Sap flow and trunk maximum daily shrinkage (MDS) measurements for diagnosing water status of Populus euphratica in an inland river basin of Northwest China

Abstract

ABSTRACTUsing sap flow flux density and trunk maximum daily shrinkage (MDS) as the main plant‐based water stress indicators and combined with soil salinity parameters and plant population characteristics, water statuses of Populus euphratica were diagnosed. Based on these parameters, optimal groundwater depth for maintaining the development of natural P. euphratica were explored in middle and lower reaches of the Tarim River. When excluding the impact of soil salinity and climatic factors, our results demonstrated that sap flow flux density in P. euphratica decreases with increase groundwater depth and that such a negative correlation is significant. It also showed that MDS has a significant positive correlation with groundwater depth. When the water table depth reached 4.5–5.0 m, our study showed a significant reduction in sap flow flux density changes of P. euphratica apparent and increasing MDS, indicating that the growth of P. euphratica is under drying stress, and the plant adapts to the environment through reducing transpirational water consumption by self‐regulation. When water table is in the range of 4–6 m, the populations characteristics (coverage, density and frequency) of P. euphratica under different groundwater depth reached the maximums. We conclude that groundwater depth between 4.5 and 5.0 m is the optimum restoring P. euphratica and its ecosystem in the middle and lower reaches of the Tarim River. Copyright © 2013 John Wiley & Sons, Ltd.