Effects of intrinsic water-use efficiency and environmental factors on radial growth of Populus euphratica, Taklamakan Desert, China

Climate warming and human activities have altered water resource distribution in desert areas, accelerated water infiltration and evaporation, disrupted the water cycle, and increased drought stress in riparian forests. However, the effects of climate varying environmental conditions on intrinsic water use efficiency ( i WUE) and tree growth in Populus euphratica Oliv. remain unexplored. Using tree-ring width and δ 13 C composition data, we analyzed the growth and i WUE of P. euphratica across three sample plots with varying groundwater depths in the Daliyaboyi Oasis. We found that P. euphratica basal area increment (BAI) and i WUE significantly increased across all sampling plots from 1980 to 2003 with no significant changes from 2004 to 2022. In the shallow-groundwater sample plot, P. euphratica BAI and i WUE were significantly positively correlated with temperature (TEM), vapor pressure difference (VPD), and runoff (RO) and significantly negatively correlated with relative humidity (RH). Conversely, in the deep-groundwater sample plot, P. euphratica i WUE was significantly and positively correlated with RH and negatively with VPD. The correlation between the intercellular and atmospheric CO 2 concentration ratio (C i /C a ) and meteorological factors shifted from non-significant to significant with increasing groundwater depth. C i /C a variations in P. euphratica were significantly positively correlated with TEM, VPD, and RO and significantly negatively correlated with RH. Thus, with continued climate warming, P. euphratica in deep-groundwater sample plots may face severe drought stress and growth declines in the future. Understanding the dynamic relationship between i WUE and BAI under varying environmental conditions is crucial for predicting forest responses to climate change and informing conservation strategies. • Groundwater depth regulates P. euphratica growth and water-use efficiency. • i WUE changes do not directly translate into radial growth changes in arid regions. • P. euphratica adopts varied water-use strategies based on groundwater availability. • C i /C a trends show regional adaptation to climate and hydrological conditions.