Abstract: Condensation water is an important water source in arid ecosystems. To understand the characteristics of soil condensation water during growing season in extreme arid regions, micro-lysimeters and neutron probe were used to measure the amounts and duration of soil condensation water on different types of underlying surfaces (Populus euphratica forest, Tamarix bushes and bare land) in the lower reaches of the Tarim River. The results showed that the maximum total soil condensation amount occurred on the surface of bare land. The minimum total soil condensation amount was accumulated on the underlying surface of Populus euphratica forest. Soil condensation amounts of the connected treatment were significantly larger than those of the unconnected treatment (t<0.01). The average daily soil condensation amount varied with types of underlying surfaces with the maximum condensation amount occurred on the underlying surface of Tamarix bushes, while the minimum condensation amount was created on the underlying surface of Populus euphratica forest. ANOVA analysis results indicated that the average daily soil condensation amounts on different types of underlying surfaces were significantly different (P<0.01). Diurnal dynamics trend of soil condensation amounts on different types of underlying surfaces showed a clear double-peak curve. Soil condensation water began at 22:00 and ended at 09:00 the next morning. The formation of soil condensation water was mainly affected by atmospheric temperature, relative humidity, soil surface temperature, wind speed and types of underlying surfaces. The results may assist in the calculation of rational ecological water demand and provide scientific supports for ecological restoration in the lower reaches of the Tarim River.

Key words: arid region, condensation water, micro-lysimeters, neutron probe, Tarim River