Daily and seasonal stem radial activity of Populus euphratica and its association with hydroclimatic factors in the lower reaches of China’s Heihe River basin

Under the increasing shortage of water resources conditions, which was affected by climate changes and the human activity, the rational water management is more important especially in the inland rivers in arid regions. The stem radial activity of four Euphrates poplars (Populus euphratica), the dominant tree species in desert riparian forests in the lower reaches of China’s Heihe River basin, was measured using the point dendrometer. The daily and seasonal rhythms of stem radial activity and their relationships to environmental factors were analyzed. Generally, the diurnal radial variation followed as parabola and the cumulative stem radial growth in the growing season followed an S-shaped curve. It showed that May–August was the main period for the stem radial growth or the growth-ring formation of Euphrates poplar. And the groundwater depth was significantly correlated with stem radial growth during this period. Therefore, the annual rings of Euphrates poplar can be used to reconstruct processes that determine the regional water regime, such as river runoff and fluctuations in groundwater depth. To desert riparian forest management, suitable groundwater depths must be maintained in the spring and summer, with spring floods every 2 years, to sustain tree health and a suitable stand structure.