Impact of long-term zero-flow and ecological water conveyance on the radial increment of Populus euphratica in the lower reaches of the Tarim River, Xinjiang, China

Based on the dendro-hydrology theory, we studied the impacts of two significant environmental occurrences (long-term zero-flow and ecological water conveyance) on the radial increment of Populus euphratica in the lower reaches of the Tarim River, Xinjiang, China. We also studied the relationships between radial increment and groundwater table as a function of the distance from the river channel. We found that the radial increment of P. euphratica respond significantly to both zero-flow and water conveyance, and these responses differed among four transects and they weakened with increasing distance from the Daxihaizi Reservoir. The depth to the groundwater table is a key factor that restricts P. euphratica growth in extremely arid regions, and the relationship between radial increment and the groundwater table was significant. The radial increment decreased remarkably with increasing duration of the zero-flow period. The influence of long-term zero-flows on P. euphratica growth was a long-term and slow process. The response of P. euphratica showed a delayed response to the groundwater changes after ecological water conveyance. This lag response differed among the monitoring transects and different distances away from river channel.