugar content in leaves across both habitats. Superoxide dismutase and ascorbate peroxidase activities, along with malondialdehyde content in leaves, were higher in the arid-hot valley for all clones compared with the arid-warm valley. Long-term water use efficiency, as indicated by δ¹³C in leaves, was significantly higher for all clones in the arid-hot valley, particularly for H1-6, T3-2 and P3-6. Increases in upper epidermis thickness were observed in clones E1, B7-4 and P3-6, while Y1-2 exhibited a higher palisade parenchyma thickness (PT) in the arid-hot valley compared with the arid-warm valley. Vein densities were higher in leaves of clones E-1, B7-4, Y1-2 and P3-6 in both valleys compared with other clones, with B7-4 showing a significant increase in mean vein width in the arid-hot valley. In conclusion, the superior growth performance of clone B7-4 in the arid-warm valley may be attributed to its stronger osmotic adjustment and higher capacity to maintain water transportation through venation. The exceptional performance of clone Y1-2 in the arid-hot valley may be associated with its compact arrangement of PT, as well as its stronger capacity for hydraulic transport and antioxidant resistance in leaves.

Key words: native poplar clone, arid valleys, venation structure, long-term water use effciency, anatomical structure of leaves